init commit

output/Libraries/BouncyCastle.Crypto/Org/BouncyCastle/Crypto/Engines/RsaBlindingEngine.cs

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+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.Math;
+
+namespace Org.BouncyCastle.Crypto.Engines;
+
+public class RsaBlindingEngine : IAsymmetricBlockCipher
+{
+	private readonly IRsa core;
+
+	private RsaKeyParameters key;
+
+	private BigInteger blindingFactor;
+
+	private bool forEncryption;
+
+	public virtual string AlgorithmName => "RSA";
+
+	public RsaBlindingEngine()
+		: this(new RsaCoreEngine())
+	{
+	}
+
+	public RsaBlindingEngine(IRsa rsa)
+	{
+		core = rsa;
+	}
+
+	public virtual void Init(bool forEncryption, ICipherParameters param)
+	{
+		RsaBlindingParameters rsaBlindingParameters;
+		if (param is ParametersWithRandom)
+		{
+			ParametersWithRandom parametersWithRandom = (ParametersWithRandom)param;
+			rsaBlindingParameters = (RsaBlindingParameters)parametersWithRandom.Parameters;
+		}
+		else
+		{
+			rsaBlindingParameters = (RsaBlindingParameters)param;
+		}
+		core.Init(forEncryption, rsaBlindingParameters.PublicKey);
+		this.forEncryption = forEncryption;
+		key = rsaBlindingParameters.PublicKey;
+		blindingFactor = rsaBlindingParameters.BlindingFactor;
+	}
+
+	public virtual int GetInputBlockSize()
+	{
+		return core.GetInputBlockSize();
+	}
+
+	public virtual int GetOutputBlockSize()
+	{
+		return core.GetOutputBlockSize();
+	}
+
+	public virtual byte[] ProcessBlock(byte[] inBuf, int inOff, int inLen)
+	{
+		BigInteger bigInteger = core.ConvertInput(inBuf, inOff, inLen);
+		bigInteger = ((!forEncryption) ? UnblindMessage(bigInteger) : BlindMessage(bigInteger));
+		return core.ConvertOutput(bigInteger);
+	}
+
+	private BigInteger BlindMessage(BigInteger msg)
+	{
+		BigInteger bigInteger = blindingFactor;
+		bigInteger = msg.Multiply(bigInteger.ModPow(key.Exponent, key.Modulus));
+		return bigInteger.Mod(key.Modulus);
+	}
+
+	private BigInteger UnblindMessage(BigInteger blindedMsg)
+	{
+		BigInteger modulus = key.Modulus;
+		BigInteger bigInteger = blindedMsg;
+		BigInteger val = blindingFactor.ModInverse(modulus);
+		bigInteger = bigInteger.Multiply(val);
+		return bigInteger.Mod(modulus);
+	}
+}