Which is the hash key on an iPhone?

Could you please elaborate on what you mean by "hash key" on an iPhone? Typically, iPhones do not have a dedicated "hash key" as a physical button or a distinct setting. However, if you're referring to a cryptographic hash key used for security purposes, such as encrypting data or verifying the integrity of an app, these are handled by the iPhone's operating system and hardware in the background. For example, when you download an app from the App Store, Apple uses cryptographic hashes to ensure that the app you're installing hasn't been tampered with. This process is automatic and doesn't require you to manually input or manage a hash key. If you're looking for a way to securely store or manage cryptographic keys on your iPhone, you might want to consider using a dedicated password manager or secure storage app that supports this functionality. Could you please clarify your question further? Are you looking for a specific feature or setting on the iPhone related to cryptographic hash keys?