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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.

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package org.bouncycastle.crypto.examples;

import java.math.BigInteger;
import java.security.SecureRandom;

import org.bouncycastle.crypto.CryptoException;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.agreement.jpake.JPAKEPrimeOrderGroup;
import org.bouncycastle.crypto.agreement.jpake.JPAKEPrimeOrderGroups;
import org.bouncycastle.crypto.agreement.jpake.JPAKEParticipant;
import org.bouncycastle.crypto.agreement.jpake.JPAKERound1Payload;
import org.bouncycastle.crypto.agreement.jpake.JPAKERound2Payload;
import org.bouncycastle.crypto.agreement.jpake.JPAKERound3Payload;
import org.bouncycastle.crypto.digests.SHA256Digest;

/**
 * An example of a J-PAKE exchange.
 * 

* * In this example, both Alice and Bob are on the same computer (in the same JVM, in fact). * In reality, Alice and Bob would be in different locations, * and would be sending their generated payloads to each other. */ public class JPAKEExample { public static void main(String args[]) throws CryptoException { /* * Initialization * * Pick an appropriate prime order group to use throughout the exchange. * Note that both participants must use the same group. */ JPAKEPrimeOrderGroup group = JPAKEPrimeOrderGroups.NIST_3072; BigInteger p = group.getP(); BigInteger q = group.getQ(); BigInteger g = group.getG(); String alicePassword = "password"; String bobPassword = "password"; System.out.println("********* Initialization **********"); System.out.println("Public parameters for the cyclic group:"); System.out.println("p (" + p.bitLength() + " bits): " + p.toString(16)); System.out.println("q (" + q.bitLength() + " bits): " + q.toString(16)); System.out.println("g (" + p.bitLength() + " bits): " + g.toString(16)); System.out.println("p mod q = " + p.mod(q).toString(16)); System.out.println("g^{q} mod p = " + g.modPow(q, p).toString(16)); System.out.println(""); System.out.println("(Secret passwords used by Alice and Bob: " + "\"" + alicePassword + "\" and \"" + bobPassword + "\")\n"); /* * Both participants must use the same hashing algorithm. */ Digest digest = new SHA256Digest(); SecureRandom random = new SecureRandom(); JPAKEParticipant alice = new JPAKEParticipant("alice", alicePassword.toCharArray(), group, digest, random); JPAKEParticipant bob = new JPAKEParticipant("bob", bobPassword.toCharArray(), group, digest, random); /* * Round 1 * * Alice and Bob each generate a round 1 payload, and send it to each other. */ JPAKERound1Payload aliceRound1Payload = alice.createRound1PayloadToSend(); JPAKERound1Payload bobRound1Payload = bob.createRound1PayloadToSend(); System.out.println("************ Round 1 **************"); System.out.println("Alice sends to Bob: "); System.out.println("g^{x1}=" + aliceRound1Payload.getGx1().toString(16)); System.out.println("g^{x2}=" + aliceRound1Payload.getGx2().toString(16)); System.out.println("KP{x1}={" + aliceRound1Payload.getKnowledgeProofForX1()[0].toString(16) + "};{" + aliceRound1Payload.getKnowledgeProofForX1()[1].toString(16) + "}"); System.out.println("KP{x2}={" + aliceRound1Payload.getKnowledgeProofForX2()[0].toString(16) + "};{" + aliceRound1Payload.getKnowledgeProofForX2()[1].toString(16) + "}"); System.out.println(""); System.out.println("Bob sends to Alice: "); System.out.println("g^{x3}=" + bobRound1Payload.getGx1().toString(16)); System.out.println("g^{x4}=" + bobRound1Payload.getGx2().toString(16)); System.out.println("KP{x3}={" + bobRound1Payload.getKnowledgeProofForX1()[0].toString(16) + "};{" + bobRound1Payload.getKnowledgeProofForX1()[1].toString(16) + "}"); System.out.println("KP{x4}={" + bobRound1Payload.getKnowledgeProofForX2()[0].toString(16) + "};{" + bobRound1Payload.getKnowledgeProofForX2()[1].toString(16) + "}"); System.out.println(""); /* * Each participant must then validate the received payload for round 1 */ alice.validateRound1PayloadReceived(bobRound1Payload); System.out.println("Alice checks g^{x4}!=1: OK"); System.out.println("Alice checks KP{x3}: OK"); System.out.println("Alice checks KP{x4}: OK"); System.out.println(""); bob.validateRound1PayloadReceived(aliceRound1Payload); System.out.println("Bob checks g^{x2}!=1: OK"); System.out.println("Bob checks KP{x1},: OK"); System.out.println("Bob checks KP{x2},: OK"); System.out.println(""); /* * Round 2 * * Alice and Bob each generate a round 2 payload, and send it to each other. */ JPAKERound2Payload aliceRound2Payload = alice.createRound2PayloadToSend(); JPAKERound2Payload bobRound2Payload = bob.createRound2PayloadToSend(); System.out.println("************ Round 2 **************"); System.out.println("Alice sends to Bob: "); System.out.println("A=" + aliceRound2Payload.getA().toString(16)); System.out.println("KP{x2*s}={" + aliceRound2Payload.getKnowledgeProofForX2s()[0].toString(16) + "},{" + aliceRound2Payload.getKnowledgeProofForX2s()[1].toString(16) + "}"); System.out.println(""); System.out.println("Bob sends to Alice"); System.out.println("B=" + bobRound2Payload.getA().toString(16)); System.out.println("KP{x4*s}={" + bobRound2Payload.getKnowledgeProofForX2s()[0].toString(16) + "},{" + bobRound2Payload.getKnowledgeProofForX2s()[1].toString(16) + "}"); System.out.println(""); /* * Each participant must then validate the received payload for round 2 */ alice.validateRound2PayloadReceived(bobRound2Payload); System.out.println("Alice checks KP{x4*s}: OK\n"); bob.validateRound2PayloadReceived(aliceRound2Payload); System.out.println("Bob checks KP{x2*s}: OK\n"); /* * After round 2, each participant computes the keying material. */ BigInteger aliceKeyingMaterial = alice.calculateKeyingMaterial(); BigInteger bobKeyingMaterial = bob.calculateKeyingMaterial(); System.out.println("********* After round 2 ***********"); System.out.println("Alice computes key material \t K=" + aliceKeyingMaterial.toString(16)); System.out.println("Bob computes key material \t K=" + bobKeyingMaterial.toString(16)); System.out.println(); /* * You must derive a session key from the keying material applicable * to whatever encryption algorithm you want to use. */ BigInteger aliceKey = deriveSessionKey(aliceKeyingMaterial); BigInteger bobKey = deriveSessionKey(bobKeyingMaterial); /* * At this point, you can stop and use the session keys if you want. * This is implicit key confirmation. * * If you want to explicitly confirm that the key material matches, * you can continue on and perform round 3. */ /* * Round 3 * * Alice and Bob each generate a round 3 payload, and send it to each other. */ JPAKERound3Payload aliceRound3Payload = alice.createRound3PayloadToSend(aliceKeyingMaterial); JPAKERound3Payload bobRound3Payload = bob.createRound3PayloadToSend(bobKeyingMaterial); System.out.println("************ Round 3 **************"); System.out.println("Alice sends to Bob: "); System.out.println("MacTag=" + aliceRound3Payload.getMacTag().toString(16)); System.out.println(""); System.out.println("Bob sends to Alice: "); System.out.println("MacTag=" + bobRound3Payload.getMacTag().toString(16)); System.out.println(""); /* * Each participant must then validate the received payload for round 3 */ alice.validateRound3PayloadReceived(bobRound3Payload, aliceKeyingMaterial); System.out.println("Alice checks MacTag: OK\n"); bob.validateRound3PayloadReceived(aliceRound3Payload, bobKeyingMaterial); System.out.println("Bob checks MacTag: OK\n"); System.out.println(); System.out.println("MacTags validated, therefore the keying material matches."); } private static BigInteger deriveSessionKey(BigInteger keyingMaterial) { /* * You should use a secure key derivation function (KDF) to derive the session key. * * For the purposes of this example, I'm just going to use a hash of the keying material. */ SHA256Digest digest = new SHA256Digest(); byte[] keyByteArray = keyingMaterial.toByteArray(); byte[] output = new byte[digest.getDigestSize()]; digest.update(keyByteArray, 0, keyByteArray.length); digest.doFinal(output, 0); return new BigInteger(output); } }





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