예제 #1
0
  public static boolean verifySignature(byte[] message, DSASignature ds, DSAPublicKey dpk)
      throws IOException {
    /* Inspired by Bouncycastle's DSASigner class */

    SHA1 md = new SHA1();
    md.update(message);
    byte[] sha_message = new byte[md.getDigestLength()];
    md.digest(sha_message);

    BigInteger m = new BigInteger(1, sha_message);

    BigInteger r = ds.getR();
    BigInteger s = ds.getS();

    BigInteger g = dpk.getG();
    BigInteger p = dpk.getP();
    BigInteger q = dpk.getQ();
    BigInteger y = dpk.getY();

    BigInteger zero = BigInteger.ZERO;

    if (log.isEnabled()) {
      log.log(60, "ssh-dss signature: m: " + m.toString(16));
      log.log(60, "ssh-dss signature: r: " + r.toString(16));
      log.log(60, "ssh-dss signature: s: " + s.toString(16));
      log.log(60, "ssh-dss signature: g: " + g.toString(16));
      log.log(60, "ssh-dss signature: p: " + p.toString(16));
      log.log(60, "ssh-dss signature: q: " + q.toString(16));
      log.log(60, "ssh-dss signature: y: " + y.toString(16));
    }

    if (zero.compareTo(r) >= 0 || q.compareTo(r) <= 0) {
      log.log(20, "ssh-dss signature: zero.compareTo(r) >= 0 || q.compareTo(r) <= 0");
      return false;
    }

    if (zero.compareTo(s) >= 0 || q.compareTo(s) <= 0) {
      log.log(20, "ssh-dss signature: zero.compareTo(s) >= 0 || q.compareTo(s) <= 0");
      return false;
    }

    BigInteger w = s.modInverse(q);

    BigInteger u1 = m.multiply(w).mod(q);
    BigInteger u2 = r.multiply(w).mod(q);

    u1 = g.modPow(u1, p);
    u2 = y.modPow(u2, p);

    BigInteger v = u1.multiply(u2).mod(p).mod(q);

    return v.equals(r);
  }
예제 #2
0
  public static DSASignature generateSignature(byte[] message, DSAPrivateKey pk, SecureRandom rnd) {
    SHA1 md = new SHA1();
    md.update(message);
    byte[] sha_message = new byte[md.getDigestLength()];
    md.digest(sha_message);

    BigInteger m = new BigInteger(1, sha_message);
    BigInteger k;
    int qBitLength = pk.getQ().bitLength();

    do {
      k = new BigInteger(qBitLength, rnd);
    } while (k.compareTo(pk.getQ()) >= 0);

    BigInteger r = pk.getG().modPow(k, pk.getP()).mod(pk.getQ());

    k = k.modInverse(pk.getQ()).multiply(m.add((pk).getX().multiply(r)));

    BigInteger s = k.mod(pk.getQ());

    return new DSASignature(r, s);
  }