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Rejigged iOS Security Guide details Apple Pay Cash, other iOS 11 improvements

Apple on Thursday unveiled a revised edition of its mobile security white paper, adding details on iOS 11.1 and 11.2 for information security professionals and intellectually curious users.

The biggest change to the oft-updated guide is a new section dedicated to Apple Pay Cash, Apple's recently released peer-to-peer payments feature that works inside of Messages. Apple Pay Cash debuted last month with iOS 11.2.

According to the document, Apple Pay Cash transactions are processed in a fashion not unlike standard Apple Pay:

When the user sends money with Apple Pay, adds money to an Apple Pay Cash account, or transfers money to a bank account, a call is made to the Apple Pay Servers to obtain a cryptographic nonce, which is similar to the value returned for Apple Pay within apps. The nonce, along with other transaction data, is passed to the Secure Element to generate a payment signature. When the payment signature comes out of the Secure Element, its passed to the Apple Pay Servers. The authentication, integrity, and correctness of the transaction is verified via the payment signature and the nonce by Apple Pay Servers. Money transfer is then initiated and the user is notified of transaction completion.

The document reveals that identity confirmation data - which Apple says is requested if an Apple Pay Cash balance reaches a predefined amount or if unusual activity is detected - is transmitted to the company's verification partner. Apple itself does not receive and cannot access that data, and the partner is unnamed.

Other changes include updates to security certifications, shared notes, CloudKit end-to-end encryption, standard Apple Pay, Shared iPad in educational environments, and Siri Suggestions. Face ID security measures, covered in a separate white paper, are also folded in.