title: Compress Guids by hashing in small data sets
body: <p>I'm working on a mobile app and i want to optimise the data that it's receiving from the server (as JSON).
  There are 3 lists returned (each containing its own class of objects, the approximate list sizes are 50, 100 and 170). Each object has a Guid id and there is some relation data for each object. E.g.:</p>
  
  <pre><code>o = { Id = "8f088552-5b24-4ba4-a6e5-8958c4353581",
        RelatedIds = ["19d2e562-0874-473f-8e05-7052e8defd9a", "615b4c47-199a-4f7d-8268-08ed43d9c891", ... ] }
  </code></pre>
  
  <p>Is there a way to compress these Guids to something sorter without storing an identity map? Perhaps using a hash function?</p>