$ cat writeup.md…
$ cat writeup.md…
duckerz
Task: custom 16-round Feistel cipher with decryption oracle; round function compresses 8 bytes to 1 via GF(2^8) polynomial then expands via SBOX. Solution: exploit F(block,0)=SBOX[0] to neutralize rounds iteratively, recover key bytes via SBOX membership test with CBC-batched queries.
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