A CTF host’s worst nightmare is unintentionally not including all the files needed for competitors to actually solve a challenge. It’s annoying for hosts, annoying for competitors, and worst of all is super easy to avoid.

Here’s a short overview of available security options on Linux and how to enable or disable them.

This was an RSA challenge, but DiceGang are always creative and they mixed it up quite a bit! The general gist is that we are given an RSA encrypted ciphertext whose e value is not coprime with its phi [(p-1)(q-1)] value. In RSA, non-coprime phi and e don’t actually make the encryption non-secure, they make it non-invertible which means we can’t uniquely decrypt the ciphertext.

Just a test to see if this works :)