How do I use the DES Algorithm in .NET?

Question

How do I use DES in .NET?

Here's how I'd do it in Java:

        public static String decrypt(byte[] pin, byte [] desKeyData ) throws Exception {
    //if (ISOConstantsLibrary.DEBUG) System.out.println("original: " + pin + " key: " + ISOUtil.bcd2str(desKeyData, 0, 2 * desKeyData.length, false) );
    String out = "";

    try {           
        SecretKeySpec desKey = new SecretKeySpec(desKeyData, "DES");
        Cipher cipher = Cipher.getInstance("DES/ECB/NoPadding");//DES/CBC/PKCS5Padding
        byte[] encrypted_password = pin;
        cipher.init(Cipher.DECRYPT_MODE, desKey);
        byte[] decrypted_password = cipher.doFinal(encrypted_password);
        out = new String(decrypted_password);
        //if (ISOConstantsLibrary.DEBUG) System.out.println("Decrypted Password " + out);
    }
    catch (Exception e) {
        e.printStackTrace();
    }

    return out;
}

Is there a library for decrypting DES encryption in .NET? If so, how do I use it?

Answer 1

Assuming your input is a stream

using System.Security.Cryptography

string key;
Stream input;
string output;
DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
//Set key and initialization vector for DES algorithm
DES.Key = ASCIIEncoding.ASCII.GetBytes(key);
DES.IV = ASCIIEncoding.ASCII.GetBytes(key);

//Create CryptoStream layer to decrypt input on reading
CryptoStream decryptStream = new CryptoStream(input, DES.CreateDecryptor(), CryptoStreamMode.Read);
//return decrypted
return new StreamReader(decryptStream ).ReadToEnd();

otherwise you can of course easily write the input into a stream. For ECB mode you also need to set the Mode of the DES object to ECB:

DES.Mode = CipherMode.ECB