1 files changed, 156 insertions, 0 deletions
diff --git a/Crypto/src/crypto/signers/ECDsaSigner.cs b/Crypto/src/crypto/signers/ECDsaSigner.cs
new file mode 100644
index 000000000..4254e5590
--- /dev/null
+++ b/Crypto/src/crypto/signers/ECDsaSigner.cs
@@ -0,0 +1,156 @@
+using System;
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Math.EC;
+using Org.BouncyCastle.Security;
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Crypto.Digests;
+using Org.BouncyCastle.Crypto.Parameters;
+
+namespace Org.BouncyCastle.Crypto.Signers
+{
+ /**
+ * EC-DSA as described in X9.62
+ */
+ public class ECDsaSigner
+ : IDsa
+ {
+ private ECKeyParameters key;
+ private SecureRandom random;
+
+ public string AlgorithmName
+ {
+ get { return "ECDSA"; }
+ }
+
+ public void Init(
+ bool forSigning,
+ ICipherParameters parameters)
+ {
+ if (forSigning)
+ {
+ if (parameters is ParametersWithRandom)
+ {
+ ParametersWithRandom rParam = (ParametersWithRandom) parameters;
+
+ this.random = rParam.Random;
+ parameters = rParam.Parameters;
+ }
+ else
+ {
+ this.random = new SecureRandom();
+ }
+
+ if (!(parameters is ECPrivateKeyParameters))
+ throw new InvalidKeyException("EC private key required for signing");
+
+ this.key = (ECPrivateKeyParameters) parameters;
+ }
+ else
+ {
+ if (!(parameters is ECPublicKeyParameters))
+ throw new InvalidKeyException("EC public key required for verification");
+
+ this.key = (ECPublicKeyParameters) parameters;
+ }
+ }
+
+ // 5.3 pg 28
+ /**
+ * Generate a signature for the given message using the key we were
+ * initialised with. For conventional DSA the message should be a SHA-1
+ * hash of the message of interest.
+ *
+ * @param message the message that will be verified later.
+ */
+ public BigInteger[] GenerateSignature(
+ byte[] message)
+ {
+ BigInteger n = key.Parameters.N;
+ BigInteger e = calculateE(n, message);
+
+ BigInteger r = null;
+ BigInteger s = null;
+
+ // 5.3.2
+ do // Generate s
+ {
+ BigInteger k = null;
+
+ do // Generate r
+ {
+ do
+ {
+ k = new BigInteger(n.BitLength, random);
+ }
+ while (k.SignValue == 0 || k.CompareTo(n) >= 0);
+
+ ECPoint p = key.Parameters.G.Multiply(k);
+
+ // 5.3.3
+ BigInteger x = p.X.ToBigInteger();
+
+ r = x.Mod(n);
+ }
+ while (r.SignValue == 0);
+
+ BigInteger d = ((ECPrivateKeyParameters)key).D;
+
+ s = k.ModInverse(n).Multiply(e.Add(d.Multiply(r).Mod(n))).Mod(n);
+ }
+ while (s.SignValue == 0);
+
+ return new BigInteger[]{ r, s };
+ }
+
+ // 5.4 pg 29
+ /**
+ * return true if the value r and s represent a DSA signature for
+ * the passed in message (for standard DSA the message should be
+ * a SHA-1 hash of the real message to be verified).
+ */
+ public bool VerifySignature(
+ byte[] message,
+ BigInteger r,
+ BigInteger s)
+ {
+ BigInteger n = key.Parameters.N;
+
+ // r and s should both in the range [1,n-1]
+ if (r.SignValue < 1 || s.SignValue < 1
+ || r.CompareTo(n) >= 0 || s.CompareTo(n) >= 0)
+ {
+ return false;
+ }
+
+ BigInteger e = calculateE(n, message);
+ BigInteger c = s.ModInverse(n);
+
+ BigInteger u1 = e.Multiply(c).Mod(n);
+ BigInteger u2 = r.Multiply(c).Mod(n);
+
+ ECPoint G = key.Parameters.G;
+ ECPoint Q = ((ECPublicKeyParameters) key).Q;
+
+ ECPoint point = ECAlgorithms.SumOfTwoMultiplies(G, u1, Q, u2);
+
+ BigInteger v = point.X.ToBigInteger().Mod(n);
+
+ return v.Equals(r);
+ }
+
+ private BigInteger calculateE(
+ BigInteger n,
+ byte[] message)
+ {
+ int messageBitLength = message.Length * 8;
+ BigInteger trunc = new BigInteger(1, message);
+
+ if (n.BitLength < messageBitLength)
+ {
+ trunc = trunc.ShiftRight(messageBitLength - n.BitLength);
+ }
+
+ return trunc;
+ }
+ }
+}
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