The extensive README is also a pretty good intro to how one can do crypto (as in cryptography: get off my lawn!) in Haskell using the excellent cryptonite library.

For those who won't click through to TFR:

    > import Crypto.Number.Hash (SHA3_256)
    > import Crypto.PubKey.ECC.ECDSA (sign, verify)
    > import Crypto.PubKey.ECC.Generate (generate)
    > import Crypto.PubKey.ECC.Types (getCurveByName, SEC_p256k1)
    
    > let msg = "hello world" :: ByteString
    > let secp256k1 = getCurveByName SEC_p256k1
    > (pubKey, privKey) <- generate secp256k1
    > sig <- sign privKey SHA3_256 msg
    > verify SHA3_256 pubKey sig msg
    True