A method for securing
payment data for transmission over
open communication networks is disclosed. The method comprises establishing a
data connection between a first and a second
transceiver device, the first
transceiver device configured as a merchant device and the second
transceiver device configured as a customer transceiver device. The merchant device transmits a first data
package which comprises a unique merchant identifier and transaction request data, to the customer transceiver device over the
data connection. The merchant device receives a
cryptogram from the customer transceiver device. The
cryptogram having been generated from using a secret key and a counter value together with the received unique merchant identifier and the transaction request data. The method comprises forming an authorisation request comprising the received
cryptogram, merchant identifier and the transaction request data and submitting said authorisation request to at least one of an issuer and an acquirer to facilitate authorisation and
processing of said transaction request data.