Polyinstantiation

Polyinstantiation is a security feature in computing, especially in database systems, where multiple instances of the same data, each with different security classifications, are created.

One of the key features in objectoriented technology useful to security is polyinstantiation. Polyinstantiation may prevent inference possibilities by creating a new version of an object, using the same identifier or key, so that different user processes have their own local copy of it. Essentially, it allows different versions of the same shared information resource to exist at different classification levels. This can prevent users or processes at a lower classification level from knowing the existence of a higher classification level. Inference is defined as the ability of authorized or unauthorized users to deduce (infer) more sensitive information from observing authorized information.

Specific objects, instantiated from a higher class, may vary their behavior depending on the data they contain. Therefore, it may be difficult to verify that inherited security properties are valid for all objects. However, this is why polyinstantiation can also be used to prevent inference attacks against databases, because it allows different versions of the same information to exist at different classification levels.