block18.ruby

def ecdsa_sign(private_key, digest, temp_key = nil)
  temp_key ||= 1 + SecureRandom.random_number(EC_n - 1)
  rx, _ry = ec_multiply(temp_key, EC_Gx, EC_Gy, EC_p)
  r = rx % EC_n
  r > 0 || raise('r is zero, try again new temp key')
  i_tk = inverse temp_key, EC_n
  m = bytes_to_bignum digest
  s = (i_tk * (m + r * private_key)) % EC_n
  s > 0 || raise('s is zero, try again new temp key')
  [r, s]
end
def ecdsa_verify?(px, py, digest, signature)
  r, s = signature
  i_s = inverse s, EC_n
  m = bytes_to_bignum digest
  u1 = i_s * m % EC_n
  u2 = i_s * r % EC_n
  u1Gx, u1Gy = ec_multiply u1, EC_Gx, EC_Gy, EC_p
  u2Px, u2Py = ec_multiply u2, px, py, EC_p
  rx, _ry = ec_add u1Gx, u1Gy, u2Px, u2Py, EC_p
  r == rx
end
Der = Struct.new :der, :length, :ri, :rl, :r, :si, :sl, :s, :sighash_type do
  def initialize(der: 0x30, length: 0x45, ri: 0x02, rl: 0x21, r: nil, si: 0x02, sl: 0x20, s: nil, sighash_type: 0x01)
    super der, length, ri, rl, r, si, sl, s, sighash_type
  end
  def serialize
    byte_to_hex(der) + byte_to_hex(length) +
      byte_to_hex(ri) + byte_to_hex(rl) + to_hex(bignum_to_bytes(r, 33)) +
      byte_to_hex(si) + byte_to_hex(sl) + to_hex(bignum_to_bytes(s, 32)) +
      byte_to_hex(sighash_type)
  end
  def self.parse(signature)
    fields = *[signature].pack('H*').unpack('CCCCH66CCH64C')
    Der.new r: fields[4], s: fields[7], sighash_type: fields[8]
  end
end