Authenticating a transaction when a connection to a network becomes unavailable

A method of authenticating a transaction between a user and an entity, the method comprising:

• operating a modified cellular telecommunications network universal integrated circuit card (UICC) module, the UICC module including at least one processor that executes software stored on a non-transitory computer readable medium and being operated to generate a time-dependent authentication code which is dependent on a time value and which is usable to authenticate the transaction only during a predetermined threshold time period, wherein the UICC module is operable to be registered with the cellular telecommunications network for which the user has a mobile telecommunications device and includes information which is usable to authenticate the user's mobile telecommunications device with the cellular telecommunications network to obtain telecommunications services therefrom;
• obtaining, via the cellular telecommunications network, a current time from a time source that is independent of a local clock of the mobile telecommunications device;
• comparing the obtained current time with a current clock time from the local clock, the current clock time being accessible without using the cellular telecommunications network;
• calculating an offset value indicative of the difference between the obtained current time from the time source and the current clock time from the local clock of the mobile telecommunications device;
• calculating a period, being a calculated period, wherein the calculated period is a difference between the current clock time and a clock time recorded when the current time was last obtained from the time source;
• and
• using the offset value to calculate the time value to enable generation of the time-dependent authentication code when a connection to the cellular telecommunications network is not available, wherein the time-dependent authentication code is usable to authenticate the transaction only when the calculated period is within the predetermined threshold time period, and wherein the predetermined threshold time period begins at a point when the current time was last obtained from the time source via the cellular telecommunications network.

A non-transitory computer readable medium storing software for authenticating a transaction between a user and an entity, the software comprising:

• executable code that operates a modified cellular telecommunications network universal integrated circuit card (UICC) module to generate a time-dependent authentication code which is dependent on a time value and which is usable to authenticate the transaction only during a predetermined time period, wherein the UICC module is operable to be registered with the cellular telecommunications network for which the user has a mobile telecommunications device and includes information which is usable to authenticate the user's mobile telecommunications device with the cellular telecommunications network to obtain telecommunications services therefrom;
• executable code that obtains, via the cellular telecommunications network, a current time from a time source that is independent of a local clock of the mobile telecommunications device;
• executable code that compares the obtained current time from the time source with a current clock time from the local clock, the current clock time being accessible without using the cellular telecommunications network;
• executable code that calculates an offset value indicative of the difference between the obtained current time from the time source and the current clock time from the local clock;
• executable code that calculates a period, being a calculated period, wherein the calculated period is a difference between the current clock time and a clock time recorded when the current time was last obtained from the time source;
• and
• executable code that uses the offset value to calculate the time value to enable generation of the time-dependent authentication code when a connection to the cellular telecommunications network is not available, wherein the time-dependent authentication code is usable to authenticate the transaction only when the calculated period is within the predetermined threshold time period, and wherein the predetermined threshold time period begins at a point when the current time was last obtained from the time source via the cellular telecommunications network.