KamilLelonek

def prepend_index(private_key), do: <<0::8, private_key::binary>>

KamilLelonek

@version_numbers %{
  private: %{
    main: <<4, 136, 173, 228>>,
    test: <<4, 53, 131, 148>>
  },
  public: %{
    main: <<4, 136, 178, 30>>,
    test: <<4, 53, 135, 207>>
  }
}

KamilLelonek

decoded_seed = Base.decode16!(seed, case: :lower)
hashed_seed = :crypto.hmac(:sha512, "Bitcoin seed", decoded_seed)
<<private_key::binary-32, chain_code::binary-32>> = hashed_seed
{private_key, chain_code}

KamilLelonek

defp iterate(_mnemonic, round_number, _previous_block, result)
  when round_number > @rounds_count,
  do: result

defp iterate(mnemonic, round_number, previous_block, result) do
  with next_block = :crypto.hmac(:sha512, mnemonic, previous_block),
    do: iterate(mnemonic, round_number + 1, next_block, :crypto.exor(next_block, result))
end

KamilLelonek

defp pbkdf2(initial_block, mnemonic),
  do: iterate(mnemonic, @initial_round_number + 1, initial_block, initial_block)

KamilLelonek

def generate(mnemonic, passphrase \\ "") do
  passphrase
  |> salt()
  |> initial_round(mnemonic)
  |> pbkdf2(mnemonic)
end

KamilLelonek

defp hmac_sha512(key, data), do: :crypto.hmac(:sha512, key, data)

KamilLelonek

defp salt(passphrase \\ ""), do: "mnemonic" <> passphrase

KamilLelonek

~r/.{1,11}/
|> Regex.scan(entropy)
|> List.flatten()
|> Enum.map(fn part ->
  index = String.to_integer(part, 2)

  Enum.at(@words, index)
end)
|> Enum.join(" ")

KamilLelonek

String.slice(binary_string, 0..(checksum_length - 1))