pkcs12 key derive

pkcs12.dart

Uint8List deriveKey(
    List<int> password, List<int> salt, int keySize, int iterations) {
  var np = Uint8List(password.length * 2 + 2);
  for (var i = 0; i < password.length; i++) {
    np[i * 2] = 0;
    np[i * 2 + 1] = password[i];
  }

  const sha1BlockSize = 64;
  const sha1DigestSize = 20;

  var D = Uint8List(sha1BlockSize);
  for (var i = 0; i < D.length; i++) {
    D[i] = 1;
  }

  var S = Uint8List(sha1BlockSize *
      ((salt.length + sha1BlockSize - 1) / sha1BlockSize).floor());
  for (var i = 0; i < S.length; i++) {
    S[i] = salt[i % salt.length];
  }

  var P = Uint8List(sha1BlockSize *
      ((np.length + sha1BlockSize - 1) / sha1BlockSize).floor());
  for (var i = 0; i < P.length; i++) {
    P[i] = np[i % np.length];
  }

  var I = S + P;

  var B = Uint8List(sha1BlockSize);
  var c = ((keySize + sha1DigestSize - 1) / sha1DigestSize).floor();
  var key = Uint8List(keySize);

  for (var i = 1; i < c + 1; i++) {
    Digest d = sha1.convert(D + I);

    for (var j = 1; j < iterations; j++) {
      d = sha1.convert(d.bytes);
    }

    for (int j = 0; j < B.length; j++) {
      B[j] = d.bytes[j % d.bytes.length];
    }

    for (int j = 0; j < (I.length / sha1BlockSize).floor(); j++) {
      var aOff = j * sha1BlockSize;
      var x = (B[B.length - 1] & 0xff) + (I[aOff + B.length - 1] & 0xff) + 1;
      I[aOff + B.length - 1] = x % 256;
      x = x >> 8;
      for (int jj = B.length - 2; jj >= 0; jj--) {
        x = x + (B[i] & 0xff) + (I[aOff + i] & 0xff);
        I[aOff + i] = x % 256;
        x = x >> 8;
      }
    }

    var start = (i - 1) * sha1DigestSize;
    if (i == c) {
      key.setRange(start, keySize, d.bytes);
    } else {
      key.setRange(start, start + d.bytes.length, d.bytes);
    }
  }

  return key;
}