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We present new candidates for quantum-resistant public-key cryptosystems based on the conjectured difficulty of finding isogenies between supersingular elliptic curves. The main technical idea in our scheme is that we transmit the images of torsion bases under the isogeny in order to allow the two parties to arrive at a common shared key despite the… (More)

The aim of this paper is to justify the common cryptographic practice of selecting elliptic curves using their order as the primary criterion. We can formalize this issue by asking whether the discrete log problem (dlog) has the same difficulty for all curves over a given finite field with the same order. We prove that this is essentially true by showing… (More)

We propose an undeniable signature scheme based on el-liptic curve isogenies, and prove its security under certain reasonable number-theoretic computational assumptions for which no efficient quantum algorithms are known. Our proposal represents only the second known quantum-resistant undeniable signature scheme, and the first such scheme secure under a… (More)

Given two elliptic curves over a finite field having the same cardinality and endomorphism ring, it is known that the curves admit an isogeny between them, but finding such an isogeny is believed to be computationally difficult. The fastest known classical algorithm takes exponential time, and prior to our work no faster quantum algorithm was known.… (More)

The Boneh-Boyen signature scheme is a pairing based short signature scheme which is provably secure in the standard model under the q-Strong Diffie-Hellman assumption. In this paper, we prove the converse of this statement, and show that forging Boneh-Boyen signatures is actually equivalent to solving the q-Strong Diffie-Hellman problem. Using this… (More)

As hardware capabilities increase, low-power devices such as smartphones represent a natural environment for the efficient implementation of cryptographic pairings. Few works in the literature have considered such platforms despite their growing importance in a post-PC world. In this paper, we investigate the efficient computation of the Optimal-Ate pairing… (More)

We present a construction of expander graphs obtained from Cay-ley graphs of narrow ray class groups, whose eigenvalue bounds follow from the Generalized Riemann Hypothesis. Our result implies that the Cayley graph of (Z/qZ) * with respect to small prime generators is an expander. As another application, we show that the graph of small prime degree… (More)

Recent work [27, 15] introduced a novel peer-to-peer application that leverages content sharing and aggregation among the peers to diagnose misconfigurations on a desktop PC. This application poses interesting challenges in preserving privacy of user configuration data and in maintaining integrity of troubleshooting results. In this paper, we provide a much… (More)

We present a method for key compression in quantumresistant isogeny-based cryptosystems, which allows a reduction in and transmission costs of per-party public information by a factor of two, with no e ect on security. We achieve this reduction by associating a canonical choice of elliptic curve to each j-invariant, and representing elements on the curve as… (More)