Patent ID: 8995669
Filing Date: 2015-03-31
Classification: H04L

Abstract:
1. A method performed by data processing apparatus, the method comprising: obtaining, at a first server, a first set of three or more keys, each key in the first set of keys being associated with a different respective time period; generating, at the first server and at a first local time read by local clock of the first server that is during a first time period associated with a first key in the first set of keys, a first piece of information based on a first request received from a first client device using the first key; receiving, at the first server and at a second local time read by the local clock of the first server that is during the first time period associated with the first key in the first set of keys, a second request from a second client device, the second request including a second piece of information generated using a second key in the first set of keys, the second key being associated with a second time period subsequent to the first time period; and validating, at the first server and at a third local time read by a local clock of the first server that is during the first time period associated with the first key, the second piece of information using the second key associated with the second time period subsequent to the first time period.