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package org.bouncycastle.crypto.generators;
import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.AsymmetricCipherKeyPairGenerator;
import org.bouncycastle.crypto.KeyGenerationParameters;
import org.bouncycastle.crypto.params.GOST3410KeyGenerationParameters;
import org.bouncycastle.crypto.params.GOST3410Parameters;
import org.bouncycastle.crypto.params.GOST3410PrivateKeyParameters;
import org.bouncycastle.crypto.params.GOST3410PublicKeyParameters;
import org.bouncycastle.math.ec.WNafUtil;
import java.math.BigInteger;
import java.security.SecureRandom;
/**
* a GOST3410 key pair generator.
* This generates GOST3410 keys in line with the method described
* in GOST R 34.10-94.
*/
public class GOST3410KeyPairGenerator
implements AsymmetricCipherKeyPairGenerator
{
private GOST3410KeyGenerationParameters param;
public void init(
KeyGenerationParameters param)
{
this.param = (GOST3410KeyGenerationParameters)param;
}
public AsymmetricCipherKeyPair generateKeyPair()
{
BigInteger p, q, a, x, y;
GOST3410Parameters GOST3410Params = param.getParameters();
SecureRandom random = param.getRandom();
q = GOST3410Params.getQ();
p = GOST3410Params.getP();
a = GOST3410Params.getA();
int minWeight = 64;
for (;;)
{
x = new BigInteger(256, random);
if (x.signum() < 1 || x.compareTo(q) >= 0)
{
continue;
}
/*
* Require a minimum weight of the NAF representation, since low-weight primes may be
* weak against a version of the number-field-sieve for the discrete-logarithm-problem.
*
* See "The number field sieve for integers of low weight", Oliver Schirokauer.
*/
if (WNafUtil.getNafWeight(x) < minWeight)
{
continue;
}
break;
}
//
// calculate the public key.
//
y = a.modPow(x, p);
return new AsymmetricCipherKeyPair(
new GOST3410PublicKeyParameters(y, GOST3410Params),
new GOST3410PrivateKeyParameters(x, GOST3410Params));
}
}
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