Which type of token generates fixed passcodes based on time?

The type of token that generates fixed passcodes based on time is a synchronous token. Synchronous tokens operate by using the current time as an input to create a passcode. They typically employ a clock or time-based algorithm ensuring that the generated passcode changes at regular intervals, usually every 30 or 60 seconds. Users must enter the correct passcode generated by their token within that time frame to authenticate successfully.

The functionality of synchronous tokens relies on precise time synchronization between the token device and the authentication server. This ensures that the server can verify the passcode entered by the user because it will produce the same passcode at the matching intervals. Therefore, the secure and dynamic nature of time-based passcodes enhances security by making it much harder for an unauthorized user to guess current passcodes since they continuously change.

Other types of tokens, like asynchronous tokens, do not generate passcodes based on time intervals but rather change based on user actions or conditions. Biometric tokens rely on physical characteristics of the user for authentication. Smart tokens can include features from both synchronous and asynchronous systems but are not exclusively characterized by time-based passcode generation.