Anonymity is the absence of information that can be used to identify an agent or a product of their agency.
Anonymity is a function of the information available in a transaction, or from records of past transactions.
For the purposes of digital identity services, anonymity exists when information used or collected by the service is insufficient to reveal the civil identity of a party – during the transaction or at a later time.
Some privacy laws and regulations allow for different kinds of anonymity, such as pseudonymity, and contain provisions to restrict forensic identification.
The way anonymity works in digital identity services is a corollary of how digital identity services use information to provide identification, continuity and trust.
The achievement of identification, continuity and trust allows for a lot of variety. These functions can be carried out with different levels of rigour and veracity. They can be achieved singly or in combination. They can use different methodologies and be based on different kinds of information from different sources. Digital identity, therefore, is divisible and variable.
Because anonymity is the absence of information used to fulfil the functions of digital identity, it too is subject to decomposition and variability. In short, anonymity is not a discrete all-or-nothing state.
For example, it is possible to have insufficient information to identify who an agent is, but still know that they are a woman, a French national living in England, and that they are same person with whom one conversed previously.
Similarly a transaction may not provide enough information to know who an agent is (identification), but sufficient information to recognise the same agent in a number transactions (continuity). Because continuity can be established, over time enough additional information might be collected to allow identification.
In many use-cases there is a requirement to explicitly allow and ensure some level of anonymity. Moreover, most jurisdictions impose on digital identity services some limit on the scope and effect of identification.
An understanding of how anonymity works is important for an understanding of how identity works, and leads to better systems and services.