Bitcoin Forum

import org.spongycastle.crypto.signers.ECDSASigner;

    /**
     * Signs the given hash and returns the R and S components as BigIntegers. In the Bitcoin protocol, they are
     * usually encoded using DER format, so you want {@link ECKey#signToDER(Sha256Hash)} instead. However sometimes
     * the independent components can be useful, for instance, if you're doing to do further EC maths on them.
     * @throws IllegalStateException if this ECKey doesn't have a private part.
     */
    public ECDSASignature sign(Sha256Hash input) {
        if (priv == null)
            throw new IllegalStateException("This ECKey does not have the private key necessary for signing.");
        ECDSASigner signer = new ECDSASigner();
        ECPrivateKeyParameters privKey = new ECPrivateKeyParameters(priv, ecParams);
        signer.init(true, privKey);
        BigInteger[] sigs = signer.generateSignature(input.getBytes());
        return new ECDSASignature(sigs[0], sigs[1]);
    }

k = new BigInteger(nBitLength, random);

1    Calculate e = HASH(m), where HASH is a cryptographic hash function, such as SHA-1.
2    Let z be the Ln leftmost bits of e, where Ln is the bit length of the group order n.
3    Select a random integer k from [1, n-1].
*4    If (k, privkey) pair is in kPrivKey dictionary, go to step 4
5    Calculate the curve point (x1, y1) = k * G.
6    Calculate r = x1 (mod n). If r = 0, go back to step 3.
7    Calculate s = k-1(z + r dA) (mod n). If s = 0, go back to step 3.
8    The signature is the pair (r, s).
*9    Insert (k, privkey) into kPrivKey dictionary

import org.spongycastle.crypto.signers.ECDSASigner;

    /**
     * Signs the given hash and returns the R and S components as BigIntegers. In the Bitcoin protocol, they are
     * usually encoded using DER format, so you want {@link ECKey#signToDER(Sha256Hash)} instead. However sometimes
     * the independent components can be useful, for instance, if you're doing to do further EC maths on them.
     * @throws IllegalStateException if this ECKey doesn't have a private part.
     */
    public ECDSASignature sign(Sha256Hash input) {
        if (priv == null)
            throw new IllegalStateException("This ECKey does not have the private key necessary for signing.");
        [b]ECDSASigner[/b] signer = new ECDSASigner();
        [b]ECPrivateKeyParameters[b] privKey = new ECPrivateKeyParameters(priv, ecParams);
        [b]signer.init(true, privKey);[/b]
        BigInteger[] sigs = signer.generateSignature(input.getBytes());
        return new ECDSASignature(sigs[0], sigs[1]);
    }

import org.spongycastle.crypto.params.ECPrivateKeyParameters;
public class ECDSASigner
    implements ECConstants, DSA
{
    ECKeyParameters key;

    SecureRandom    random;

    public void init(
        boolean                 forSigning,
        CipherParameters        param)
    {
        if (forSigning)
        {
            [b]if (param instanceof ParametersWithRandom)[/b]
            {
                ParametersWithRandom    rParam = (ParametersWithRandom)param;

                this.random = rParam.getRandom();
                this.key = (ECPrivateKeyParameters)rParam.getParameters();
            }
            else
            {
                this.random = new SecureRandom();
                this.key = (ECPrivateKeyParameters)param;
            }
        }
        else
        {
            this.key = (ECPublicKeyParameters)param;
        }
    }

public class ECPrivateKeyParameters
    extends ECKeyParameters

public class ECKeyParameters
    extends AsymmetricKeyParameter

public class AsymmetricKeyParameter
    implements CipherParameters

public interface CipherParameters
{
}

SecureRandom r = SecureRandom.getInstance(....);

r.setSeed(0x0123456789ABCDEFL);

SecureRandom r = SecureRandom.getInstance(....);

r.nextInt();

r.setSeed(0x0123456789ABCDEFL);