title: how can i sign a file in Qt using sha1 digest?
body: <p>I need to sign a file using QCA and qca-ossl in Qt.
  the input is a private key and a zip file.
  in ruby this can be done like this</p>
  
  <pre><code>@sig = @key.sign(OpenSSL::Digest::SHA1.new, plain)
  </code></pre>
  
  <p>in Linux I can do this by with command:</p>
  
  <pre><code>openssl rsautl -sign -in file -inkey key.pem -out sig
  </code></pre>
  
  <p>Here the private key I got in qt by</p>
  
  <pre><code>QCA::PrivateKey seckey = QCA::KeyGenerator().createRSA(1024);
  </code></pre>
  
  <p>now I need to do the signing in qt</p>
  
  <p>can anybody help me on this?</p>