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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 with debug enabled.

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package org.bouncycastle.crypto.prng;

import org.bouncycastle.crypto.Digest;

/**
 * Random generation based on the digest with counter. Calling addSeedMaterial will
 * always increase the entropy of the hash.
 * 

* Internal access to the digest is synchronized so a single one of these can be shared. *

*/ public class DigestRandomGenerator implements RandomGenerator { private static long CYCLE_COUNT = 10; private long stateCounter; private long seedCounter; private Digest digest; private byte[] state; private byte[] seed; // public constructors public DigestRandomGenerator( Digest digest) { this.digest = digest; this.seed = new byte[digest.getDigestSize()]; this.seedCounter = 1; this.state = new byte[digest.getDigestSize()]; this.stateCounter = 1; } public void addSeedMaterial(byte[] inSeed) { synchronized (this) { digestUpdate(inSeed); digestUpdate(seed); digestDoFinal(seed); } } public void addSeedMaterial(long rSeed) { synchronized (this) { digestAddCounter(rSeed); digestUpdate(seed); digestDoFinal(seed); } } public void nextBytes(byte[] bytes) { nextBytes(bytes, 0, bytes.length); } public void nextBytes(byte[] bytes, int start, int len) { synchronized (this) { int stateOff = 0; generateState(); int end = start + len; for (int i = start; i != end; i++) { if (stateOff == state.length) { generateState(); stateOff = 0; } bytes[i] = state[stateOff++]; } } } private void cycleSeed() { digestUpdate(seed); digestAddCounter(seedCounter++); digestDoFinal(seed); } private void generateState() { digestAddCounter(stateCounter++); digestUpdate(state); digestUpdate(seed); digestDoFinal(state); if ((stateCounter % CYCLE_COUNT) == 0) { cycleSeed(); } } private void digestAddCounter(long seed) { for (int i = 0; i != 8; i++) { digest.update((byte)seed); seed >>>= 8; } } private void digestUpdate(byte[] inSeed) { digest.update(inSeed, 0, inSeed.length); } private void digestDoFinal(byte[] result) { digest.doFinal(result, 0); } }




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