https://bschaatsbergen.com/posts/Recent content in Posts on Bruno SchaatsbergenHugoen-usSun, 26 Jul 2026 00:00:00 +0000https://bschaatsbergen.com/posts/tpm-clock/Sun, 26 Jul 2026 00:00:00 +0000https://bschaatsbergen.com/posts/tpm-clock/<p>I have a confidential VM running for some attestation work. It has a virtual TPM, which reports its manufacturer as <code>GOOG</code>. I was poking at it and ran <code>tpm2_readclock</code>, expecting a timestamp somewhere in there.</p> <pre tabindex="0"><code>$ sudo tpm2_readclock time: 964062646 clock_info: clock: 964065681 reset_count: 15 restart_count: 0 safe: yes </code></pre><p>No date. I went looking for why, assuming I&rsquo;d missed a command.</p> <h2 id="what-a-tpm-is">what a TPM is</h2> <p>A <a href="https://trustedcomputinggroup.org/resource/tpm-library-specification/">TPM</a> is a small, slow processor that holds keys and won&rsquo;t give them back. You can ask it to sign something. You can&rsquo;t ask it for the key.</p>