Systems, methods, and software can be used to improve security of an authentication process in a cargo shipping system. In some aspect, an authentication request message is received at a sensor from a cargo tracking device. The authentication request message includes a key that the sensor will use to decrypt its encrypted public key/private key pair. In response to the authentication request message, the sensor sends an authentication response message to the cargo tracking device that is encrypted using a derived symmetric key. The cargo tracking device sends an authentication confirmation message to the sensor in response to the authentication response message.