Only Asymmetric session key encryption is supported. Only AES128, AES192, AES256, and Blowfish supported. MDC checks are not done yet, but non-MDC packets have not been tested. Key decryption is not implemented yet. Some of the tooling that will be needed for encryption is in, but this is not done yet. Additionally checking that the session key is the right one may be needed in the wildcard case. Possibly up to actually trying to decrypt the message itself. There is a Util module now. That reorg should not be in this commit, but it is. A test has been added to check that decryption works at all.