This is the solution of the “circus” and “cccircus” challenges of HXP 38C3 CTF 2024. The challenges were a CRC computed over a 128-bit finite field and raised to a power. The solution is found with two queries allowing to recover the correct root and finally the key is revealed by a linear equation.

Original writeup (https://sylvainpelissier.gitlab.io/posts/2024-12-28-hxp-38c3-ctf-circus/).