cryptoPromedium

Crypto Leak

RingZer0 CTF

Task: decrypt a WAV encrypted with a custom 64-bit Fibonacci-LFSR stream cipher (RC8) given redacted source and ciphertext. Solution: observe the keystream is the raw sliding-window LFSR bit stream, recover the seed from a known WAV header, then solve the key taps over GF(2) and decrypt.

known_plaintext stream_cipher gf2 lfsr wav fibonacci_lfsr

known_plaintext_attackgf2_gaussian_eliminationsliding_window_lfsr_recoverykeystream_reconstruction

$ ls tags/ techniques/

known_plaintext stream_cipher gf2 lfsr wav fibonacci_lfsr

known_plaintext_attackgf2_gaussian_eliminationsliding_window_lfsr_recoverykeystream_reconstruction

Analysis

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$ python3 exploit.py --target 192.168.1.1 --port 8080
[*] Connecting to target...
[+] Shell obtained!

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