Org.BouncyCastle.Crypto.Generators.RsaBlindingFactorGenerator.GenerateBlindingFactor C# (CSharp) Method

		public BigInteger GenerateBlindingFactor()
		{
			if (key == null)
				throw new InvalidOperationException("generator not initialised");

			BigInteger m = key.Modulus;
			int length = m.BitLength - 1; // must be less than m.BitLength
			BigInteger factor;
			BigInteger gcd;

			do
			{
				factor = new BigInteger(length, random);
				gcd = factor.Gcd(m);
			}
			while (factor.SignValue == 0 || factor.Equals(BigInteger.One) || !gcd.Equals(BigInteger.One));

			return factor;
		}
	}

		private bool isProcessingOkay(
			RsaKeyParameters    pub,
			RsaKeyParameters    prv,
			byte[]              data,
			SecureRandom        random)
		{
			RsaBlindingFactorGenerator blindFactorGen = new RsaBlindingFactorGenerator();
			RsaBlindingEngine blindingEngine = new RsaBlindingEngine();
			PssSigner blindSigner = new PssSigner(blindingEngine, new Sha1Digest(), 20);
			PssSigner pssEng = new PssSigner(new RsaEngine(), new Sha1Digest(), 20);

			random.NextBytes(data);

			blindFactorGen.Init(pub);

			BigInteger blindFactor = blindFactorGen.GenerateBlindingFactor();
			RsaBlindingParameters parameters = new RsaBlindingParameters(pub, blindFactor);

			// generate a blind signature
			blindSigner.Init(true, new ParametersWithRandom(parameters, random));

			blindSigner.BlockUpdate(data, 0, data.Length);

			byte[] blindedData = blindSigner.GenerateSignature();

			RsaEngine signerEngine = new RsaEngine();

			signerEngine.Init(true, prv);

			byte[] blindedSig = signerEngine.ProcessBlock(blindedData, 0, blindedData.Length);

			// unblind the signature
			blindingEngine.Init(false, parameters);

			byte[] s = blindingEngine.ProcessBlock(blindedSig, 0, blindedSig.Length);

			//verify signature with PssSigner
			pssEng.Init(false, pub);
			pssEng.BlockUpdate(data, 0, data.Length);

			return pssEng.VerifySignature(s);
		}