Every IPA must be signed with a valid Apple-issued certificate. For apps downloaded from the App Store, the signature matches Apple’s root certificate. For sideloaded apps, you need a developer certificate. “Patched” often means .
Given that Apple no longer signs iOS 7.1.2 (you cannot restore to it officially unless you have SHSH blobs), the community keeping these devices alive is essentially running a preservation society. ipa files for ios 712 patched