 Perfect digital invariant

A **Perfect Digital Invariant (PDI)** is a concept often discussed in the field of cryptography and computer security, particularly in relation to password storage and authentication processes. In a general sense, a PDI refers to a transformation of sensitive information (like a password) such that it remains secure even when it undergoes a number of operations. This concept exemplifies the principle that, despite the operations applied, the invariant retains certain properties that make the original information difficult to derive or reconstruct.