Trusted-HB: a low-cost version of HB+ secure against Man-in-The-Middle attacks

Since the introduction at Crypto'05 by Juels and Weis of the protocol HB+, a lightweight protocol secure against active attacks but only in a detection based-model, many works have tried to enhance its security. We propose here a new approach to achieve resistance against Man-in-The-Middle attacks. Our requirements - in terms of extra communications and hardware - are surprisingly low.Comment: submitted to IEEE Transactions on Information Theor

A New Algorithm for Solving Ring-LPN with a Reducible Polynomial

The LPN (Learning Parity with Noise) problem has recently proved to be of great importance in cryptology. A special and very useful case is the RING-LPN problem, which typically provides improved efficiency in the constructed cryptographic primitive. We present a new algorithm for solving the RING-LPN problem in the case when the polynomial used is reducible. It greatly outperforms previous algorithms for solving this problem. Using the algorithm, we can break the Lapin authentication protocol for the proposed instance using a reducible polynomial, in about 2^70 bit operations

Composable security of delegated quantum computation

Delegating difficult computations to remote large computation facilities, with appropriate security guarantees, is a possible solution for the ever-growing needs of personal computing power. For delegated computation protocols to be usable in a larger context---or simply to securely run two protocols in parallel---the security definitions need to be composable. Here, we define composable security for delegated quantum computation. We distinguish between protocols which provide only blindness---the computation is hidden from the server---and those that are also verifiable---the client can check that it has received the correct result. We show that the composable security definition capturing both these notions can be reduced to a combination of several distinct "trace-distance-type" criteria---which are, individually, non-composable security definitions. Additionally, we study the security of some known delegated quantum computation protocols, including Broadbent, Fitzsimons and Kashefi's Universal Blind Quantum Computation protocol. Even though these protocols were originally proposed with insufficient security criteria, they turn out to still be secure given the stronger composable definitions.Comment: 37+9 pages, 13 figures. v3: minor changes, new references. v2: extended the reduction between composable and local security to include entangled inputs, substantially rewritten the introduction to the Abstract Cryptography (AC) framewor

KEDGEN2: A key establishment and derivation protocol for EPC Gen2 RFID systems

International audienceThe EPC Class-1 Generation-2 (Gen2 for short) is a Radio Frequency IDentification (RFID) technology that is gaining a prominent place in several domains. However, the Gen2 standard lacks verifiable security functionalities. Eavesdropping attacks can, for instance, affect the security of applications based on the Gen2 technology. To address this problem, RFID tags must be equipped with a robust mechanism to authenticate readers before authorising them to access their data. In this paper, we propose a key establishment and derivation protocol, which is applied at both identification phase and those remainder operations requiring security. Our solution is based on a pseudorandom number generator that uses a low computational workload, while ensuring long term secure communication to protect the secrecy of the exchanged data. Mutual authentication of the tag and the sensor and strong notions of secrecy such as forward and backward secrecy are analysed, and we prove formally that after being amended, our protocol is secure with respect to these properties