98 lines
1.9 KiB
C#
98 lines
1.9 KiB
C#
using System;
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using System.Threading;
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namespace Org.BouncyCastle.Crypto.Prng
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{
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/**
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* A thread based seed generator - one source of randomness.
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* <p>
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* Based on an idea from Marcus Lippert.
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* </p>
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*/
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public class ThreadedSeedGenerator
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{
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private class SeedGenerator
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{
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#if NETCF_1_0
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// No volatile keyword, but all fields implicitly volatile anyway
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private int counter = 0;
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private bool stop = false;
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#else
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private volatile int counter = 0;
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private volatile bool stop = false;
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#endif
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private void Run(object ignored)
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{
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while (!this.stop)
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{
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this.counter++;
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}
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}
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public byte[] GenerateSeed(
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int numBytes,
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bool fast)
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{
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this.counter = 0;
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this.stop = false;
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byte[] result = new byte[numBytes];
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int last = 0;
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int end = fast ? numBytes : numBytes * 8;
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ThreadPool.QueueUserWorkItem(new WaitCallback(Run));
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for (int i = 0; i < end; i++)
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{
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while (this.counter == last)
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{
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try
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{
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Thread.Sleep(1);
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}
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catch (Exception)
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{
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// ignore
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}
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}
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last = this.counter;
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if (fast)
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{
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result[i] = (byte) last;
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}
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else
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{
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int bytepos = i / 8;
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result[bytepos] = (byte) ((result[bytepos] << 1) | (last & 1));
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}
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}
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this.stop = true;
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return result;
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}
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}
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/**
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* Generate seed bytes. Set fast to false for best quality.
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* <p>
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* If fast is set to true, the code should be round about 8 times faster when
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* generating a long sequence of random bytes. 20 bytes of random values using
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* the fast mode take less than half a second on a Nokia e70. If fast is set to false,
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* it takes round about 2500 ms.
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* </p>
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* @param numBytes the number of bytes to generate
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* @param fast true if fast mode should be used
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*/
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public byte[] GenerateSeed(
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int numBytes,
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bool fast)
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{
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return new SeedGenerator().GenerateSeed(numBytes, fast);
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}
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}
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}
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