A method comprising: receiving (S534), by a mobile device from a base station , a first transmission comprising a first session identifier; transmitting (S536), by the mobile device to the base station, a second transmission comprising a second session identifier and a first processing time value, wherein the base station generates a first distance measurement corresponding to a distance between the mobile device and the base station using at least the first processing time value; receiving (S538), by the mobile device from the base station, a third transmission comprising a second processing time value; responsive to the third transmission, generating (S540), by the mobile device, a second distance measurement corresponding to the distance between the mobile device and the base station using at least the second processing time value; generating, by the mobile device, a first cryptogram using the second distance measurement, and one or more of the first session identifier, the second session identifier and/or a mobile device identifier associated with the mobile device; and transmitting (S544), by the mobile device, a fourth transmission comprising the first cryptogram to an access device in communication with the base station, wherein the access device receives (S542) a data element from the base station, the data element generated by the base station using the first distance measurement, and one or more of the first session identifier, the second session identifier, and/or the mobile device identifier, and wherein the access device validates (S546) the first cryptogram using the data element. receiving (S534), by a mobile device from a base station , a first transmission comprising a first session identifier; transmitting (S536), by the mobile device to the base station, a second transmission comprising a second session identifier and a first processing time value, wherein the base station generates a first distance measurement corresponding to a distance between the mobile device and the base station using at least the first processing time value; receiving (S538), by the mobile device from the base station, a third transmission comprising a second processing time value; responsive to the third transmission, generating (S540), by the mobile device, a second distance measurement corresponding to the distance between the mobile device and the base station using at least the second processing time value; generating, by the mobile device, a first cryptogram using the second distance measurement, and one or more of the first session identifier, the second session identifier and/or a mobile device identifier associated with the mobile device; and transmitting (S544), by the mobile device, a fourth transmission comprising the first cryptogram to an access device in communication with the base station, wherein the access device receives (S542) a data element from the base station, the data element generated by the base station using the first distance measurement, and one or more of the first session identifier, the second session identifier, and/or the mobile device identifier, and wherein the access device validates (S546) the first cryptogram using the data element. <EOS>