cryptomedium

Noncesense Encryption

hackthebox

Task: Custom stream cipher with XOR encryption where flag is used as generator for key derivation. Solution: Known-plaintext XOR recovery, reverse GF(2) key mixing transformation, and Chinese Remainder Theorem to recover the flag from multiple modular equations.

$ ls tags/ techniques/

xor known_plaintext_attack key_recovery stream_cipher crt chinese_remainder_theorem modular_arithmetic custom_cipher gf2_linear_algebra nonce

known_plaintext_xor_recoverygf2_matrix_inversionreversible_key_mixingchinese_remainder_theoremnonce_estimationtime_synchronization

Analysis

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

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