monkeysphere binary package in Ubuntu Precise i386

 SSH key-based authentication is tried-and-true, but it lacks a true
 Public Key Infrastructure for key certification, revocation and
 expiration. Monkeysphere is a framework that uses the OpenPGP web of
 trust for these PKI functions. It can be used in both directions:
 for users to get validated host keys, and for hosts to authenticate
 users. Current monkeysphere SSH tools are designed to integrate
 with the OpenSSH implementation of the Secure Shell protocol.
 .
 Monkeysphere can also be used by a validation agent to validate TLS
 connections (e.g. https).

Source package