128-byte xprv a key format in Cardano that some software still uses or requires the traditional 96-byte xprv is simply encoded as prv | chaincode however, because some software may not know how to compute a public key from a private key, the 128-byte inlines the public key in the following format prv | pub | chaincode so be careful if you see the term "xprv" as it could refer to either one our library does not require the pub (instead we compute the pub key when needed)