compared to the normal fromJust, it take an extra string to report
what kind of fromJust we were doing. it's quite valuable when
shuffling code and assertion break.
at some point, it need to be removed completely in favor of better types
that better reflect the actual state on the connection.
Remove need for spoon, since RSA will fails gracefully.
Add support for full private key format for fast decryption.
Generalization of key exchange to add future support for DH, etc.
despite the fact that it works, it's missing a step at key block set time,
so that we don't use the computed IV, but use a random generated one seeded by
the computed IV.
the API stays mostly similar except for clientkeyxchg that need a bytes instead of [word8].
remove lots of unnessary packing/unpacking when setting up ciphers.
