Jul 19, 2019

I still don't understand the question. If you have an xpriv, look here for deriving private keys: https://github.com/libbitcoin/libbitcoin-system/blob/master/src/wallet/hd_private.cpp . If you want wif encoding, look at the private key class: https://github.com/libbitcoin/libbitcoin-system/blob/master/src/wallet/ec_private.cpp#L160