Example embodiments of systems and methods for data transmission system between transmitting and receiving devices for use in a tap and walk store are provided. In an example embodiment, the transmitting device can generate a diversified key using the master key, protect a counter value and encrypt data prior to transmitting to the receiving device, which can generate the diversified key based on the master key and can decrypt the data and validate the protected counter value using the diversified key. Disclosed systems allow a user to purchase items utilizing the disclosed transmitting device.