An example intermediary system allows a control system to securely identify and communicate with a device. The device uses master secret and time data shared with the control system to generate and advertise a time-dependent device identifier and potentially an encrypted device message. The intermediary system augments the received device data with a message (e.g., an estimate of the device's location) encrypted using the time-dependent device identifier as an encryption key. Furthermore, it hashes the time-dependent device identifier for additional security. The augmented data is provided for retrieval and processing by the control system. The owner uses the shared master secret, time data and hash function to generate a hashed time-dependent device identifier used to retrieve matching augmented data from the server. The retrieved message data is decrypted using the reverse of the encryption operations.