Quelle AES.java Sprache: JAVA

/*
* Created on 06.10.2004
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/

/**
* @author Jens
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/

import javax.crypto.*;
import javax.crypto.spec.*;

/**
* This program generates a AES key, retrieves its raw bytes, and
* then reinstantiates a AES key from the key bytes.
* The reinstantiated key is used to initialize a AES cipher for
* encryption and decryption.
*/

public class AES {

  /**
  * Turns array of bytes into string
  *
  * @param buf Array of bytes to convert to hex string
  * @return Generated hex string
  */
  public static String asHex (byte buf[]) {
   StringBuffer strbuf = new StringBuffer(buf.length * 2);
   int i;

   for (i = 0; i < buf.length; i++) {
    if (((int) buf[i] & 0xff) < 0x10)
     strbuf.append("0");

    strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
   }

   return strbuf.toString();
  }

  public static void main(String[] args) throws Exception {

    String message="This is just an example";

    // Get the KeyGenerator

    KeyGenerator kgen = KeyGenerator.getInstance("AES");
    kgen.init(128); // 192 and 256 bits may not be available

    // Generate the secret key specs.
    SecretKey skey = kgen.generateKey();
    byte[] raw = skey.getEncoded();

    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");

    // Instantiate the cipher

    Cipher cipher = Cipher.getInstance("AES");

    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);

    byte[] encrypted =
      cipher.doFinal((args.length == 0 ?
       "This is just an example" : args[0]).getBytes());
    System.out.println("encrypted string: " + asHex(encrypted));

    cipher.init(Cipher.DECRYPT_MODE, skeySpec);
    byte[] original =
      cipher.doFinal(encrypted);
    String originalString = new String(original);
    System.out.println("Original string: " +
      originalString + " " + asHex(original));
  }
}

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