This tutorial shows how to setup an open proxy in ubuntu. I am using such a setup for scraping purposes and it works quite well.

Modoboa is a nice all-in-one email package. Sadly it lacks configuration possibilities for certificates and the default config uses just self signed certificates. This tutorial explains how to create and configure lets encrypt for your mail server.

I will show how to attack RSA, if two private keys share a same factor . This is the solution of an exercice - We had to decrypt a message given the ciphertext (encrypted message) and two public RSA keys (where a common factor was used to generate them).

I had to decrypt a weak RSA encrypted message. Why weak? Because a (only) 268-bit key was used for encryption. So RSA is not bad, but please use a suitable key size.