Registry

AI-generated Key Takeaways

• The Registry in Tink is a global entity responsible for generating new keys and primitives, but it is intended for internal use only and is slated for removal.

• The Registry forwards calls from getPrimitive() to objects that create keys and primitives, and these objects must be registered for the process to work.

• It's essential to explicitly register the primitives you intend to use (e.g., MacConfig.register()), to ensure your code works consistently and doesn't rely on the unpredictable behavior of other libraries.

• Relying on other libraries to register primitives can lead to unexpected code breakage if the library's registration practices change, making it crucial to self-manage registrations.

This page describes an area that undergoes a major redesign at the moment. The status depends on the programming language used.

Starting with the basics, here is an informal definition of Registry:

Key Term: Registry is a global entity in Tink that knows how to generate new keys and primitives.

But:

Warning: This class is intended to be used only by internal interfaces. You should NOT call its methods directly, but instead access them through higher level APIs like KeysetHandle.

Warning: This class is going to be removed.

That being said, it may be useful to understand this class in order to work with Tink efficiently for the time being.

What happens when you call getPrimitive() on a keyset handle? It forwards your call to the Registry¹, which contains objects with concrete methods to create keys and primitives, such as an AesGcm key or a ChunkedMac instance. The Registry's task is to forward the call to the correct object. This only works if the object is registered, which is why it's important to always register the primitives you are going to use.

But what if I use a library that already registered the primitives I need?

That's precisely the problem. And one of the reasons Registry is being removed. Because in this case your code works only until the library authors decide to not register that primitive anymore. At this point your code breaks, and the reason is non-obvious and confusing. So always register what you use. For example, if you intend you use MAC in your Java code, you should do the following in the setup phase:

MacConfig.register()

This code ensures that all the necessary objects are registered in the necessary places for you to use the MAC primitive.

There is one more side to this problem. Some of your dependencies may register things you actually don't need and would prefer to not depend on. This is another reason to remove the global Registry.

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1. to the global singleton instance of the class Registry, to be precise. We use the name "Registry" for both, the class and the singleton, interchangeably. ↩