| 主权项 |
1. One or more non-transitory computer-readable media storing instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising:
receiving, at a server, a validation request from a processing system associated with a validation entity, the validation request comprising a set of alphanumeric characters, wherein the set of alphanumeric characters were derived from a time-varying representation for a credential, wherein the time-varying representation for the credential comprises at least one from the group consisting of (i) a time-varying optical machine-readable representation for the credential and (ii) a time-varying code rendered as a sound signal, the sound signal having a frequency greater than 20 kHz, the set of alphanumeric characters comprising data corresponding to a key associated with a user, a credential identifier identifying the credential, and a first time at a client device; determining, at the server, that the key is associated with the credential identifier; obtaining, at the server, a second time from a timing device; determining, at the server, that the second time from the timing device is within a predetermined amount of time of the first time at the client device; and at the server, responsive to determining that the key is associated with the credential identifier, and that the second time is within a predetermined amount of time of the first time, communicating to the processing system a validation response indicating that the credential is validated. |
