TripleDES: Specified key is a known weak key for 'TripleDES' and cannot be used

Question

I\'m using the .NET 3.0 class System.Security.Cryptography.MACTripleDES class to generate a MAC value. Unfortunately, I am working with a hardware device that

Answer 1

Instead of using MACTripleDES with the DES key repeated to fake a single DES CBC-MAC, you could just implement CBC-MAC yourself on top of DESCryptoServiceProvider.

<1111111111111111> is not a weak DES key.

This will calculate a DES CBC-MAC:

public static byte[] CalcDesMac(byte[] key, byte[] data){
        DESCryptoServiceProvider des = new DESCryptoServiceProvider();
        des.Key = key;
        des.IV = new byte[8];
        des.Padding = PaddingMode.Zeros;
        MemoryStream ms = new MemoryStream();
        using(CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write)){
          cs.Write(data, 0, data.Length);
        }
        byte[] encryption = ms.ToArray();
        byte[] mac = new byte[8];
        Array.Copy(encryption, encryption.Length-8, mac, 0, 8);
        PrintByteArray(encryption);
        return mac;
    }