- Add `config.rejectPublicKeyAlgorithms` to disallow using the given algorithms
to verify, sign or encrypt new messages or third-party certifications.
- Consider `config.minRsaBits` when signing, verifying and encrypting messages
and third-party certifications, not just on key generation.
- When verifying a message, if the verification key is not found (i.e. not
provided or too weak), the corresponding `signature` will have
`signature.valid=false` (used to be `signature.valid=null`).
`signature.error` will detail whether the key is missing/too weak/etc.
Generating and verifying key certification signatures is still permitted in all cases.