title: What is the role of the -signkey option in openssl-req?
body: <pre><code>openssl genrsa -out server.key 1024
  openssl req -new -key server.key -out server.csr
  openssl x509 -req -in server.csr -out server.crt -signkey server.key -days 3650
  </code></pre>
  <p>This is a popular command for generating self-signed SSL certificates using OpenSSL.</p>
  <p>What confuses me is the <code>-signkey</code> parameter in the third command line, what is the use of this option? I don't see it in <code>openssl req -help</code>.</p>
  <p>Can anyone answer it please? Thanks in advance!</p>