private BigInteger[] ParsePublicKey(DSA_Public_Key dpkKey)
{
BigInteger[] biReturn = new BigInteger[4];
biReturn[0] = dpkKey.p;
biReturn[1] = dpkKey.q;
biReturn[2] = dpkKey.g;
biReturn[3] = dpkKey.y;
return(biReturn);
}
private DSA_Public_Key ParsePublicKey(PublicKeyPacket pkpKey)
{
DSA_Public_Key dpkKey = new DSA_Public_Key();
if (pkpKey.Algorithm != AsymAlgorithms.DSA)
{
throw(new System.ArgumentException("The given key is not supposed to be used with DSA!"));
}
if (pkpKey.KeyMaterial.Length != 4)
{
throw(new System.ArgumentException("The given key is not a valid key for DSA!"));
}
dpkKey.p = pkpKey.KeyMaterial[0];
dpkKey.q = pkpKey.KeyMaterial[1];
dpkKey.g = pkpKey.KeyMaterial[2];
dpkKey.y = pkpKey.KeyMaterial[3];
return(dpkKey);
}
/// <summary>
/// Public key operation. Verifies biSignature with the keydata
/// in the given public key packet and returns true if the signature
/// is valid.
/// </summary>
/// <param name="biSignature">The signature that is about to
/// be verified</param>
/// <param name="biHash">The hash value of the signed message.</param>
/// <param name="pkpKey">The public key packet with the key
/// material for the verification.</param>
/// <returns>True if the signature is valid, otherwise
/// false</returns>
/// <remarks>No remarks</remarks>
public override bool Verify(BigInteger[] biSignature, BigInteger biHash, PublicKeyPacket pkpKey)
{
if (biSignature == null)
{
throw new ArgumentNullException("rgbSignature");
}
DSA_Public_Key dpkKey = new DSA_Public_Key();
dpkKey = ParsePublicKey(pkpKey);
try {
BigInteger m = biHash;
BigInteger r = biSignature[0];
BigInteger s = biSignature[1];
if ((r < 0) || (dpkKey.q <= r))
{
return(false);
}
if ((s < 0) || (dpkKey.q <= s))
{
return(false);
}
BigInteger w = s.modInverse(dpkKey.q);
BigInteger u1 = m * w % dpkKey.q;
BigInteger u2 = r * w % dpkKey.q;
u1 = dpkKey.g.modPow(u1, dpkKey.p);
u2 = dpkKey.y.modPow(u2, dpkKey.p);
BigInteger v = ((u1 * u2 % dpkKey.p) % dpkKey.q);
return(v == r);
} catch {
throw new CryptographicException();
}
}
private BigInteger[] ParsePublicKey(DSA_Public_Key dpkKey)
{
BigInteger[] biReturn = new BigInteger[4];
biReturn[0] = dpkKey.p;
biReturn[1] = dpkKey.q;
biReturn[2] = dpkKey.g;
biReturn[3] = dpkKey.y;
return biReturn;
}
private DSA_Public_Key ParsePublicKey(PublicKeyPacket pkpKey)
{
DSA_Public_Key dpkKey = new DSA_Public_Key();
if (pkpKey.Algorithm != AsymAlgorithms.DSA)
throw(new System.ArgumentException("The given key is not supposed to be used with DSA!"));
if (pkpKey.KeyMaterial.Length != 4)
throw(new System.ArgumentException("The given key is not a valid key for DSA!"));
dpkKey.p = pkpKey.KeyMaterial[0];
dpkKey.q = pkpKey.KeyMaterial[1];
dpkKey.g = pkpKey.KeyMaterial[2];
dpkKey.y = pkpKey.KeyMaterial[3];
return dpkKey;
}
/// <summary>
/// Public key operation. Verifies biSignature with the keydata
/// in the given public key packet and returns true if the signature
/// is valid.
/// </summary>
/// <param name="biSignature">The signature that is about to
/// be verified</param>
/// <param name="biHash">The hash value of the signed message.</param>
/// <param name="pkpKey">The public key packet with the key
/// material for the verification.</param>
/// <returns>True if the signature is valid, otherwise
/// false</returns>
/// <remarks>No remarks</remarks>
public override bool Verify(BigInteger[] biSignature, BigInteger biHash, PublicKeyPacket pkpKey)
{
if (biSignature == null)
throw new ArgumentNullException("rgbSignature");
DSA_Public_Key dpkKey = new DSA_Public_Key();
dpkKey = ParsePublicKey(pkpKey);
try {
BigInteger m = biHash;
BigInteger r = biSignature[0];
BigInteger s = biSignature[1];
if ((r < 0) || (dpkKey.q <= r))
return false;
if ((s < 0) || (dpkKey.q <= s))
return false;
BigInteger w = s.modInverse(dpkKey.q);
BigInteger u1 = m * w % dpkKey.q;
BigInteger u2 = r * w % dpkKey.q;
u1 = dpkKey.g.modPow(u1, dpkKey.p);
u2 = dpkKey.y.modPow(u2, dpkKey.p);
BigInteger v = ((u1 * u2 % dpkKey.p) % dpkKey.q);
return (v == r);
} catch {
throw new CryptographicException();
}
}