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: 2018
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
Apr 02
0CTF 2018 Quals – zer0SPN (Crypto 550)
0ops SPN, hope you enjoy it:) zer0SPN.zip Summary: linear cryptanalysis on toy block cipher
Apr 02
0CTF 2018 Quals – zer0TC (Crypto 916)
0ops Toy Cipher, hope you enjoy it:) zer0TC.zip Summary: meet-in-the-middle and key-schedule constraints