Solution by 5l1m on 2025-12-16 14:53:

Solution by SenorGPT on 2025-12-17 17:01:
Java `.jar` crackme. Using JADX, I recovered `checkValidity()` which scores the 10-character key by counting how many characters satisfy `(ch & 3) == 0` (i.e., ASCII divisible by 4). A key is valid if the score is exactly 4. I also wrote a small Python keygen to generate valid keys.

Solution by 0xDuB on 2025-12-21 14:05:

Solution by LogRob01 on 2026-01-17 22:18:
Java crackme solved using static analysis. The JAR file was decompiled with CFR to analyze the validation logic. No patching or keygen was used. The solution is based on understanding the character-based validation conditions.

Solution by idanhajbeko on 2026-02-17 20:25:
explaining everything step by step uses --math-- to determine how many valid keys (spoiler: a lot!)