Patent ID: 8799655

Claim:
In a mobile device, a method of authenticating a user, the method comprising: storing a set of expected one-time passcodes (OTPs) in memory of the mobile device, the set of expected OTPs having been previously generated by and acquired from an external authentication server; after the set of expected OTPs is stored in the memory of the mobile device, receiving an authentication request from a user of the mobile device, the authentication request including a user-provided OTP; and performing, by processing circuitry of the mobile device, a local authentication operation which provides an authentication result based on a comparison between the user-provided OTP and an expected OTP of the set of expected OTPs stored in the memory of the mobile device, the authentication result indicating whether authentication of the user is successful or unsuccessful; wherein storing the set of expected OTPs in the memory of the mobile device includes saving, in the memory of the mobile device, an OTP file holding multiple time-indexed OTPs as the set of OTPs, each time-indexed OTP corresponding to a respective window of time; and wherein performing the local authentication operation includes: obtaining a current time value, identifying, from the OTP file, particular time-indexed OTPs corresponding to windows of time covering the current time value, and comparing the user-provided OTP to each time-indexed OTP of the particular time-indexed OTPs to determine whether authentication of the user is successful or unsuccessful.