Analysis of the Texas Instruments DST RFID
"... Our next step was to recover the secret key from a deployed DST device, using a brute-force key search. Unfortunately, it would have taken more than 2 weeks for our software implementation to find a key when running on 10 very fast PCs. We therefore implemented our key-search on a field programmable gate array (FPGA). The FPGA evaluation board we used is available online for under $200 in single quantities with all of the neccesary development software and cabling. Our implementation cracks 32 keys in parallel on a single FPGA running at 100MHz. At this rate, a single FPGA is expected to crack a key in just over 10 hours.
To decrease this key-cracking time even furthur, we connected 16 FPGAs together at a total cost of under $3,500. Texas Instruments provided us with 5 DST tags whose keys we did not know. The 16-way parallel cracker was able to recover all 5 keys in well under 2 hours. ..."