protected virtual AsymmetricCipherKeyPair GenerateECKeyPair(ECDomainParameters ecParams)
{
ECKeyPairGenerator keyPairGenerator = new ECKeyPairGenerator();
ECKeyGenerationParameters keyGenerationParameters = new ECKeyGenerationParameters(ecParams,
context.SecureRandom);
keyPairGenerator.Init(keyGenerationParameters);
return keyPairGenerator.GenerateKeyPair();
}
// Section 7.2.5 ECSP-NR, pg 34
/**
* generate a signature for the given message using the key we were
* initialised with. Generally, the order of the curve should be at
* least as long as the hash of the message of interest, and with
* ECNR it *must* be at least as long.
*
* @param digest the digest to be signed.
* @exception DataLengthException if the digest is longer than the key allows
*/
public BigInteger[] GenerateSignature(
byte[] message)
{
if (!this.forSigning)
{
// not properly initilaized... deal with it
throw new InvalidOperationException("not initialised for signing");
}
BigInteger n = ((ECPrivateKeyParameters) this.key).Parameters.N;
int nBitLength = n.BitLength;
BigInteger e = new BigInteger(1, message);
int eBitLength = e.BitLength;
ECPrivateKeyParameters privKey = (ECPrivateKeyParameters)key;
if (eBitLength > nBitLength)
{
throw new DataLengthException("input too large for ECNR key.");
}
BigInteger r = null;
BigInteger s = null;
AsymmetricCipherKeyPair tempPair;
do // generate r
{
// generate another, but very temporary, key pair using
// the same EC parameters
ECKeyPairGenerator keyGen = new ECKeyPairGenerator();
keyGen.Init(new ECKeyGenerationParameters(privKey.Parameters, this.random));
tempPair = keyGen.GenerateKeyPair();
// BigInteger Vx = tempPair.getPublic().getW().getAffineX();
ECPublicKeyParameters V = (ECPublicKeyParameters) tempPair.Public; // get temp's public key
BigInteger Vx = V.Q.X.ToBigInteger(); // get the point's x coordinate
r = Vx.Add(e).Mod(n);
}
while (r.Sign == 0);
// generate s
BigInteger x = privKey.D; // private key value
BigInteger u = ((ECPrivateKeyParameters) tempPair.Private).D; // temp's private key value
s = u.Subtract(r.Multiply(x)).Mod(n);
return new BigInteger[]{ r, s };
}
