CSAW Quals 2018 – holywater

This was my favorite crypto challenge from this year's CSAW Quals (and probably my favorite crypto challenge that I've done in a while). On the surface, it's relatively standard: we have a flag encrypted with some cryptosystem (along with a Python implementation of this cryptosystem) and we have to decrypt it. The cryptosystem itself is… Continue reading CSAW Quals 2018 – holywater

Tokyo Westerns CTF 2017 – Palindromes Pairs (Challenge Phase)

This challenge was a follow-up to an earlier challenge, titled "Palindromes Pairs - Coding Phase". In that earlier warmup ppc challenge, the goal was to write an algorithm to solve the following problem: given up to 1000 strings $latex s_i$, each of length at most 1000, count the number of pairs $latex (i, j)$ such… Continue reading Tokyo Westerns CTF 2017 – Palindromes Pairs (Challenge Phase)