posted Jan 6, 2016, 2:41 AM by Khaled salama
updated Apr 6, 2016, 6:32 PM
Pseudorandom number generators (PRNGs) have increasingly become crucial components in communication systems, cryptography, and stochastic simulations. With a deterministic yet unpredictable nature, chaos-based PRNGs (CB-PRNGs) implement a chaotic equation that produces randomized symbols when initialized by a seed. Digital implementation of CB-PRNGs, area efficiency, repeatability, portability, power consumption, high throughput and integrability with IC technology strongly motivate researchers to create an effective post-processing technique to overcome statistical flaws in their output. The Von Neumann technique, XOR correctors, truncation of defective bits, hash-function post-processing, and linear code correctors are examples of well-known solutions that overcome bias and enhance random properties of PRNGs. While most previous solutions can solve statistical defects, none of them preserve the raw RNG throughput and some incur a huge hardware overhead. At the sensors lab, Prof. K.N. Salama and Prof Ahmed Radwan and a team of KAUST students M. Barakat, M. Zidan and A. Mansingka developed a a generalized post-processing technique for enhancing the pseudorandomness of digital chaotic oscillators through a nonlinear XOR-based operation with rotation and feedback. Such random bits are statistically independent by the nature of the chaotic dynamics similar to noise. Compared to the solution of the ODE, adding noise to the MSBs creates large deviations, which emulate the instability in the original chaotic trajectories, resulting in a random walk process in the discrete time. The technique allows full utilization of the chaotic output as pseudorandom number generators and improves throughput without a significant area penalty. The new technique is evaluated against known techniques and shows superior performance, enabling full utilization of all output bits as a CB-PRNG, successfully passing all NIST SP. 800-22 tests. Furthermore, the technique is applied to four different chaotic oscillators to prove its generalized effect, resulting in the same enhancement of randomness. We developed the first all digital fully controllable chaotic systems with wide noise margins, high throughput (>15Gbits/sec), compact area (<5% of Vertix 4), reproducibility, environmental insensitivity. The systems implemented pass the NIST SP 800-90 with 100% success rate and exhibit a 100x improvement in their Maximum Lyaponov Exponent compared to original systems.
Applications:Image Encryption: Chaos-based image encryption using stream ciphers is a vivid, yet challenging, application of chaos because of the high correlation between image pixels. Unlike block ciphers, stream ciphering operates on smaller data units and satisfies the high throughput requirement for data transmission applications such as wireless communications. Chaotic stream ciphers utilise CB-PRNGs to generate a key stream necessary for masking and defusing image pixels. Nevertheless, flaws in CB-PRNGs result in weak encryption prone to various cryptanalysis attacks; and therefore are solved by the hybridization of two or more chaotic systems. None of the popular encryption systems have been realized on hardware as they occupy a larger area and operate on lower throughput rates losing the sole advantages of stream encryption. To the best of our knowledge, this presents the first hardware realization of a lightweight chaotic stream cipher utilized for colored image encryption satisfying three corner requirements: (i) high throughput, (ii) robust encryption and (iii) small hardware area. The encryption adopted in this work is a simple encoder that directly XORs image pixels with the key stream bits generated by the chaotic oscillator. A thorough security analysis is provided for several images and the results are compared with the previously reported software-based encryption systems showing a superior performance. Benchmarked against standard stream and block cipher hardware systems,
- RC4 used in 802.11 Wi-Fi security protocol,
- E0 used in Bluetooth protocol,
- A5/1 used in GSM communications,
- SNOW 3G used by the 3GPP group as a mobile cellular standard,
- Advanced encryption standard (AES) adopted in many applications
The proposed system yields the highest area throughput ratio compared with all other systems and therefore achieved the best hardware efficiency. Together with the high security accomplished, the proposed stream cipher can be considered a new encryption standard.
Secure Communications: Chaos-based communication is considered advantageous because chaotic signals are inherently unpredictable, wideband and have low cross-correlation, thus enabling multiple users in a spread-spectrum communication environment. Fully digital multiscroll chaos can provide repeatable chaotic spreading codes while also having complex dynamical behavior that provides security over communication channels. Chaotic spreading sequences surpass m-sequences and Gold codes and it is already well-known that fully orthogonal Walsh codes perform very poorly in a multi path environment because of poor cross-correlation properties under delay. The implemented system provides 512 distinct code streams with low cross-correlation and is easily scalable based on implementation parameters. The spreading code shows strong performance in a multiple access environment with additive white Gaussian noise (AWGN) and multipath channels, equivalent to Gold codes while simultaneously providing security through aperiodic and complex nonlinear dynamics that pass tests for statistical randomness. The resulting chaotic spreading code sources are experimentally verified on a Xilinx Virtex 4 FPGA with logic utilizations less than 1.25% and throughput up to 10.92 Gbits/s.
This work is described in detail in publications that were highly praised by the independent reviewers. For more detail see:
- M. barakat, A. Mansingka, A.G. Radwan and K. N. Salama," Generalized Hardware Post Processing Technique for Chaos-Based Pseudorandom Number Generators," ETRI, vol.35, no.3, pp.448-458, May 2013
- M. barakat, A. Mansingka, A.G. Radwan and K. N. Salama,, Hardware Stream Cipher with Controllable Chaos Generator for Color Image Encryption, IET image processing, Volume 8, Issue 1, p. 33 – 43, 2014.
- Mohamd Barakat, Ahmed Radwan and Khaled Salama "Hardware Realization of Chaos Based Block Cipher for Image Encryption", IEEE international Conference on Microelectronics (ICM), 2011
- A. S. Mansingka, M. L. Barakat, M. Affan Zidan, A. G. Radwan, K. N. Salama, Fully Digital Jerk-Based Chaotic Oscillators for High Throughput Pseudo Random Number Generators up to 8.77 Gbits/s Microelectronics journal, vol 44, no 9, pp 744-752, 2013
- A. S. Mansingka, A. G. Radwan and K. N. SalamaSecure Ds-CDMA Spreading Codes Using Fully Digital Multidimensional Multiscroll Chaos,56th IEEE International Midwest Symposium on Circuits and Systems (MWSCAS), August 2013