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Assets/BestHTTP/SecureProtocol/crypto/prng/DigestRandomGenerator.cs

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+#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
+
+using System;
+
+using Org.BouncyCastle.Crypto.Digests;
+using Org.BouncyCastle.Crypto.Utilities;
+
+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)
+		{
+            byte[] bytes = new byte[8];
+            Pack.UInt64_To_LE((ulong)seedVal, bytes);
+            digest.BlockUpdate(bytes, 0, bytes.Length);
+		}
+
+        private void DigestUpdate(byte[] inSeed)
+		{
+			digest.BlockUpdate(inSeed, 0, inSeed.Length);
+		}
+
+		private void DigestDoFinal(byte[] result)
+		{
+			digest.DoFinal(result, 0);
+		}
+	}
+}
+
+#endif