Blowfish ECB encryption in C# implementation

Question

I have a client who needs us to use Blowfish ECB encryption with cipherMode 0, output 1. I have tried to solve for this, but I'm getting stuck. How do I fix my code?

Here are the full client instructions:

Algorithm： Blowfish ・　Mode： ECB ・　Padding： PKCS5Padding *Initial vector is unnecessary because we use ECB mode.

Example ・Encrypt Key： 2fs5uhnjcnpxcpg9 　→　Plain Text ： 3280:99:20120201123050 　→　Cipher Text ： daa745f1901364c0bd42b9658db3db96336758cd34b2a576 *　Please keep Cipher Text with 16 hexadecimal characters . *　Please generate Cipher Text without “salt”.

I need to write this in C#. Here's what I did, but it doesn't seem to be working:

string member_id = "3280";
        string panelType = "99";
        string RandomString = "20120201123050";
        string encryptionKey = "2fs5uhnjcnpxcpg9";
        string cryptstr = member_id + ":" + panelType + ":" + RandomString;
        string plainText = cryptstr;
        BlowFish b = new BlowFish(encryptionKey);
        string cipherText = b.Encrypt_ECB("3280:99:20120201123050");

The result is not daa745f1901364c0bd42b9658db3db96336758cd34b2a576. Where did I go wrong?

Answer 1

Encrypt_ECB() so I assume its Schneier's class.

The ctor expects a hexadecimal string if one is passed, you need the overload for a byte array:

BlowFish b = new BlowFish(Encoding.UTF8.GetBytes(encryptionKey));

The output is still not correct, lets see what it really should be by decrypting their example:

string clear = b.Decrypt_ECB("daa745f1901364c0bd42b9658db3db96336758cd34b2a576");

gives us:

"3280:99:20120201123050\u0002\u0002"

Which is good but there are 2 0x2 bytes on the end, the N x 0xN is due to the PKCS padding. To get the match you need to pad the input:

// input to bytes
List<byte> clearBytes = new List<byte>(Encoding.UTF8.GetBytes("3280:99:20120201123050"));

// how many padding bytes?
int needPaddingBytes = 8 - (clearBytes.Count % 8);

// add them
clearBytes.AddRange(Enumerable.Repeat((byte)needPaddingBytes, needPaddingBytes));

// encrypt
byte[] cipherText = b.Encrypt_ECB(clearBytes.ToArray());

// to hex
string cipherTextHex = BitConverter.ToString(cipherText).Replace("-", "").ToLowerInvariant();