title: libssh trying to authenticate with public and private keys
body: <p>I've been trying to use libssh to connect to a server and download files via SFTP. I have a PuTTY private key file containing 6 lines of key for the public key and 12 for the private key yet I can't find any decent help or documentation of taking these keys and using them to authenticate a connection to the server. Does anybody know how to do this?</p>
  
  <p>So far the only options for authentication I can find are what I found in the libssh header file:</p>
  
  <pre class="lang-c prettyprint-override"><code>LIBSSH_API int ssh_userauth_pubkey(ssh_session session, const char *username, ssh_string publickey, ssh_private_key privatekey);
  </code></pre>
  
  <p>However, I don't know how a key from a PuTTY <code>.ppk</code> file can translate into an <code>ssh_string</code> for the public key or a <code>ssh_private_key</code> for the private key.</p>