title: SKPaymentTransaction transactionIdentifier format
body: <p>We have recently implemented Apple in-app purchases of consumable products for our ios app. As part of the buy-flow we log the completed transaction ids on our server (i.e. the transactionIdentifier of SKPaymentTransaction). When we check our logs we see two types of transaction ids:</p>
  
  <ol>
  <li>Many have this form "120000094272147"</li>
  <li>Some have this form "C12B6264-2D30-41B4-B193-34F878BEF0B7", i.e., a guid.</li>
  </ol>
  
  <p>Searching the net, we have not been able to find any information of the expected format of the transaction id. We are wondering whether we should be alarmed by the two different types showing up, or if it is normal behavior. What are your experiences with the format of the transactionIdentifier?</p>
  
  <p>Update:
  We have found the problem. When we started looking at the json receipt that apples sends back when calling <a href="https://buy.itunes.apple.com/verifyReceipt" rel="noreferrer">https://buy.itunes.apple.com/verifyReceipt</a>, we could see that the product id was com.zeptolab.ctrbonus.superpower1. A quick search on the net brings up lots of hits where this is a well-known receipt used in hacks.</p>