package org.bouncycastle.crypto.agreement.srp;

import java.math.BigInteger;

import org.bouncycastle.crypto.Digest;

Generates new SRP verifier for user
/**
 * Generates new SRP verifier for user
 */
public class SRP6VerifierGenerator
{
    protected BigInteger N;
    protected BigInteger g;
    protected Digest digest;

    public SRP6VerifierGenerator()
    {
    }

    
Initialises generator to create new verifiers
Params:
N – The safe prime to use (see DHParametersGenerator)
g – The group parameter to use (see DHParametersGenerator)
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./**
     * 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 void init(BigInteger N, BigInteger g, Digest digest)
    {
        this.N = N;
        this.g = g;
        this.digest = digest;
    }

    
Creates a new SRP verifier
Params:
salt – The salt to use, generally should be large and random
identity – The user's identifying information (eg. username)
password – The user's password
Returns:
A new verifier for use in future SRP authentication/**
     * 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 BigInteger generateVerifier(byte[] salt, byte[] identity, byte[] password)
    {
        BigInteger x = SRP6Util.calculateX(digest, N, salt, identity, password);

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