title: Swift 3 export SecKey to String
body: <p>I am developing an iOS app using swift 3.</p>
  
  <p>I need to export an <code>SecKey</code> (which is the user RSA publickey reference) to a string (e.g base64) in order to share it through a generated QRCode.</p>
  
  <p>It also has to work the other way since the other user that scans the <code>QRCode</code>, will be able to rebuild a <code>SecKey</code> reference from the string extracted from the QRCode.</p>
  
  <p>I found few tutorials but I don't understand exactly what I need to extract from the <code>SecKey</code> reference, and I don't know how to convert it to a <code>String</code>.</p>