A new and secure chaos-based block cipher for image encryption in wireless sensor networks is proposed. The security analysis and the performances of the proposed algorithm have been investigated. The statistical analysis includes the histograms and correlation coefficients of adjacent pixels. In the differential analysis, the authors use the Number of Pixels Change Rate (NPCR) and the Unified Changing Average (UACI) measures to demonstrate the security against differential attacks. Key sensitivity analysis and key space analysis show that the proposed cipher is secure and resistant to brute force attack. The authors demonstrate that the performance of the cipher exceeds the studied encryption algorithms as well as AES (Advanced Encryption Standard). An implementation on a real wireless sensor network testbed is realized, and the energy consumption is investigated.
TopIntroduction
The unprecedented development of information technology and miniaturization has accelerated the growth and the spread of the Wireless Sensor Networks (WSN).
A wireless sensor network is a network of active tiny nodes that collect data from environment through a sensor unit, treat the information, and forward it via the processing and transmission units.
These tiny and smart devices are invading our daily life and give rise to many applications of wireless sensor network. Ranging from military applications to agriculture, transport, environment, etc., the security of collected and transmitted information has become imperative but also critical (Kavitha & Sridharan, 2010).
Concerns of data security in a WSN are facing sensors with a reduced volume, a limited storage space and especially limited battery power. The design of an encryption algorithm must meet these restrictions, creating a compromise between security on one hand and the speed and energy consumption on the other.
The type of information collected by wireless sensors may be temperature, luminosity, or image in some specific applications.
Multimedia data especially image contain often private or confidential information or even financial interests. For example, smartphone security threats can be countered by biometric identification. Access to the smartphones will be limited to owners who are identified by their identity image.
The exchanges of these data are secured by techniques that guarantee the integrity, confidentiality, and authenticity. Image encryption is a widely studied discipline and chaotic dynamics is a potential rival of conventional cryptosystems.
In fact, according to (Socek, Li, Magliveras, & Furht, 2005) and (Furht, Socek, & Eskicioglu, 2004), the conventional encryption algorithms such as DES (Data Encryption Standard) or AES are not adequate to image and video encryption. Their main argument was the real-time speed reduced by these algorithms.
The author in (Lian, 2009) shows that images encrypted with the AES algorithm are still intelligible. Thereby, the author questions the reliability of AES.
Several studies suggest improving or replacing these algorithms with chaotic ciphers (Socek et al., 2005; Furht et al., 2004; Lian, 2009; Mansour, Chalhoub, & Bakhache, 2012; Zaibi, Peyrard, Kachouri, Fournier-Prunaret, & Samet, 2010).
Chaos theory is part of the most recent and advanced contemporary research fields. It is defined as a study of nonlinear and complex dynamical systems. These complex systems are expressed by recurrences and mathematical algorithms. Furthermore, they are dynamic, variable and some of these systems show no periodic behaviour.
Chaos is having a growing interest in secure communications due to many attractive properties like the sensitivity to initial conditions and parameters variations as well as the random-like behavior of chaotic sequences.
The main purpose of this chapter is proposing a low-power and secure chaos based cryptosystem suitable for wireless sensor network.
In the first section, we give first a brief state of the art of different chaotic cryptosystems and some existing chaotic ciphers for wireless sensor networks. The second part presents image encryption algorithms based on chaos and the AES algorithm. Then we detail our contribution, in the second section. Our algorithm focused on the confusion and diffusion properties as well as the simplicity of the used operations. A security analysis and a comparison with AES and chaotic ciphers are depicted.
The last section describes in the first subsection the wireless sensor networks and their application areas. The second subsection is a brief overview of the existing and the used simulators, the simulation process with the chosen simulators as well as the implementation of our proposal on a real Wireless Sensor Network testbed equipped with 16-bit microcontrollers. We exhibit also the operation mode of the chosen platform. Finally, a study on energy consumption of the proposed and investigated ciphers is exposed in both simulation and experimental tests.