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Assets/BestHTTP/SecureProtocol/crypto/generators/DsaKeyPairGenerator.cs

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+#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
+
+using System;
+
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Math.EC.Multiplier;
+using Org.BouncyCastle.Security;
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Generators
+{
+    /**
+     * a DSA key pair generator.
+     *
+     * This Generates DSA keys in line with the method described
+     * in <i>FIPS 186-3 B.1 FFC Key Pair Generation</i>.
+     */
+    public class DsaKeyPairGenerator
+        : IAsymmetricCipherKeyPairGenerator
+    {
+        private static readonly BigInteger One = BigInteger.One;
+
+        private DsaKeyGenerationParameters param;
+
+        public void Init(
+            KeyGenerationParameters parameters)
+        {
+            if (parameters == null)
+                throw new ArgumentNullException("parameters");
+
+            // Note: If we start accepting instances of KeyGenerationParameters,
+            // must apply constraint checking on strength (see DsaParametersGenerator.Init)
+
+            this.param = (DsaKeyGenerationParameters) parameters;
+        }
+
+        public AsymmetricCipherKeyPair GenerateKeyPair()
+        {
+            DsaParameters dsaParams = param.Parameters;
+
+            BigInteger x = GeneratePrivateKey(dsaParams.Q, param.Random);
+            BigInteger y = CalculatePublicKey(dsaParams.P, dsaParams.G, x);
+
+            return new AsymmetricCipherKeyPair(
+                new DsaPublicKeyParameters(y, dsaParams),
+                new DsaPrivateKeyParameters(x, dsaParams));
+        }
+
+        private static BigInteger GeneratePrivateKey(BigInteger q, SecureRandom random)
+        {
+            // B.1.2 Key Pair Generation by Testing Candidates
+            int minWeight = q.BitLength >> 2;
+            for (;;)
+            {
+                // TODO Prefer this method? (change test cases that used fixed random)
+                // B.1.1 Key Pair Generation Using Extra Random Bits
+                //BigInteger x = new BigInteger(q.BitLength + 64, random).Mod(q.Subtract(One)).Add(One);
+
+                BigInteger x = BigIntegers.CreateRandomInRange(One, q.Subtract(One), random);
+                if (WNafUtilities.GetNafWeight(x) >= minWeight)
+                {
+                    return x;
+                }
+            }
+        }
+
+        private static BigInteger CalculatePublicKey(BigInteger p, BigInteger g, BigInteger x)
+        {
+            return g.ModPow(x, p);
+        }
+    }
+}
+
+#endif