Monkeysphere
The Monkeysphere tools allow to verify secure connections, servers and clients, without the need to trust any (often commercial) third party.
Instead the proven Web-of-Trust from PGP is used to certify secure connections.
Currently this can be used to verify TLS/SSL servers and SSH servers and clients.
Software-Installation
Monkeysphere is in the Ubuntu Software repository, but those packages are often out of date. Installation from the projects own repositories is recommended.
Software Package Signing Key
Software packages published by the Monkeysphere project are signed with their own release key.
Your Ubuntu system needs to trust the “Monkeysphere Archive Signing Key” to be able to verity and install software packages from the Monkeysphere project:
$ sudo apt-key adv --keyserver keys.gnupg.net --recv-keys 0x18e667f1eb8af314
Software Package Repository
$ sudo add-apt-repository 'deb http://archive.monkeysphere.info/debian experimental monkeysphere'
Software Installation
$ sudo apt-get install monkeysphere