author        = {Christoph Nagl and Michael Hutter},
  title         = {Coupon Recalculation for the Schnorr and GPS Identification Scheme: A Performance Evaluation},
  booktitle     = {Workshop on RFID Security 2009 -- RFIDSec 2009, 5th edition, Leuven, Belgium, June 30-July 2},
  year          = {2009},
  editor        = {Lejla Batina},
  pages         = {1--10},
  keywords      = {Radio-Frequency Identification, RFID, Authentication, Schnorr, GPS, Elliptic Curve Cryptography, ECC, Information Security.}
..abstract      = {One of the most important challenges in the last few years has been the integration of authentication services to low-cost RFID tags. Especially elliptic-curve-based implementations have proven to be a good option for asymmetric and light-weight cryptography. In this article, we evaluate two elliptic-curve based versions of the Schnorr and GPS identification schemes that have been designed for use in resource-constrained environments. Both schemes have been implemented on an RFID-tag prototype that runs at 13.56 MHz. Our results show that if the schemes make use of a pre-computation approach using coupons, Schnorr leads to a higher performance in terms of memory consumption, computational complexity, and communication bandwidth. Furthermore, we show that the challenge-response calculation of the Schnorr identification scheme can be performed even within the frame-delay timings of most common RFID standards such as ISO/IEC 14443 and ISO/IEC 15693 which encourages the use of Schnorr in scenarios where coupons are recalculated on the tag to allow fast and "on-the-fly" authentication.}