title: Google AMP how to use private key to sign the update-cache request?
body: <p>On <a href="https://developers.google.com/amp/cache/update-cache#rsa-keys" rel="nofollow noreferrer">this page</a>, it's mentioned </p>
  
  <blockquote>
    <p>Use the private key to sign the update-cache request. For example: echo -n >url.txt '/update-cache/c/s/example.com/article?amp_action=flush&amp;amp_ts=1484941817' cat url.txt | openssl dgst -sha256 -sign private-key.pem >signature.bin<br>
    The output to signature.bin is a binary RSA signature.</p>
  </blockquote>
  
  <p>So, I'm expecting this command to generate a <code>signature.bin</code> file.</p>
  
  <p>However, when I try to enter command <code>echo -n &gt;url.txt '/update-cache/c/s/example.com/article?amp_action=flush&amp;amp_ts=1484941817' cat url.txt | openssl dgst -sha256 -sign private-key.pem &gt;signature.bin
  </code> in my Windows command prompt I get the error: </p>
  
  <blockquote>
    <p>'amp_ts' is not recognized as an internal or external command,
    operable program or batch file.</p>
  </blockquote>
  
  <p>I'm now unsure where I should enter this command.</p>