Web of trust

A decentralized reputation model, originating with PGP in 1991, in which users vouch for one another's keys or identities and trust is followed along chains of vouches rather than issued by a central authority. The ancestor of the reputation family — and a cautionary one: Douceur (2002) showed a web of trust does not, by itself, achieve Sybil-resistance, because an attacker who mints identities freely can manufacture the vouches too.