  Trust Management (TM) systems for authentication are vital to the security of
online interactions, which are ubiquitous in our everyday lives. Various
systems, like the Web PKI (X.509) and PGP's Web of Trust are used to manage
trust in this setting. In recent years, blockchain technology has been
introduced as a panacea to our security problems, including that of
authentication, without sufficient reasoning, as to its merits.In this work, we
investigate the merits of using open distributed ledgers (ODLs), such as the
one implemented by blockchain technology, for securing TM systems for
authentication. We formally model such systems, and explore how blockchain can
help mitigate attacks against them. After formal argumentation, we conclude
that in the context of Trust Management for authentication, blockchain
technology, and ODLs in general, can offer considerable advantages compared to
previous approaches. Our analysis is, to the best of our knowledge, the first
to formally model and argue about the security of TM systems for
authentication, based on blockchain technology. To achieve this result, we
first provide an abstract model for TM systems for authentication. Then, we
show how this model can be conceptually encoded in a blockchain, by expressing
it as a series of state transitions. As a next step, we examine five prevalent
attacks on TM systems, and provide evidence that blockchain-based solutions can
be beneficial to the security of such systems, by mitigating, or completely
negating such attacks.
