input, // ignoring leading zeroes. func (x *Nat) resetToBytes(b []byte) *Nat { x.reset((len(b) + _S - 1) / _S) if err := x.setBytes(b); err != nil { panic("bigmod: internal error: bad arithmetic") } return x.trim() } // trim reduces the size of x to match its value. func (x *Nat) trim() *Nat { // Trim most significant (trailing in little-endian) zero limbs. // We assume comparison with zero (but not the branch) is constant time. for i := len(x.limbs) - 1; i >= 0; i-- { if x.limbs[i] != 0 { break } x.limbs...