RSA blind signature using .NET cryptographic API?

Question

I would like to use RSA blind signature in .NET. Is there a way to use the standard System.Security.Cryptography APIs to achieve this?

The “obvious” idea does not work:

 using (var rsa = new RSACryptoServiceProvider()) signed = rsa.Decrypt(messageBytes, false); // CryptographicException: bad data 

I appreciate the dangers of blind signature, but for a moment ignore them. Also, I'm not interested in other types of digital signatures.

Answer 1

You will have to fold you. You can use the BigInteger.NET 4 class or just use the C # Bouncycastle library.

Answer 2

You can use the SignData method to sign any data. It has overloads for byte arrays and streams. As for blinding, you probably want to use encrypted data (using a key that is not available to the subscriber), and then sign it.