A method of generating wireless communications from a transmit-only device, the method comprising: generating, at the transmit-only device, a first current session key; generating, at the transmit-only device, operational data; generating, at the transmit-only device, crypto-data by performing a cryptographic operation on the operational data using the first current session key; transmitting, from the transmit-only device, a first identifier to enable a resource derive the first current session key; transmitting, from the transmit-only device, the crypto-data.