  Since the dawn of human civilization, trust has been the core challenge of
social organization. Trust functions to reduce the effort spent in constantly
monitoring others' actions in order to verify their assertions, thus
facilitating cooperation by allowing groups to function with reduced
complexity. To date, in modern societies, large scale trust is almost
exclusively provided by large centralized institutions. Specifically in the
case of the Internet, Big Tech companies maintain the largest Internet
platforms where users can interact, transact and share information. Thus, they
control who can interact and conduct transactions through their monopoly of
online trust. However, as recent events have shown, allowing for-profit
corporations to act as gatekeepers to the online world comes with a litany of
problems. While so far ecosystems of trust on the Internet could only be
feasibly created by large institutions, Web3 proponents have a vision of the
Internet where trust is generated without centralised actors. They attempt to
do so by creating an ecosystem of trust constructed using decentralised
technology. This survey explores this elusive goal of Web3 to create a
"Universal Trust Machine", which in a true decentralised paradigm would be
owned by both nobody and everybody. In order to do so, we first motivate the
decades-old problem of generating trust without an intermediary by discussing
Robert Axelrod's research on the evolution of cooperation. Next, we present the
challenges that would have to be overcome in order to enable long term
cooperation. We proceed to present various reputation systems, all of which
present promising techniques for encouraging trustworthy behaviour. Then, we
discuss Distributed Ledger technologies whose secure transaction facilitating
and privacy preserving techniques promise to be a good complement to the
current limitations of vanilla reputation systems.
