Abstract: The present invention describes a system and method for securely identifying and authenticating devices in a symmetric encryption system. An RFID tag can generate indicators using encryption state variables and a symmetric key. An RFID reader, after receiving the encryption state variables from the tag, may identify the tag by performing an exhaustive key search in a key database. Each key in the database may be tested by using the key and encryption state variables to perform an encryption operation similar to that performed by the tag. The result is then compared with the received tag indicators to determine if the tag has been identified. A rotor-based encryption scheme provides for a low cost key search while providing resilience against cloning, tracking, tampering and replay attacks.