What is the Principal of a user in Authentication?

About

A principal in security is the unique identifier of an identity ie:

• object,
• service,
• person (users),
• groups,
• domains,
• service accounts.

The identity key or principal is typically an account’s user name such as:

• the Security Accounts Manager (SAM) account name
• for LDAP, the Distinguished Name (DN) of the LDAP user
• for Kerberos, the User Principal Name (UPN).
• for the PKI model, the subject ¹⁾

Example

• A principal for a simple user/password based auth

{
 "username": "alice"
}