EmailSender is an easy to use library to send email based on Net::SMTP. It supports the well-known encryption and authentication methods, and you can use it very easily with Gmail account.

Very simple file system driver for EM-FTPD server; including common FTP commands, authentication and before and after operation hooks.

An engine that provides a basic User model, authentication logic, and remote credential management for G5 applications.

DataMapper models for RESTful Authentication with Role-based Authorization

Session-oriented authentication and account management system for Ruby on Rails and PostgreSQL

CAS Authentication via Rack Middleware

API library for GAuthify.com (Google Authenticator, SMS, email multi factor authentication).

Simple authentication for Rails applications

Gem in a box with basic HTTP authentication and forced SSL, designed for use on Heroku or other cloud-based hosting services

Access token for client-side and API authentication.

Authentication engine.

Re-usable Devise-based authentication mountable engine

A gem for Autodesk 2-phase authentication service.

A wrapper around Ruby's net-ldap library to ease authentication and record finding

Merb authentication gem

An authentication client for the Audiosocket API.

A Simple Authentication Server

Client provider library for the authentication token storage service

Authentication via JWT (with encryption)

Simple Rails authentication generator