The dumbest authentication system you could think of

Apppend rows to a Google Sheets spreadsheet. Uses Google Sheets API v4 with server-to-server authentication

Garage extension to use JWT as authentication strategy.

SMS Authentication

A Rails engine for quickly adding SMS authentication to a Rails API

Frame will setup various Ruby on Rails projects with an instantly usable application. The user can choose if they want authentication with devise, omniauth, and uses active_admin.

Rails authentication

BotDelive is a Push Notification and 2-factor authentication API service that works over the chat bots (Telegram and Messenger).

Makes it possible to protect selected Sinatra routes with HTTP Basic Authentication

Simple implementation of authentication for Rails

Multi-token authentication Rails engine.

Simple and safe token authentication library that uses Rails' `authenticate_or_request_with_http_token` method

OmniAuth provider that supports authentication against UOC REST apis.

Rails authentication with email & password. You can customize the behaviour of the remember me token.

Basic token based authentication for APIs

A simple Forge authentication client

Low level Rack authentication enforcement

This gem make authentication very simple

Signature authentication

SignedApi gem offers easy way to make your web APIs secure by using secret key based signature authentication.