Apple Encrypted Archive

Apple Encrypted Archive is a proprietary archive format that can compress, encrypt, and/or sign a file. Its magic number is the 4 ASCII characters " ".

macOS Monterey ships an  command line tool that can create and extract (decrypt) these archives (see aea manpage). They can also be handled with public Swift API and private C API in.

It's notably used since iOS 15 for signed .shortcut files created in Shortcuts.