However, first-time users that do not have an account at a web site yet cannot benefit from DVCert during regis- tration. Moreover, DVCert is not suitable to secure sites that are available without any authentication at all. Finally, as with certificate pinning, DVCert has to be implemented in each and every website, which conflicts with our design goal to build a system that does not rely on any coopera- tion on the server side.
MonkeySphere [31] builds upon the PGP Web of Trust (WoT) concepts of a network of people who trust other people: Users who never met before can safely authenti- cate their identities due to the presence of a trust path in the network between them, established by friends who trust their friends, respectively. Whenever the Monkey- Sphere daemon encounters a self-signed or invalid cer- tificate, it searches public key servers for a PGP key associated with that website’s name. The certificate is trusted only if the daemon can construct a trust path from the user’s key to the server’s key. This approach could effectively abolish the need for CAs and allow users to trust self-signed certificates, also providing a theoretically sound way of trusting remote certificates and detecting MitM attacks.
However, MonkeySphere relies on the cooperation of the administrators of the webservers, which conflicts with our design goals: Clients can only validate the certificates of those servers, whose administrators have signed their certificates and uploaded them to a key server. Moreover, administrators have to ensure that their certificates are extensively connected with other users within the PGP Web of Trust to ensure that as many users as possible will be able to find a trust path to the server.
Strictly relying on trust paths between users and target servers may lead to bootstrapping issues: Users will only be able to validate server certificates with high probabil- ity, if PGP and MonkeySphere are widely adopted and all users actively contribute to the Web of Trust. However, so far, PGP suffers from poor adoption due to usability issues resulting from its intrinsic complexity.
In contrast, Laribus users can validate the certificate of any server at any time, even when the server is completely oblivious of Laribus. Moreover, bootstrap- ping Laribus may be easier because users do not have to establish trust paths from them to individual desti- nation servers. In Laribus certificate validation is possi- ble even if only a few small user groups (cliques based on real-world social relationships) participate in the system.