/tags/retired/ Recent content in Retired on Zero's Blog Hugo en-us Fri, 27 Feb 2026 09:58:00 +0700 /posts/htb-crypto-quick-maffs/ Fri, 27 Feb 2026 09:58:00 +0700 /posts/htb-crypto-quick-maffs/ <h2 id="challenge-summary">Challenge Summary</h2> <ul> <li><strong>Name:</strong> quick maffs</li> <li><strong>Category:</strong> Crypto</li> <li><strong>Difficulty:</strong> Hard</li> <li><strong>Goal:</strong> Recover the plaintext triplet and reconstruct the flag.</li> </ul> <h2 id="root-cause">Root Cause</h2> <p>The service encrypts three related plaintext chunks under the same RSA modulus/exponent pair:</p> <ul> <li><code>c1 = m1^e mod N</code></li> <li><code>c2 = m2^e mod N</code></li> <li><code>c3 = m3^e mod N</code></li> <li>and leaks <code>m1 + m2 + m3 = hint</code></li> </ul> <p>Because <code>e</code> is a prime <code>&lt; 1024</code>, we can iterate candidate exponents and solve the algebraic system directly.</p>