Digital signature transponder

<p>The <a href="/facts/Texas_Instruments/88NUhuHF">Texas Instruments</a> digital signature transponder (DST) is a cryptographically enabled <a href="/facts/RFID/4CnmIV2b">radio-frequency identification</a> (RFID) device used in a variety of wireless authentication applications.  The largest deployments of the DST include the <a href="/facts/Exxon-Mobil/0qXyFrM4">Exxon-Mobil</a> <a href="/facts/Speedpass/u0BE0tMc">Speedpass</a> payment system (approximately 7 million transponders), as well as a variety of <a href="/facts/Vehicle_immobilizer/T3sDwfej">vehicle immobilizer</a> systems used in many late model Ford, Lincoln, Mercury, Toyota, Nissan, Kia, Hyundai and Tesla vehicles.
</p><p>The DST is an unpowered "passive" transponder which uses a proprietary <a href="/facts/Block_cipher/MJywAyfQ">block cipher</a> to implement a <a href="/facts/Challenge%25E2%2580%2593response_authentication/QTMRmhpM">challenge–response authentication</a> protocol.  Each DST tag contains a quantity of <a href="/facts/NVRAM/CIYnqh4E">non-volatile RAM</a>, which stores a 40-bit encryption key.  This key is used to encipher a 40-bit challenge issued by the reader, producing a 40-bit <a href="/facts/Ciphertext/luNTs4sY">ciphertext</a>, which is then truncated to produce a 24-bit response transmitted back to the reader.  Verifiers (who also possess the encryption key) verify this challenge by computing the expected result and comparing it to the tag response.  Transponder encryption keys are user programmable, using a simple over-the-air protocol.  Once correctly programmed, transponders may be "locked" through a separate command, which prevents further changes to the internal key value.  Each transponder is factory provisioned with a 24-bit serial number and 8-bit manufacturer code.  These values are fixed and cannot be altered if the transponder is locked.
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Digital signature transponder open-in-new

Digital signature transponder