In this challenge we have a stream cipher based on LFSR and nonlinear filtering function. It has 128-bit LFSR secret state and we are also given 1600 keystream bits. Our goal is simply to recover the key which is the initial state. Here is the nonlinear filtering function: f(v) = v[0] ^ v[1] ^ v[2] …
Tag: stream cipher
Apr 02
0CTF 2018 Quals – zer0C5 (Crypto 785)
0ops Cipher 4, hope you enjoy it:) zer0C4.zip nc 202.120.7.220 1234 Summary: related-key attack on weakened variant of RC4
Jun 17
Defcon CTF Quals 2013 – All Web Challenges (3dub)
Summary: 3dub (1) – babysfirst: SQLite SQL injection 3dub (2) – badmedicine: Stream cipher bit flipping 3dub (3) – hypeman: Rack/Sinatra session secret disclosure 3dub (4) – rememberme: Bruteforce 3dub (5) – worsemedicine: Block cipher bit flipping