ECDSASignature module for Elixir

ecdsa_signature.ex

defmodule ECDSASignature do
  require Record

  Record.defrecord(
    :ecdsa_signature,
    :"ECDSA-Sig-Value",
    Record.extract(:"ECDSA-Sig-Value", from_lib: "public_key/include/OTP-PUB-KEY.hrl")
  )

  def new(r, s) when is_integer(r) and is_integer(s) do
    ecdsa_signature(r: r, s: s)
  end

  def new(raw) when is_binary(raw) do
    size = raw |> byte_size() |> div(2)
    <<r::size(size)-unit(8), s::size(size)-unit(8)>> = raw
    new(r, s)
  end

  # Export to DER binary format, for use with :public_key.verify/4
  def to_der(ecdsa_signature() = signature) do
    :public_key.der_encode(:"ECDSA-Sig-Value", signature)
  end
end