So what do you miss? There are of course other crypto primitives involved: even when public key algorithms are used, the whole message is encrypted with the sym

So what do you miss? There are of course other crypto primitives involved: even when public key algorithms are used, the whole message is encrypted with the symmetric cipher, only the key for the message is encrypted with the public key cryptography. An example for symmetric cipher is AES, https://en.wikipedia.org/wiki/Advanced_Encryption_Standard https://en.wikipedia.org/wiki/Advanced_Encryption_Standard but note that older GPG's used less strong symmetric ciphers by default. There's the RFC about the format of the OpenPGP message: https://tools.ietf.org/html/rfc4880 https://tools.ietf.org/html/rfc4880