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    No mention of whether the images are “burned” by the server after the first retrieval. If so, I could detect your background image downloader by sending an image and seeing if you can retrieve it on your phone in front of me.

    I wonder if snap chat could use the push notifications as a kind of two factor auth to verify its the app doing the downloading.

    Then again, any app requires at least some trust of the recipient. They could always just take a picture of their phone. The self deleting functionality is just a reminder to play by the rules.