Area58 is a library to encode and decode base58check. Base58check is used in Bitcoin whenever there is a need for a user to read or transcribe a number, such a bitcoin adresses, encrypted key, private key, or script hash.

This can't be used to generate bitcoin address from a private key. It's only a base58check encoder/decoder. But it's easy to generate a bitcoin address from the private key.

Example: If you want to generate a (uncompressed) bitcoin address using this library you can...

iex> privkey = "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF" |> Base.decode16!()
iex> {uncompressed_pubkey, _priv_key} = :crypto.generate_key(:ecdh, :crypto.ec_curve(:secp256k1), privkey)
iex> uncompressed_pubkey = :crypto.hash(:ripemd160, :crypto.hash(:sha256, uncompressed_pubkey))
iex> Area58check.encode(uncompressed_pubkey, <<0>>)
%Area58check{
  encoded: "1CLrrRUwXswyF2EVAtuXyqdk4qb8DSUHCX",
  decoded: <<1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239>>,
  version: :p2pkh,
  version_bin: <<0>>}

or you can use another library that does all that for you.

Base58 charset is based on easy to trancribe characters, upper and lower case letters and numbers excluding 0, O, l, I.

Usually there is a version (binary number) to signal what kind of string is being encoded. list of bitcoin prefixes

Example: for standard bitcoin address, is used the hexadecimal number 0x00, for compressed WIF (allows to import a private key in bitcoin) is used 0x80, etc.

When a string is encoded, 4 bytes (or 32bits), are added to the end by Area58check.encode function as a checksum to make sure that no characters were wrongly transcribed. This checksum is not meant to allow to fix a wrong transcribed string, but it allows to verify if string is correct or not.

Encode a private key into WIF (Wallet Import Format):

iex> privkey = "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF" |> Base.decode16!()
iex> Area58check.encode(privkey, :wif)
%Area58check{encoded: "5HpneLQNKrcznVCQpzodYwAmZ4AoHeyjuRf9iAHAa498rP5kuWb",
  decoded: <<1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239>>,
  version: :wif,
  version_bin: <<128>>}
iex> Area58check.encode(privkey, [128])
%Area58check{encoded: "5HpneLQNKrcznVCQpzodYwAmZ4AoHeyjuRf9iAHAa498rP5kuWb",
  decoded: <<1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239>>,
  version: :wif,
  version_bin: <<128>>}
iex> Area58check.encode(privkey, <<128>>)
%Area58check{encoded: "5HpneLQNKrcznVCQpzodYwAmZ4AoHeyjuRf9iAHAa498rP5kuWb",
  decoded: <<1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239>>,
  version: :wif,
  version_bin: <<128>>}
iex> Area58check.encode(privkey, 0x80)
%Area58check{encoded: "5HpneLQNKrcznVCQpzodYwAmZ4AoHeyjuRf9iAHAa498rP5kuWb",
  decoded: <<1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239>>,
  version: :wif,
  version_bin: <<128>>}

Encode a public key into an address:

iex> {uncompressed_pubkey, _priv_key} = :crypto.generate_key(:ecdh, :crypto.ec_curve(:secp256k1), privkey)
iex> derived_uncomp_pubkey = :crypto.hash(:ripemd160, :crypto.hash(:sha256, uncompressed_pubkey))
iex> Area58check.encode(derived_uncomp_pubkey, 0x00)
%Area58check{
  decoded: <<124, 106, 230, 190, 9, 150, 81, 133, 169, 75, 13, 161, 139, 201, 42, 157, 252, 238, 97, 23>>,
  encoded: "1CLrrRUwXswyF2EVAtuXyqdk4qb8DSUHCX",
  version: :p2pkh,
  version_bin: <<0>>}

Error when version is unknown:

iex> Area58check.encode(privkey, :jhkdsfajhkfdasjhkfd)
** (ArgumentError) :jhkdsfajhkfdasjhkfd is not a recognized version.
You can either pass a charlist (ex: [4, 136, 178, 30]), number (ex:
70617039), hexadecimal (ex: 0x043587CF), binary version (ex: <<4,
136, 178, 30>>), or a recognized atom like any of: :bip32_privkey,
:bip32_pubkey, :p2pkh, :p2sh, :testnet_bip32_privkey,
:testnet_bip32_pubkey, :testnet_p2pkh, :testnet_p2sh, :testnet_wif, :wif

Decoding strings encoded with base58check:

iex> Area58check.decode("1CLrrRUwXswyF2EVAtuXyqdk4qb8DSUHCX")
{:ok, %Area58check{decoded: <<124, 106, 230, 190, 9, 150, 81, 133, 169, 75, 13, 161, 139, 201, 42, 157, 252, 238, 97, 23>>,
  encoded: "1CLrrRUwXswyF2EVAtuXyqdk4qb8DSUHCX",
  version: :p2pkh,
  version_bin: <<0>>}}
iex> Area58check.decode("5HpneLQNKrcznVCQpzodYwAmZ4AoHeyjuRf9iAHAa498rP5kuWb")
{:ok, %Area58check{
  decoded: <<1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239, 1, 35, 69, 103, 137, 171, 205, 239>>,
  encoded: "5HpneLQNKrcznVCQpzodYwAmZ4AoHeyjuRf9iAHAa498rP5kuWb",
  version: :wif,
  version_bin: <<128>>
}}

If checksum is not valid returns error:

iex> Area58check.decode("1CheckSumError")
{:error, :checksum_incorrect}

If contains a non valid character like 0, O, l, I, returns error:

iex> Area58check.decode("ContainsInvalidCharacter0")
{:error, :incorrect_base58}

If available in Hex, the package can be installed by adding area58check to your list of dependencies in mix.exs:

def deps do
  [
    {:area58check, "~> 0.1"},
  ]
end

The docs can be found at https://hexdocs.pm/area58check.