crypto_scalarmult static method

Uint8List crypto_scalarmult(Uint8List q, Uint8List n, Uint8List p)

Implementation

static Uint8List crypto_scalarmult(Uint8List q, Uint8List n, Uint8List p) {
  final z = Int8List(32);
  final x = Int32List(80);
  int r, i;
  final a = Int32List(16),
      b = Int32List(16),
      c = Int32List(16),
      d = Int32List(16),
      e = Int32List(16),
      f = Int32List(16);

  for (i = 0; i < 31; i++) {
    z[i] = n[i];
  }

  z[31] = (n[31] & 127) | 64;
  z[0] &= 248;

  _unpack25519(x, Uint8List.fromList(p));

  for (i = 0; i < 16; i++) {
    b[i] = x[i];
    d[i] = a[i] = c[i] = 0;
  }

  a[0] = d[0] = 1;

  for (i = 254; i >= 0; --i) {
    r = (z[i >> 3] >> (i & 7)) & 1;

    _sel25519(a, b, r);
    _sel25519(c, d, r);
    _A(e, a, c);
    _Z(a, a, c);
    _A(c, b, d);
    _Z(b, b, d);
    _S(d, e);
    _S(f, a);
    _M(a, c, a);
    _M(c, b, e);
    _A(e, a, c);
    _Z(a, a, c);
    _S(b, a);
    _Z(c, d, f);
    _M(a, c, _121665);
    _A(a, a, d);
    _M(c, c, a);
    _M(a, d, f);
    _M(d, b, x);
    _S(b, e);
    _sel25519(a, b, r);
    _sel25519(c, d, r);
  }

  for (i = 0; i < 16; i++) {
    x[i + 16] = a[i];
    x[i + 32] = c[i];
    x[i + 48] = b[i];
    x[i + 64] = d[i];
  }

  _inv25519(x, 32, x, 32);
  _M_off(x, 16, x, 16, x, 32);
  _pack25519(q, x, 16);

  return q;
}