securityprincipal

A security principal is an entity that can be authenticated by a computer system and that may be granted access to resources. In security architectures, the principal represents the subject in authorization decisions. The term is distinct from identity in that the identity is the factual person or entity, while the principal denotes the security context used during access checks. Principals can be humans, services, computers, or other devices.

Principals are authenticated and then held in a security context, often as a token or credential. This context is used to determine what resources the entity may access and what operations it may perform. Access control mechanisms compare the principal’s identity and associated attributes against access control lists, policies, or claims to decide whether access should be allowed.

Types of principals include: user accounts, groups (or role memberships), service accounts, and computer or device accounts. In cloud and enterprise environments, principals can also be represented by service principals or application identities, including claims-based identities where a set of claims defines the principal’s attributes.

In Windows, for example, an access token contains the user’s security identifier (SID) and the SIDs of groups the user belongs to. Resources have access control lists that reference SIDs, and access checks use the token to determine whether the principal is permitted to perform an action. In other systems, principals may be represented by certificates, Kerberos principals, or claims in a token.

Security design emphasizes proper management of principals, including least privilege, careful token handling, and clear separation of duties, to minimize the risk of unauthorized access or privilege escalation.