It could be like Digest Encryption...The server sends a encoded key the client uses to send back.  I noticed the data isnt consistent, it may change the key.  Several ideas on this is that the key may be a date or time signature.  If you can get duplicate data returned from 2 calls made at the same time, you can determine if this is an issue.  If the data differs, the key may be a random code sent by the server that you are missing. 
		
	
		
		
		
		
		
		
		
		
		
	
		
		
	
	
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