This gem make authentication very simple

A Faraday middleware for NTLM authentication

Simple HTTP proxy which adds Conjur authentication headers

Rack webmoney authentication

SimpleAuth HMAC authentication

Rack Middleware for OAuth Authorization and Authentication via/twitter

OAuth Echo authentication by a rack middleware

a Rack module for testing NTLM Authentication in an HTTP client

A warden/sinatra mini-app providing authentication and user management for any rack-based framework.

JWT-based token authentication middleware for Rack.

rack-auth-ldap : provide LDAP authentication for Rack middelware

A modular implementation of Rack Auth

Rack middleware for authentication using JSON Web Tokens using the jwt_claims and json_web_token gems.

Rack middleware for authentication using CAS and/or token

This gem provides an easy-to-use interface to interact with the Shapeways API, including authentication, model management, and order processing.

A rails authentication and authorization engine that reduces clutter in your controllers and views. Includes aliased link_to and button_to helpers that return an empty string if the current user is not permitted to follow the link. ...

Client to microservice proxy authentication

A Chef cookbook cookbook to download files over HTTPS using TLS client certificate authentication.

A Ruby gem for simplifying random password generation, password strength testing, password hashing and salting, and password-hash authentication.

Token-based authentication for your Rails API.