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Encryption 101

Challenge​

just classes no code

Solution​

The JAR contains an encrypted byte array and a short XOR-based decoder path.

Steps used:

  1. Enumerated classes in challenge.jar.
  2. Reversed constants and extracted encrypted bytes from the checker logic.
  3. Recovered the 4-byte XOR key used by the program (RAM!).
  4. XOR-decrypted the encrypted byte array to plaintext.

Decryption output: VBD{9809b485d2acb7396b328c41a0b19aa8}

Flag​

VBD{9809b485d2acb7396b328c41a0b19aa8}