Encrypting and Decrypting String using a Java equilavent of the C# CryptoStream

Question

I am looking at developing an application in Java for a mobile platform operating system.

I have developed an application in C# WPF for the Windows Environment. I am using a cryptostream in order to encrypt and decrypt a string using the following code. the code shown below is the encryption only

public string encrypt(string encryptionString)
    {
        byte[] clearTextBytes = Encoding.UTF8.GetBytes(encryptionString);

        SymmetricAlgorithm rijn = SymmetricAlgorithm.Create();

        MemoryStream ms = new MemoryStream();
        byte[] rgbIV = Encoding.ASCII.GetBytes("ryojvlzmdalyglrj");
        byte[] key = Encoding.ASCII.GetBytes("hcxilkqbbhczfeultgbskdmaunivmfuo");
        CryptoStream cs = new CryptoStream(ms, rijn.CreateEncryptor(key, rgbIV), CryptoStreamMode.Write);

        cs.Write(clearTextBytes, 0, clearTextBytes.Length);

        cs.Close();

        return Convert.ToBase64String(ms.ToArray());
    }

The encrypted string is stored in an online database. What I need to be able to do is for the java application to be able to read the string from the database and decrypt the string using the same encryption keys from the C# application.

Thanks for your help.

Answer 1

Personally, I like BouncyCastle for Java crypto. This code (using the BouncyCastle lightweight API) should do the trick:

String decrypt(byte[] cryptoBytes, byte[] key, byte[] iv) {
    BlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(new AESEngine()));
    cipher.init(false, new ParametersWithIV(new KeyParameter(key), iv));
    byte[] out = new byte[cipher.getOutputSize(cryptoBytes.length)];
    int offset = cipher.processBytes(cryptoBytes, 0, cryptoBytes.length, out, 0);
    cipher.doFinal(out, offset);
    return new String(out);
}

I find BouncyCastle's lightweight API to be less painful than the JCE provider stuff but you can use it as a provider if you wish.

It looks like both the .net SymmetricAlgorithm and BC's PaddedBufferedBlockCipher default to PKCS7 padding so you should be OK with using the defaults.

Answer 2

You may want to check out javax.crypto.CipherInputStream and javax.crypto.CipherOutputStream.

http://download.oracle.com/javase/1.5.0/docs/api/javax/crypto/CipherInputStream.html http://download.oracle.com/javase/1.5.0/docs/api/javax/crypto/CipherOutputStream.html

They are used almost the exact same way as your sample above, though initialization of the Cipher objects may be slightly different.

Answer 3

I use the following for encrypting between .net and java

In .net i use:

    /// <summary>
    /// DES Encryption method - used to encryp password for the java.
    /// </summary>
    /// <param name="plainText"></param>
    /// <returns></returns>
    public string EncryptData(string plainText)
    {
        DES des = new DESCryptoServiceProvider();
        des.Mode = CipherMode.ECB;
        des.Padding = PaddingMode.PKCS7;

        des.Key = Encoding.UTF8.GetBytes(_secretPhrase.Substring(0, 8));
        des.IV = Encoding.UTF8.GetBytes(_secretPhrase.Substring(0, 8));

        byte[] bytes = Encoding.UTF8.GetBytes(plainText);
        byte[] resultBytes = des.CreateEncryptor().TransformFinalBlock(bytes, 0, bytes.Length);

        return Convert.ToBase64String(resultBytes);
    }

    /// <summary>
    /// DES Decryption method - used the decrypt password encrypted in java
    /// </summary>
    /// <param name="encryptedText"></param>
    /// <returns></returns>
    public string DecryptData(string encryptedText)
    {
        DES des = new DESCryptoServiceProvider();
        des.Mode = CipherMode.ECB;
        des.Padding = PaddingMode.PKCS7;
        des.Key = Encoding.UTF8.GetBytes(_secretPhrase.Substring(0, 8));
        des.IV = System.Text.Encoding.UTF8.GetBytes(_secretPhrase.Substring(0, 8));

        byte[] bytes = Convert.FromBase64String(encryptedText);
        byte[] resultBytes = des.CreateDecryptor().TransformFinalBlock(bytes, 0, bytes.Length);

        return Encoding.UTF8.GetString(resultBytes);
    }

and in java I use:

public class CryptoUtil {

public static final Logger LOG = Logger.getLogger(CryptoUtil.class);

private Cipher cipher = null;

private SecretKey key = null;

// This variable holds a string based on which a unique key will be generated
private static final String SECRET_PHRASE = "SECRET PHRASE GOES HERE";

// Charset will be used to convert between String and ByteArray
private static final String CHARSET = "UTF8";

 // The algorithm to be used for encryption/decryption DES(Data Encryption Standard)
private static final String ALGORITHM = "DES";

public CryptoUtil() throws DDICryptoException {
    try {
        // generate a key from SecretKeyFactory
        DESKeySpec keySpec = new DESKeySpec(SECRET_PHRASE.getBytes(CHARSET));
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(ALGORITHM);
        key = keyFactory.generateSecret(keySpec);
        cipher = Cipher.getInstance(ALGORITHM);
    } catch (Exception e) {
        LOG.error(e);
        throw new DDICryptoException(e);
    }
}


/**
 * This method takes a plain text string and returns encrypted string using DES algorithm
 * @param plainText
 * @return String
 * @throws DDICryptoException
 */
public String encrypt(String plainText) throws DDICryptoException {
    String encryptedString = null;
    try {
        // initializes the cipher with a key.
        cipher.init(Cipher.ENCRYPT_MODE, key);

        byte[] plainTextAsUTF8 = plainText.getBytes(CHARSET);

        // decrypts data in a single-part or multi-part operation
        byte[] encryptedBytes = cipher.doFinal(plainTextAsUTF8);

        encryptedString = new sun.misc.BASE64Encoder().encode(encryptedBytes);
    } catch (Exception e) {
        LOG.error(e);
        throw new DDICryptoException(e);

    }
    return encryptedString;

}

/**
 * This method takes a plain text string and returns encrypted string using DES algorithm
 * @param encryptedString
 * @return
 * @throws DDICryptoException
 */
public String decrypt(String encryptedString) throws DDICryptoException {    
    String decryptedString = null;
    try {
        byte[] decodedString = new sun.misc.BASE64Decoder().decodeBuffer(encryptedString);

        // initializes the cipher with a key.
        cipher.init(Cipher.DECRYPT_MODE, key);

        // decrypts data in a single-part or multi-part operation
        byte[] decryptedBytes = cipher.doFinal(decodedString);
        decryptedString = new String(decryptedBytes, CHARSET);
    } catch (Exception e) {
        LOG.error(e);
        throw new DDICryptoException(e);
    }
    return decryptedString;
}

}

Answer 4

I have sort of managed to resolve the problem. The decryption now works fine. Using the following code

    String plainPassword = "";
            try
            {
                SecretKeySpec key = new SecretKeySpec("hcxilkqbbhczfeultgbskdmaunivmfuo".getBytes("US-ASCII"), "AES");

                IvParameterSpec iv = new IvParameterSpec("ryojvlzmdalyglrj".getBytes("US_ASCII"));

                Cipher cipher = Cipher.getInsta

nce("AES/CBC/PKCS7Padding");

            cipher.init(Cipher.DECRYPT_MODE, key, iv);

            byte[] encoded = cipher.doFinal(Base64.decodeBase64(encryptedPassword.getBytes()));
            plainPassword = new String(encoded);
        }
        catch (Exception ex)
        {
            Log.d("Decryption Error", ex.toString());
        }

        return plainPassword;

The problem is now with the encryption. I have used the same code except changed the cipher from decrypt mode to encrypt mode but for some reason when I print out the encrypted string it just prints a load of rubbish that's nothing like the string that C# creates. Below is teh code for the encryption

public String encrypt(String plainPasword)
    {
        String password = "";
        try
        {
            SecretKeySpec key = new SecretKeySpec("hcxilkqbbhczfeultgbskdmaunivmfuo".getBytes("US-ASCII"), "AES");

            IvParameterSpec iv = new IvParameterSpec("ryojvlzmdalyglrj".getBytes("US_ASCII"));

            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");

            cipher.init(Cipher.ENCRYPT_MODE, key, iv);

            byte[] encoded = cipher.doFinal(plainPasword.getBytes());
            password = new String(encoded);


        }
        catch (Exception ex)
        {
            Log.d("Encryption Error", ex.toString());
        }
        return password;
    }

What seems to be wrong with this i can't work it out. Thanks

Answer 5

        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));
        }

You have to encode the resulting byte array before converting it to string. The code above did the trick for me, while my actual encryption function is below.

public String encrypt(String data) throws Exception{
    try {
        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        Key k = new SecretKeySpec(key.getBytes(), 0, key.length(), "AES");

        // Calculate ciphertext size.
        int blocksize = 16;
        int ciphertextLength = 0;
        int remainder = data.getBytes().length % blocksize;
        if (remainder == 0) {
            ciphertextLength = data.getBytes().length + blocksize;
        } else {
            ciphertextLength = data.getBytes().length - remainder + blocksize;
        }


        cipher.init(Cipher.ENCRYPT_MODE, k);
        byte[] buf = new byte[ciphertextLength];
        cipher.doFinal(data.getBytes(), 0, data.length(), buf, 0);

        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();
    } catch (Exception e) {
        Logger.logException(e);
    }
    return null;
}

Answer 6

See Answer #5 on Equivalent to CryptoStream .NET in Java?

Be sure to read the comments at the bottom...

KeySpec ks = new DESKeySpec("key12345".getBytes("UTF-8")); SecretKey key = SecretKeyFactory.getInstance("DES").generateSecret(ks);
IvParameterSpec iv = new IvParameterSpec( Hex.decodeHex("1234567890ABCDEF".toCharArray()));
Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding"); cipher.init(Cipher.DECRYPT_MODE, key, iv);
byte[] decoded = cipher.doFinal(Base64.decodeBase64("B3xogi/Qfsc="));
System.out.println("Decoded: " + new String(decoded, "UTF-8"));

Hope this helps...
JK

Answer 7

Cemeron, Neat code there!

I came across an interesting situation where our customer had given the IV the same as the key.

After trying out various combinations where I was getting bad padding exception, the solution that worked was

byte[] iv=new byte[8]; // assuming RC2
System.arraycopy(key.getBytes(), 0, iv, 0, key.getBytes().length > iv.length ? key.getBytes().length);

// Now decrypt and hopefully this should work