SSL Cipher.java Interaktion und
PortierbarkeitJAVA

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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package javax.crypto;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.regex.*;

import java.security.*;
import java.security.Provider.Service;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidParameterSpecException;
import java.security.cert.Certificate;
import java.security.cert.X509Certificate;

import javax.crypto.spec.*;

import java.nio.ByteBuffer;
import java.nio.ReadOnlyBufferException;

import sun.security.util.Debug;
import sun.security.jca.*;
import sun.security.util.KnownOIDs;

/**
* This class provides the functionality of a cryptographic cipher for
* encryption and decryption. It forms the core of the Java Cryptographic
* Extension (JCE) framework.
*
* In order to create a {@code Cipher} object, the application calls the
* cipher's {@code getInstance} method, and passes the name of the
* requested transformation to it. Optionally, the name of a provider
* may be specified.
*
* A transformation is a string that describes the operation (or
* set of operations) to be performed on the given input, to produce some
* output. A transformation always includes the name of a cryptographic
* algorithm (e.g., AES), and may be followed by a feedback mode and
* padding scheme.
*
* A transformation is of the form:
*
* <ul>
* <li>"algorithm/mode/padding" or
*
* <li>"algorithm"
* </ul>
*
* (in the latter case,
* provider-specific default values for the mode and padding scheme are used).
* For example, the following is a valid transformation:
*
* <pre>
* Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
* </pre>
*
* Using modes such as {@code CFB} and {@code OFB}, block
* ciphers can encrypt data in units smaller than the cipher's actual
* block size. When requesting such a mode, you may optionally specify
* the number of bits to be processed at a time by appending this number
* to the mode name as shown in the "{@code AES/CFB8/NoPadding}" and
* "{@code AES/OFB32/PKCS5Padding}" transformations. If no such
* number is specified, a provider-specific default is used.
* (See the
* {@extLink security_guide_jdk_providers JDK Providers Documentation}
* for the JDK Providers default values.)
* Thus, block ciphers can be turned into byte-oriented stream ciphers by
* using an 8 bit mode such as CFB8 or OFB8.
* 
* Modes such as Authenticated Encryption with Associated Data (AEAD)
* provide authenticity assurances for both confidential data and
* Additional Associated Data (AAD) that is not encrypted. (Please see
* <a href="http://www.ietf.org/rfc/rfc5116.txt"> RFC 5116 </a> for more
* information on AEAD and AAD algorithms such as GCM/CCM.) Both
* confidential and AAD data can be used when calculating the
* authentication tag (similar to a {@link Mac}). This tag is appended
* to the ciphertext during encryption, and is verified on decryption.
* 
* AEAD modes such as GCM/CCM perform all AAD authenticity calculations
* before starting the ciphertext authenticity calculations. To avoid
* implementations having to internally buffer ciphertext, all AAD data
* must be supplied to GCM/CCM implementations (via the {@code updateAAD}
* methods) before the ciphertext is processed (via
* the {@code update} and {@code doFinal} methods).
* 
* Note that GCM mode has a uniqueness requirement on IVs used in
* encryption with a given key. When IVs are repeated for GCM
* encryption, such usages are subject to forgery attacks. Thus, after
* each encryption operation using GCM mode, callers should re-initialize
* the {@code Cipher} objects with GCM parameters which have a different IV
* value.
* <pre>
* GCMParameterSpec s = ...;
* cipher.init(..., s);
*
* // If the GCM parameters were generated by the provider, it can
* // be retrieved by:
* // cipher.getParameters().getParameterSpec(GCMParameterSpec.class);
*
* cipher.updateAAD(...); // AAD
* cipher.update(...); // Multi-part update
* cipher.doFinal(...); // conclusion of operation
*
* // Use a different IV value for every encryption
* byte[] newIv = ...;
* s = new GCMParameterSpec(s.getTLen(), newIv);
* cipher.init(..., s);
* ...
*
* </pre>
* The ChaCha20 and ChaCha20-Poly1305 algorithms have a similar requirement
* for unique nonces with a given key. After each encryption or decryption
* operation, callers should re-initialize their ChaCha20 or ChaCha20-Poly1305
* ciphers with parameters that specify a different nonce value. Please
* see <a href="https://tools.ietf.org/html/rfc7539">RFC 7539</a> for more
* information on the ChaCha20 and ChaCha20-Poly1305 algorithms.
* 
* Every implementation of the Java platform is required to support
* the following standard {@code Cipher} object transformations with
* the keysizes in parentheses:
* <ul>
* <li>{@code AES/CBC/NoPadding} (128)</li>
* <li>{@code AES/CBC/PKCS5Padding} (128)</li>
* <li>{@code AES/ECB/NoPadding} (128)</li>
* <li>{@code AES/ECB/PKCS5Padding} (128)</li>
* <li>{@code AES/GCM/NoPadding} (128)</li>
* <li>{@code DESede/CBC/NoPadding} (168)</li>
* <li>{@code DESede/CBC/PKCS5Padding} (168)</li>
* <li>{@code DESede/ECB/NoPadding} (168)</li>
* <li>{@code DESede/ECB/PKCS5Padding} (168)</li>
* <li>{@code RSA/ECB/PKCS1Padding} (1024, 2048)</li>
* <li>{@code RSA/ECB/OAEPWithSHA-1AndMGF1Padding} (1024, 2048)</li>
* <li>{@code RSA/ECB/OAEPWithSHA-256AndMGF1Padding} (1024, 2048)</li>
* </ul>
* These transformations are described in the
* <a href="{@docRoot}/../specs/security/standard-names.html#cipher-algorithms">
* Cipher section</a> of the
* Java Security Standard Algorithm Names Specification.
* Consult the release documentation for your implementation to see if any
* other transformations are supported.
*
* @author Jan Luehe
* @see KeyGenerator
* @see SecretKey
* @since 1.4
*/

public class Cipher {

 private static final Debug debug =
 Debug.getInstance("jca", "Cipher");

 private static final Debug pdebug =
 Debug.getInstance("provider", "Provider");
 private static final boolean skipDebug =
 Debug.isOn("engine=") && !Debug.isOn("cipher");

 /**
 * Constant used to initialize cipher to encryption mode.
 */
 public static final int ENCRYPT_MODE = 1;

 /**
 * Constant used to initialize cipher to decryption mode.
 */
 public static final int DECRYPT_MODE = 2;

 /**
 * Constant used to initialize cipher to key-wrapping mode.
 */
 public static final int WRAP_MODE = 3;

 /**
 * Constant used to initialize cipher to key-unwrapping mode.
 */
 public static final int UNWRAP_MODE = 4;

 /**
 * Constant used to indicate the to-be-unwrapped key is a "public key".
 */
 public static final int PUBLIC_KEY = 1;

 /**
 * Constant used to indicate the to-be-unwrapped key is a "private key".
 */
 public static final int PRIVATE_KEY = 2;

 /**
 * Constant used to indicate the to-be-unwrapped key is a "secret key".
 */
 public static final int SECRET_KEY = 3;

 // The provider
 private Provider provider;

 // The provider implementation (delegate)
 private CipherSpi spi;

 // The transformation
 private final String transformation;

 // Crypto permission representing the maximum allowable cryptographic
 // strength that this cipher can be used for. (The cryptographic
 // strength is a function of the keysize and algorithm parameters encoded
 // in the crypto permission.)
 private CryptoPermission cryptoPerm;

 // The exemption mechanism that needs to be enforced
 private ExemptionMechanism exmech;

 // Flag which indicates whether or not this cipher has been initialized
 private boolean initialized = false;

 // The operation mode - store the operation mode after the
 // cipher has been initialized.
 private int opmode = 0;

 // next SPI to try in provider selection
 // null once provider is selected
 private CipherSpi firstSpi;

 // next service to try in provider selection
 // null once provider is selected
 private Service firstService;

 // remaining services to try in provider selection
 // null once provider is selected
 private Iterator<Service> serviceIterator;

 // list of transform Strings to lookup in the provider
 private List<Transform> transforms;

 private final Object lock;

 /**
 * Creates a {@code Cipher} object.
 *
 * @param cipherSpi the delegate
 * @param provider the provider
 * @param transformation the transformation
 * @throws NullPointerException if {@code provider} is {@code null}
 * @throws IllegalArgumentException if the supplied arguments
 * are deemed invalid for constructing the {@code Cipher} object
 */
 protected Cipher(CipherSpi cipherSpi,
 Provider provider,
 String transformation) {
 // See bug 4341369 & 4334690 for more info.
 // If the caller is trusted, then okay.
 // Otherwise throw an IllegalArgumentException.
 if (!JceSecurityManager.INSTANCE.isCallerTrusted(
 JceSecurityManager.WALKER.getCallerClass(), provider)) {
 throw new IllegalArgumentException("Cannot construct cipher");
 }
 this.spi = cipherSpi;
 this.provider = provider;
 this.transformation = transformation;
 this.cryptoPerm = CryptoAllPermission.INSTANCE;
 this.lock = null;
 }

 /**
 * Creates a {code Cipher} object. Called internally by {code NullCipher}.
 *
 * @param cipherSpi the delegate
 * @param transformation the transformation
 */
 Cipher(CipherSpi cipherSpi, String transformation) {
 this.spi = cipherSpi;
 this.transformation = transformation;
 this.cryptoPerm = CryptoAllPermission.INSTANCE;
 this.lock = null;
 }

 private Cipher(CipherSpi firstSpi, Service firstService,
 Iterator<Service> serviceIterator, String transformation,
 List<Transform> transforms) {
 this.firstSpi = firstSpi;
 this.firstService = firstService;
 this.serviceIterator = serviceIterator;
 this.transforms = transforms;
 this.transformation = transformation;
 this.lock = new Object();
 }

 private static String[] tokenizeTransformation(String transformation)
 throws NoSuchAlgorithmException {
 if (transformation == null) {
 throw new NoSuchAlgorithmException("No transformation given");
 }
 /*
 * array containing the components of a cipher transformation:
 *
 * index 0: algorithm component (e.g., AES)
 * index 1: feedback component (e.g., CFB)
 * index 2: padding component (e.g., PKCS5Padding)
 */
 String[] parts = new String[3];
 int count = 0;
 StringTokenizer parser = new StringTokenizer(transformation, "/");
 try {
 while (parser.hasMoreTokens() && count < 3) {
 parts[count++] = parser.nextToken().trim();
 }
 if (count == 0 || count == 2) {
 throw new NoSuchAlgorithmException("Invalid transformation"
 + " format:" +
 transformation);
 }
 // treats all subsequent tokens as part of padding
 if (count == 3 && parser.hasMoreTokens()) {
 parts[2] = parts[2] + parser.nextToken("\r\n");
 }
 } catch (NoSuchElementException e) {
 throw new NoSuchAlgorithmException("Invalid transformation " +
 "format:" + transformation);
 }
 if ((parts[0] == null) || (parts[0].isEmpty())) {
 throw new NoSuchAlgorithmException("Invalid transformation: " +
 "algorithm not specified-"
 + transformation);
 }
 return parts;
 }

 // Provider attribute name for supported chaining mode
 private static final String ATTR_MODE = "SupportedModes";
 // Provider attribute name for supported padding names
 private static final String ATTR_PAD = "SupportedPaddings";

 // constants indicating whether the provider supports
 // a given mode or padding
 private static final int S_NO = 0; // does not support
 private static final int S_MAYBE = 1; // unable to determine
 private static final int S_YES = 2; // does support

 /**
 * Nested class to deal with modes and paddings.
 */
 private static class Transform {
 // transform string to lookup in the provider
 final String transform;
 // the mode/padding suffix in upper case. for example, if the algorithm
 // to lookup is "AES/CBC/PKCS5Padding" suffix is "/CBC/PKCS5PADDING"
 // if lookup is "AES", suffix is the empty string
 // needed because aliases prevent straight transform.equals()
 final String suffix;
 // value to pass to setMode() or null if no such call required
 final String mode;
 // value to pass to setPadding() or null if no such call required
 final String pad;
 Transform(String alg, String suffix, String mode, String pad) {
 this.transform = alg + suffix;
 this.suffix = suffix.toUpperCase(Locale.ENGLISH);
 this.mode = mode;
 this.pad = pad;
 }
 // set mode and padding for the given SPI
 void setModePadding(CipherSpi spi) throws NoSuchAlgorithmException,
 NoSuchPaddingException {
 if (mode != null) {
 spi.engineSetMode(mode);
 }
 if (pad != null) {
 spi.engineSetPadding(pad);
 }
 }
 // check whether the given services supports the mode and
 // padding described by this Transform
 int supportsModePadding(Service s) {
 int smode = supportsMode(s);
 if (smode == S_NO) {
 return smode;
 }
 int spad = supportsPadding(s);
 // our constants are defined so that Math.min() is a tri-valued AND
 return Math.min(smode, spad);
 }

 // separate methods for mode and padding
 // called directly by cipher only to throw the correct exception
 int supportsMode(Service s) {
 return supports(s, ATTR_MODE, mode);
 }
 int supportsPadding(Service s) {
 return supports(s, ATTR_PAD, pad);
 }

 private static int supports(Service s, String attrName, String value) {
 if (value == null) {
 return S_YES;
 }
 String regexp = s.getAttribute(attrName);
 if (regexp == null) {
 return S_MAYBE;
 }
 return matches(regexp, value) ? S_YES : S_NO;
 }

 // ConcurrentMap<String,Pattern> for previously compiled patterns
 private static final ConcurrentMap<String, Pattern> patternCache =
 new ConcurrentHashMap<String, Pattern>();

 private static boolean matches(String regexp, String str) {
 Pattern pattern = patternCache.get(regexp);
 if (pattern == null) {
 pattern = Pattern.compile(regexp);
 patternCache.putIfAbsent(regexp, pattern);
 }
 return pattern.matcher(str.toUpperCase(Locale.ENGLISH)).matches();
 }

 }

 private static List<Transform> getTransforms(String transformation)
 throws NoSuchAlgorithmException {
 String[] parts = tokenizeTransformation(transformation);

 String alg = parts[0];
 String mode = parts[1];
 String pad = parts[2];
 if ((mode != null) && (mode.isEmpty())) {
 mode = null;
 }
 if ((pad != null) && (pad.isEmpty())) {
 pad = null;
 }

 if ((mode == null) && (pad == null)) {
 // AES
 Transform tr = new Transform(alg, "", null, null);
 return Collections.singletonList(tr);
 } else { // if ((mode != null) && (pad != null)) {
 // AES/CBC/PKCS5Padding
 List<Transform> list = new ArrayList<>(4);
 list.add(new Transform(alg, "/" + mode + "/" + pad, null, null));
 list.add(new Transform(alg, "/" + mode, null, pad));
 list.add(new Transform(alg, "//" + pad, mode, null));
 list.add(new Transform(alg, "", mode, pad));
 return list;
 }
 }

 // get the transform matching the specified service
 private static Transform getTransform(Service s,
 List<Transform> transforms) {
 String alg = s.getAlgorithm().toUpperCase(Locale.ENGLISH);
 for (Transform tr : transforms) {
 if (alg.endsWith(tr.suffix)) {
 return tr;
 }
 }
 return null;
 }

 /**
 * Returns a {@code Cipher} object that implements the specified
 * transformation.
 *
 * This method traverses the list of registered security providers,
 * starting with the most preferred provider.
 * A new {@code Cipher} object encapsulating the
 * {@code CipherSpi} implementation from the first
 * provider that supports the specified algorithm is returned.
 *
 * Note that the list of registered providers may be retrieved via
 * the {@link Security#getProviders() Security.getProviders()} method.
 *
 * @apiNote
 * It is recommended to use a transformation that fully specifies the
 * algorithm, mode, and padding. By not doing so, the provider will
 * use a default for the mode and padding which may not meet the security
 * requirements of your application.
 *
 * @implNote
 * The JDK Reference Implementation additionally uses the
 * {@code jdk.security.provider.preferred}
 * {@link Security#getProperty(String) Security} property to determine
 * the preferred provider order for the specified algorithm. This
 * may be different than the order of providers returned by
 * {@link Security#getProviders() Security.getProviders()}.
 * See also the Cipher Transformations section of the {@extLink
 * security_guide_jdk_providers JDK Providers} document for information
 * on the transformation defaults used by JDK providers.
 *
 * @param transformation the name of the transformation, e.g.,
 * AES/CBC/PKCS5Padding.
 * See the Cipher section in the <a href=
 * "{@docRoot}/../specs/security/standard-names.html#cipher-algorithms">
 * Java Security Standard Algorithm Names Specification</a>
 * for information about standard transformation names.
 *
 * @return a {@code Cipher} object that implements the requested
 * transformation
 *
 * @throws NoSuchAlgorithmException if {@code transformation}
 * is {@code null}, empty, in an invalid format,
 * or if no provider supports a {@code CipherSpi}
 * implementation for the specified algorithm
 *
 * @throws NoSuchPaddingException if {@code transformation}
 * contains a padding scheme that is not available
 *
 * @see java.security.Provider
 */
 public static final Cipher getInstance(String transformation)
 throws NoSuchAlgorithmException, NoSuchPaddingException
 {
 if ((transformation == null) || transformation.isEmpty()) {
 throw new NoSuchAlgorithmException("Null or empty transformation");
 }
 List<Transform> transforms = getTransforms(transformation);
 List<ServiceId> cipherServices = new ArrayList<>(transforms.size());
 for (Transform transform : transforms) {
 cipherServices.add(new ServiceId("Cipher", transform.transform));
 }
 List<Service> services = GetInstance.getServices(cipherServices);
 // make sure there is at least one service from a signed provider
 // and that it can use the specified mode and padding
 Iterator<Service> t = services.iterator();
 Exception failure = null;
 while (t.hasNext()) {
 Service s = t.next();
 if (JceSecurity.canUseProvider(s.getProvider()) == false) {
 continue;
 }
 Transform tr = getTransform(s, transforms);
 if (tr == null) {
 // should never happen
 continue;
 }
 int canuse = tr.supportsModePadding(s);
 if (canuse == S_NO) {
 // does not support mode or padding we need, ignore
 continue;
 }
 // S_YES, S_MAYBE
 // even when mode and padding are both supported, they
 // may not be used together, try out and see if it works
 try {
 CipherSpi spi = (CipherSpi)s.newInstance(null);
 tr.setModePadding(spi);
 // specify null instead of spi for delayed provider selection
 return new Cipher(null, s, t, transformation, transforms);
 } catch (Exception e) {
 failure = e;
 }
 }
 throw new NoSuchAlgorithmException
 ("Cannot find any provider supporting " + transformation, failure);
 }

 /**
 * Returns a {@code Cipher} object that implements the specified
 * transformation.
 *
 * A new {@code Cipher} object encapsulating the
 * {@code CipherSpi} implementation from the specified provider
 * is returned. The specified provider must be registered
 * in the security provider list.
 *
 * Note that the list of registered providers may be retrieved via
 * the {@link Security#getProviders() Security.getProviders()} method.
 *
 * @apiNote
 * It is recommended to use a transformation that fully specifies the
 * algorithm, mode, and padding. By not doing so, the provider will
 * use a default for the mode and padding which may not meet the security
 * requirements of your application.
 *
 * @implNote
 * See the Cipher Transformations section of the {@extLink
 * security_guide_jdk_providers JDK Providers} document for information
 * on the transformation defaults used by JDK providers.
 *
 * @param transformation the name of the transformation,
 * e.g., AES/CBC/PKCS5Padding.
 * See the Cipher section in the <a href=
 * "{@docRoot}/../specs/security/standard-names.html#cipher-algorithms">
 * Java Security Standard Algorithm Names Specification</a>
 * for information about standard transformation names.
 *
 * @param provider the name of the provider
 *
 * @return a {@code Cipher} object that implements the requested
 * transformation
 *
 * @throws IllegalArgumentException if the {@code provider}
 * is {@code null} or empty
 *
 * @throws NoSuchAlgorithmException if {@code transformation}
 * is {@code null}, empty, in an invalid format,
 * or if a {@code CipherSpi} implementation for the
 * specified algorithm is not available from the specified
 * provider
 *
 * @throws NoSuchPaddingException if {@code transformation}
 * contains a padding scheme that is not available
 *
 * @throws NoSuchProviderException if the specified provider is not
 * registered in the security provider list
 *
 * @see java.security.Provider
 */
 public static final Cipher getInstance(String transformation,
 String provider)
 throws NoSuchAlgorithmException, NoSuchProviderException,
 NoSuchPaddingException
 {
 if ((transformation == null) || transformation.isEmpty()) {
 throw new NoSuchAlgorithmException("Null or empty transformation");
 }
 if ((provider == null) || (provider.isEmpty())) {
 throw new IllegalArgumentException("Missing provider");
 }
 Provider p = Security.getProvider(provider);
 if (p == null) {
 throw new NoSuchProviderException("No such provider: " +
 provider);
 }
 return getInstance(transformation, p);
 }

 private String getProviderName() {
 return (provider == null) ? "(no provider)" : provider.getName();
 }

 /**
 * Returns a {@code Cipher} object that implements the specified
 * transformation.
 *
 * A new {@code Cipher} object encapsulating the
 * {@code CipherSpi} implementation from the specified {@code provider}
 * object is returned. Note that the specified {@code provider} object
 * does not have to be registered in the provider list.
 *
 * @apiNote
 * It is recommended to use a transformation that fully specifies the
 * algorithm, mode, and padding. By not doing so, the provider will
 * use a default for the mode and padding which may not meet the security
 * requirements of your application.
 *
 * @implNote
 * See the Cipher Transformations section of the {@extLink
 * security_guide_jdk_providers JDK Providers} document for information
 * on the transformation defaults used by JDK providers.
 *
 * @param transformation the name of the transformation,
 * e.g., AES/CBC/PKCS5Padding.
 * See the Cipher section in the <a href=
 * "{@docRoot}/../specs/security/standard-names.html#cipher-algorithms">
 * Java Security Standard Algorithm Names Specification</a>
 * for information about standard transformation names.
 *
 * @param provider the provider
 *
 * @return a {@code Cipher} object that implements the requested
 * transformation
 *
 * @throws IllegalArgumentException if the {@code provider}
 * is {@code null}
 *
 * @throws NoSuchAlgorithmException if {@code transformation}
 * is {@code null}, empty, in an invalid format,
 * or if a {@code CipherSpi} implementation for the
 * specified algorithm is not available from the specified
 * {@code provider} object
 *
 * @throws NoSuchPaddingException if {@code transformation}
 * contains a padding scheme that is not available
 *
 * @see java.security.Provider
 */
 public static final Cipher getInstance(String transformation,
 Provider provider)
 throws NoSuchAlgorithmException, NoSuchPaddingException
 {
 if ((transformation == null) || transformation.isEmpty()) {
 throw new NoSuchAlgorithmException("Null or empty transformation");
 }
 if (provider == null) {
 throw new IllegalArgumentException("Missing provider");
 }
 Exception failure = null;
 List<Transform> transforms = getTransforms(transformation);
 boolean providerChecked = false;
 String paddingError = null;
 for (Transform tr : transforms) {
 Service s = provider.getService("Cipher", tr.transform);
 if (s == null) {
 continue;
 }
 if (providerChecked == false) {
 // for compatibility, first do the lookup and then verify
 // the provider. this makes the difference between a NSAE
 // and a SecurityException if the
 // provider does not support the algorithm.
 Exception ve = JceSecurity.getVerificationResult(provider);
 if (ve != null) {
 String msg = "JCE cannot authenticate the provider "
 + provider.getName();
 throw new SecurityException(msg, ve);
 }
 providerChecked = true;
 }
 if (tr.supportsMode(s) == S_NO) {
 continue;
 }
 if (tr.supportsPadding(s) == S_NO) {
 paddingError = tr.pad;
 continue;
 }
 try {
 CipherSpi spi = (CipherSpi)s.newInstance(null);
 tr.setModePadding(spi);
 Cipher cipher = new Cipher(spi, transformation);
 cipher.provider = s.getProvider();
 cipher.initCryptoPermission();
 return cipher;
 } catch (Exception e) {
 failure = e;
 }
 }

 // throw NoSuchPaddingException if the problem is with padding
 if (failure instanceof NoSuchPaddingException) {
 throw (NoSuchPaddingException)failure;
 }
 if (paddingError != null) {
 throw new NoSuchPaddingException
 ("Padding not supported: " + paddingError);
 }
 throw new NoSuchAlgorithmException
 ("No such algorithm: " + transformation, failure);
 }

 // If the requested crypto service is export-controlled,
 // determine the maximum allowable keysize.
 private void initCryptoPermission() throws NoSuchAlgorithmException {
 if (JceSecurity.isRestricted() == false) {
 cryptoPerm = CryptoAllPermission.INSTANCE;
 exmech = null;
 return;
 }
 cryptoPerm = getConfiguredPermission(transformation);
 // Instantiate the exemption mechanism (if required)
 String exmechName = cryptoPerm.getExemptionMechanism();
 if (exmechName != null) {
 exmech = ExemptionMechanism.getInstance(exmechName);
 }
 }

 // max number of debug warnings to print from chooseFirstProvider()
 private static int warnCount = 10;

 /**
 * Choose the Spi from the first provider available. Used if
 * delayed provider selection is not possible because init()
 * is not the first method called.
 */
 void chooseFirstProvider() {
 if (spi != null) {
 return;
 }
 synchronized (lock) {
 if (spi != null) {
 return;
 }
 if (debug != null) {
 int w = --warnCount;
 if (w >= 0) {
 debug.println("Cipher.init() not first method "
 + "called, disabling delayed provider selection");
 if (w == 0) {
 debug.println("Further warnings of this type will "
 + "be suppressed");
 }
 new Exception("Call trace").printStackTrace();
 }
 }
 Exception lastException = null;
 while ((firstService != null) || serviceIterator.hasNext()) {
 Service s;
 CipherSpi thisSpi;
 if (firstService != null) {
 s = firstService;
 thisSpi = firstSpi;
 firstService = null;
 firstSpi = null;
 } else {
 s = serviceIterator.next();
 thisSpi = null;
 }
 if (JceSecurity.canUseProvider(s.getProvider()) == false) {
 continue;
 }
 Transform tr = getTransform(s, transforms);
 if (tr == null) {
 // should never happen
 continue;
 }
 if (tr.supportsModePadding(s) == S_NO) {
 continue;
 }
 try {
 if (thisSpi == null) {
 Object obj = s.newInstance(null);
 if (obj instanceof CipherSpi == false) {
 continue;
 }
 thisSpi = (CipherSpi)obj;
 }
 tr.setModePadding(thisSpi);
 initCryptoPermission();
 spi = thisSpi;
 provider = s.getProvider();
 // not needed any more
 firstService = null;
 serviceIterator = null;
 transforms = null;
 return;
 } catch (Exception e) {
 lastException = e;
 }
 }
 ProviderException e = new ProviderException
 ("Could not construct CipherSpi instance");
 if (lastException != null) {
 e.initCause(lastException);
 }
 throw e;
 }
 }

 private static final int I_KEY = 1;
 private static final int I_PARAMSPEC = 2;
 private static final int I_PARAMS = 3;
 private static final int I_CERT = 4;

 private void implInit(CipherSpi thisSpi, int type, int opmode, Key key,
 AlgorithmParameterSpec paramSpec, AlgorithmParameters params,
 SecureRandom random) throws InvalidKeyException,
 InvalidAlgorithmParameterException {
 switch (type) {
 case I_KEY:
 checkCryptoPerm(thisSpi, key);
 thisSpi.engineInit(opmode, key, random);
 break;
 case I_PARAMSPEC:
 checkCryptoPerm(thisSpi, key, paramSpec);
 thisSpi.engineInit(opmode, key, paramSpec, random);
 break;
 case I_PARAMS:
 checkCryptoPerm(thisSpi, key, params);
 thisSpi.engineInit(opmode, key, params, random);
 break;
 case I_CERT:
 checkCryptoPerm(thisSpi, key);
 thisSpi.engineInit(opmode, key, random);
 break;
 default:
 throw new AssertionError("Internal Cipher error: " + type);
 }
 }

 private void chooseProvider(int initType, int opmode, Key key,
 AlgorithmParameterSpec paramSpec,
 AlgorithmParameters params, SecureRandom random)
 throws InvalidKeyException, InvalidAlgorithmParameterException {
 synchronized (lock) {
 if (spi != null) {
 implInit(spi, initType, opmode, key, paramSpec, params, random);
 return;
 }
 Exception lastException = null;
 while ((firstService != null) || serviceIterator.hasNext()) {
 Service s;
 CipherSpi thisSpi;
 if (firstService != null) {
 s = firstService;
 thisSpi = firstSpi;
 firstService = null;
 firstSpi = null;
 } else {
 s = serviceIterator.next();
 thisSpi = null;
 }
 // if provider says it does not support this key, ignore it
 if (s.supportsParameter(key) == false) {
 continue;
 }
 if (JceSecurity.canUseProvider(s.getProvider()) == false) {
 continue;
 }
 Transform tr = getTransform(s, transforms);
 if (tr == null) {
 // should never happen
 continue;
 }
 if (tr.supportsModePadding(s) == S_NO) {
 continue;
 }
 try {
 if (thisSpi == null) {
 thisSpi = (CipherSpi)s.newInstance(null);
 }
 tr.setModePadding(thisSpi);
 initCryptoPermission();
 implInit(thisSpi, initType, opmode, key, paramSpec,
 params, random);
 provider = s.getProvider();
 this.spi = thisSpi;
 firstService = null;
 serviceIterator = null;
 transforms = null;
 return;
 } catch (Exception e) {
 // NoSuchAlgorithmException from newInstance()
 // InvalidKeyException from init()
 // RuntimeException (ProviderException) from init()
 // SecurityException from crypto permission check
 if (lastException == null) {
 lastException = e;
 }
 }
 }
 // no working provider found, fail
 if (lastException instanceof InvalidKeyException) {
 throw (InvalidKeyException)lastException;
 }
 if (lastException instanceof InvalidAlgorithmParameterException) {
 throw (InvalidAlgorithmParameterException)lastException;
 }
 if (lastException instanceof RuntimeException) {
 throw (RuntimeException)lastException;
 }
 String kName = (key != null) ? key.getClass().getName() : "(null)";
 throw new InvalidKeyException
 ("No installed provider supports this key: "
 + kName, lastException);
 }
 }

 /**
 * Returns the provider of this {@code Cipher} object.
 *
 * @return the provider of this {@code Cipher} object
 */
 public final Provider getProvider() {
 chooseFirstProvider();
 return this.provider;
 }

 /**
 * Returns the algorithm name of this {@code Cipher} object.
 *
 * This is the same name that was specified in one of the
 * {@code getInstance} calls that created this {@code Cipher}
 * object.
 *
 * @return the algorithm name of this {@code Cipher} object
 */
 public final String getAlgorithm() {
 return this.transformation;
 }

 /**
 * Returns the block size (in bytes).
 *
 * @return the block size (in bytes), or 0 if this cipher is
 * not a block cipher
 */
 public final int getBlockSize() {
 chooseFirstProvider();
 return spi.engineGetBlockSize();
 }

 /**
 * Returns the length in bytes that an output buffer would need to be in
 * order to hold the result of the next {@code update} or
 * {@code doFinal} operation, given the input length
 * {@code inputLen} (in bytes).
 *
 * This call takes into account any unprocessed (buffered) data from a
 * previous {@code update} call, padding, and AEAD tagging.
 *
 * The actual output length of the next {@code update} or
 * {@code doFinal} call may be smaller than the length returned by
 * this method.
 *
 * @param inputLen the input length (in bytes)
 *
 * @return the required output buffer size (in bytes)
 *
 * @throws IllegalStateException if this {@code Cipher} object is in a
 * wrong state (e.g., has not yet been initialized)
 */
 public final int getOutputSize(int inputLen) {

 if (!initialized && !(this instanceof NullCipher)) {
 throw new IllegalStateException("Cipher not initialized");
 }
 if (inputLen < 0) {
 throw new IllegalArgumentException("Input size must be equal " +
 "to or greater than zero");
 }
 chooseFirstProvider();
 return spi.engineGetOutputSize(inputLen);
 }

 /**
 * Returns the initialization vector (IV) in a new buffer.
 *
 * This is useful in the case where a random IV was created,
 * or in the context of password-based encryption or
 * decryption, where the IV is derived from a user-supplied password.
 *
 * @return the initialization vector in a new buffer, or {@code null} if
 * this cipher does not use an IV, or if the IV has not yet
 * been set.
 */
 public final byte[] getIV() {
 chooseFirstProvider();
 return spi.engineGetIV();
 }

 /**
 * Returns the parameters used with this {@code Cipher} object.
 *
 * The returned parameters may be the same that were used to initialize
 * this cipher, or may contain additional default or random parameter
 * values used by the underlying cipher implementation. If the required
 * parameters were not supplied and can be generated by the cipher, the
 * generated parameters are returned. Otherwise, {@code null} is returned.
 *
 * @return the parameters used with this cipher, or {@code null}
 */
 public final AlgorithmParameters getParameters() {
 chooseFirstProvider();
 return spi.engineGetParameters();
 }

 /**
 * Returns the exemption mechanism object used with this {@code Cipher}
 * object.
 *
 * @return the exemption mechanism object used with this {@code Cipher}
 * object, or {@code null} if this {@code Cipher} object does not use any
 * exemption mechanism.
 */
 public final ExemptionMechanism getExemptionMechanism() {
 chooseFirstProvider();
 return exmech;
 }

 //
 // Crypto permission check code below
 //
 private void checkCryptoPerm(CipherSpi checkSpi, Key key)
 throws InvalidKeyException {
 if (cryptoPerm == CryptoAllPermission.INSTANCE) {
 return;
 }
 // Check if key size and default parameters are within legal limits
 AlgorithmParameterSpec params;
 try {
 params = getAlgorithmParameterSpec(checkSpi.engineGetParameters());
 } catch (InvalidParameterSpecException ipse) {
 throw new InvalidKeyException
 ("Unsupported default algorithm parameters");
 }
 if (!passCryptoPermCheck(checkSpi, key, params)) {
 throw new InvalidKeyException(
 "Illegal key size or default parameters");
 }
 }

 private void checkCryptoPerm(CipherSpi checkSpi, Key key,
 AlgorithmParameterSpec params) throws InvalidKeyException,
 InvalidAlgorithmParameterException {
 if (cryptoPerm == CryptoAllPermission.INSTANCE) {
 return;
 }
 // Determine keysize and check if it is within legal limits
 if (!passCryptoPermCheck(checkSpi, key, null)) {
 throw new InvalidKeyException("Illegal key size");
 }
 if ((params != null) && (!passCryptoPermCheck(checkSpi, key, params))) {
 throw new InvalidAlgorithmParameterException("Illegal parameters");
 }
 }

 private void checkCryptoPerm(CipherSpi checkSpi, Key key,
 AlgorithmParameters params)
 throws InvalidKeyException, InvalidAlgorithmParameterException {
 if (cryptoPerm == CryptoAllPermission.INSTANCE) {
 return;
 }
 // Convert the specified parameters into specs and then delegate.
 AlgorithmParameterSpec pSpec;
 try {
 pSpec = getAlgorithmParameterSpec(params);
 } catch (InvalidParameterSpecException ipse) {
 throw new InvalidAlgorithmParameterException
 ("Failed to retrieve algorithm parameter specification");
 }
 checkCryptoPerm(checkSpi, key, pSpec);
 }

 private boolean passCryptoPermCheck(CipherSpi checkSpi, Key key,
 AlgorithmParameterSpec params)
 throws InvalidKeyException {
 String em = cryptoPerm.getExemptionMechanism();
 int keySize = checkSpi.engineGetKeySize(key);
 // Use the "algorithm" component of the cipher
 // transformation so that the perm check would
 // work when the key has the "aliased" algo.
 String algComponent;
 int index = transformation.indexOf('/');
 if (index != -1) {
 algComponent = transformation.substring(0, index);
 } else {
 algComponent = transformation;
 }
 CryptoPermission checkPerm =
 new CryptoPermission(algComponent, keySize, params, em);

 if (!cryptoPerm.implies(checkPerm)) {
 if (debug != null) {
 debug.println("Crypto Permission check failed");
 debug.println("granted: " + cryptoPerm);
 debug.println("requesting: " + checkPerm);
 }
 return false;
 }
 if (exmech == null) {
 return true;
 }
 try {
 if (!exmech.isCryptoAllowed(key)) {
 if (debug != null) {
 debug.println(exmech.getName() + " isn't enforced");
 }
 return false;
 }
 } catch (ExemptionMechanismException eme) {
 if (debug != null) {
 debug.println("Cannot determine whether "+
 exmech.getName() + " has been enforced");
 eme.printStackTrace();
 }
 return false;
 }
 return true;
 }

 // check if opmode is one of the defined constants
 // throw InvalidParameterException if not
 private static void checkOpmode(int opmode) {
 if ((opmode < ENCRYPT_MODE) || (opmode > UNWRAP_MODE)) {
 throw new InvalidParameterException("Invalid operation mode");
 }
 }

 /**
 * Initializes this {@code Cipher} object with a key.
 *
 * The {@code Cipher} object is initialized for one of the following four
 * operations:
 * encryption, decryption, key wrapping or key unwrapping, depending
 * on the value of {@code opmode}.
 *
 * If this cipher requires any algorithm parameters that cannot be
 * derived from the given {@code key}, the underlying cipher
 * implementation is supposed to generate the required parameters itself
 * (using provider-specific default or random values) if it is being
 * initialized for encryption or key wrapping, and raise an
 * {@code InvalidKeyException} if it is being
 * initialized for decryption or key unwrapping.
 * The generated parameters can be retrieved using
 * {@link #getParameters() getParameters} or
 * {@link #getIV() getIV} (if the parameter is an IV).
 *
 * If this cipher requires algorithm parameters that cannot be
 * derived from the input parameters, and there are no reasonable
 * provider-specific default values, initialization will
 * necessarily fail.
 *
 * If this cipher (including its feedback or padding scheme)
 * requires any random bytes (e.g., for parameter generation), it will get
 * them using the {@link java.security.SecureRandom}
 * implementation of the highest-priority
 * installed provider as the source of randomness.
 * (If none of the installed providers supply an implementation of
 * SecureRandom, a system-provided source of randomness will be used.)
 *
 * Note that when a {@code Cipher} object is initialized, it loses all
 * previously-acquired state. In other words, initializing a {@code Cipher}
 * object is equivalent to creating a new instance of that {@code Cipher}
 * object and initializing it.
 *
 * @param opmode the operation mode of this {@code Cipher} object
 * (this is one of the following:
 * {@code ENCRYPT_MODE}, {@code DECRYPT_MODE},
 * {@code WRAP_MODE} or {@code UNWRAP_MODE})
 * @param key the key
 *
 * @throws InvalidKeyException if the given key is inappropriate for
 * initializing this cipher, or requires
 * algorithm parameters that cannot be
 * determined from the given key, or if the given key has a keysize that
 * exceeds the maximum allowable keysize (as determined from the
 * configured jurisdiction policy files)
 * @throws UnsupportedOperationException if {@code opmode} is
 * {@code WRAP_MODE} or {@code UNWRAP_MODE} but the mode is not implemented
 * by the underlying {@code CipherSpi}
 * @throws InvalidParameterException if {@code opmode} is not one of the
 * recognized values
 */
 public final void init(int opmode, Key key) throws InvalidKeyException {
 init(opmode, key, JCAUtil.getDefSecureRandom());
 }

 /**
 * Initializes this {@code Cipher} object with a key and a
 * source of randomness.
 *
 * The {@code Cipher} object is initialized for one of the following four
 * operations:
 * encryption, decryption, key wrapping or key unwrapping, depending
 * on the value of {@code opmode}.
 *
 * If this cipher requires any algorithm parameters that cannot be
 * derived from the given {@code key}, the underlying cipher
 * implementation is supposed to generate the required parameters itself
 * (using provider-specific default or random values) if it is being
 * initialized for encryption or key wrapping, and raise an
 * {@code InvalidKeyException} if it is being
 * initialized for decryption or key unwrapping.
 * The generated parameters can be retrieved using
 * {@link #getParameters() getParameters} or
 * {@link #getIV() getIV} (if the parameter is an IV).
 *
 * If this cipher requires algorithm parameters that cannot be
 * derived from the input parameters, and there are no reasonable
 * provider-specific default values, initialization will
 * necessarily fail.
 *
 * If this cipher (including its feedback or padding scheme)
 * requires any random bytes (e.g., for parameter generation), it will get
 * them from {@code random}.
 *
 * Note that when a {@code Cipher} object is initialized, it loses all
 * previously-acquired state. In other words, initializing a {@code Cipher}
 * object is equivalent to creating a new instance of that
 * {@code Cipher} object and initializing it.
 *
 * @param opmode the operation mode of this {@code Cipher} object
 * (this is one of the following:
 * {@code ENCRYPT_MODE}, {@code DECRYPT_MODE},
 * {@code WRAP_MODE} or {@code UNWRAP_MODE})
 * @param key the encryption key
 * @param random the source of randomness
 *
 * @throws InvalidKeyException if the given key is inappropriate for
 * initializing this cipher, or requires
 * algorithm parameters that cannot be
 * determined from the given key, or if the given key has a keysize that
 * exceeds the maximum allowable keysize (as determined from the
 * configured jurisdiction policy files)
 * @throws UnsupportedOperationException if {@code opmode} is
 * {@code WRAP_MODE} or {@code UNWRAP_MODE} but the mode is not implemented
 * by the underlying {@code CipherSpi}
 * @throws InvalidParameterException if {@code opmode} is not one of the
 * recognized values
 */
 public final void init(int opmode, Key key, SecureRandom random)
 throws InvalidKeyException
 {
 initialized = false;
 checkOpmode(opmode);

 if (spi != null) {
 checkCryptoPerm(spi, key);
 spi.engineInit(opmode, key, random);
 } else {
 try {
 chooseProvider(I_KEY, opmode, key, null, null, random);
 } catch (InvalidAlgorithmParameterException e) {
 // should never occur
 throw new InvalidKeyException(e);
 }
 }

 initialized = true;
 this.opmode = opmode;

 if (!skipDebug && pdebug != null) {
 pdebug.println(this.toString());
 }
 }

 /**
 * Initializes this {@code Cipher} object with a key and a set of algorithm
 * parameters.
 *
 * The {@code Cipher} object is initialized for one of the following four
 * operations:
 * encryption, decryption, key wrapping or key unwrapping, depending
 * on the value of {@code opmode}.
 *
 * If this cipher requires any algorithm parameters and
 * {@code params} is {@code null}, the underlying cipher implementation is
 * supposed to generate the required parameters itself (using
 * provider-specific default or random values) if it is being
 * initialized for encryption or key wrapping, and raise an
 * {@code InvalidAlgorithmParameterException} if it is being
 * initialized for decryption or key unwrapping.
 * The generated parameters can be retrieved using
 * {@link #getParameters() getParameters} or
 * {@link #getIV() getIV} (if the parameter is an IV).
 *
 * If this cipher requires algorithm parameters that cannot be
 * derived from the input parameters, and there are no reasonable
 * provider-specific default values, initialization will
 * necessarily fail.
 *
 * If this cipher (including its feedback or padding scheme)
 * requires any random bytes (e.g., for parameter generation), it will get
 * them using the {@link java.security.SecureRandom}
 * implementation of the highest-priority
 * installed provider as the source of randomness.
 * (If none of the installed providers supply an implementation of
 * SecureRandom, a system-provided source of randomness will be used.)
 *
 * Note that when a {@code Cipher} object is initialized, it loses all
 * previously-acquired state. In other words, initializing a {@code Cipher}
 * object is equivalent to creating a new instance of that {@code Cipher}
 * object and initializing it.
 *
 * @param opmode the operation mode of this {@code Cipher} object
 * (this is one of the following:
 * {@code ENCRYPT_MODE}, {@code DECRYPT_MODE},
 * {@code WRAP_MODE} or {@code UNWRAP_MODE})
 * @param key the encryption key
 * @param params the algorithm parameters
 *
 * @throws InvalidKeyException if the given key is inappropriate for
 * initializing this cipher, or its keysize exceeds the maximum allowable
 * keysize (as determined from the configured jurisdiction policy files)
 * @throws InvalidAlgorithmParameterException if the given algorithm
 * parameters are inappropriate for this cipher,
 * or this cipher requires
 * algorithm parameters and {@code params} is {@code null}, or the given
 * algorithm parameters imply a cryptographic strength that would exceed
 * the legal limits (as determined from the configured jurisdiction
 * policy files)
 * @throws UnsupportedOperationException if {@code opmode} is
 * {@code WRAP_MODE} or {@code UNWRAP_MODE} but the mode is not implemented
 * by the underlying {@code CipherSpi}
 * @throws InvalidParameterException if {@code opmode} is not one of the
 * recognized values
 *
 */
 public final void init(int opmode, Key key, AlgorithmParameterSpec params)
 throws InvalidKeyException, InvalidAlgorithmParameterException
 {
 init(opmode, key, params, JCAUtil.getDefSecureRandom());
 }

 /**
 * Initializes this {@code Cipher} object with a key, a set of algorithm
 * parameters, and a source of randomness.
 *
 * The {@code Cipher} object is initialized for one of the following four
 * operations:
 * encryption, decryption, key wrapping or key unwrapping, depending
 * on the value of {@code opmode}.
 *
 * If this cipher requires any algorithm parameters and
 * {@code params} is {@code null}, the underlying cipher implementation is
 * supposed to generate the required parameters itself (using
 * provider-specific default or random values) if it is being
 * initialized for encryption or key wrapping, and raise an
 * {@code InvalidAlgorithmParameterException} if it is being
 * initialized for decryption or key unwrapping.
 * The generated parameters can be retrieved using
 * {@link #getParameters() getParameters} or
 * {@link #getIV() getIV} (if the parameter is an IV).
 *
 * If this cipher requires algorithm parameters that cannot be
 * derived from the input parameters, and there are no reasonable
 * provider-specific default values, initialization will
 * necessarily fail.
 *
 * If this cipher (including its feedback or padding scheme)
 * requires any random bytes (e.g., for parameter generation), it will get
 * them from {@code random}.
 *
 * Note that when a {@code Cipher} object is initialized, it loses all
 * previously-acquired state. In other words, initializing a {@code Cipher}
 * object is equivalent to creating a new instance of that {@code Cipher}
 * object and initializing it.
 *
 * @param opmode the operation mode of this {@code Cipher} object
 * (this is one of the following:
 * {@code ENCRYPT_MODE}, {@code DECRYPT_MODE},
 * {@code WRAP_MODE} or {@code UNWRAP_MODE})
 * @param key the encryption key
 * @param params the algorithm parameters
 * @param random the source of randomness
 *
 * @throws InvalidKeyException if the given key is inappropriate for
 * initializing this cipher, or its keysize exceeds the maximum allowable
 * keysize (as determined from the configured jurisdiction policy files)
 * @throws InvalidAlgorithmParameterException if the given algorithm
 * parameters are inappropriate for this cipher,
 * or this cipher requires
 * algorithm parameters and {@code params} is {@code null}, or the given
 * algorithm parameters imply a cryptographic strength that would exceed
 * the legal limits (as determined from the configured jurisdiction
 * policy files)
 * @throws UnsupportedOperationException if {@code opmode} is
 * {@code WRAP_MODE} or {@code UNWRAP_MODE} but the mode is not implemented
 * by the underlying {@code CipherSpi}
 * @throws InvalidParameterException if {@code opmode} is not one of the
 * recognized values
 *
 */
 public final void init(int opmode, Key key, AlgorithmParameterSpec params,
 SecureRandom random)
 throws InvalidKeyException, InvalidAlgorithmParameterException
 {
 initialized = false;
 checkOpmode(opmode);

 if (spi != null) {
 checkCryptoPerm(spi, key, params);
 spi.engineInit(opmode, key, params, random);
 } else {
 chooseProvider(I_PARAMSPEC, opmode, key, params, null, random);
 }

 initialized = true;
 this.opmode = opmode;

 if (!skipDebug && pdebug != null) {
 pdebug.println(this.toString());
 }
 }

 /**
 * Initializes this {@code Cipher} object with a key and a set of algorithm
 * parameters.
 *
 * The {@code Cipher} object is initialized for one of the following four
 * operations:
 * encryption, decryption, key wrapping or key unwrapping, depending
 * on the value of {@code opmode}.
 *
 * If this cipher requires any algorithm parameters and
 * {@code params} is {@code null}, the underlying cipher implementation is
 * supposed to generate the required parameters itself (using
 * provider-specific default or random values) if it is being
 * initialized for encryption or key wrapping, and raise an
 * {@code InvalidAlgorithmParameterException} if it is being
 * initialized for decryption or key unwrapping.
 * The generated parameters can be retrieved using
 * {@link #getParameters() getParameters} or
 * {@link #getIV() getIV} (if the parameter is an IV).
 *
 * If this cipher requires algorithm parameters that cannot be
 * derived from the input parameters, and there are no reasonable
 * provider-specific default values, initialization will
 * necessarily fail.
 *
 * If this cipher (including its feedback or padding scheme)
 * requires any random bytes (e.g., for parameter generation), it will get
 * them using the {@link java.security.SecureRandom}
 * implementation of the highest-priority
 * installed provider as the source of randomness.
 * (If none of the installed providers supply an implementation of
 * SecureRandom, a system-provided source of randomness will be used.)
 *
 * Note that when a {@code Cipher} object is initialized, it loses all
 * previously-acquired state. In other words, initializing a {@code Cipher}
 * object is equivalent to creating a new instance of that {@code Cipher}
 * object and initializing it.
 *
 * @param opmode the operation mode of this {@code Cipher} object
 * this is one of the following: {@code ENCRYPT_MODE},
 * {@code DECRYPT_MODE}, {@code WRAP_MODE}
 * or {@code UNWRAP_MODE})
 * @param key the encryption key
 * @param params the algorithm parameters
 *
 * @throws InvalidKeyException if the given key is inappropriate for
 * initializing this cipher, or its keysize exceeds the maximum allowable
 * keysize (as determined from the configured jurisdiction policy files).
 * @throws InvalidAlgorithmParameterException if the given algorithm
 * parameters are inappropriate for this cipher,
 * or this cipher requires
 * algorithm parameters and {@code params} is {@code null}, or the given
 * algorithm parameters imply a cryptographic strength that would exceed
 * the legal limits (as determined from the configured jurisdiction
 * policy files)
 * @throws UnsupportedOperationException if {@code opmode} is
 * {@code WRAP_MODE} or {@code UNWRAP_MODE} but the mode is not implemented
 * by the underlying {@code CipherSpi}
 * @throws InvalidParameterException if {@code opmode} is not one of the
 * recognized values
 */
 public final void init(int opmode, Key key, AlgorithmParameters params)
 throws InvalidKeyException, InvalidAlgorithmParameterException
 {
 init(opmode, key, params, JCAUtil.getDefSecureRandom());
 }

 /**
 * Initializes this {@code Cipher} object with a key, a set of algorithm
 * parameters, and a source of randomness.
 *
 * The {@code Cipher} object is initialized for one of the following four
 * operations:
 * encryption, decryption, key wrapping or key unwrapping, depending
 * on the value of {@code opmode}.
 *
 * If this cipher requires any algorithm parameters and
 * {@code params} is {@code null}, the underlying cipher implementation is
 * supposed to generate the required parameters itself (using
 * provider-specific default or random values) if it is being
 * initialized for encryption or key wrapping, and raise an
 * {@code InvalidAlgorithmParameterException} if it is being
 * initialized for decryption or key unwrapping.
 * The generated parameters can be retrieved using
 * {@link #getParameters() getParameters} or
 * {@link #getIV() getIV} (if the parameter is an IV).
 *
 * If this cipher requires algorithm parameters that cannot be
 * derived from the input parameters, and there are no reasonable
 * provider-specific default values, initialization will
 * necessarily fail.
 *
 * If this cipher (including its feedback or padding scheme)
 * requires any random bytes (e.g., for parameter generation), it will get
 * them from {@code random}.
 *
 * Note that when a {@code Cipher} object is initialized, it loses all
 * previously-acquired state. In other words, initializing a {@code Cipher}
 * object is equivalent to creating a new instance of that {@code Cipher}
 * object and initializing it.
 *
 * @param opmode the operation mode of this {@code Cipher} object
 * (this is one of the following: {@code ENCRYPT_MODE},
 * {@code DECRYPT_MODE}, {@code WRAP_MODE}
 * or {@code UNWRAP_MODE})
 * @param key the encryption key
 * @param params the algorithm parameters
 * @param random the source of randomness
 *
 * @throws InvalidKeyException if the given key is inappropriate for
 * initializing this cipher, or its keysize exceeds the maximum allowable
 * keysize (as determined from the configured jurisdiction policy files)
 * @throws InvalidAlgorithmParameterException if the given algorithm
 * parameters are inappropriate for this cipher,
 * or this cipher requires
 * algorithm parameters and {@code params} is {@code null}, or the given
 * algorithm parameters imply a cryptographic strength that would exceed
 * the legal limits (as determined from the configured jurisdiction
 * policy files)
 * @throws UnsupportedOperationException if {@code opmode} is
 * {@code WRAP_MODE} or {@code UNWRAP_MODE} but the mode is not implemented
 * by the underlying {@code CipherSpi}
 * @throws InvalidParameterException if {@code opmode} is not one of the
 * recognized values
 */
 public final void init(int opmode, Key key, AlgorithmParameters params,
 SecureRandom random)
 throws InvalidKeyException, InvalidAlgorithmParameterException
 {
 initialized = false;
 checkOpmode(opmode);

 if (spi != null) {
 checkCryptoPerm(spi, key, params);
 spi.engineInit(opmode, key, params, random);
 } else {
 chooseProvider(I_PARAMS, opmode, key, null, params, random);
 }

 initialized = true;
 this.opmode = opmode;

 if (!skipDebug && pdebug != null) {
 pdebug.println(this.toString());
 }
 }

 /**
 * Initializes this {@code Cipher} object with the public key from the given
 * certificate.
 * The {@code Cipher} object is initialized for one of the following
 * four operations:
 * encryption, decryption, key wrapping or key unwrapping, depending
 * on the value of {@code opmode}.
 *
 * If the certificate is of type X.509 and has a key usage
 * extension field marked as critical, and the value of the key usage
 * extension field implies that the public key in
 * the certificate and its corresponding private key are not
 * supposed to be used for the operation represented by the value
 * of {@code opmode},
 * an {@code InvalidKeyException}
 * is thrown.
 *
 * If this cipher requires any algorithm parameters that cannot be
 * derived from the public key in the given certificate, the underlying
 * cipher
 * implementation is supposed to generate the required parameters itself
 * (using provider-specific default or random values) if it is being
 * initialized for encryption or key wrapping, and raise an
 * {@code InvalidKeyException} if it is being initialized for decryption or
 * key unwrapping.
 * The generated parameters can be retrieved using
 * {@link #getParameters() getParameters} or
 * {@link #getIV() getIV} (if the parameter is an IV).
 *
 * If this cipher requires algorithm parameters that cannot be
 * derived from the input parameters, and there are no reasonable
 * provider-specific default values, initialization will
 * necessarily fail.
 *
 * If this cipher (including its feedback or padding scheme)
 * requires any random bytes (e.g., for parameter generation), it will get
 * them using the
 * {@code SecureRandom}
 * implementation of the highest-priority
 * installed provider as the source of randomness.
 * (If none of the installed providers supply an implementation of
 * SecureRandom, a system-provided source of randomness will be used.)
 *
 * Note that when a {@code Cipher} object is initialized, it loses all
 * previously-acquired state. In other words, initializing a {@code Cipher}
 * object is equivalent to creating a new instance of that {@code Cipher}
 * object and initializing it.
 *
 * @param opmode the operation mode of this {@code Cipher} object
 * (this is one of the following:
 * {@code ENCRYPT_MODE}, {@code DECRYPT_MODE},
 * {@code WRAP_MODE} or {@code UNWRAP_MODE})
 * @param certificate the certificate
 *
 * @throws InvalidKeyException if the public key in the given
 * certificate is inappropriate for initializing this cipher, or this
 * cipher requires algorithm parameters that cannot be determined from the
 * public key in the given certificate, or the keysize of the public key
 * in the given certificate has a keysize that exceeds the maximum
 * allowable keysize (as determined by the configured jurisdiction policy
 * files)
 * @throws UnsupportedOperationException if {@code opmode} is
 * {@code WRAP_MODE} or {@code UNWRAP_MODE} but the mode is not implemented
 * by the underlying {@code CipherSpi}
 * @throws InvalidParameterException if {@code opmode} is not one of the
 * recognized values
 */
 public final void init(int opmode, Certificate certificate)
 throws InvalidKeyException
 {
 init(opmode, certificate, JCAUtil.getDefSecureRandom());
 }

 /**
 * Initializes this {@code Cipher} object with the public key from the given
 * certificate and a source of randomness.
 *
 * The {@code Cipher} object is initialized for one of the following four
 * operations: encryption, decryption, key wrapping
 * or key unwrapping, depending on
 * the value of {@code opmode}.
 *
 * If the certificate is of type X.509 and has a key usage
 * extension field marked as critical, and the value of the key usage
 * extension field implies that the public key in
 * the certificate and its corresponding private key are not
 * supposed to be used for the operation represented by the value of
 * {@code opmode},
 * an {@code InvalidKeyException}
 * is thrown.
 *
 * If this cipher requires any algorithm parameters that cannot be
 * derived from the public key in the given {@code certificate},
 * the underlying cipher
 * implementation is supposed to generate the required parameters itself
 * (using provider-specific default or random values) if it is being
 * initialized for encryption or key wrapping, and raise an
 * {@code InvalidKeyException} if it is being
 * initialized for decryption or key unwrapping.
 * The generated parameters can be retrieved using
 * {@link #getParameters() getParameters} or
 * {@link #getIV() getIV} (if the parameter is an IV).
 *
 * If this cipher requires algorithm parameters that cannot be
 * derived from the input parameters, and there are no reasonable
 * provider-specific default values, initialization will
 * necessarily fail.
 *
 * If this cipher (including its feedback or padding scheme)
 * requires any random bytes (e.g., for parameter generation), it will get
 * them from {@code random}.
 *
 * Note that when a {@code Cipher} object is initialized, it loses all
 * previously-acquired state. In other words, initializing a {@code Cipher}
 * object is equivalent to creating a new instance of that {@code Cipher}
 * object and initializing it.
 *
 * @param opmode the operation mode of this {@code Cipher} object
 * (this is one of the following:
 * {@code ENCRYPT_MODE}, {@code DECRYPT_MODE},
 * {@code WRAP_MODE} or {@code UNWRAP_MODE})
 * @param certificate the certificate
 * @param random the source of randomness
 *
 * @throws InvalidKeyException if the public key in the given
 * certificate is inappropriate for initializing this cipher, or this
 * cipher
 * requires algorithm parameters that cannot be determined from the
 * public key in the given certificate, or the keysize of the public key
 * in the given certificate has a keysize that exceeds the maximum
 * allowable keysize (as determined by the configured jurisdiction policy
 * files)
 * @throws UnsupportedOperationException if {@code opmode} is
 * {@code WRAP_MODE} or {@code UNWRAP_MODE} but the mode is not implemented
 * by the underlying {@code CipherSpi}
 * @throws InvalidParameterException if {@code opmode} is not one of the
 * recognized values
 */
 public final void init(int opmode, Certificate certificate,
 SecureRandom random)
 throws InvalidKeyException
 {
 initialized = false;
 checkOpmode(opmode);

 // Check key usage if the certificate is of type X.509.
 if (certificate instanceof java.security.cert.X509Certificate) {
 // Check whether the cert has a key usage extension
 // marked as a critical extension.
 X509Certificate cert = (X509Certificate)certificate;
 Set<String> critSet = cert.getCriticalExtensionOIDs();

 if (critSet != null && !critSet.isEmpty()
 && critSet.contains(KnownOIDs.KeyUsage.value())) {
 boolean[] keyUsageInfo = cert.getKeyUsage();
 // keyUsageInfo[2] is for keyEncipherment;
 // keyUsageInfo[3] is for dataEncipherment.
 if ((keyUsageInfo != null) &&
 (((opmode == Cipher.ENCRYPT_MODE) &&
 (keyUsageInfo.length > 3) &&
 (keyUsageInfo[3] == false)) ||
 ((opmode == Cipher.WRAP_MODE) &&
 (keyUsageInfo.length > 2) &&
 (keyUsageInfo[2] == false)))) {
 throw new InvalidKeyException("Wrong key usage");
 }
 }
 }

 PublicKey publicKey =
 (certificate==null? null:certificate.getPublicKey());

 if (spi != null) {
 checkCryptoPerm(spi, publicKey);
 spi.engineInit(opmode, publicKey, random);
 } else {
 try {
 chooseProvider(I_CERT, opmode, publicKey, null, null, random);
 } catch (InvalidAlgorithmParameterException e) {
 // should never occur
 throw new InvalidKeyException(e);
 }
 }

 initialized = true;
 this.opmode = opmode;

 if (!skipDebug && pdebug != null) {
 pdebug.println(this.toString());
 }
 }

 /**
 * Ensures that {@code Cipher} object is in a valid state for update() and
 * doFinal() calls - should be initialized and in ENCRYPT_MODE or
 * DECRYPT_MODE.
 * @throws IllegalStateException if this {@code Cipher} object is not in
 * valid state
 */
 private void checkCipherState() {
 if (!(this instanceof NullCipher)) {
 if (!initialized) {
 throw new IllegalStateException("Cipher not initialized");
 }
 if ((opmode != Cipher.ENCRYPT_MODE) &&
 (opmode != Cipher.DECRYPT_MODE)) {
 throw new IllegalStateException("Cipher not initialized " +
 "for encryption/decryption");
 }
 }
 }

 /**
 * Continues a multiple-part encryption or decryption operation
 * (depending on how this {@code Cipher} object was initialized),
 * processing another data part.
 *
 * The bytes in the {@code input} buffer are processed, and the
 * result is stored in a new buffer.
 *
 * If {@code input} has a length of zero, this method returns
 * {@code null}.
 *
 * @param input the input buffer
 *
 * @return the new buffer with the result, or {@code null} if this
 * cipher is a block cipher and the input data is too short to result in a
 * new block
 *
 * @throws IllegalStateException if this {@code Cipher} object is in a
 * wrong state (e.g., has not been initialized)
 */
 public final byte[] update(byte[] input) {
 checkCipherState();

 // Input sanity check
 if (input == null) {
 throw new IllegalArgumentException("Null input buffer");
 }

 chooseFirstProvider();
 if (input.length == 0) {
 return null;
 }
 return spi.engineUpdate(input, 0, input.length);
 }

 /**
 * Continues a multiple-part encryption or decryption operation
 * (depending on how this {@code Cipher} object was initialized),
 * processing another data part.
 *
 * The first {@code inputLen} bytes in the {@code input}
 * buffer, starting at {@code inputOffset} inclusive, are processed,
 * and the result is stored in a new buffer.
 *
 * If {@code inputLen} is zero, this method returns
 * {@code null}.
 *
 * @param input the input buffer
 * @param inputOffset the offset in {@code input} where the input
 * starts
 * @param inputLen the input length
 *
 * @return the new buffer with the result, or {@code null} if this
 * cipher is a block cipher and the input data is too short to result in a
 * new block.
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 */
 public final byte[] update(byte[] input, int inputOffset, int inputLen) {
 checkCipherState();

 // Input sanity check
 if (input == null || inputOffset < 0
 || inputLen > (input.length - inputOffset) || inputLen < 0) {
 throw new IllegalArgumentException("Bad arguments");
 }

 chooseFirstProvider();
 if (inputLen == 0) {
 return null;
 }
 return spi.engineUpdate(input, inputOffset, inputLen);
 }

 /**
 * Continues a multiple-part encryption or decryption operation
 * (depending on how this {@code Cipher} object was initialized),
 * processing another data part.
 *
 * The first {@code inputLen} bytes in the {@code input}
 * buffer, starting at {@code inputOffset} inclusive, are processed,
 * and the result is stored in the {@code output} buffer.
 *
 * If the {@code output} buffer is too small to hold the result,
 * a {@code ShortBufferException} is thrown. In this case, repeat this
 * call with a larger output buffer. Use
 * {@link #getOutputSize(int) getOutputSize} to determine how big
 * the output buffer should be.
 *
 * If {@code inputLen} is zero, this method returns
 * a length of zero.
 *
 * Note: this method should be copy-safe, which means the
 * {@code input} and {@code output} buffers can reference
 * the same byte array and no unprocessed input data is overwritten
 * when the result is copied into the output buffer.
 *
 * @param input the input buffer
 * @param inputOffset the offset in {@code input} where the input
 * starts
 * @param inputLen the input length
 * @param output the buffer for the result
 *
 * @return the number of bytes stored in {@code output}
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws ShortBufferException if the given output buffer is too small
 * to hold the result
 */
 public final int update(byte[] input, int inputOffset, int inputLen,
 byte[] output)
 throws ShortBufferException {
 checkCipherState();

 // Input sanity check
 if (input == null || inputOffset < 0
 || inputLen > (input.length - inputOffset) || inputLen < 0) {
 throw new IllegalArgumentException("Bad arguments");
 }

 chooseFirstProvider();
 if (inputLen == 0) {
 return 0;
 }
 return spi.engineUpdate(input, inputOffset, inputLen,
 output, 0);
 }

 /**
 * Continues a multiple-part encryption or decryption operation
 * (depending on how this {@code Cipher} object was initialized),
 * processing another data part.
 *
 * The first {@code inputLen} bytes in the {@code input}
 * buffer, starting at {@code inputOffset} inclusive, are processed,
 * and the result is stored in the {@code output} buffer, starting at
 * {@code outputOffset} inclusive.
 *
 * If the {@code output} buffer is too small to hold the result,
 * a {@code ShortBufferException} is thrown. In this case, repeat this
 * call with a larger output buffer. Use
 * {@link #getOutputSize(int) getOutputSize} to determine how big
 * the output buffer should be.
 *
 * If {@code inputLen} is zero, this method returns
 * a length of zero.
 *
 * Note: this method should be copy-safe, which means the
 * {@code input} and {@code output} buffers can reference
 * the same byte array and no unprocessed input data is overwritten
 * when the result is copied into the output buffer.
 *
 * @param input the input buffer
 * @param inputOffset the offset in {@code input} where the input
 * starts
 * @param inputLen the input length
 * @param output the buffer for the result
 * @param outputOffset the offset in {@code output} where the result
 * is stored
 *
 * @return the number of bytes stored in {@code output}
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws ShortBufferException if the given output buffer is too small
 * to hold the result
 */
 public final int update(byte[] input, int inputOffset, int inputLen,
 byte[] output, int outputOffset)
 throws ShortBufferException {
 checkCipherState();

 // Input sanity check
 if (input == null || inputOffset < 0
 || inputLen > (input.length - inputOffset) || inputLen < 0
 || outputOffset < 0) {
 throw new IllegalArgumentException("Bad arguments");
 }

 chooseFirstProvider();
 if (inputLen == 0) {
 return 0;
 }
 return spi.engineUpdate(input, inputOffset, inputLen,
 output, outputOffset);
 }

 /**
 * Continues a multiple-part encryption or decryption operation
 * (depending on how this {@code Cipher} object was initialized),
 * processing another data part.
 *
 * All {@code input.remaining()} bytes starting at
 * {@code input.position()} are processed. The result is stored
 * in the output buffer.
 * Upon return, the input buffer's position will be equal
 * to its limit; its limit will not have changed. The output buffer's
 * position will have advanced by n, where n is the value returned
 * by this method; the output buffer's limit will not have changed.
 *
 * If {@code output.remaining()} bytes are insufficient to
 * hold the result, a {@code ShortBufferException} is thrown.
 * In this case, repeat this call with a larger output buffer. Use
 * {@link #getOutputSize(int) getOutputSize} to determine how big
 * the output buffer should be.
 *
 * Note: this method should be copy-safe, which means the
 * {@code input} and {@code output} buffers can reference
 * the same block of memory and no unprocessed input data is overwritten
 * when the result is copied into the output buffer.
 *
 * @param input the input ByteBuffer
 * @param output the output ByteByffer
 *
 * @return the number of bytes stored in {@code output}
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws IllegalArgumentException if input and output are the
 * same object
 * @throws ReadOnlyBufferException if the output buffer is read-only
 * @throws ShortBufferException if there is insufficient space in the
 * output buffer
 * @since 1.5
 */
 public final int update(ByteBuffer input, ByteBuffer output)
 throws ShortBufferException {
 checkCipherState();

 if ((input == null) || (output == null)) {
 throw new IllegalArgumentException("Buffers must not be null");
 }
 if (input == output) {
 throw new IllegalArgumentException("Input and output buffers must "
 + "not be the same object, consider using buffer.duplicate()");
 }
 if (output.isReadOnly()) {
 throw new ReadOnlyBufferException();
 }

 chooseFirstProvider();
 return spi.engineUpdate(input, output);
 }

 /**
 * Finishes a multiple-part encryption or decryption operation, depending
 * on how this {@code Cipher} object was initialized.
 *
 * Input data that may have been buffered during a previous
 * {@code update} operation is processed, with padding (if requested)
 * being applied.
 * If an AEAD mode such as GCM/CCM is being used, the authentication
 * tag is appended in the case of encryption, or verified in the
 * case of decryption.
 * The result is stored in a new buffer.
 *
 * Upon finishing, this method resets this {@code Cipher} object
 * to the state it was in when previously initialized via a call to
 * {@code init}.
 * That is, the object is reset and available to encrypt or decrypt
 * (depending on the operation mode that was specified in the call to
 * {@code init}) more data.
 *
 * Note: if any exception is thrown, this {@code Cipher} object
 * may need to be reset before it can be used again.
 *
 * @return the new buffer with the result
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws IllegalBlockSizeException if this cipher is a block cipher,
 * no padding has been requested (only in encryption mode), and the total
 * input length of the data processed by this cipher is not a multiple of
 * block size; or if this encryption algorithm is unable to
 * process the input data provided.
 * @throws BadPaddingException if this {@code Cipher} object is in
 * decryption mode, and (un)padding has been requested, but the decrypted
 * data is not bounded by the appropriate padding bytes
 * @throws AEADBadTagException if this {@code Cipher} object is decrypting
 * in an AEAD mode (such as GCM/CCM), and the received authentication tag
 * does not match the calculated value
 */
 public final byte[] doFinal()
 throws IllegalBlockSizeException, BadPaddingException {
 checkCipherState();

 chooseFirstProvider();
 return spi.engineDoFinal(null, 0, 0);
 }

 /**
 * Finishes a multiple-part encryption or decryption operation, depending
 * on how this {@code Cipher} object was initialized.
 *
 * Input data that may have been buffered during a previous
 * {@code update} operation is processed, with padding (if requested)
 * being applied.
 * If an AEAD mode such as GCM/CCM is being used, the authentication
 * tag is appended in the case of encryption, or verified in the
 * case of decryption.
 * The result is stored in the {@code output} buffer, starting at
 * {@code outputOffset} inclusive.
 *
 * If the {@code output} buffer is too small to hold the result,
 * a {@code ShortBufferException} is thrown. In this case, repeat this
 * call with a larger output buffer. Use
 * {@link #getOutputSize(int) getOutputSize} to determine how big
 * the output buffer should be.
 *
 * Upon finishing, this method resets this {@code Cipher} object
 * to the state it was in when previously initialized via a call to
 * {@code init}.
 * That is, the object is reset and available to encrypt or decrypt
 * (depending on the operation mode that was specified in the call to
 * {@code init}) more data.
 *
 * Note: if any exception is thrown, this {@code Cipher} object
 * may need to be reset before it can be used again.
 *
 * @param output the buffer for the result
 * @param outputOffset the offset in {@code output} where the result
 * is stored
 *
 * @return the number of bytes stored in {@code output}
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws IllegalBlockSizeException if this cipher is a block cipher,
 * no padding has been requested (only in encryption mode), and the total
 * input length of the data processed by this cipher is not a multiple of
 * block size; or if this encryption algorithm is unable to
 * process the input data provided.
 * @throws ShortBufferException if the given output buffer is too small
 * to hold the result
 * @throws BadPaddingException if this {@code Cipher} object is in
 * decryption mode, and (un)padding has been requested, but the
 * decrypted data is not bounded by the appropriate padding bytes
 * @throws AEADBadTagException if this {@code Cipher} object is decrypting
 * in an AEAD mode (such as GCM/CCM), and the received authentication tag
 * does not match the calculated value
 */
 public final int doFinal(byte[] output, int outputOffset)
 throws IllegalBlockSizeException, ShortBufferException,
 BadPaddingException {
 checkCipherState();

 // Input sanity check
 if ((output == null) || (outputOffset < 0)) {
 throw new IllegalArgumentException("Bad arguments");
 }

 chooseFirstProvider();
 return spi.engineDoFinal(null, 0, 0, output, outputOffset);
 }

 /**
 * Encrypts or decrypts data in a single-part operation, or finishes a
 * multiple-part operation. The data is encrypted or decrypted,
 * depending on how this {@code Cipher} object was initialized.
 *
 * The bytes in the {@code input} buffer, and any input bytes that
 * may have been buffered during a previous {@code update} operation,
 * are processed, with padding (if requested) being applied.
 * If an AEAD mode such as GCM/CCM is being used, the authentication
 * tag is appended in the case of encryption, or verified in the
 * case of decryption.
 * The result is stored in a new buffer.
 *
 * Upon finishing, this method resets this {@code Cipher} object
 * to the state it was in when previously initialized via a call to
 * {@code init}.
 * That is, the object is reset and available to encrypt or decrypt
 * (depending on the operation mode that was specified in the call to
 * {@code init}) more data.
 *
 * Note: if any exception is thrown, this {@code Cipher} object
 * may need to be reset before it can be used again.
 *
 * @param input the input buffer
 *
 * @return the new buffer with the result
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws IllegalBlockSizeException if this cipher is a block cipher,
 * no padding has been requested (only in encryption mode), and the total
 * input length of the data processed by this cipher is not a multiple of
 * block size; or if this encryption algorithm is unable to
 * process the input data provided.
 * @throws BadPaddingException if this {@code Cipher} object is in
 * decryption mode, and (un)padding has been requested, but the
 * decrypted data is not bounded by the appropriate padding bytes
 * @throws AEADBadTagException if this {@code Cipher} object is decrypting
 * in an AEAD mode (such as GCM/CCM), and the received authentication tag
 * does not match the calculated value
 */
 public final byte[] doFinal(byte[] input)
 throws IllegalBlockSizeException, BadPaddingException {
 checkCipherState();

 // Input sanity check
 if (input == null) {
 throw new IllegalArgumentException("Null input buffer");
 }

 chooseFirstProvider();
 return spi.engineDoFinal(input, 0, input.length);
 }

 /**
 * Encrypts or decrypts data in a single-part operation, or finishes a
 * multiple-part operation. The data is encrypted or decrypted,
 * depending on how this {@code Cipher} object was initialized.
 *
 * The first {@code inputLen} bytes in the {@code input}
 * buffer, starting at {@code inputOffset} inclusive, and any input
 * bytes that may have been buffered during a previous {@code update}
 * operation, are processed, with padding (if requested) being applied.
 * If an AEAD mode such as GCM/CCM is being used, the authentication
 * tag is appended in the case of encryption, or verified in the
 * case of decryption.
 * The result is stored in a new buffer.
 *
 * Upon finishing, this method resets this {@code Cipher} object
 * to the state it was in when previously initialized via a call to
 * {@code init}.
 * That is, the object is reset and available to encrypt or decrypt
 * (depending on the operation mode that was specified in the call to
 * {@code init}) more data.
 *
 * Note: if any exception is thrown, this {@code Cipher} object
 * may need to be reset before it can be used again.
 *
 * @param input the input buffer
 * @param inputOffset the offset in {@code input} where the input
 * starts
 * @param inputLen the input length
 *
 * @return the new buffer with the result
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws IllegalBlockSizeException if this cipher is a block cipher,
 * no padding has been requested (only in encryption mode), and the total
 * input length of the data processed by this cipher is not a multiple of
 * block size; or if this encryption algorithm is unable to
 * process the input data provided.
 * @throws BadPaddingException if this {@code Cipher} object is in
 * decryption mode, and (un)padding has been requested, but the decrypted
 * data is not bounded by the appropriate padding bytes
 * @throws AEADBadTagException if this {@code Cipher} object is decrypting
 * in an AEAD mode (such as GCM/CCM), and the received authentication tag
 * does not match the calculated value
 */
 public final byte[] doFinal(byte[] input, int inputOffset, int inputLen)
 throws IllegalBlockSizeException, BadPaddingException {
 checkCipherState();

 // Input sanity check
 if (input == null || inputOffset < 0
 || inputLen > (input.length - inputOffset) || inputLen < 0) {
 throw new IllegalArgumentException("Bad arguments");
 }

 chooseFirstProvider();
 return spi.engineDoFinal(input, inputOffset, inputLen);
 }

 /**
 * Encrypts or decrypts data in a single-part operation, or finishes a
 * multiple-part operation. The data is encrypted or decrypted,
 * depending on how this {@code Cipher} object was initialized.
 *
 * The first {@code inputLen} bytes in the {@code input}
 * buffer, starting at {@code inputOffset} inclusive, and any input
 * bytes that may have been buffered during a previous {@code update}
 * operation, are processed, with padding (if requested) being applied.
 * If an AEAD mode such as GCM/CCM is being used, the authentication
 * tag is appended in the case of encryption, or verified in the
 * case of decryption.
 * The result is stored in the {@code output} buffer.
 *
 * If the {@code output} buffer is too small to hold the result,
 * a {@code ShortBufferException} is thrown. In this case, repeat this
 * call with a larger output buffer. Use
 * {@link #getOutputSize(int) getOutputSize} to determine how big
 * the output buffer should be.
 *
 * Upon finishing, this method resets this {@code Cipher} object
 * to the state it was in when previously initialized via a call to
 * {@code init}.
 * That is, the object is reset and available to encrypt or decrypt
 * (depending on the operation mode that was specified in the call to
 * {@code init}) more data.
 *
 * Note: if any exception is thrown, this {@code Cipher} object
 * may need to be reset before it can be used again.
 *
 * Note: this method should be copy-safe, which means the
 * {@code input} and {@code output} buffers can reference
 * the same byte array and no unprocessed input data is overwritten
 * when the result is copied into the output buffer.
 *
 * @param input the input buffer
 * @param inputOffset the offset in {@code input} where the input
 * starts
 * @param inputLen the input length
 * @param output the buffer for the result
 *
 * @return the number of bytes stored in {@code output}
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws IllegalBlockSizeException if this cipher is a block cipher,
 * no padding has been requested (only in encryption mode), and the total
 * input length of the data processed by this cipher is not a multiple of
 * block size; or if this encryption algorithm is unable to
 * process the input data provided.
 * @throws ShortBufferException if the given output buffer is too small
 * to hold the result
 * @throws BadPaddingException if this {@code Cipher} object is in
 * decryption mode, and (un)padding has been requested, but the decrypted
 * data is not bounded by the appropriate padding bytes
 * @throws AEADBadTagException if this {@code Cipher} object is decrypting
 * in an AEAD mode (such as GCM/CCM), and the received authentication tag
 * does not match the calculated value
 */
 public final int doFinal(byte[] input, int inputOffset, int inputLen,
 byte[] output)
 throws ShortBufferException, IllegalBlockSizeException,
 BadPaddingException {
 checkCipherState();

 // Input sanity check
 if (input == null || inputOffset < 0
 || inputLen > (input.length - inputOffset) || inputLen < 0) {
 throw new IllegalArgumentException("Bad arguments");
 }

 chooseFirstProvider();
 return spi.engineDoFinal(input, inputOffset, inputLen,
 output, 0);
 }

 /**
 * Encrypts or decrypts data in a single-part operation, or finishes a
 * multiple-part operation. The data is encrypted or decrypted,
 * depending on how this {@code Cipher} object was initialized.
 *
 * The first {@code inputLen} bytes in the {@code input}
 * buffer, starting at {@code inputOffset} inclusive, and any input
 * bytes that may have been buffered during a previous
 * {@code update} operation, are processed, with padding
 * (if requested) being applied.
 * If an AEAD mode such as GCM/CCM is being used, the authentication
 * tag is appended in the case of encryption, or verified in the
 * case of decryption.
 * The result is stored in the {@code output} buffer, starting at
 * {@code outputOffset} inclusive.
 *
 * If the {@code output} buffer is too small to hold the result,
 * a {@code ShortBufferException} is thrown. In this case, repeat this
 * call with a larger output buffer. Use
 * {@link #getOutputSize(int) getOutputSize} to determine how big
 * the output buffer should be.
 *
 * Upon finishing, this method resets this {@code Cipher} object
 * to the state it was in when previously initialized via a call to
 * {@code init}.
 * That is, the object is reset and available to encrypt or decrypt
 * (depending on the operation mode that was specified in the call to
 * {@code init}) more data.
 *
 * Note: if any exception is thrown, this {@code Cipher} object
 * may need to be reset before it can be used again.
 *
 * Note: this method should be copy-safe, which means the
 * {@code input} and {@code output} buffers can reference
 * the same byte array and no unprocessed input data is overwritten
 * when the result is copied into the output buffer.
 *
 * @param input the input buffer
 * @param inputOffset the offset in {@code input} where the input
 * starts
 * @param inputLen the input length
 * @param output the buffer for the result
 * @param outputOffset the offset in {@code output} where the result
 * is stored
 *
 * @return the number of bytes stored in {@code output}
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws IllegalBlockSizeException if this cipher is a block cipher,
 * no padding has been requested (only in encryption mode), and the total
 * input length of the data processed by this cipher is not a multiple of
 * block size; or if this encryption algorithm is unable to
 * process the input data provided.
 * @throws ShortBufferException if the given output buffer is too small
 * to hold the result
 * @throws BadPaddingException if this {@code Cipher} object is in
 * decryption mode, and (un)padding has been requested, but the decrypted
 * data is not bounded by the appropriate padding bytes
 * @throws AEADBadTagException if this {@code Cipher} object is decrypting
 * in an AEAD mode (such as GCM/CCM), and the received authentication tag
 * does not match the calculated value
 */
 public final int doFinal(byte[] input, int inputOffset, int inputLen,
 byte[] output, int outputOffset)
 throws ShortBufferException, IllegalBlockSizeException,
 BadPaddingException {
 checkCipherState();

 // Input sanity check
 if (input == null || inputOffset < 0
 || inputLen > (input.length - inputOffset) || inputLen < 0
 || outputOffset < 0) {
 throw new IllegalArgumentException("Bad arguments");
 }

 chooseFirstProvider();
 return spi.engineDoFinal(input, inputOffset, inputLen,
 output, outputOffset);
 }

 /**
 * Encrypts or decrypts data in a single-part operation, or finishes a
 * multiple-part operation. The data is encrypted or decrypted,
 * depending on how this {@code Cipher} object was initialized.
 *
 * All {@code input.remaining()} bytes starting at
 * {@code input.position()} are processed.
 * If an AEAD mode such as GCM/CCM is being used, the authentication
 * tag is appended in the case of encryption, or verified in the
 * case of decryption.
 * The result is stored in the output buffer.
 * Upon return, the input buffer's position will be equal
 * to its limit; its limit will not have changed. The output buffer's
 * position will have advanced by n, where n is the value returned
 * by this method; the output buffer's limit will not have changed.
 *
 * If {@code output.remaining()} bytes are insufficient to
 * hold the result, a {@code ShortBufferException} is thrown.
 * In this case, repeat this call with a larger output buffer. Use
 * {@link #getOutputSize(int) getOutputSize} to determine how big
 * the output buffer should be.
 *
 * Upon finishing, this method resets this {@code Cipher} object
 * to the state it was in when previously initialized via a call to
 * {@code init}.
 * That is, the object is reset and available to encrypt or decrypt
 * (depending on the operation mode that was specified in the call to
 * {@code init}) more data.
 *
 * Note: if any exception is thrown, this {@code Cipher} object
 * may need to be reset before it can be used again.
 *
 * Note: this method should be copy-safe, which means the
 * {@code input} and {@code output} buffers can reference
 * the same byte array and no unprocessed input data is overwritten
 * when the result is copied into the output buffer.
 *
 * @param input the input ByteBuffer
 * @param output the output ByteBuffer
 *
 * @return the number of bytes stored in {@code output}
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 * @throws IllegalArgumentException if input and output are the
 * same object
 * @throws ReadOnlyBufferException if the output buffer is read-only
 * @throws IllegalBlockSizeException if this cipher is a block cipher,
 * no padding has been requested (only in encryption mode), and the total
 * input length of the data processed by this cipher is not a multiple of
 * block size; or if this encryption algorithm is unable to
 * process the input data provided.
 * @throws ShortBufferException if there is insufficient space in the
 * output buffer
 * @throws BadPaddingException if this {@code Cipher} object is in
 * decryption mode, and (un)padding has been requested, but the
 * decrypted data is not bounded by the appropriate padding bytes
 * @throws AEADBadTagException if this {@code Cipher} object is decrypting
 * in an AEAD mode (such as GCM/CCM), and the received authentication tag
 * does not match the calculated value
 *
 * @since 1.5
 */
 public final int doFinal(ByteBuffer input, ByteBuffer output)
 throws ShortBufferException, IllegalBlockSizeException,
 BadPaddingException {
 checkCipherState();

 if ((input == null) || (output == null)) {
 throw new IllegalArgumentException("Buffers must not be null");
 }
 if (input == output) {
 throw new IllegalArgumentException("Input and output buffers must "
 + "not be the same object, consider using buffer.duplicate()");
 }
 if (output.isReadOnly()) {
 throw new ReadOnlyBufferException();
 }

 chooseFirstProvider();
 return spi.engineDoFinal(input, output);
 }

 /**
 * Wrap a key.
 *
 * @param key the key to be wrapped
 *
 * @return the wrapped key
 *
 * @throws IllegalStateException if this {@code Cipher} object is in a wrong
 * state (e.g., has not been initialized)
 *
 * @throws IllegalBlockSizeException if this cipher is a block
 * cipher, no padding has been requested, and the length of the
 * encoding of the key to be wrapped is not a
 * multiple of the block size
 *
 * @throws InvalidKeyException if it is impossible or unsafe to
 * wrap the key with this cipher (e.g., a hardware protected key is
 * being passed to a software-only cipher)
 *
 * @throws UnsupportedOperationException if the corresponding method in the
 * {@code CipherSpi} is not supported
 */
 public final byte[] wrap(Key key)
 throws IllegalBlockSizeException, InvalidKeyException {
 if (!(this instanceof NullCipher)) {
 if (!initialized) {
 throw new IllegalStateException("Cipher not initialized");
 }
 if (opmode != Cipher.WRAP_MODE) {
 throw new IllegalStateException("Cipher not initialized " +
 "for wrapping keys");
 }
 }

 chooseFirstProvider();
 return spi.engineWrap(key);
 }

 /**
 * Unwrap a previously wrapped key.
 *
 * @param wrappedKey the key to be unwrapped
 *
 * @param wrappedKeyAlgorithm the algorithm associated with the wrapped
 * key
 *
 * @param wrappedKeyType the type of the wrapped key. This must be one of
 * {@code SECRET_KEY}, {@code PRIVATE_KEY}, or
 * {@code PUBLIC_KEY}
 *
 * @return the unwrapped key
 *
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized)
 *
 * @throws NoSuchAlgorithmException if no installed providers
 * can create keys of type {@code wrappedKeyType} for the
 * {@code wrappedKeyAlgorithm}
 *
 * @throws InvalidKeyException if {@code wrappedKey} does not
 * represent a wrapped key of type {@code wrappedKeyType} for
 * the {@code wrappedKeyAlgorithm}
 *
 * @throws UnsupportedOperationException if the corresponding method in the
 * {@code CipherSpi} is not supported
 */
 public final Key unwrap(byte[] wrappedKey,
 String wrappedKeyAlgorithm,
 int wrappedKeyType)
 throws InvalidKeyException, NoSuchAlgorithmException {

 if (!(this instanceof NullCipher)) {
 if (!initialized) {
 throw new IllegalStateException("Cipher not initialized");
 }
 if (opmode != Cipher.UNWRAP_MODE) {
 throw new IllegalStateException("Cipher not initialized " +
 "for unwrapping keys");
 }
 }
 if ((wrappedKeyType != SECRET_KEY) &&
 (wrappedKeyType != PRIVATE_KEY) &&
 (wrappedKeyType != PUBLIC_KEY)) {
 throw new InvalidParameterException("Invalid key type");
 }

 chooseFirstProvider();
 return spi.engineUnwrap(wrappedKey,
 wrappedKeyAlgorithm,
 wrappedKeyType);
 }

 private AlgorithmParameterSpec getAlgorithmParameterSpec(
 AlgorithmParameters params)
 throws InvalidParameterSpecException {
 if (params == null) {
 return null;
 }

 String alg = params.getAlgorithm().toUpperCase(Locale.ENGLISH);

 if (alg.equalsIgnoreCase("RC2")) {
 return params.getParameterSpec(RC2ParameterSpec.class);
 }

 if (alg.equalsIgnoreCase("RC5")) {
 return params.getParameterSpec(RC5ParameterSpec.class);
 }

 if (alg.startsWith("PBE")) {
 return params.getParameterSpec(PBEParameterSpec.class);
 }

 if (alg.startsWith("DES")) {
 return params.getParameterSpec(IvParameterSpec.class);
 }
 return null;
 }

 private static CryptoPermission getConfiguredPermission(
 String transformation) throws NullPointerException,
 NoSuchAlgorithmException {
 if (transformation == null) throw new NullPointerException();
 String[] parts = tokenizeTransformation(transformation);
 return JceSecurityManager.INSTANCE.getCryptoPermission(parts[0]);
 }

 /**
 * Returns the maximum key length for the specified transformation
 * according to the installed JCE jurisdiction policy files. If
 * JCE unlimited strength jurisdiction policy files are installed,
 * {@code Integer.MAX_VALUE} will be returned.
 * For more information on the default key sizes and the JCE jurisdiction
 * policy files, please see the Cryptographic defaults and limitations in
 * the {@extLink security_guide_jdk_providers JDK Providers Documentation}.
 *
 * @param transformation the cipher transformation
 * @return the maximum key length in bits or {@code Integer.MAX_VALUE}
 * @throws NullPointerException if {@code transformation} is {@code null}
 * @throws NoSuchAlgorithmException if {@code transformation}
 * is not a valid transformation, i.e. in the form of "algorithm" or
 * "algorithm/mode/padding"
 * @since 1.5
 */
 public static final int getMaxAllowedKeyLength(String transformation)
 throws NoSuchAlgorithmException {
 CryptoPermission cp = getConfiguredPermission(transformation);
 return cp.getMaxKeySize();
 }

 /**
 * Returns an {code AlgorithmParameterSpec} object which contains
 * the maximum {@code Cipher} parameter value according to the
 * jurisdiction policy file. If JCE unlimited strength jurisdiction
 * policy files are installed or there is no maximum limit on the
 * parameters for the specified transformation in the policy file,
 * {@code null} will be returned.
 *
 * @param transformation the cipher transformation
 * @return an {code AlgorithmParameterSpec} object which holds the maximum
 * value or {@code null}
 * @throws NullPointerException if {@code transformation}
 * is {@code null}
 * @throws NoSuchAlgorithmException if {@code transformation}
 * is not a valid transformation, i.e. in the form of "algorithm" or
 * "algorithm/mode/padding"
 * @since 1.5
 */
 public static final AlgorithmParameterSpec getMaxAllowedParameterSpec(
 String transformation) throws NoSuchAlgorithmException {
 CryptoPermission cp = getConfiguredPermission(transformation);
 return cp.getAlgorithmParameterSpec();
 }

 /**
 * Continues a multi-part update of the Additional Authentication
 * Data (AAD).
 * 
 * Calls to this method provide AAD to the {@code Cipher} object
 * when operating in modes such as AEAD (GCM/CCM). If this
 * {@code Cipher} object is operating in either GCM or CCM mode, all AAD
 * must be supplied before beginning operations on the ciphertext
 * (via the {@code update} and {@code doFinal} methods).
 *
 * @param src the buffer containing the Additional Authentication Data
 *
 * @throws IllegalArgumentException if the {@code src}
 * byte array is {@code null}
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized),
 * does not accept AAD, or if operating in either GCM or CCM mode and
 * one of the {@code update} methods has already been called for the active
 * encryption/decryption operation
 * @throws UnsupportedOperationException if the corresponding method
 * in the {@code CipherSpi} has not been overridden by an
 * implementation
 *
 * @since 1.7
 */
 public final void updateAAD(byte[] src) {
 if (src == null) {
 throw new IllegalArgumentException("src buffer is null");
 }

 updateAAD(src, 0, src.length);
 }

 /**
 * Continues a multi-part update of the Additional Authentication
 * Data (AAD), using a subset of the provided buffer.
 * 
 * Calls to this method provide AAD to the {@code Cipher} object
 * when operating in modes such as AEAD (GCM/CCM). If this
 * {@code Cipher} object is operating in either GCM or CCM mode,
 * all AAD must be supplied before beginning operations on the
 * ciphertext (via the {@code update} and {@code doFinal} methods).
 *
 * @param src the buffer containing the AAD
 * @param offset the offset in {@code src} where the AAD input starts
 * @param len the number of AAD bytes
 *
 * @throws IllegalArgumentException if the {@code src}
 * byte array is {@code null}, or the {@code offset} or {@code length}
 * is less than 0, or the sum of the {@code offset} and
 * {@code len} is greater than the length of the
 * {@code src} byte array
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized),
 * does not accept AAD, or if operating in either GCM or CCM mode and
 * one of the {@code update} methods has already been called for the active
 * encryption/decryption operation
 * @throws UnsupportedOperationException if the corresponding method
 * in the {@code CipherSpi} has not been overridden by an
 * implementation
 *
 * @since 1.7
 */
 public final void updateAAD(byte[] src, int offset, int len) {
 checkCipherState();

 // Input sanity check
 if ((src == null) || (offset < 0) || (len < 0)
 || len > (src.length - offset)) {
 throw new IllegalArgumentException("Bad arguments");
 }

 chooseFirstProvider();
 if (len == 0) {
 return;
 }
 spi.engineUpdateAAD(src, offset, len);
 }

 /**
 * Continues a multi-part update of the Additional Authentication
 * Data (AAD).
 * 
 * Calls to this method provide AAD to the {@code Cipher} object
 * when operating in modes such as AEAD (GCM/CCM). If this
 * {@code Cipher} object is operating in either GCM or CCM mode, all AAD
 * must be supplied before beginning operations on the ciphertext
 * (via the {@code update} and {@code doFinal} methods).
 * 
 * All {@code src.remaining()} bytes starting at
 * {@code src.position()} are processed.
 * Upon return, the input buffer's position will be equal
 * to its limit; its limit will not have changed.
 *
 * @param src the buffer containing the AAD
 *
 * @throws IllegalArgumentException if the {@code src ByteBuffer}
 * is {@code null}
 * @throws IllegalStateException if this {@code Cipher} object
 * is in a wrong state (e.g., has not been initialized),
 * does not accept AAD, or if operating in either GCM or CCM mode and
 * one of the {@code update} methods has already been called for the active
 * encryption/decryption operation
 * @throws UnsupportedOperationException if the corresponding method
 * in the {@code CipherSpi} has not been overridden by an
 * implementation
 *
 * @since 1.7
 */
 public final void updateAAD(ByteBuffer src) {
 checkCipherState();

 // Input sanity check
 if (src == null) {
 throw new IllegalArgumentException("src ByteBuffer is null");
 }

 chooseFirstProvider();
 if (src.remaining() == 0) {
 return;
 }
 spi.engineUpdateAAD(src);
 }

 /**
 * Returns a {@code String} representation of this {@code Cipher} object.
 *
 * @implNote
 * This implementation returns a {@code String} containing the
 * transformation, mode, and provider of this {@code Cipher} object.
 * The exact format of the {@code String} is unspecified and is subject
 * to change.
 *
 * @return a String describing this {@code Cipher} object
 */
 @Override
 public String toString() {
 final StringBuilder sb = new StringBuilder();
 sb.append("Cipher.")
 .append(transformation)
 .append(", mode: ");
 switch (opmode) {
 case 0:
 sb.append("not initialized");
 break;
 case ENCRYPT_MODE:
 sb.append("encryption");
 break;
 case DECRYPT_MODE:
 sb.append("decryption");
 break;
 case WRAP_MODE:
 sb.append("key wrapping");
 break;
 case UNWRAP_MODE:
 sb.append("key unwrapping");
 break;
 default:
 // should never happen
 sb.append("error:").append(opmode);
 }
 sb.append(", algorithm from: ").append(getProviderName());
 return sb.toString();
 }
}

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