Java on Linux vs. Windows

Question

Dear All,
I was able to write below AES/CFB/NoPadding encryption/decryption program (with many thanks to the Internet) and it works fine on Windows. But it's "getByte()" gives problems on Linux.
Which is the "symmKey.length()" inside "SymmCipher" constructor is only 15 chars. But "symmKey.getBytes().length" has become 33.
Can anybody answer?
Thanks in advanced.
- amilww
// aesDemo.java
class aesDemo
     public static void main(String[] args) throws Exception
          String keyHexStr = "CAABBCCDDEE11223344556677889900F";
          String ivStr     = "0000000000000001";
          String inputStr  = "This in a test message";
          // Intermediate variables
          String cipherTextStr, plainTextStr,
                 reqHexMsgStr,  repHexMsgStr,
                 repMsgStr;
          SymmCipher symmCipher = new SymmCipher("AES/CFB/NoPadding",
                                                 new String(Util.hex2Bytes(keyHexStr)),
                                                 ivStr);
          // Encrypt the input string
          cipherTextStr = symmCipher.encrypt(inputStr);
          // Convert to an uppercase Hex request string
          reqHexMsgStr = Util.bytes2Hex(cipherTextStr.getBytes()).toUpperCase();
          // Obtain the reply; assume to be the request
          repHexMsgStr = reqHexMsgStr;
          // Convert reply hex message to a string
          repMsgStr = new String(Util.hex2Bytes(repHexMsgStr));
          // Decrypt the reply string
          plainTextStr = symmCipher.decrypt(repMsgStr);
          // Debub output
          System.out.println("=============================================");
          System.out.println("Encrypting/decrypting using AES/CFB/NoPadding");
          System.out.println("---------------------------------------------");
          System.out.println("Input String: '" + inputStr + "'");
          System.out.println("Encr request: '" + cipherTextStr + "'");
          System.out.println("Req Hex Msg:  '" + reqHexMsgStr + "'");
          System.out.println("Rep Hex Msg:  '" + repHexMsgStr + "'");
          System.out.println("Encr reply:   '" + repMsgStr + "'");
          System.out.println("Response:     '" + plainTextStr + "'");
          System.out.println("=============================================");
// SymmCipher.java
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
class SymmCipher
     private String cipherForm;
     // e.g.: "AES/CFB/NoPadding", "DES/CTR/NoPadding", "DES/ECB/PKCS5Padding"
     private String cipherMethod;
     private SecretKeySpec   keySpec;
     private IvParameterSpec ivSpec;
     private Cipher          cipher;
     public SymmCipher(String cipherForm, String symmKey, String iv) throws Exception
          this.cipherForm   = cipherForm;
          this.cipherMethod = this.cipherForm.split("/")[0];
          this.keySpec = new SecretKeySpec(symmKey.getBytes(), this.cipherMethod);
          this.ivSpec  = new IvParameterSpec(iv.getBytes());
          this.cipher = Cipher.getInstance(this.cipherForm);
     public String encrypt(String plainText) throws Exception
          // Encrypting...
          this.cipher.init(Cipher.ENCRYPT_MODE, this.keySpec, this.ivSpec);
          return new String(this.cipher.doFinal(plainText.getBytes()));
     public String decrypt(String cipherText) throws Exception
          // Decrypting...
          this.cipher.init(Cipher.DECRYPT_MODE, this.keySpec, this.ivSpec);
          return new String(this.cipher.doFinal(cipherText.getBytes()));
// Util.java
class Util
     public static String bytes2Hex(byte buf[])
          StringBuffer strbuf = new StringBuffer(2 * buf.length);
          for (int 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 byte[] hex2Bytes(String hex)
          int    len = hex.length();
          byte[] buf = new byte[((len + 1) / 2)];
          int i = 0, j = 0;
          if (1 == (len % 2))
               buf[j++] = (byte) hexDigit(hex.charAt(i++));
          while (i < len)
               buf[j++] = (byte) ((hexDigit(hex.charAt(i++)) << 4) |
               hexDigit(hex.charAt(i++)));
          return buf;
      * Returns the number from 0 to 15 corresponding to the hex digit <i>ch</i>.
      * @param ch hex digit character (must be 0-9A-Fa-f)
      * @return   numeric equivalent of hex digit (0-15)
     public static int hexDigit(char ch)
          if (('0' <= ch) && ('9' >= ch))
               return ch - '0';
          if (('A' <= ch) && ('F' >= ch))
               return ch - 'A' + 10;
          if (('a' <= ch) && ('f' >= ch))
               return ch - 'a' + 10;
          return(0);     // any other char is treated as 0
}

Answer 1

This statement
     return new String(this.cipher.doFinal(plainText.getBytes()));     has two problems.
1) It relies on the default character encoding when converting the plainText to bytes and the default character encoding is platform, operating system and user dependent. It is far far better to specify an encoding yourself - I always use utf-8.
2) You are converting the essentially random binary result of the encryption to a String using new String(encrypted bytes). String should never be used as a container for binary data unless something like Hex or Base64 is used because, depending on the character encoding, it is not reversible for most character encoding. If you need a Hex or Base64 encoder then Google for Jakarta Commons Codec.