How to retrieve private key

We are working on a project where we would like to retrieve a users private key when we are supplied with their username and passphrase. We are using code from https://github.com/keybase/node-login/blob/master/lib/login.js and retrieve a session and a user object. In the user object there is a triplesec encrypted private key. None of the attempts that we have used allowed us to decrypt it. We would like to know how it is encrypted and how it is decrypted because the decrypt function requires a key and data. We are supplying the users passphrase as the key and the encrypted private key as the data but are getting an error back: "bad header; couldn't find a good version (got 1647465013)".

Start with lib/login.js in keybase/node-login and inspect how the session and user object expose the triplesec-encrypted private key. Compare that representation with the decrypt inputs and the reported bad-header error. Done means documenting the encryption and decryption expectations or identifying the missing input needed to retrieve the key.

Written by the indexing model from the issue text.