Example #1
0
        // 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 virtual 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).Normalize();

            if (point.IsInfinity)
                return false;

            BigInteger v = point.AffineXCoord.ToBigInteger().Mod(n);

            return v.Equals(r);
        }
Example #2
0
        /**
         * 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 virtual bool VerifySignature(byte[] message, BigInteger r, BigInteger s)
        {
            DsaParameters parameters = key.Parameters;
            BigInteger q = parameters.Q;
            BigInteger m = CalculateE(q, message);

            if (r.SignValue <= 0 || q.CompareTo(r) <= 0)
            {
                return false;
            }

            if (s.SignValue <= 0 || q.CompareTo(s) <= 0)
            {
                return false;
            }

            BigInteger w = s.ModInverse(q);

            BigInteger u1 = m.Multiply(w).Mod(q);
            BigInteger u2 = r.Multiply(w).Mod(q);

            BigInteger p = parameters.P;
            u1 = parameters.G.ModPow(u1, p);
            u2 = ((DsaPublicKeyParameters)key).Y.ModPow(u2, p);

            BigInteger v = u1.Multiply(u2).Mod(p).Mod(q);

            return v.Equals(r);
        }
Example #3
0
		// 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 virtual 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);

			if(point.IsInfinity)
				return false;

			/*
             * If possible, avoid normalizing the point (to save a modular inversion in the curve field).
             * 
             * There are ~cofactor elements of the curve field that reduce (modulo the group order) to 'r'.
             * If the cofactor is known and small, we generate those possible field values and project each
             * of them to the same "denominator" (depending on the particular projective coordinates in use)
             * as the calculated point.X. If any of the projected values matches point.X, then we have:
             *     (point.X / Denominator mod p) mod n == r
             * as required, and verification succeeds.
             * 
             * Based on an original idea by Gregory Maxwell (https://github.com/gmaxwell), as implemented in
             * the libsecp256k1 project (https://github.com/bitcoin/secp256k1).
             */
			ECCurve curve = point.Curve;
			if(curve != null)
			{
				BigInteger cofactor = curve.Cofactor;
				if(cofactor != null && cofactor.CompareTo(Eight) <= 0)
				{
					ECFieldElement D = GetDenominator(curve.CoordinateSystem, point);
					if(D != null && !D.IsZero)
					{
						ECFieldElement X = point.XCoord;
						while(curve.IsValidFieldElement(r))
						{
							ECFieldElement R = curve.FromBigInteger(r).Multiply(D);
							if(R.Equals(X))
							{
								return true;
							}
							r = r.Add(n);
						}
						return false;
					}
				}
			}

			BigInteger v = point.Normalize().AffineXCoord.ToBigInteger().Mod(n);
			return v.Equals(r);
		}
Example #4
0
        /**
         * return true if the value r and s represent a GOST3410 signature for
         * the passed in message (for standard GOST3410 the message should be
         * a GOST3411 hash of the real message to be verified).
         */
        public bool VerifySignature(
            byte[]		message,
            BigInteger	r,
            BigInteger	s)
        {
            byte[] mRev = new byte[message.Length]; // conversion is little-endian
            for (int i = 0; i != mRev.Length; i++)
            {
                mRev[i] = message[mRev.Length - 1 - i];
            }

            BigInteger e = new BigInteger(1, mRev);
            BigInteger n = key.Parameters.N;

            // r in the range [1,n-1]
            if (r.CompareTo(BigInteger.One) < 0 || r.CompareTo(n) >= 0)
            {
                return false;
            }

            // s in the range [1,n-1]
            if (s.CompareTo(BigInteger.One) < 0 || s.CompareTo(n) >= 0)
            {
                return false;
            }

            BigInteger v = e.ModInverse(n);

            BigInteger z1 = s.Multiply(v).Mod(n);
            BigInteger z2 = (n.Subtract(r)).Multiply(v).Mod(n);

            ECPoint G = key.Parameters.G; // P
            ECPoint Q = ((ECPublicKeyParameters)key).Q;

            ECPoint point = ECAlgorithms.SumOfTwoMultiplies(G, z1, Q, z2).Normalize();

            if (point.IsInfinity)
                return false;

            BigInteger R = point.AffineXCoord.ToBigInteger().Mod(n);

            return R.Equals(r);
        }