Pasqualina Fragneto

Efficient Software Implementation of AES on 32-Bit Platforms

Rijndael is the winner algorithm of the AES contest; therefore it should become the most used symmetric-key cryptographic algorithm. One important application of this new standard is cryptography on smart cards. In this paper we present an optimisation of the Rijndael algorithm to speed up execution on 32-bits processors with memory constraints, such as those used in smart cards. First a theoretical analysis of the Rijndael algorithm and of the proposed optimisation is discussed, and then simulation results of the optimised algorithm on different processors are presented and compared with other reference implementations, as known from the technical literature.

Power-efficient ASIC synthesis of cryptographic sboxes

In this paper we present a novel methodology that can be used to design efficient hardware structures for a certain class of combinatorial functions. The methodology is primarily intended to achieve low-power synthesis of non-linear one-to-one functions on ASIC technology libraries and fits well for the synthesis of small cryptographic substitution box (Sbox) functional components; the latter are found in most secret key cryptographic algorithms, and usually represent their most relevant part in terms of required computational power. We also describe an extension that allows us to apply the method to general vectorial Boolean functions.

ECG Monitoring in Wearable Devices by Sparse Models

Because of user movements and activities, heartbeats recorded from wearable devices typically feature a large degree of variability in their morphology. Learning problems, which in ECG monitoring often involve learning a user-specific model to describe the heartbeat morphology, become more challenging.

About the performances of the Advanced Encryption Standard in embedded systems with cache memory

Modem networked embedded systems represent a growing market segment in which security is becoming an essential requirement. The Advanced Encryption Standard (AES) specification is becoming the default choice for such type of systems; however, a proper software implementation of AES is of fundamental importance in order to achieve significant performance. Current implementations presented in the literature differ in terms of the amount of look-up tables used for precomputing the functions of the encryption/decryption phase. This raises some questions regarding which AES implementation is optimal for a specific system configuration that, up to now, has been only empirically solved. In this work, we present an analytical model to study and evaluate the performance of the possible AES implementations in the early phases of system development. We then show that the proposed high-level timing model captures, with significant accuracy, the actual performance of current AES applications and thus it can be used for the early evaluation of optimal AES implementations and to support the design space exploration phase. Validating experiments have been carried out on the Lx architecture, a scalable and customizable VLIW architecture developed by STMicroelectronics and HP Labs. Some final considerations are eventually reported about the relevant characteristics of the analyzed implementations and the role of the cache memory.

Uncalibrated dynamic stereo using parallax

In this paper a novel method for computing parallax maps from monocular and uncalibrated video sequences is described. Acquired frames are processed pairwise, starting from a first reference and progressively integrating information coming from subsequent frames in temporal order using a Kalman filter. In this way, temporal stabilization of the generated maps is obtained as well as more consistency with the real video content. Results and evidences coming from the benchmark of the system on both synthetic and natural images have also been reported, showing significant improvements with respect to the parallax maps obtained without temporal integration.

Uncalibrated View Synthesis with Homography Interpolation

This paper presents a novel approach to uncalibrated view synthesis that overcomes the sensitivity to the epipole of existing methods. The approach follows a interpolate-then-derectify scheme, as opposed to the previous derectify-then-interpolate strategy. Both approaches generate a trajectory in an uncalibrated framework that is related to a specific Euclidean counterpart, but our method yields a warping map that is more resilient to errors in the estimate of the epipole, as it is confirmed by synthetic experiments.

Packetizing scalable streams in heterogenus peer-to-peer networks

After the extensive effort dedicated by both Academia and Industry in the area of peer-to-peer (P2P) streaming by looking at models and network algorithms to achieve optimal load distribution, recent works are moving forward to enhance the overall P2P systems efficiency by focusing on specific video codecs and packetization techniques at application layer. The purpose to integrate different technologies with the aim to design full streaming solutions requires a joint efforts from the market and EU projects community. Many engineering issues have been brought out in terms of compatibility and integration that need to be addressed. In this paper we focused on a bottleneck discovered during the packetization step between the Scalable Video Coding (SVC) streaming module (during content creation) and the P2P engine before delivering the packets over the network. We compared the a priori fixed packet size solution adopted in P2P-Next project with a codec aware approach, gaining performance in terms of network overhead. We performed experiments with various sequences aiming at overall P2P streaming efficiency and measured the bandwidth cost under various conditions. Since we focused on the application layer, our statistics analysis can be helpful in designing P2P streaming solutions dealing with any network type.

A combined color-correlation visual model for object tracking using particle filters

In this paper we consider the problem of tracking semi-rigid objects in video sequences using particle filters, with a particular focus on hand tracking applications. Although many different feature descriptors have been developed, none of them alone is good enough to deal with this complex tracking scenarios. Approaches which use a statistical representation of the target tend to fail in presence of visually similar objects, while holistic representations are usually very sensible to motion blur, object deformations and rotations. We present here a visual model which combines color histograms and the MOSSE Correlation Filter. The fusion of two complementary features creates a robust descriptor of the target which is capable of tracking fast moving objects in complex tracking applications with real-time performances, using a low number of particles.

Smart 3D video coding

In this paper we explore a method to encode/decode multiview textures and associated supplementary data (depth map as an example) together in a single bitstream. Least significant bit (LSB) of last two levels in each transform block has been modified according to the depth encoded bits, thus resulting in very minimal loss in PSNR of textures (0.1 - 0.5dB) with overall bitrate gain of about 13% for natural scenes. The remaining encoded information have been inserted after the slice NAL of corresponding texture ensuring backward compatibility and correct extraction and decoding by a modified decoder. Benchmarking results in terms of compression efficiency and quality on HD sequences have been reported to explore further the viability of using this technique for Free Viewpoint Video (FVV) or 3DV use cases. Experiments are also carried out to evaluate subjective quality of the synthesized views.

Software implementation of Tate pairing over GF(2/sup m/)

Recently, the interest about the Tate pairing over binary fields has decreased due to the existence of efficient attacks to the discrete logarithm problem in the subgroups of such fields. We show that the choice of fields of large size to make these attacks infeasible does not lead to a degradation of the computation performance of the pairing. We describe and evaluate by simulation an implementation of the Tate pairing that allows to achieve good timing results, comparable with those reported in the literature but with a higher level of security