INS - Ingénierie Numérique et Sécurité

Control theory for synchronization in private communications – THE CASCADE

Control theory for synchronization issues in private communications

Synchronization is not only an ubiquitous phenomenon in natural world, but can also be an interesting <br />solution for different problems encountered in engineering area. In particular, it turns out <br />that synchronization between coupled entities in a unidirectional way, that is in a master-slave <br />configuration, is a mechanism used in private communication, more precisely in cryptographic <br />setups involving ciphers called self-synchronizing stream ciphers.

Towards new classes of self-synchronizing stream ciphers

The aim of the project THE CASCADE is to propose new architectures of Self Synchronizing <br />Stream Ciphers. An SSSC-based private and secure communication can be modelled as a masterslave <br />configuration involving dynamical systems. However, not all dynamical systems are proper <br />ones. In order for a dynamical system to be a good candidate to serve as an SSSC, the resulting <br />master-slave setup must match three major conditions <br />a) it must get the self-synchronization property <br />b) it must agree with cryptographic purposes in particular the security criteria <br />c) it must be viable in a real-world situation <br />So, the challenge is threefold.

The specificity and the originality of the project is the combination of modern tools from
control theory and timely cryptographic purposes. Indeed, synchronization can be interpreted as a state reconstruction problem while
the recovery of the information at the receiver side can be viewed as a left inversion problem.

Synchronization
- Necessary and sufficient conditions of self-synchronization in terms of graphical conditions ensuring the property of flatness [I2b]
- conditions of synchronization for different classes of Linear Parameter Varying (LPV) systems [I1b, I3b, I4b]
- General methodology of constructing stream ciphers having the self-synchronization property based on the result [I2b]
- Polynomial time algorithm for the search of all the flat ouputs of a system [I5b][J2b]
- Flatness characterization for PieceWiseLinear systems based on the spectral radius [J1b]

Securiy
- A unified representation of vectorial Boolean functions [J1a]
- Proof of the IND-CPA security of the canonical form of self-syncjronizing stream ciphers [I2a][J2b]
- Statistical attacks, algebraic attacks and physical attacks. In particular, for the first time regarding the literature, fault induction attacks on SSSC (publication in progress)

Implémentation
- ISC/SCADA platfom incorporating our SSSC algorithms

Synchronization
- Extension of the graphical characterization of flatness for MIMO systems

Securiy
- Further investigation regarding the cryptanalysis

Architecture and implementation
- Comparison of performances with respect to existing SSSC algorithms and potential enhancements

For the sake of space limitation, the scientific production has been splitted into the french and english dedicated columns. Appologize

International Conference papers
[I2a] B. DRAVIE, P. GUILLOT and G. MILLERIOUX, April 2015 Security P

Synchronization is not only an ubiquitous phenomenon in natural world, but can also be an interesting solution for different problems encountered in engineering area. In particular, it turns out that synchronization between coupled entities in a unidirectional way, that is in a master-slave configuration, is a mechanism used in private communication, more precisely in cryptographic setups involving ciphers called self-synchronizing stream ciphers. The main principle of such ciphers is based on generators delivering complex sequences used to conceal information. Those generators must be synchronized at the transmitter (ciphering) and receiver (deciphering) sides for proper information recovery. The aim of the project THE CASCADE is to propose new self-synchronizing architectures for private communications. On the upgrowing field of group communications, self-synchronization is a key feature for high speed communications like PMR (Professional Mobile Radio) systems and for a lot of new devices which are small, mobile, at low consumption and low cost such as some Bluetooth equipments, RFID tags, sensors that require lightweight cryptography, survivable Cyber-Physical Systems.

The specificity and the originality of the project is the combination of modern tools from control theory and timely cryptographic purposes. More precisely, the use of dynamical systems and modern control theoretical concepts will allow to provide and suggest new self-synchronizing architectures.

Clearly, even though control theory is central for the purpose of the project, issues related to security assessment and implementation will also be deeply examined. Hence, investigations for provable security will be carried out and resistance to distinct attacks will be assessed: algebraic attacks addressed as aparameter identifiability problem, distinguisher-based attacks, side channel attacks. Some of the attacks will be particularized owing to the specificity of the generators which will be proposed. A real-world communication platform for tests and validation will be designed by the companies involved in the project.

Project coordinator

Monsieur gilles MILLERIOUX (Centre de Recherche en Automatique de Nancy)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CAS Cassidian CyberSecurity SAS
LIASD Laboratoire d'Informatique Avancée de Saint-Denis
LAGA Laboratoire Analyse, Géométrie et Applications
CRAN Centre de Recherche en Automatique de Nancy

Help of the ANR 319,896 euros
Beginning and duration of the scientific project: March 2014 - 42 Months

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