Digital identity refers to the aspect of digital technology that is concerned with the mediation of people's experience of their own identity and the identity of other people and things. Digital identity also has another common usage as the digital representation of a set of claims made by one digital subject about itself or another digital subject.

Digital subject

A digital subject is an entity represented or existing in the digital realm which is being described or dealt with. Every digital subject has a finite, but unlimited number of identity attributes. A digital subject can be human or non-human. Non-human examples include:

• Devices and computers1 (which allow us to penetrate the "digital realm" in the first place);
• Digital resources (which attract us to it);
• Policies and relationships between other digital subjects (e.g., between humans and devices or documents or services).

Identity through relationship

An observer's perception of the digital identity of an entity is inevitably mediated by the subjective viewpoint of that observer (just as it is with physical identity). In order to attribute a digital representation to an entity, and so to elide the two as a digital subject, the attributing party (the observer) must trust that the representation does indeed pertain to the entity (see Authentication below). Conversely, the entity may only grant the observer selective access to its informational attributes (according to the identity of the observer from the perspective of the entity). In this way, digital identity is better understood as a particular viewpoint within a mutually-agreed relationship than as an objective property. This contextual nature of digital identity is referred to as contextual identity.

Authentication

Authentication is a key aspect of trust-based identity attribution, providing a codified assurance of the identity of one entity to another. Authentication methodologies include the presentation of a unique object such as a bank credit card, the provision of confidential information such as a password or the answer to a pre-arranged question, the confirmation of ownership of an e-mail address, and more robust but relatively costly solutions utilising encryption methodologies. In general, business-to-business authentication prioritises security while user to business authentication tends towards simplicity. New physical authentication techniques such as iris scanning, handprinting, and voiceprinting are currently being developed and in the hope of providing improved protection against identity theft.

Identifiers

Digital identity fundamentally requires digital identifiersstrings or tokens that are unique within a given scope (globally or locally within a specific domain, community, directory, application, etc.). Identifiers are the key used by the parties to an identification relationship to agree on the entity being represented. Identifiers may be classified as omnidirectional and unidirectional. 2 Omnidirectional identifiers are intended to be public and easily discoverable, while unidirectional identifiers are intended to be private and used only in the context of a specific identity relationship.