Access sharing model with keychain item created by Secure Enclave on MacOS

Can anyone confirm that theory is correct?

That’s basically correct. macOS supports two types of keychain, the traditional file-based keychain and the modern iOS-style keychain. Secure Enclave protected keys only work in the iOS-style keychain and, when you use the iOS-style keychain on macOS, you get iOS-style access control (keychain access groups and so on).

The only gotcha relates the doc you referenced. It lists three ways to make a keychain access group available to your app. These all work on the Mac except for App Groups. App Groups work very differently on the Mac and, because of this, they can’t be used as keychain access groups.

There is, I believe, an exception to this exception, namely Mac Catalyst, where App Groups work just like they do on iOS, starting with… oh gosh, I’m being vague here… but I think that changed with macOS 11.

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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
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Thank you @eskimo for your confirmation!