Splatoon 3 Anticheat Seed Randomization Weakness

Summary

In Splatoon 3's anticheat system (internally referred to as ch), a mathematical oversight severely weakened the game's ability to detect tampered code. Here is a quick breakdown of how the exploit worked:

• The Problem: The anticheat starts with a strong primary seed that has over 4 billion possibilities. However, the shuffling logic used to generate the secondary seed for the main game code check (ch1) accidentally collapses this number down to just 1,024 actual possibilities.
• The Exploit: Because 1,024 is such a tiny pool of seeds, an attacker can precalculate every valid ch1 hash for the unmodified game in just a few minutes. By intercepting the game's anticheat function and feeding it these "pre-approved" answers from a saved file on the SD card, an attacker can trick the system into thinking nothing is wrong. This leaves them free to modify the live game code and run cheats, like infinite ink or invincibility, without getting caught.
• The Fix: Nintendo addressed this in game version 10.0.0 and the seed is now reasonably random, so this class of exploit is fixed.