An approach for facilitating a one-time password (OTP) authentication procedure is described. A dedicated validation appliance receives a one-time password authentication request via an application programming interface, which is a single point of access to the dedicated validation appliance. The dedicated validation appliance then determines a validity of the request based on the correlating of a submitted OTP against OTP values independently generated by the dedicated validation appliance based on a large secret key exclusive to a client device that initiated the request. The single point of access to the dedicated validation appliance as well as exclusive sharing of the secret key with only another dedicated validation appliance or one-time with the client device reduces the likelihood of attackers discovering the secret keys.