https://omega-coder.github.io/tags/cryptography/ Recent content in cryptography on CHERIEF Yassine Hugo -- gohugo.io en-us Yassine CHERIEF Wed, 24 Apr 2019 00:00:00 +0000 https://omega-coder.github.io/posts/angstromctf-2019-secret-sheep-society-writeup-crypto/ Wed, 24 Apr 2019 00:00:00 +0000 https://omega-coder.github.io/posts/angstromctf-2019-secret-sheep-society-writeup-crypto/ Challenge details Category Points Solves Crypto 120 98 TL;DR Spotting the weakness (AES with CBC Mode). Get token. Flipping specific bytes in session json (turn false to true ). manipulate token with flipped bytes. Send manipulated token to page. Get the flag. Challenge Description The sheep are up to no good. They have a web portal for their secret society, which we have the source for.