Simple Power Analysis on Fast Modular Reduction with Generalized Mersenne Prime for Elliptic Curve Cryptosystems

Yasuyuki SAKAI
Kouichi SAKURAI

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A    No.1    pp.231-237
Publication Date: 2006/01/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.1.231
Print ISSN: 0916-8508
Type of Manuscript: Special Section LETTER (Special Section on Cryptography and Information Security)
Category: Side Channel Analysis
Keyword: 
side channel analysis,  elliptic curve cryptosystem,  modular reduction,  generalized Mersenne prime,  unified code,  

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Summary: 
We discuss side channel leakage from modular reduction for NIST recommended domain parameters. FIPS 186-2 has 5 recommended prime fields. These primes have a special form which is referred to as generalized Mersenne prime. These special form primes facilitate especially efficient implementation. A typical implementation of efficient modular reduction with such primes includes conditional reduction. A conditional reduction in modular reduction can constitute an information channel on the secret exponent. Several researchers have produced unified code for elliptic point addition and doubling in order to avoid a simple power analysis (SPA). However, Walter showed that SPA still be possible if Montgomery multiplication with conditional reduction is implemented within the unified code. In this paper we show SPA on the modular reduction with NIST recommended primes, combining with the unified code for elliptic point operations. As Walter stated, our results also indicate that even if the unified codes are implemented for elliptic point operations, underlying field operations should be implemented in constant time. The unified approach in itself can not be a countermeasure for side channel attacks.

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