Casascius Minikey Generator

minikey.hs

#!/usr/bin/env stack
{- stack
   --resolver lts-16.28
   --nix 
   --nix-packages "secp256k1 pkg-config zlib"
   script
   --package haskoin-core
   --package entropy
   --package bytestring
   --package text
   --extra-dep haskoin-core-0.18.0
   --extra-dep secp256k1-haskell-0.5.0
-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE LambdaCase #-}
import Haskoin
import System.Entropy
import qualified Data.ByteString as B
import qualified Data.ByteString.Char8 as B8
import qualified Data.Text.IO as T
import Data.Maybe

alphabet :: [Char]
alphabet = "23456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"

genKey :: IO (B.ByteString, SecKeyI)
genKey =
  g >>= \case
    Nothing -> genKey
    Just x -> return x
 where
  g = do
    ent <- B.filter (< (l * 4)) <$> getEntropy 512
    let chars = B8.cons 'S'
              $ B8.pack
              $ take 21
              $ map (\x -> alphabet !! fromIntegral (x `mod` l))
              $ B.unpack ent
    if (B.length chars < 22)
      then return Nothing
      else case fromMiniKey chars of
        Nothing -> return Nothing
        Just k -> return (Just (chars, k))
  l = fromIntegral $ length alphabet

main :: IO ()
main = do
  (char, key) <- genKey
  B8.putStrLn char
  T.putStrLn (toWif btc key)
  T.putStrLn (fromJust (addrToText btc (pubKeyAddr (derivePubKeyI key))))