When it comes to guarantee data confidentiality on the wire or on the disk we cannot be exempt to know how to use cryptography: this post provides a quick guide of both symmetric and asymmetric cryptography along with an overview of their bricks: RSA and DSA keys, Elliptic Curves keys, PGP Keys, Message Digest, HMAC, digital signature and encipherment. The aim is to provide the necessary terms and concepts to understand how to operate with cryptographic tools, providing examples with openssl.