GenTOTP (sk, C_T) -> \tau On input the secret key sk and a time counter C_T, it computes the TOTP result \tau at counter C_T.

KeyGenTOTP TOTPGen() -> sk On input a security parameter 1^lambda, it generates a secret key $sk$.

VerifyTOTP (sk, \tau, C_T) -> {0, 1} On input the secret key sk, the time counter C_T and TOTP result \tau, it outputs true if and only if \tau = TOTPGen(sk, C_T).