PFS #833

A new address version that contains expiring ephemeral subkeys (which are not a part of the address itself) would allow something like PFS. It requires some design, to make sure they keys are not deleted prematurely for example.

For a proposal, see here: https://www.reddit.com/r/bitmessage/comments/3zzevp/forward_secrecy_for_bitmessage/