Refresh tokens and access tokens are both integral parts of authentication and authorization processes, particularly in systems that employ OAuth 2.0, such as many modern web applications and APIs.
Access Token: An access token is a credential that represents the authorization a user grants to the application to access their resources (like data, services, etc.) on their behalf. These tokens are usually short-lived and have limited permissions. Once obtained, an access token can be sent with each API request to prove the user's authorization. Access tokens typically expire after a set period, necessitating the use of refresh tokens to obtain new access tokens.
Refresh Token: A refresh token is a credential used to obtain a new access token when the current one expires. Unlike access tokens, refresh tokens are long-lived and typically not meant to be sent with every request to the server. Instead, they are securely stored on the client side and exchanged for a new access token when needed. This helps enhance security since refresh tokens are less frequently transmitted over the network.
Here's a typical flow:
The client application (such as a web or mobile app) requests authorization from the user.
The authorization server grants an access token and a refresh token to the client.
The client uses the access token to access protected resources on behalf of the user.
When the access token expires, the client can use the refresh token to request a new access token from the authorization server without requiring the user to re-authenticate.
This process repeats until the refresh token itself expires or is revoked.
Refresh tokens are important for security because they limit the exposure of access tokens. If an access token is stolen, its limited lifespan reduces the window of opportunity for malicious actors to misuse it. Refresh tokens, being long-lived and not transmitted as frequently, are less susceptible to interception. However, they still need to be securely stored to prevent unauthorized access to them.