1 files changed, 85 insertions, 0 deletions
diff --git a/Crypto/src/crypto/agreement/srp/SRP6Utilities.cs b/Crypto/src/crypto/agreement/srp/SRP6Utilities.cs
new file mode 100644
index 000000000..4e790f572
--- /dev/null
+++ b/Crypto/src/crypto/agreement/srp/SRP6Utilities.cs
@@ -0,0 +1,85 @@
+using System;
+
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Security;
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Agreement.Srp
+{
+	public class Srp6Utilities
+	{
+		public static BigInteger CalculateK(IDigest digest, BigInteger N, BigInteger g)
+		{
+			return HashPaddedPair(digest, N, N, g);
+		}
+
+	    public static BigInteger CalculateU(IDigest digest, BigInteger N, BigInteger A, BigInteger B)
+	    {
+	    	return HashPaddedPair(digest, N, A, B);
+	    }
+
+		public static BigInteger CalculateX(IDigest digest, BigInteger N, byte[] salt, byte[] identity, byte[] password)
+	    {
+	        byte[] output = new byte[digest.GetDigestSize()];
+
+	        digest.BlockUpdate(identity, 0, identity.Length);
+	        digest.Update((byte)':');
+	        digest.BlockUpdate(password, 0, password.Length);
+	        digest.DoFinal(output, 0);
+
+	        digest.BlockUpdate(salt, 0, salt.Length);
+	        digest.BlockUpdate(output, 0, output.Length);
+	        digest.DoFinal(output, 0);
+
+	        return new BigInteger(1, output);
+	    }
+
+		public static BigInteger GeneratePrivateValue(IDigest digest, BigInteger N, BigInteger g, SecureRandom random)
+	    {
+			int minBits = System.Math.Min(256, N.BitLength / 2);
+	        BigInteger min = BigInteger.One.ShiftLeft(minBits - 1);
+	        BigInteger max = N.Subtract(BigInteger.One);
+
+	        return BigIntegers.CreateRandomInRange(min, max, random);
+	    }
+
+		public static BigInteger ValidatePublicValue(BigInteger N, BigInteger val)
+		{
+		    val = val.Mod(N);
+
+	        // Check that val % N != 0
+	        if (val.Equals(BigInteger.Zero))
+	            throw new CryptoException("Invalid public value: 0");
+
+		    return val;
+		}
+
+		private static BigInteger HashPaddedPair(IDigest digest, BigInteger N, BigInteger n1, BigInteger n2)
+		{
+	    	int padLength = (N.BitLength + 7) / 8;
+
+	    	byte[] n1_bytes = GetPadded(n1, padLength);
+	    	byte[] n2_bytes = GetPadded(n2, padLength);
+
+	        digest.BlockUpdate(n1_bytes, 0, n1_bytes.Length);
+	        digest.BlockUpdate(n2_bytes, 0, n2_bytes.Length);
+
+	        byte[] output = new byte[digest.GetDigestSize()];
+	        digest.DoFinal(output, 0);
+
+	        return new BigInteger(1, output);
+		}
+
+		private static byte[] GetPadded(BigInteger n, int length)
+		{
+			byte[] bs = BigIntegers.AsUnsignedByteArray(n);
+			if (bs.Length < length)
+			{
+				byte[] tmp = new byte[length];
+				Array.Copy(bs, 0, tmp, length - bs.Length, bs.Length);
+				bs = tmp;
+			}
+			return bs;
+		}
+	}
+}