An algorithmically-generated code that is deterministic based on the current date and time and a secret “seed” value. The server knows the seed, and can easily verify that a given code is valid for the current time period. TOTP can significantly increase security because even if a code is intercepted, it is worthless after the time window has passed (usually less than a minute). This makes the logistics of an attack much more difficult. TOTP can be implemented on a simple and inexpensive hardware device or on a smartphone. The seed is installed and is made difficult or impossible to recover or duplicate.