https://en.wikipedia.org/wiki/Solid_(web_decentralization_project) it mentions peer to peer but nothing on this authentication it has. Only thing that would make sense to me is something like the distributed ledger:

In more detail, Solid consists of the following components:

An organized collection of standards and data formats/vocabularies providing the same capabilities that centralized social media services offer, such as identity, authentication, login, permission lists, contact management, messaging, feed subscriptions, comments, discussions, and others.
Specifications and design notes describing a REST API to extend existing standards, to guide developers building servers or applications.
Servers that implement the Solid specification.
A test suite for testing and validating Solid implementations.
An ecosystem of social applications, identity providers, and helper libraries that run on the Solid platform.
A community providing documentation, discussion, tutorials, and presentations.