Secure key fob electronics integrated in micromodule

April 25, 2012 // By Christoph Hammerschmidt
Atmel Corp. has announced a secure ultra-low-power micromodule transponder based on an Atmel AVR microcontroller (MCU). Used for remote keyless entry systems in vehicles, the ATA5580 transponder includes the Atmel open immobilizer protocol stack with a built-in, high-performance AES-128 hardware cryptographic unit, a low-frequency (LF) immobilizer interface for power supply and bi-directional communication, and an LF antenna.

The ATA5580 standalone immobilizer transponder is intended to be over-molded in simple mechanical keys which are usually accompanying full featured remote keyless entry key fobs. For this purpose, the ATA5580 immobilizer transponder and the ATA5795 remote keyless entry AVR microcontroller feature the same LF, protocol and AES implementations allowing seamless deployment of both types of keys in a single system.

Based on a land grid array- (LGA-) like package, the ATA5580 transponder avoids usage of a lead frame construction providing best-in-class electrostatic discharge (ESD) protection that is especially important in harsh environments such as over-molding processes. The ultra-low power design along with the high modulation index delivers a typical coupling factor in the range of 1% while running a complete AES authentication. Since typical AES immobilizer transponders exhibit significantly higher coupling factor requirements, the ATA5580 is unique in allowing car manufacturers to transition from deprecated cryptographic systems to AES without the necessity for expensive lock cylinder mechanical redesigns.

The AVR microcontroller embeds 8kB Flash and 2kB EEPROM memory hosting the Atmel open immobilizer software stack programmed during manufacturing. The protocol stack, released under an open source license allows true peer-reviewing process and security audits.

While all traditional competitive offering has a one-size-fits-all approach, the ATA5580's immobilizer protocol is made heavily configurable via EEPROM allowing designers to easily optimize system parameters such as authentication time against coupling factor/bit security, maximizing the communication link robustness for a given environment.

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