133 lines
3.2 KiB
C#
133 lines
3.2 KiB
C#
using System;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.Math;
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using Org.BouncyCastle.Security;
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namespace Org.BouncyCastle.Crypto.Signers
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{
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/**
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* Gost R 34.10-94 Signature Algorithm
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*/
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public class Gost3410Signer
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: IDsa
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{
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private Gost3410KeyParameters key;
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private SecureRandom random;
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public string AlgorithmName
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{
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get { return "GOST3410"; }
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}
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public void Init(
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bool forSigning,
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ICipherParameters parameters)
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{
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if (forSigning)
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{
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if (parameters is ParametersWithRandom)
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{
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ParametersWithRandom rParam = (ParametersWithRandom)parameters;
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this.random = rParam.Random;
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parameters = rParam.Parameters;
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}
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else
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{
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this.random = new SecureRandom();
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}
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if (!(parameters is Gost3410PrivateKeyParameters))
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throw new InvalidKeyException("GOST3410 private key required for signing");
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this.key = (Gost3410PrivateKeyParameters) parameters;
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}
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else
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{
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if (!(parameters is Gost3410PublicKeyParameters))
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throw new InvalidKeyException("GOST3410 public key required for signing");
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this.key = (Gost3410PublicKeyParameters) parameters;
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}
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}
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/**
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* generate a signature for the given message using the key we were
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* initialised with. For conventional Gost3410 the message should be a Gost3411
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* hash of the message of interest.
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*
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* @param message the message that will be verified later.
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*/
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public BigInteger[] GenerateSignature(
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byte[] message)
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{
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byte[] mRev = new byte[message.Length]; // conversion is little-endian
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for (int i = 0; i != mRev.Length; i++)
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{
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mRev[i] = message[mRev.Length - 1 - i];
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}
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BigInteger m = new BigInteger(1, mRev);
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Gost3410Parameters parameters = key.Parameters;
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BigInteger k;
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do
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{
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k = new BigInteger(parameters.Q.BitLength, random);
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}
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while (k.CompareTo(parameters.Q) >= 0);
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BigInteger r = parameters.A.ModPow(k, parameters.P).Mod(parameters.Q);
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BigInteger s = k.Multiply(m).
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Add(((Gost3410PrivateKeyParameters)key).X.Multiply(r)).
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Mod(parameters.Q);
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return new BigInteger[]{ r, s };
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}
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/**
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* return true if the value r and s represent a Gost3410 signature for
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* the passed in message for standard Gost3410 the message should be a
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* Gost3411 hash of the real message to be verified.
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*/
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public bool VerifySignature(
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byte[] message,
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BigInteger r,
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BigInteger s)
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{
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byte[] mRev = new byte[message.Length]; // conversion is little-endian
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for (int i = 0; i != mRev.Length; i++)
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{
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mRev[i] = message[mRev.Length - 1 - i];
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}
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BigInteger m = new BigInteger(1, mRev);
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Gost3410Parameters parameters = key.Parameters;
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if (r.SignValue < 0 || parameters.Q.CompareTo(r) <= 0)
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{
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return false;
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}
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if (s.SignValue < 0 || parameters.Q.CompareTo(s) <= 0)
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{
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return false;
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}
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BigInteger v = m.ModPow(parameters.Q.Subtract(BigInteger.Two), parameters.Q);
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BigInteger z1 = s.Multiply(v).Mod(parameters.Q);
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BigInteger z2 = (parameters.Q.Subtract(r)).Multiply(v).Mod(parameters.Q);
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z1 = parameters.A.ModPow(z1, parameters.P);
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z2 = ((Gost3410PublicKeyParameters)key).Y.ModPow(z2, parameters.P);
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BigInteger u = z1.Multiply(z2).Mod(parameters.P).Mod(parameters.Q);
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return u.Equals(r);
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}
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}
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}
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