Communication system, communication method, and sensor unit

The present disclosure is a sensor unit that is installed in an automatic vending machine, and unlocks the automatic vending machine, based on encrypted data transmitted from a terminal apparatus. The sensor unit includes: an encryption processor that generates a public key and a private key, and encrypts an unlocking code with the public key; a hash generator that hashes, through a hash function, sensor information including at least a sensor ID and position information on a sensor, and outputs a hash value; a manager that stores, in a storage, at least the public key and the hash value in association with each other, and manages the public key and the hash value; and an unlocker that determines success or failure of encrypted data transmitted from the terminal apparatus, and unlocks the automatic vending machine when the encrypted data matches with encrypted data generated by the encryption processor.