About

A token is a authentication material

An access token is a token (string) representing an access authorization.

Authentication

Token-based authentication is implemented by:

• generating a token when the user authenticates
• and then setting that token in the Authorization header of each subsequent request to an API.

They carry just enough information to either:

• authorize the user to perform an action,
• or allow a client to get additional information about the authorization process (to then complete it).

The concept behind using tokens is that you can authenticate to a central authority and then have permissions granted to a separate system without needing to give that system your credentials.

If the server providing the service was compromised, credentials would still be safe, and the attacker would only have access to resources until the token expired. Hence tokens are generally short lived.

Benefits

• Unique – tokens are specific and can be generated per use or per device
• Revocable – tokens can can be individually revoked at any time without needing to update unaffected credentials
• Limited – tokens can be narrowly scoped to allow only the access necessary for the use case
• Random – tokens are not subject to the types of dictionary or brute force attempts that simpler passwords that you need to remember or enter regularly might be

Usage

• Oauth - Token
  • What is a Oauth Access Token?
  • Oauth - Refresh token

Format

Access tokens:

• have an expiration date
• are short-lived.

This information may live:

• inside the structure of the token
• or in a database/map