Dvdes-631 Patched Today

A quick glance shows:

We see the flag format, confirming the binary will simply puts the flag once the right key is supplied. dvdes-631

is a tiny 32‑bit function that expands R to 48 bits, XORs with the round sub‑key, passes it through the classic DES S‑boxes, and finally applies the P‑permutation. The implementation is a direct copy of the reference DES algorithm, except that the S‑boxes have been re‑ordered (the svdes-631 custom S‑boxes) – they are embedded as a static table in .rodata . A quick glance shows: We see the flag

$ checksec --file=./dvdes-631 RELRO STACK CANARY NX PIE RPATH RUNPATH SYMBOLS No RELRO No canary NX No PIE - - No $ checksec --file=

Despite the many benefits of sustainable agriculture, there are still significant challenges to be overcome. Some of the most pressing challenges include:

cur_0 = user_key cur_i+1 = rotl64(cur_i, i+1) ^ magic sub_i = cur_i+1

Category: Reversing / Binary Exploitation Difficulty: Medium (≈ 3/5) Platform: Linux x86‑64 (glibc 2.31) – static binary, no source provided Points: 500 (CTF 2023‑2024)