The IT Law Wiki


NIST, Digital Identity Guidelines (NIST Special Publication 800-63) (June 22, 2017) (full-text).


Digital identity is the online persona of a subject, and a single definition is widely debated internationally. The term persona is apropos as a subject can represent themselves online in many ways. An individual may have a digital identity for email, and another for personal finances. A personal laptop can be someone's streaming music server yet also be a worker-bot in a distributed network of computers performing complex genome calculations. Without context, it is difficult to land on a single definition that satisfies all.

Digital identity as a legal identity further complicates the definition and ability to use digital identities across a range of social and economic use cases. Digital identity is hard. Proving someone is who they say they are &mash; especially remotely, via a digital service — is fraught with opportunities for an attacker to successfully impersonate someone. As correctly captured by Peter Steiner in The New Yorker, "On the internet, nobody knows you're a dog." These guidelines provide mitigations to the vulnerabilities inherent online, while recognizing and encouraging that when accessing some low-risk digital services, "being a dog" is just fine; while other, high-risk services need a level of confidence that the digital identity accessing the service is the legitimate proxy to the real-life subject.

For these guidelines, digital identity is the unique representation of a subject engaged in an online transaction. A digital identity is always unique in the context of a digital service, but does not necessarily need to uniquely identify the subject in all contexts. In other words, accessing a digital service may not mean that the subject's real-life identity is known.

Identity proofing establishes that a subject is who they claim to be. Digital authentication establishes that a subject attempting to access a digital service is in control of one or more valid authenticators associated with that subject's digital identity. For services in which return visits are applicable, successfully authenticating provides reasonable risk-based assurances that the subject accessing the service today is the same as that which accessed the service previously. Digital identity presents a technical challenge because this process often involves proofing individuals over an open network, and always involves the authentication of individual subjects over an open network to access digital government services. The processes and technologies to establish and use digital identities offer multiple opportunities for impersonation and other attacks.

These technical guidelines supersede NIST Special Publication 800-63-2. Agencies use these guidelines as part of the risk assessment and implementation of their digital service(s). These guidelines provide mitigations of an authentication error's negative impacts by separating the individual elements of identity assurance into discrete, component parts.

This set includes:

  • SP 800-63A Enrollment and Identity Proofing (full-text)
  • SP 800-63B Authentication and Lifecycle Management (full-text)
  • SP 800-63C Federation and Assertions (full-text).