I found some more information...
the fairplay streaming key url is modified by UVD. The original looks more like this.
Quote:
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skd://netflix/AAAABAAAAAAD0WX938O7NZ/lEP/7WDg6urvmT5yjzMeLP/WcEJWnvzxNb6M=
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the value is a base64 encoded data from data in the pssh(Protection Specific Header Box)with a system ID of 0x29701FE43CC74A348C5BAE90C7439A47 in the video file itself.
It also retrieves an application certificate signed by apple that is some how used in the process of retrieving the key.
For the the old playready HLS streams I think the decryption key is actually stored in the video itself in an encrypted envelope. I don't know the details of how that works though.