Examples with SHA1Digest org.gudy.bouncycastle.crypto.digests.SHA1Digest used on opensource projects

Example 1 with SHA1Digest

use of org.gudy.bouncycastle.crypto.digests.SHA1Digest in project BiglyBT by BiglySoftware.

the class DSAParametersGenerator method generateParameters.

/**
 * which generates the p and g values from the given parameters,
 * returning the DSAParameters object.
 * <p>
 * Note: can take a while...
 */
public DSAParameters generateParameters() {
    byte[] seed = new byte[20];
    byte[] part1 = new byte[20];
    byte[] part2 = new byte[20];
    byte[] u = new byte[20];
    SHA1Digest sha1 = new SHA1Digest();
    int n = (size - 1) / 160;
    byte[] w = new byte[size / 8];
    BigInteger q = null, p = null, g = null;
    int counter = 0;
    boolean primesFound = false;
    while (!primesFound) {
        do {
            random.nextBytes(seed);
            sha1.update(seed, 0, seed.length);
            sha1.doFinal(part1, 0);
            System.arraycopy(seed, 0, part2, 0, seed.length);
            add(part2, seed, 1);
            sha1.update(part2, 0, part2.length);
            sha1.doFinal(part2, 0);
            for (int i = 0; i != u.length; i++) {
                u[i] = (byte) (part1[i] ^ part2[i]);
            }
            u[0] |= (byte) 0x80;
            u[19] |= (byte) 0x01;
            q = new BigInteger(1, u);
        } while (!q.isProbablePrime(certainty));
        counter = 0;
        int offset = 2;
        while (counter < 4096) {
            for (int k = 0; k < n; k++) {
                add(part1, seed, offset + k);
                sha1.update(part1, 0, part1.length);
                sha1.doFinal(part1, 0);
                System.arraycopy(part1, 0, w, w.length - (k + 1) * part1.length, part1.length);
            }
            add(part1, seed, offset + n);
            sha1.update(part1, 0, part1.length);
            sha1.doFinal(part1, 0);
            System.arraycopy(part1, part1.length - ((w.length - (n) * part1.length)), w, 0, w.length - n * part1.length);
            w[0] |= (byte) 0x80;
            BigInteger x = new BigInteger(1, w);
            BigInteger c = x.mod(q.multiply(TWO));
            p = x.subtract(c.subtract(ONE));
            if (p.testBit(size - 1)) {
                if (p.isProbablePrime(certainty)) {
                    primesFound = true;
                    break;
                }
            }
            counter += 1;
            offset += n + 1;
        }
    }
    // 
    // calculate the generator g
    // 
    BigInteger pMinusOneOverQ = p.subtract(ONE).divide(q);
    for (; ; ) {
        BigInteger h = new BigInteger(size, random);
        if (h.compareTo(ONE) <= 0 || h.compareTo(p.subtract(ONE)) >= 0) {
            continue;
        }
        g = h.modPow(pMinusOneOverQ, p);
        if (g.compareTo(ONE) <= 0) {
            continue;
        }
        break;
    }
    return new DSAParameters(p, q, g, new DSAValidationParameters(seed, counter));
}