AES-128
Advanced Encryption Standard with a 128-bit key. The cipher used by modern transponder chips (Hitag-PRO, DST-AES, PCF7952) to authenticate to the vehicle immobilizer. Computationally infeasible to brute-force, which is why 2017+ proximity vehicles cannot be paired by onboard procedures.
All-keys-lost
The scenario where zero working keys remain. Recovery always requires a programmer that can read the security PIN from the body control module over OBD-II. No onboard procedure works for all-keys-lost, on any vehicle, ever.
BCM (Body Control Module)
The electronic control unit that manages doors, lights, locks, and the keyless entry receiver. The BCM stores the security PIN that programmers need to read before pairing a new key.
CAN bus
Controller Area Network. The internal vehicle network that programmers use to talk to the immobilizer module. CAN traffic is what travels through the OBD-II port.
DST (Digital Signature Transponder)
The Texas Instruments cipher family used by 4D63 (40-bit), 4D63 80-bit, 4D67, DST80, and DST-AES chips. Older DST variants (40-bit) are cryptographically weak; DST-AES is fully secure.
EEPROM read
Reading the contents of an immobilizer module's non-volatile memory directly, usually by removing the module and connecting to its memory chip with a pro programmer. Required for some all-keys-lost scenarios where the security PIN can't be read over OBD-II.
FCC ID
The Federal Communications Commission identifier printed on every legal RKE remote. The most reliable cross-reference for confirming a replacement fob will pair with your vehicle's keyless entry receiver.
Hitag2
NXP's mature 96-bit cipher used in PCF7936 and PCF7937 chips. Widely deployed across Ford, GM, Mopar, Hyundai/Kia, and Nissan transponder fobs through the early 2010s. Fully supported by all aftermarket programmers in our index.
Hitag-PRO
NXP's AES-128 successor to Hitag2, used in the PCF7953 chip found in late-model Ford, Lincoln, Mopar, and Subaru proximity vehicles.
ID46 / ID47
Honda/Acura's chip generations. ID46 (PCF7961) is the 2005–2014 transponder; ID47 (PCF7938 / Hitag-3) is the AES-128 successor used 2014 onward.
Immobilizer
The vehicle subsystem that prevents the engine from starting unless an authenticated transponder is present. Independent of the keyless entry system — this is why a wrong-chip aftermarket fob can lock the doors but fail to crank the engine.
LF / 125 kHz
Low Frequency. The 125 kHz radio band used between the vehicle's antenna ring and the passive transponder chip in the head of your key. Range is intentionally short (a few centimeters) to enforce that the key be in or near the ignition cylinder.
Megamos AES
The EM Microelectronic AES-128 chip used by Volkswagen Group, Audi, Skoda, SEAT, and select MQB-platform vehicles 2015 onward.
OBD-II
On-Board Diagnostics II. The standardized 16-pin connector under your dashboard that programmers use to talk to the immobilizer module.
PCF
NXP's product prefix for transponder chips. PCF7936 (Hitag2), PCF7937 (Hitag2 extended), PCF7945 (early AES), PCF7952 (PEPS AES), PCF7953 (Hitag-PRO), PCF7961 (ID46), PCF7938 (ID47).
PEPS (Passive Entry Passive Start)
The full name for proximity smart key systems — passive entry (doors unlock as you approach) plus passive start (push-button ignition with the fob in your pocket).
PIN / security seed
The vehicle-specific authentication code stored in the body control module that programmers must read before pairing a new key. Sometimes called "incode" depending on OEM terminology.
Rolling code
A sequence-counter scheme on the RKE radio side that prevents replay attacks against lock/unlock signals. Distinct from the cryptographic authentication used by the immobilizer transponder.
RKE (Remote Keyless Entry)
The lock/unlock/panic radio side of a fob, operating at 315 MHz (U.S.) or 433 MHz (some 2020+ harmonized vehicles). Independent of the transponder side.
Transponder
The passive low-frequency chip in the head of your key that authenticates to the vehicle immobilizer. Powered by the LF antenna ring; no battery required.
UHF / 315 MHz / 433 MHz
Ultra High Frequency. The radio band used by the lock/unlock side of an RKE remote. 315 MHz dominates U.S. vehicles; 433 MHz appears on some 2020+ harmonized models and most European-market vehicles.