title: have HMAC SHA256 in pure Swift (Vapor) project
body: <p>I am new in Swift based <a href="https://github.com/vapor/vapor" rel="nofollow noreferrer">Vapor</a> backend framework, I just setup the HelloWorld project. </p>
  
  <p>I need to use <strong>HMAC SHA256</strong> algorithm to encrypt data. I searched on internet, and found <a href="https://stackoverflow.com/questions/35620960/generating-hmac-sha256-from-byte-array-in-swift">something like this</a>, but they are all based on iOS or OSX framework, which uses C library and can be added by <code>import &lt;CommonCrypto/CommonHMAC.h&gt;</code>.</p>
  
  <p>How can I add CommonCrypto or HMAC to my Vapor project? If it is impossible, how can I have a pure swift HMAC Sha256 algorithm? Is there such dependency I can add to <em>Package.swift</em> ?</p>