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An Elliptic Curve Processor Suitable for RFID-Tags. L. Batina 1 , J. Guajardo 2 , T. Kerins 2 , N. Mentens 1 , P. Tuyls 2 and I. Verbauwhede 1 Katholieke Universiteit Leuven, ESAT-SCD/COSIC 2 Philips Research, The Netherlands. WISSec 2006 Antwerpen, Belgium November 8-9, 2006. Outline.
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An Elliptic Curve Processor Suitable for RFID-Tags L. Batina1, J. Guajardo2, T. Kerins2, N. Mentens1, P. Tuyls2 and I. Verbauwhede 1 Katholieke Universiteit Leuven, ESAT-SCD/COSIC 2Philips Research, The Netherlands WISSec 2006 Antwerpen, Belgium November 8-9, 2006
Outline • Introduction and Motivation • Related Work • Secure Identification Protocols • Elliptic Curve Cryptography (ECC) • Low-cost ECC processor • Results • Conclusions
Motivation • Emerging new applications: wireless applications, sensor networks, RFIDs, car immobilizers, key chains... • resource limited: area, memory, power, bandwidth • low-cost, low-power, low-energy • Pure hardware solutions are energy and cost effective
New challenging applications: RFID tags RFID applications: • Supply chain management • Access control • Payment systems • Product authentication • Vehicles tracking • Medical care • Key rings More recent applications: Anti-counterfeiting
Related Work • Juels: use RFIDs for anti-counterfeiting • [TB06]: EC-based solution could be possible • RFID workshop: several papers considering ECC processors for RFID tags • [McLR07]: limit number of authen. • Other embedded security applications
In short • PKC would be quite useful • We would like to know • Are existing protocols feasible on RFID tags? • How small/cheap is the most compact solution? • If known solutions are too expensive we should think about new, light-weight protocols
Our contributions • Feasibility of ECC on RFID TAGS • Protocols of Schnorr and Okamoto evaluated • Performance vs. area trade-off • Our solution is based on identification schemes • ECDSA is not necessary
Authentication options Question: Can we perform ECC on RFID Tags? Cost? • Options: • ECDSA Signature • one point multiplication + hash • Identification Protocols: Schnorr or Okamoto • one or two point multiplications
Protocol Anatomy Prover Verifier witness challenge response Secure Identification Protocols Set-up: an elliptic curve E(GF(2m)) a point P of order n and a commitment Z = aP to the secret a
Schnorr Identification Protocol Reader (Z=aP) Tag (a) 1. request 2. Choose 3. Compute X = rP 4. X 5. Choose challenge 6. e 7. Compute y = ae + rmod n 7. y 8. If yP – eZ = X = rP (ae + r) P – e(aP) = X accept Else reject
ECC over binary fields Arithmetic can be performed very efficiently (carry-free). An elliptic curveE over GF(2n)is defined by an equation of the form: where a, b GF(2n),Points are (x, y)which satisfy the equation, where x, y GF(2n). Exists a group operation i.e. addition such that for any 2 points, sum is a third point.
Low-power design • Architectural decisions are important • Frequency as low as possible • Power consumption and energy efficiency are both crucial • ECC arithmetic should be revisited to optimize those parameters • The circuit size should be minimized • Flexibility can be sacrificed
Parameter Choice (EC operations) • Use Montgomery representation • Use Lopez-Dahab projective coordinates • Minimize number of registers • Use only x-coordinate of point during protocol
Conclusions • ECC suitable for certain RFID applications • More research on low cost protocols and low cost implementations • See also paper in ePrint Archive