It is common but undocumented to use a JPEG file for .[5]
自 2017 年以來,Apple 在 IPA 中使用 LZFSE 而不是註冊 Zip 算法。本例中的“壓縮方法”字段設置為 99。
Since 2017, Apple has used LZFSE instead of registered Zip algorithms in IPAs. The "compression method" field in this case is set to 99.[6]
Code signing is handled in the .app bundle directory. The META-INF folder only contains metadata about what program was used to create the IPA.[7]
Unsigned .ipa executables
An unsigned .ipa can be created by copying the folder with the extension .app from the Products folder of the application in Xcode to a folder called Payload and compressing the latter using the command zip -0 -y -r myAppName.ipa Payload/
.
It is then possible to install unsigned .ipa files on iOS jailbroken devices using third party software. AppSync is the tool for installing such homebrew apps. Similar to the case of game console hacking, people are known to use this installation for piracy, against the tool developer's wishes:[8] some underground communities form around buying an app and then sharing its DRM-free unsigned version.