Previously the `cert_msg` in the fidelity bond protocol involves a
binary public key. This is additional unnecessary complexity given
that we want other wallets to also implement the fidelity bond
protocol (see issue #993 for full discussion). So its good to move
to a certificate message which is entirely ascii.
This commit has ascii certficiate messages also be accepted as valid
along with the old certificate messages.
If a yield generator is run with a fidelity bond wallet then the
most-valuable bond will be found and announced.
The announcement includes a proof of a UTXO and its locktime. Also a
proof that the maker's IRC nickname controls the UTXO.
There is also an intermediate signature called the certificate
signature which can later be used when holding fidelity bond UTXOs in
cold storage without the protocol needing to change. Right now this
feature is unused so certificates are generated dynamically on each
request. The certificates have an expiry block height, which is defined
as the number of 2016-block retargeting periods since the genesis
block, so to check if the expiry was passed the taker will check
`current_block_height > cert_expiry*2016`.
Parse incoming and announce outgoing fidelity bond messages
Fidelity bond proof messages will be checked and added to the internal
database just like offers. Such messages are not announced in public
but only directly to takers who ask for them, this is because the
signature proofs must commmit to the maker's and taker's IRC nicknames
in order to avoid replay attacks.