Apple Fortifies App Store Security with SHA-256 Upgrade for Receipt Verification

In its step further toward privacy and security, Apple recently announced an important update regarding the receipt signing intermediate certificate of the App Store, which will be able to switch over to the SHA-256 cryptographic algorithm.

This changes the requirements for app validation as well as in-app purchases, and so shall be fully enforced by January 24, 2025.

With this upgrade, Apple will aim to improve cryptographic standards throughout its ecosystem and make a few changes at the developer’s level, which relies on receipt validation for managing access to PS.

Why the Shift to SHA-256?

SHA-256 is less vulnerable to attacks than its predecessor, SHA-1, due to its significant vulnerability. SHA-2 family is the category to which SHA-256 belongs. SHA-256 provides robust integrity, security, and less attack resistance than others.

For these reasons, it is a preferred standard of secure data validation. Applying SHA-256 on signed App Store receipts will ensure this proof-of-purchase information is secure against risks of forgery or tampering by any risk about user transactions.

Implementation Timeline and Phased Rollout

Carefully introducing this certificate update across the Apple ecosystem should provide plenty of time for developers to prepare.

• Sandbox Environment: SHA-256 certificate began usage on June 20, 2023. So developers can start making preliminary tests.
• TestFlight: SHA-256 was released to the TestFlight environment on August 16, 2023, which introduced another environment apart from the local one in a developer’s development environment before it transitioned fully.
• App Store: This phase is finished on January 24, 2025, when the SHA-1 certificate expires, thereby completely transitioning the certificate to SHA-256.

By rolling this out slowly, Apple gives developers a long lead time to ensure their apps are SHA-256 ready, especially if they validate receipts on the device.

How Does This Affect Developers?

This update by Apple requires developers to ensure their receipt validation processes are SHA-256 compliant so as not to disturb their services. This mainly applies to those developers who validate receipts on-device, where app functionality relies on validating purchases locally on the user’s device end.

Receipt validation will fail if an app’s receipt validation process does not update to include SHA-256 by January 2025. For users, this may mean that something that previously was a premium feature or app content is no longer available. Apple has appealed to developers to take timely action to avoid user disruptions.

Apple’s Recommendations for a Smooth Transition

Apple has provided developers two primary options to move their receipt validation to SHA-256.

• Update Cryptographic Support: Developers using custom cryptographic code to verify the receipt must update their codebase to include support for SHA-256. Achieved by ensuring that any library or functions are updated for compatibility with the new certificate.
• Leverage the AppTransaction and Transaction APIs: They are designed to achieve transaction validation, supporting SHA-256. It would keep supporting more direct implementations of custom cryptographic techniques instead of having compatibility issues with new certificate standards.

Testing and Validation Before Full Transition

SHA-256 has been in use in the sandbox environment since mid-2023. Meanwhile, the developers must test their applications to ensure app receipts comply with the new certificate.

Extensive testing here would ensure proper working of receipt validation during the production phase when the change is fully rolled out on 24th January 2025.

Furthermore, Apple also suggests developers check for a full certificate chain test with SHA-256 compliance to prevent validation errors. It would be essential to ensure the receipt validation code could decode certificates successfully so that users can have unproblematic access.

Server-to-Server Receipt Verification: Not Directly Impacted

Apple says this certificate update does not affect server-to-server receipt validation using the now-deprecated verify receipt endpoint, as they do not rely on on-device validation.

Instead, developers implementing server-side receipt validation should transition to on-device validation or the latest Transaction APIs, which promise better security and performance.

Aligning with Stronger Cryptographic Standards

Apple changed to SHA-256 due to the current industry trend of better cryptographic standards. SHA-1 was the norm for the previous years but has become incompatible with recent security standards; hence, there was a need for a change.

Apple continues to emphasize that transactions are verified on digital sites while paying attention to new threats emanating from them and, therefore, protecting users’ data.

Secure Your iOS Apps with Certera’s SHA-256 Readiness Solutions!

With Apple’s shift to SHA-256 for App Store receipt validation, ensuring your app’s compliance is crucial to maintaining uninterrupted services and secure user transactions. Certera is here to seamlessly guide you through this vital upgrade.