Laravel Passport provides OAuth2 server support to Laravel
A high-level OpenPGP library
Extensible security first OAuth 2.0 and OpenID Connect SDK for Go
AS2 1.1 server implementation in Java
PHP strong authentication library, web interface & CLI, OATH certified
Centralized signing and verification
Toolkit aimed to perform lateral movement in restricted environments
GMR digital signature system
password safe / manager for linux and windows (and mac ?) via qt