SRP6VerifierGenerator.cs :  » PDF » iTextSharp » Org » BouncyCastle » Crypto » Agreement » Srp » C# / CSharp Open Source

using System;

using Org.BouncyCastle.Math;

namespace Org.BouncyCastle.Crypto.Agreement.Srp{
  /**
   * Generates new SRP verifier for user
   */
  public class Srp6VerifierGenerator
  {
      protected BigInteger N;
      protected BigInteger g;
      protected IDigest digest;

      public Srp6VerifierGenerator()
      {
      }

      /**
       * Initialises generator to create new verifiers
       * @param N The safe prime to use (see DHParametersGenerator)
       * @param g The group parameter to use (see DHParametersGenerator)
       * @param digest The digest to use. The same digest type will need to be used later for the actual authentication
       * attempt. Also note that the final session key size is dependent on the chosen digest.
       */
      public virtual void Init(BigInteger N, BigInteger g, IDigest digest)
      {
          this.N = N;
          this.g = g;
          this.digest = digest;
      }

      /**
       * Creates a new SRP verifier
       * @param salt The salt to use, generally should be large and random
       * @param identity The user's identifying information (eg. username)
       * @param password The user's password
       * @return A new verifier for use in future SRP authentication
       */
      public virtual BigInteger GenerateVerifier(byte[] salt, byte[] identity, byte[] password)
      {
        BigInteger x = Srp6Utilities.CalculateX(digest, N, salt, identity, password);

          return g.ModPow(x, N);
      }
  }
}