Reverse – Vault door 3

Vault door 3 - 200pt

Challenge

This vault uses for-loops and byte arrays. The source code for this vault is here: VaultDoor3.java

Hints

Make a table that contains each value of the loop variables and the corresponding buffer index that it writes to.

Solution

The function inside the source file scrambles the flag. To decode it, you have to sort it correctly.
First, create a sorted list of integers from 0 to 32. Then, apply the anagram function found in the source file to this list. You now have a list of indexes. Build a string using the scrambled string that’s in the source file, mapping its chars with said indexes. The string built this way is the flag.
picoCTF{jU5t_a_s1mpl3_an48r4m_4_u_e9af18}

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