Secondhand

Cyber Apocalypse CTF 2026

Task: not-stripped x86-64 crackme with three nested layers of misdirection (a rolling-key check, a 16-byte SIMD cipher, and a self-decoding shellcode path) plus ptrace anti-debug. Solution: identify the len-8 branch as the real path, decode the mmap'd shellcode transform X(pw), exploit a computed-goto that jumps mid-instruction into a movabs to satisfy a magic-constant compare, invert X with a modular inverse, then splitmix64-decrypt the flag.