This may be dropped in favour of a SOX indication. In some circumstances the server certificate will be stored here. The presence here of the cert does not signify it is valid. Purposes of Keys PGP keys have a userid field which for Ricardian Contract purposes includes a Ricardian key purpose tag. The following intentional purposes for keys are defined.
Appended numbers indicate minimum recommended key sizes, in bits.
A future detail. The signer, as legal contract issuer, is making some statement about the value of the contract. On restart, this is the key it has available to authenticate any session setup work. To guard against a swapped key attack, user software should check that the purpose is correct. Both the contract and the SOX protocol require a public key signing chain in order to authenticate dynamic actions initiated by a client such as WebFunds.