8,487 research outputs found
A Simple Attack on Some Clock-Controlled Generators
We present a new approach to edit distance attacks on certain
clock-controlled generators, which applies basic concepts of Graph Theory to
simplify the search trees of the original attacks in such a way that only the
most promising branches are analyzed. In particular, the proposed improvement
is based on cut sets defined on some graphs so that certain shortest paths
provide the edit distances. The strongest aspects of the proposal are that the
obtained results from the attack are absolutely deterministic, and that many
inconsistent initial states of the target registers are recognized beforehand
and avoided during search
Modelling Nonlinear Sequence Generators in terms of Linear Cellular Automata
In this work, a wide family of LFSR-based sequence generators, the so-called
Clock-Controlled Shrinking Generators (CCSGs), has been analyzed and identified
with a subset of linear Cellular Automata (CA). In fact, a pair of linear
models describing the behavior of the CCSGs can be derived. The algorithm that
converts a given CCSG into a CA-based linear model is very simple and can be
applied to CCSGs in a range of practical interest. The linearity of these
cellular models can be advantageously used in two different ways: (a) for the
analysis and/or cryptanalysis of the CCSGs and (b) for the reconstruction of
the output sequence obtained from this kind of generators.Comment: 15 pages, 0 figure
Platform for Testing and Evaluation of PUF and TRNG Implementations in FPGAs
Implementation of cryptographic primitives like
Physical Unclonable Functions (PUFs) and True Random Number
Generators (TRNGs) depends significantly on the underlying
hardware. Common evaluation boards offered by FPGA vendors
are not suitable for a fair benchmarking, since they have different
vendor dependent configuration and contain noisy switching
power supplies. The proposed hardware platform is primary
aimed at testing and evaluation of cryptographic primitives
across different FPGA and ASIC families. The modular platform
consists of a motherboard and exchangeable daughter board
modules. These are designed to be as simple as possible to
allow cheap and independent evaluation of cryptographic blocks
and namely PUFs. The motherboard is based on the Microsemi
SmartFusion 2 SoC FPGA. It features a low-noise power supply,
which simplifies evaluation of vulnerability to the side channel
attacks. It provides also means of communication between the
PC and the daughter module. Available software tools can be
easily customized, for example to collect data from the random
number generator located in the daughter module and to read it
via USB interface. The daughter module can be plugged into
the motherboard or connected using an HDMI cable to be
placed inside a Faraday cage or a temperature control chamber.
The whole platform was designed and optimized to fullfil the
European HECTOR project (H2020) requirements
Design and validation of a platform for electromagnetic fault injection
Security is acknowledged as one of the main challenges in the design and deployment of embedded circuits. Devices need to operate on-the-field safely and correctly, even when at physical reach of potential adversaries. One of the most powerful techniques to compromise the correct functioning of a device are fault injection attacks. They enable an active adversary to trigger errors on a circuit in order to bypass security features or to gain knowledge of security-sensitive information. There are several methods to induce such errors. In this work we focus on the injection of faults through the electromagnetic (EM) channel. In particular, we document our efforts towards building a suitable platform for EM pulse injection. We design a pulse injection circuit that can provide currents over 20 A to an EM injector in order to generate abrupt variations of the EM field on the vicinity of a circuit. We validate the suitability of our platform by applying a well-know attack on an embedded 8-bit microcontroller implementing the AES block cipher. In particular, we show how to extract the AES secret cryptographic keys stored in the device by careful injection of faults during the encryption operations and simple analysis of the erroneous outputs.Peer ReviewedPostprint (published version
Graph-Based Approach to the Edit Distance Cryptanalysis of Irregularly Clocked Linear Feedback Shift Registers
This paper proposes a speed-up of a known-plaintext attack on some stream ciphers
based on Linear Feedback Shift Registers (LFSRs). The algorithm consists of two basic steps:
first, to guess the initial seed value of one of the LFSRs, and then to use the resulting binary
sequence in order to deduce useful information about the cipher parameters. In particular, the
proposed divide-and-conquer attack is based on a combination of graph-based techniques with
edit distance concepts. While the original edit distance attack requires the exhaustive search over
the set of all possible initial states of the involved LFSR, this work presents a new heuristic optimization
that avoids the evaluation of an important number of initial states through the identification
of the most promising branches of the search graph. The strongest aspects of the proposal
are the facts that the obtained results from the attack are absolutely deterministic, and that many
inconsistent initial states of the target LFSRs are recognized and avoided during search.This work was supported by the Spanish Ministry of Science and Innovation and European
FEDER Fund under Project TIN2008-02236/TSI as well as by CDTI (Spain)and the companies INDRA, Unin Fenosa, Tecnobit, Visual Tool, Brainstorm, SAC and
Technosafe under Project Cenit-HESPERIA.Peer reviewe
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