C# and Java DES Encryption value are not identical

Question

I am trying to encrypt the same data using C# and Java. If the data is more than 7 bytes then Java and C#'s encrypted value are not identical.

Input 1: a
java output: FrOzOp/2Io8=
C# output: FrOzOp/2Io8=
Input 2: abc
j : H9A/ahl8K7I=
c#: H9A/ahl8K7I=
Input 3: aaaaaaaa (Problem)
j : Gxl7e0aWPd7j6l7uIEuMxA==
c#: Gxl7e0aWPd7sf1xR6hK4VQ==

Here is the implementation of C# and Java methods.
C# code:

public String saltTxt = "12345678";
public String Encrypt(String txt)
{
        byte[] data = Encrypt(Encoding.UTF8.GetBytes(txt));
        
        DESCryptoServiceProvider alg = new DESCryptoServiceProvider();

        alg.Key = Encoding.UTF8.GetBytes(saltTxt.ToCharArray(), 0, cprovider.KeySize / 8);
        alg.IV = new byte[8];

        MemoryStream ms = new MemoryStream();
        CryptoStream stem = new CryptoStream( ms, cprovider.CreateEncryptor(),CryptoStreamMode.Write);

        stem.Write(txt, 0, txt.Length);
        stem.FlushFinalBlock();

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

Java Code:

public String saltTxt = "12345678";
public String Encrypt(String str) {
    try {
        KeySpec myKey = new DESKeySpec(saltTxt.getBytes("UTF8"));
        SecretKey key = SecretKeyFactory.getInstance("DES").generateSecret(myKey);
        Cipher ecipher = Cipher.getInstance("DES");
        ecipher.init(Cipher.ENCRYPT_MODE, key);

        byte[] data = str.getBytes("UTF8");

        byte[] crypt = ecipher.doFinal(data);
        
        return new BASE64Encoder().encode(crypt);
    } catch (Exception ex) {
    }

    return null;
}

Any idea why it's not working as expected?

Sounds like a padding problem. See msdn.microsoft.com/en-us/library/… — Jon Skeet
– Jon Skeet, Commented Oct 15, 2012 at 11:34
The important thing is that roundtripping between the two should work. Does it? — spender
– spender, Commented Oct 15, 2012 at 11:39
@JonSkeet yes it is padding problem. what is the default padding mechanism of java? if i specify DES/CBC/PKCS5Padding in java part then both value are getting identical. — Nikson Kanti Paul
– Nikson Kanti Paul, Commented Oct 15, 2012 at 12:13

Nikson Kanti Paul · Accepted Answer · 2021-12-31 12:12:29Z

9

The problem was in mode of encryption.

SunJCE provider uses ECB as the default mode, and PKCS5Padding as the default padding scheme for DES, DES-EDE and Blowfish ciphers. (JCA Doc)

and

In .Net, The default operation mode for the symmetric algorithm is CipherMode.CBC and default padding is PaddingMode.PKCS7. (msdn..SymmetricAlgorithm)

The following changes resolve the problem.

// in C# 
DESCryptoServiceProvider alg = new DESCryptoServiceProvider();
alg.Mode = CipherMode.ECB;  // specified

or

// in java
chiper = Cipher.getInstance("DES/CBC/PKCS5Padding");

don't change in both sides.

edited Dec 31, 2021 at 12:12

answered Oct 21, 2012 at 7:53

Nikson Kanti Paul

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Comments

SLaks · Accepted Answer · 2012-10-15 11:34:19Z

1

You're probably seeing ISO 10126 padding, which appends random bytes to the plaintext to fill it up t oa multiple of the block size.
This behavior is by design.

answered Oct 15, 2012 at 11:34

SLaks

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1 Comment

SLaks Over a year ago

@NiksonKantiPaul: Not in Java.

Mike Laren · Accepted Answer · 2015-01-24 00:43:45Z

The code (Java/Android) bellow worke for me. I used the same approach on C#.

public static String Cripto(String Password)
{
    String PasswordCripto = "";
    try
    {
        String encryptionKey = "anyEncryptionString";
        MessageDigest messageDigest = MessageDigest.getInstance("MD5");
        messageDigest.update(encryptionKey.getBytes("UTF-8"), 0, encryptionKey.length());
        byte[] encryptionKeyBytes = messageDigest.digest();

        SecretKeySpec Key = new SecretKeySpec(encryptionKeyBytes,"DESede");
        Cipher cipher = Cipher.getInstance("DESEDE/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, Key);
        byte[] encryptedBytes = cipher.doFinal(Password.getBytes("UTF-8"));

        PasswordCripto = new String(Base64.encode(encryptedBytes, Base64.DEFAULT), "UTF-8");
    } catch(Exception e) { }
    return PasswordCripto ;
}

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