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Python Automation - Custom Cipher Decryption
Mission
cipher.txt holds the flag encrypted with a custom cipher (hex). Encryption applies per byte: add (key), xor (position-dependent), rotl (bit rotation). Implement the inverse in Python to recover the flag (run python3 challenge.py for the full spec).
Hints
Hint 1 Show
Run python3 challenge.py for the full cipher spec; the key is b"kinoco"
Hint 2 Show
Decrypt by inverting the steps in reverse: rotr(i%8) -> xor((i*7+0x5A)%256) -> sub(key) per byte
Hint 3 Show
Mind the 8-bit rotate rotr(v,n)=((v>>n)|(v<<(8-n)))&0xFF, then UTF-8 decode the bytes