Writeup for 3 crypto challenges in 虎符CTF 2020 (2020-04-19 09:00 +8h). - (easy) GM: recover every bit of RSA message by using legendre symbol - (medium) mceliece: break a Mceliece cryptosystem with small parameters - (easy) pell: solve specified pell equations.
In this post, we give a concise study of several attaks against DSS, including, reused $k$, $k$ generated via LCG, and lattice attack against short $k$.