cryptoPromedium

Весёлый RSA (Funny RSA)

hackerlab

Task: Same message encrypted with RSA for three parties using different small moduli. Solution: Factor the small moduli, find the one where gcd(e, phi(n))=1, decrypt with standard RSA, compute SHA256 hash of message.

sha256 rsa small_modulus factorization broadcast_attack hastad multi_recipient same_message

Small modulus factorization (trial division)Standard RSA decryption with computed private keySHA256 hash computation for flag formatVerification across multiple ciphertexts

$ ls tags/ techniques/

sha256 rsa small_modulus factorization broadcast_attack hastad multi_recipient same_message

Small modulus factorization (trial division)Standard RSA decryption with computed private keySHA256 hash computation for flag formatVerification across multiple ciphertexts

Analysis

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

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