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1 package org.bouncycastle.crypto.agreement.srp;
2
3 import java.math.BigInteger;
4
5 import org.bouncycastle.crypto.Digest;
6
7 /**
8 * Generates new SRP verifier for user
9 */
10 public class SRP6VerifierGenerator
11 {
12 protected BigInteger N;
13 protected BigInteger g;
14 protected Digest digest;
15
16 public SRP6VerifierGenerator()
17 {
18 }
19
20 /**
21 * Initialises generator to create new verifiers
22 * @param N The safe prime to use (see DHParametersGenerator)
23 * @param g The group parameter to use (see DHParametersGenerator)
24 * @param digest The digest to use. The same digest type will need to be used later for the actual authentication
25 * attempt. Also note that the final session key size is dependent on the chosen digest.
26 */
27 public void init(BigInteger N, BigInteger g, Digest digest)
28 {
29 this.N = N;
30 this.g = g;
31 this.digest = digest;
32 }
33
34 /**
35 * Creates a new SRP verifier
36 * @param salt The salt to use, generally should be large and random
37 * @param identity The user's identifying information (eg. username)
38 * @param password The user's password
39 * @return A new verifier for use in future SRP authentication
40 */
41 public BigInteger generateVerifier(byte[] salt, byte[] identity, byte[] password)
42 {
43 BigInteger x = SRP6Util.calculateX(digest, N, salt, identity, password);
44
45 return g.modPow(x, N);
46 }
47 }