1 files changed, 129 insertions, 0 deletions
diff --git a/crypto/src/crypto/prng/DigestRandomGenerator.cs b/crypto/src/crypto/prng/DigestRandomGenerator.cs
new file mode 100644
index 000000000..cbd2ef060
--- /dev/null
+++ b/crypto/src/crypto/prng/DigestRandomGenerator.cs
@@ -0,0 +1,129 @@
+using System;
+
+using Org.BouncyCastle.Crypto.Digests;
+
+namespace Org.BouncyCastle.Crypto.Prng
+{
+ /**
+ * Random generation based on the digest with counter. Calling AddSeedMaterial will
+ * always increase the entropy of the hash.
+ * <p>
+ * Internal access to the digest is synchronized so a single one of these can be shared.
+ * </p>
+ */
+ public class DigestRandomGenerator
+ : IRandomGenerator
+ {
+ private const long CYCLE_COUNT = 10;
+
+ private long stateCounter;
+ private long seedCounter;
+ private IDigest digest;
+ private byte[] state;
+ private byte[] seed;
+
+ public DigestRandomGenerator(
+ IDigest 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)
+ {
+ lock (this)
+ {
+ DigestUpdate(inSeed);
+ DigestUpdate(seed);
+ DigestDoFinal(seed);
+ }
+ }
+
+ public void AddSeedMaterial(
+ long rSeed)
+ {
+ lock (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)
+ {
+ lock (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 seedVal)
+ {
+ ulong seed = (ulong)seedVal;
+ for (int i = 0; i != 8; i++)
+ {
+ digest.Update((byte)seed);
+ seed >>= 8;
+ }
+ }
+
+ private void DigestUpdate(byte[] inSeed)
+ {
+ digest.BlockUpdate(inSeed, 0, inSeed.Length);
+ }
+
+ private void DigestDoFinal(byte[] result)
+ {
+ digest.DoFinal(result, 0);
+ }
+ }
+}
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