4.2. Description

4.2. Description

Basically, we define TOTP as TOTP = HOTP(K, T), where T is an integer and represents the number of time steps between the initial counter time T0 and the current Unix time.

More specifically, T = (Current Unix time - T0) / X, where the default floor function is used in the computation.

For example, with T0 = 0 and Time Step X = 30, T = 1 if the current Unix time is 59 seconds, and T = 2 if the current Unix time is 60 seconds.

The implementation of this algorithm MUST support a time value T larger than a 32-bit integer when it is beyond the year 2038. The value of the system parameters X and T0 are pre-established during the provisioning process and communicated between a prover and verifier as part of the provisioning step. The provisioning flow is out of scope of this document; refer to [RFC6030] for such provisioning container specifications.