Overall Objectives
Scientific Foundations
Application Domains
New Results
Contracts and Grants with Industry
Other Grants and Activities

Section: New Results



[40] , [46] There is currently a lack of cryptographic primitives for authentication of aggregated data. The theoretical background for Aggregated Message Authentication Codes (AMACs) has been proposed by Chan and Castelluccia at ISIT 08. In this paper, we propose a MAC design based on universal hash functions and more precisely on the Krawczyk's constructions. We show how those designs can be used for aggregation and how it can be easily adapted for WSNs. Our two AMAC constructions offer a small memory footprint and a signification speed to fit into a sensor. Moreover, when compared with scenarios without aggregation, the method proposed here induces a simulated energy gain between 3 and 9.

[12] have been proposed as an alternative to Linear Feedback Shift Registers (LFSRs) for the design of stream ciphers. FCSRs have good statistical proper- ties and they provide a built-in non-linearity. However, two attacks have shown that the current representations of FCSRs can introduce weak- nesses in the cipher. We propose a new “ring” representation of FCSRs based upon matrix definition which generalizes the Galois and Fibonacci representations. Our approach preserves the statistical properties and circumvents the weaknesses of the Fibonacci and Galois representations. Moreover, the ring representation leads to automata with a quicker diffu- sion characteristic and better implementation results. As an application, we describe a new version of F-FCSR stream ciphers. These new representations were extented a step further in order to obtain efficient software implementation of FCSRs in [14] .

In [30] , we give a natural formalization to capture the notion of known-key distinguishers in an effort to view block cipher security from an alternative perspective e.g. a block cipher viewed as a primitive underlying some other cryptographic construction such as a hash function. We applied this concept to construct a 7-round distinguisher for the AES and a 7-round Feistel cipher. We then use our model to construct known-key distinguishers for Rijndael with Large Blocks up to 7 and 8 rounds.

WSN security:

The security of WSNs is studied in the thesis of Wassim Znaidi. In [41] , a solution to the replication attack is proposed. Due to the use of low-cost materials, hardware components are not tamper-resistant and an adversary could access a sensor's internal state. Thus, an adversary can easily capture even a single node and insert duplicated nodes at any location in the network for malicious purpose. We propose a hierarchical distributed algorithm for detecting node replication attacks using a Bloom filter mechanism and a cluster head selection. The problem of establishing key between the nodes to enforce confidentiality is addressed in [47]


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