Patent attributes
Disclosed herein is a method for performing an integrated contactless point-of-sale transaction. More particularly, there is disclose a method comprising: receiving, by a mobile device 1, a seed number from a communications network; generating, by the mobile device 1, one or more session keys, in dependence on the received seed number, for use in encrypted communication with the mobile device 1; and/or generating, by the mobile device 1, a pre-image, in dependence on the received seed number, for use in generating an unpredictable number for use in secure communication with the mobile device. Advantageously, the generation of session keys and/or a pre-image in dependence on a seed number provided to the mobile device improves the security of the system since the source of the seed number can detect incorrect session keys and/or unpredictable number derived from an incorrect pre-image.