/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.sshd.common.random;
import java.security.SecureRandom;
import org.apache.sshd.common.NamedFactory;
import org.apache.sshd.common.Random;
import org.bouncycastle.crypto.prng.RandomGenerator;
import org.bouncycastle.crypto.prng.VMPCRandomGenerator;
/**
* BouncyCastle <code>Random</code>.
* This pseudo random number generator uses the a very fast PRNG from BouncyCastle.
* The JRE random will be used when creating a new generator to add some random
* data to the seed.
*
* @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
*/
public class BouncyCastleRandom implements Random {
/**
* Named factory for the BouncyCastle <code>Random</code>
*/
public static class Factory implements NamedFactory<Random> {
public String getName() {
return "bouncycastle";
}
public Random create() {
return new BouncyCastleRandom();
}
}
private final RandomGenerator random;
public BouncyCastleRandom() {
this.random = new VMPCRandomGenerator();
byte[] seed = new SecureRandom().generateSeed(8);
this.random.addSeedMaterial(seed);
}
public void fill(byte[] bytes, int start, int len) {
this.random.nextBytes(bytes, start, len);
}
/**
* Returns a pseudo-random uniformly distributed {@code int}
* in the half-open range [0, n).
*/
public int random(int n) {
if (n > 0) {
if ((n & -n) == n) {
return (int)((n * (long) next(31)) >> 31);
}
int bits, val;
do {
bits = next(31);
val = bits % n;
} while (bits - val + (n-1) < 0);
return val;
}
throw new IllegalArgumentException();
}
final protected int next(int numBits) {
int bytes = (numBits+7)/8;
byte next[] = new byte[bytes];
int ret = 0;
random.nextBytes(next);
for (int i = 0; i < bytes; i++) {
ret = (next[i] & 0xFF) | (ret << 8);
}
return ret >>> (bytes*8 - numBits);
}
}