Using OAuth 2.0 to Access Google APIs

https://developers.google.com/identity/protocols/OAuth2

How HTTPS work..

Simple and cool article on the subject..

http://robertheaton.com/2014/03/27/how-does-https-actually-work/

PGP Introduction

Fantastic article to refresh your Cryptography knowledge

http://www.pgpi.org/doc/pgpintro/