A mustsee when doing TF autographs! Testflight signed source quote list..

TF signature (Trusted Facility Signature, referred to as TF signature) is a technology used for application signing and distribution on iOS devices. It is mainly used to bypass Apple's official app review and distribution restrictions. Through TF signatures, applications can be installed and run directly on iOS devices without going through Apple's App Store review.
tf signature is recommended for fast download and installation, and no blocking at home and abroad. When downloading applications on TF shelves, you no longer need to click on the trust certificate and can be downloaded and used directly. TestFlight's new distribution model avoids the trouble of frequent corporate signature drops. The distribution link no longer has to worry about the risk of blocking, and there is no limit on the number of times. It can be downloaded and used on any Apple device; the powerful TF signature can avoid the expensive price of super signatures. Users can use it for 90 days after downloading it.
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