We present a general technique for the efficient computation of pairings on supersingular Abelian varieties. As particular cases, we describe efficient pairing algorithms for elliptic and hyperelliptic curves in characteristic 2. The latter is faster than all previously known pairing algorithms, and as a bonus also gives rise to faster conventional Jacobian arithmetic.

Abstract. For counting points of Jacobians of genus 2 curves defined over large prime fields, the best known method is a variant of Schoof’s algorithm. We present several improvements on the algorithms described by Gaudry and Harley in 2000. In particular we rebuild the symmetry that had been broken by the use of Cantor’s division polynomials and design a faster division by 2 and a division by 3. Combined with the algorithm by Matsuo, Chao and Tsujii, our implementation can count the points on a Jacobian of size 164 bits within about one week on a PC. 1

Abstract. We present an implementation of elliptic curves and of hyperelliptic curves of genus 2 and 3 over prime fields. To achieve a fair comparison between the different types of groups, we developed an ad-hoc arithmetic library, designed to remove most of the overheads that penalize implementations of curve-based cryptography over prime fields. These overheads get worse for smaller fields, and thus for larger genera for a fixed group size. We also use techniques for delaying modular reductions to reduce the amount of modular reductions in the formulae for the group operations. The result is that the performance of hyperelliptic curves of genus 2 over prime fields is much closer to the performance of elliptic curves than previously thought. For groups of 192 and 256 bits the difference is about 14 % and 15 % respectively.

Abstract. In most algorithms involving elliptic and hyperelliptic curves, the costliest part consists in computing multiples of ideal classes. This paper investigates how to compute faster doubling over fields of characteristic two. We derive explicit doubling formulae making strong use of the defining equation of the curve. We analyze how many field operations are needed depending on the curve making clear how much generality one loses by the respective choices. Note, that none of the proposed types is known to be weak – one only could be suspicious because of the more special types. Our results allow to choose curves from a large enough variety which have extremely fast doubling needing only half the time of an addition. Combined with a sliding window method this leads to fast computation of scalar multiples. We also speed up the general case.

Abstract. In 1986, D. V. Chudnovsky and G. V. Chudnovsky proposed to use formulae coming from Theta functions for the arithmetic in Jacobians of genus 2 curves. We follow this idea and derive fast formulae for the scalar multiplication in the Kummer surface associated to a genus 2 curve, using a Montgomery ladder. Our formulae can be used to design very efficient genus 2 cryptosystems that should be faster than elliptic curve cryptosystems in some hardware configurations.

Nowadays, there exists a manifold variety of cryptographic applications: from low level embedded crypto implementations up to high end cryptographic engines for servers. The latter require a exible implementation of a variety of cryptographic primitives in order to be capable of communicating with several clients. On the other hand, on the client it only requires an implementation of one speci c algorithm with xed parameters such as a xed eld size or xed curve parameters if using ECC/ HECC. In particular for embedded environments like PDAs or mobile communication devices, xing these parameters can be crucial regarding speed and power consumption. In this contribution, we propose a highly ecient algorithm for a hyperelliptic curve cryptosystem of genus two, well suited for these constraint devices.

Abstract. In this paper, we present several improvements on the best known explicit formulæ for hyperelliptic curves of genus three and four in characteristic two, including the issue of reducing memory requirements. To show the effectiveness of these improvements and to allow a fair comparison of the curves of different genera, we implement all formulæ using a highly optimized software library for arithmetic in binary fields. This library was designed to minimize the impact of a whole series of overheads which have a larger significance as the genus of the curves increases. The current state of the art in attacks against the discrete logarithm problem is taken into account for the choice of the field and group sizes. Performance tests are done on two personal computers with very different architectures. Our results can be shortly summarized as follows: Curves of genus three provide performance similar, or better, to that of curves of genus two, and these two types of curves can perform faster than elliptic curves – indeed on some processors often twice as fast. Curves of genus four attain a performance level comparable to elliptic curves. A large choice of curves is therefore available for the deployment of curve-based cryptography, with curves of genus three and four providing their own advantages as larger cofactors can be allowed for the group order.

Abstract. Cryptographic algorithms are used in a large variety of different applications to ensure security services. It is, thus, very interesting to investigate various implementation platforms. Hyperelliptic curve schemes are cryptographic primitives to which a lot of attention was recently given due to the short operand size compared to other algorithms. They are specifically interesting for special-purpose hardware. This paper provides a comprehensive investigation of high-efficient HEC architectures. We propose a genus-2 hyperelliptic curve cryptographic coprocessor using affine coordinates. We implemented a special class of hyperelliptic curves, namely using the parameter h(x) = x and f = x 5 + f1x + f0 and the base field GF(2 89). In addition, we only consider the most frequent case in our implementation and assume that the other cases are handled, e.g. by the protocol. We provide three different implementations ranging from high speed to moderate area. Hence, we provide a solution for a variety of applications. Our high performance HECC coprocessor is 78.5 % faster than the best previous implementation and our low area implementation utilizes only 22.7 % of the area that the smallest published design uses. Taking into account both area and latency, our coprocessor is an order of magnitude more efficient than previous implementations. We hope that the work at hand provides a step towards introducing HEC systems in practical applications.

Regarding the overall speed and power consumption, cryptographic applications in embedded environments like PDAs or mobile communication devices can benefit from specially designed cryptosystems with fixed parameters. In this contribution, we propose a highly efficient algorithm for a hyperelliptic curve cryptosystem (HECC) of genus two, well suited for these applications on constrained devices. This work presents a major improvement of HECC arithmetic for certain non-supersingular curves defined over fields of characteristic two. We optimized the group doubling operation and managed to speed up the whole cryptosystem by approximately 27 % compared to the previously known most efficient case. Furthermore, an actual implementation of the new formulae on an embedded processor shows its practical relevance. A scalar multiplication can be performed in approximately 50¢¤ £ on an 80MHz embedded device. 1.

We survey recent research on pairings on hyperelliptic curves and present a comparison of the performance characteristics of pairings on elliptic curves and hyperelliptic curves. Our analysis indicates that hyperelliptic curves are not more efficient than elliptic curves for general pairing applications.