A method for authenticating a computing device includes: storing an account profile, the profile including data related to a service account including an alphanumeric code; generating a session identifier and a seed value; computing a first hash using the session identifier; computing a second hash using the session identifier and the alphanumeric code; computing a third hash using the second hash and a utilized seed value; transmitting the session identifier to a computing device via a first communication protocol; transmitting the session identifier and first hash to a remote notification service for transmission to the computing device via a second communication protocol; receiving a fourth hash and the session identifier from the computing device via the first communication protocol; validating the fourth hash based on a comparison of the fourth hash and the computed third hash; and transmitting a validation result to the computing device based on the validation step.