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Question:

AES128/CBC/PKCS5Padding

Feb 11 '15 at 10:52

Hello,

I am using the following Delphi code: (http://www.example-code.com/delphi/aes_javaJceAesCbc.asp)

*** BEGIN DELPHI ****

procedure TForm1.Button2Click(Sender: TObject);
var
  success: integer;
  crypt:   TChilkatCrypt2;
  crypt2:  TChilkatCrypt2;
  pswhex:  String;
  text:    String;
  encText: String;
  encText1:String;
  ivhex:   String;
begin

crypt   := TChilkatCrypt2.Create(Self);
  success := crypt.UnlockComponent('30-day trial');
  if (success <> 1) then
    ShowMessage('Crypt component unlock failed');

crypt2  := TChilkatCrypt2.Create(Self);
  success := crypt2.UnlockComponent('30-day trial');
  if (success <> 1) then
    ShowMessage('Crypt component unlock failed');

crypt.CryptAlgorithm := 'aes';
  crypt.CipherMode     := 'cbc';
  crypt.KeyLength      := 128;
  crypt.PaddingScheme  := 0;
  crypt.EncodingMode   := 'hex';

// IV
  ivhex := '605bd70efed2c6374823b54bbc560b58';
  crypt.SetEncodedIV(ivhex, 'hex');

// Key
  pswhex := '605bd70efed2c6374823b54bbc560b58';
  crypt.SetEncodedKey(pswhex,'hex');

// Encrypted text
  text := 'Test';
  encText := crypt.EncryptStringENC(text);

crypt2.CryptAlgorithm := 'none';
  crypt2.EncodingMode   := 'base64';

encText1 := crypt.GetEncodedIV('hex') + encText;
  encText1 := crypt2.EncryptStringENC(encText1);
  Memo1.Lines.Add(encText1);

end;

*** END DELPHI
****

... to implement the following Java function:

*** BEGIN JAVA
****

private static final String ALGORITMO = "AES/CBC/PKCS5Padding";
private static final String CODIFICACION = "UTF-8";

public static String encrypt(String plaintext, String key)
        throws NoSuchAlgorithmException, NoSuchPaddingException,
        InvalidKeyException, IllegalBlockSizeException,
        BadPaddingException, IOException, DecoderException {

    byte[] raw = DatatypeConverter.parseHexBinary(key);

    SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
    Cipher cipher = Cipher.getInstance(ALGORITMO);
    cipher.init(Cipher.ENCRYPT_MODE, skeySpec);

    byte[] cipherText = cipher.doFinal(plaintext.getBytes(CODIFICACION));
    byte[] iv = cipher.getIV();

    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    outputStream.write(iv);
    outputStream.write(cipherText);

    byte[] finalData = outputStream.toByteArray();

    String encodedFinalData = DatatypeConverter
            .printBase64Binary(finalData);

    return encodedFinalData;

}

*** END JAVA
****

But Delphi encryption is different to Java encryption.

Please, Can you tell me why?

---

Answer

In Java, you are encrypting a UTF-8 byte array, but in Delphi you are encrypting a String - I'm unfamiliar with Delphi Strings, but are they UTF-8 encoded? If not, this could be the source of the different results.

What about your IVs? Are you sure they are the same in Delphi and in Java?

Lastly - It looks like you are encrypting twice in your Delphi code? Once to hex, then again by merging the IV and encrypted hex, and then re-encrypting to Base64? Why not use bas64 encoding for the first pass, and skip the second encryption step?

---

Answer

Your Java code was not following the same as what was provided in the reference example:

This is the equivalent code using Java JCE:

String password = "secretPassphrase";

MessageDigest md = MessageDigest.getInstance("MD5");
md.update(password.getBytes("UTF-8"), 0, password.length());
byte[] rawKey = md.digest();
String text = "Though this be madness, yet there is method in 't";

SecretKeySpec skeySpec = new SecretKeySpec(rawKey, "AES");
IvParameterSpec ivSpec = new IvParameterSpec(rawKey);

Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, ivSpec);

byte[] encrypted = cipher.doFinal(text.getBytes("UTF-8"));

System.out.println(toHex(encrypted));

This is the toHex method in Java:
public static String toHex (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();
}