AES-128 Chip Solutions

Question

Project

The system is effectively a sensor network that connects to a star topology routing network. The Identities of each node's identity must be kept secret from all listeners as the range of the RF transmission and relay may be on the order of tens of miles. Each sensor node has its own Identification number, as required by laws pertaining to our systems target deployment.

This means that if someone is able to read the identifier on the node then the security has not value, so a side channel attack on our implementation is a waste of time, unless they can implement it from a long distance, but I do not believe our SPI will radiate that well when sandwiched between a power and ground layer.

Security Options

This question is asking for solutions to using AES-128. I will explain what I found in an answer that I was lead to directly by Joby Taffey. Thank you Joby. I was looking for off-chip low cost solutions that could speed up our system greatly, it ends up i missed something from my chip supplier.

Answer 1

Having a separate encryption co-processor could be risky. Anyone with a Bus Pirate or logic analyser and physical access can sniff the bus and pluck out the plaintext data.

You can mitigate the risk a bit with BGAs and/or epoxy, but the best solution is likely to be a SoC which combines MCU with AES.

One approach might be to use a SoC ZigBee chip and ignore the radio part, eg. CC2430, or EM250.

Or, you could go with a Stellaris Cortex-M3 (some have AES tables in ROM)

Or, do it in software. I've used Brian Gladman's code before in projects.

Answer 2

As said before, off-chip is risky as its very hard to control the keys and other important information.

There are microcontrollers which contain AES accelerators or function tables. The AVR XMEGA has an engine which can do AES fairly quickly (its not super security hardened though, including known power attacks). The aforementioned Stellaris controllers have the large tables in ROM which saves quite a bit of storage space.

Answer 3

Joby pointed me to the CC2430 as a device that can do AES. I went to TIs site intrigued by this and did some research. TI also makes our transceiver for our frequency bands(CC1100) and the new CC1100 merged with an MSP430 for a SoC now has AES-128 built in.

This saves us board space and was a planned change already, but this results in full support for AES-128 automatically. Completely internal encryption and decryption, which for our chip without Multiply or divide hardware took more than 10mS to complete on its own.