/tags/quantum/ Recent content in Quantum on Zero's Blog Hugo en-us Wed, 04 Mar 2026 10:55:00 +0700 /posts/htb-quantum-phase-madness/ Wed, 04 Mar 2026 10:55:00 +0700 /posts/htb-quantum-phase-madness/ <h2 id="challenge-summary">Challenge Summary</h2> <ul> <li><strong>Name:</strong> Phase Madness</li> <li><strong>Category:</strong> Quantum</li> <li><strong>Difficulty:</strong> Medium-Hard</li> <li><strong>Goal:</strong> Recover all encoded bytes from qubit phase rotations.</li> </ul> <pagevault hint="Ask bz for access"> <h2 id="root-cause">Root Cause</h2> <p>Each flag byte is encoded directly as a rotation angle in degrees.</p> <p>From source:</p> <ul> <li>index <code>% 3 == 0</code>: <code>RX(byte)</code></li> <li>index <code>% 3 == 1</code>: <code>RY(byte)</code></li> <li>index <code>% 3 == 2</code>: <code>H</code> then <code>RZ(byte)</code></li> </ul> <p>The service lets us:</p> <ul> <li>choose qubit index,</li> <li>apply extra known rotations (<code>RX/RY/RZ</code>),</li> <li>receive high-shot measurement counts.</li> </ul> <p>That is enough to estimate sin/cos components and recover the original angle (thus byte).</p> /posts/htb-quantum-flagportation/ Wed, 04 Mar 2026 10:50:00 +0700 /posts/htb-quantum-flagportation/ <h2 id="challenge-summary">Challenge Summary</h2> <ul> <li><strong>Name:</strong> Flagportation</li> <li><strong>Category:</strong> Quantum</li> <li><strong>Difficulty:</strong> Easy-Medium</li> <li><strong>Goal:</strong> Decode all teleported 2-bit symbols and recover the flag.</li> </ul> <pagevault hint="Ask bz for access"> <h2 id="root-cause">Root Cause</h2> <p>The challenge is a teleportation protocol correctness trap. The server reveals:</p> <ul> <li>encoding basis (<code>Z</code> or <code>X</code>),</li> <li>Bell-side measurement bits (<code>qubit 0</code>, <code>qubit 1</code>),</li> <li>then asks user operations before measuring receiver (<code>qubit 2</code>).</li> </ul> <p>If the correction mapping is wrong, decoded bits are wrong.</p> <p>Correct mapping for this implementation:</p> /posts/htb-quantum-global-hyperlink-zone/ Wed, 04 Mar 2026 10:45:00 +0700 /posts/htb-quantum-global-hyperlink-zone/ <h2 id="challenge-summary">Challenge Summary</h2> <ul> <li><strong>Name:</strong> Global Hyperlink Zone</li> <li><strong>Category:</strong> Quantum</li> <li><strong>Difficulty:</strong> Medium</li> <li><strong>Goal:</strong> Satisfy the hidden hyperlink pattern check and print the flag.</li> </ul> <pagevault hint="Ask bz for access"> <h2 id="root-cause">Root Cause</h2> <p>The server checks only a specific relationship between measured bitstreams (<code>shares</code>) and does not constrain users to a trusted circuit template.</p> <p>From source analysis, success requires:</p> <ul> <li><code>shares[0] == shares[1] == shares[3]</code></li> <li><code>shares[2] == shares[4]</code></li> <li><code>shares[2] != shares[0]</code></li> <li>and no share may be all-0 or all-1 bytes.</li> </ul> <p>Because arbitrary gate sequences are allowed, we can construct a circuit that enforces exactly those relations.</p>