Org.BouncyCastle.Crypto.Signers.DsaSigner.VerifySignature C# (CSharp) Method

		public 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);
		}

        public void TestNONEwithDSA()
        {
            byte[] dummySha1 = Hex.Decode("01020304050607080910111213141516");

            SecureRandom rand = new SecureRandom();

            DsaParametersGenerator pGen = new DsaParametersGenerator();
            pGen.Init(512, 80, rand);

            IAsymmetricCipherKeyPairGenerator g = GeneratorUtilities.GetKeyPairGenerator("DSA");
            g.Init(new DsaKeyGenerationParameters(rand, pGen.GenerateParameters()));

            IAsymmetricCipherKeyPair kp = g.GenerateKeyPair();

            ISigner sig = SignerUtilities.GetSigner("NONEwithDSA");
            sig.Init(true, kp.Private);
            sig.BlockUpdate(dummySha1, 0, dummySha1.Length);
            byte[] sigBytes = sig.GenerateSignature();

            sig.Init(false, kp.Public);
            sig.BlockUpdate(dummySha1, 0, dummySha1.Length);
            sig.VerifySignature(sigBytes);

            // reset test

            sig.BlockUpdate(dummySha1, 0, dummySha1.Length);

            if (!sig.VerifySignature(sigBytes))
            {
                Fail("NONEwithDSA failed to reset");
            }

            // lightweight test
            DsaSigner signer = new DsaSigner();
            Asn1Sequence derSig = Asn1Sequence.GetInstance(Asn1Object.FromByteArray(sigBytes));

            signer.Init(false, kp.Public);

            if (!signer.VerifySignature(dummySha1,
                DerInteger.GetInstance(derSig[0]).Value, DerInteger.GetInstance(derSig[1]).Value))
            {
                Fail("NONEwithDSA not really NONE!");
            }
        }