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Power analysis presents the typical example of successful attacks against trusted cryptographic devices such as RFID (Radio-Frequency 1 Identifications) and contact smart cards. In recent years, the cryptographic community has explored new approaches in power analysis based on machine learning models such as Support Vector Machine (SVM), RF (Random Forest) and Multi-Layer Perceptron (MLP). In this paper, we made an extensive comparison of machine learning algorithms in the power analysis. For this purpose, we implemented a verification program that always chooses the optimal settings of individual machine learning models in order to obtain the best classification accuracy. In our research, we used three datasets, the first contains the power traces of an unprotected AES (Advanced Encryption Standard) implementation. The second and third datasets are created independently from public available power traces corresponding to a masked AES implementation (DPA Contest v4). The obtained results revealed some interesting facts, namely, an elementary k-NN (k-Nearest Neighbors) algorithm, which has not been commonly used in power analysis yet, shows great application potential in practice. [ABSTRACT FROM AUTHOR]

This paper presents a novel privacy-preserving cryptographic protocol for secure many-to-one communication systems, for example, data collection systems, data gathering systems, vehicular networks, smart-grids, and so on. The proposed solution provides message authenticity, integrity, and non-repudiation, while message senders are anonymous and untraceable. The protocol is based on group signatures with a time-bound membership. The protocol is designed to achieve efficiency on the client side where restricted devices are usually employed. On the other hand, the verification of many messages is efficient as well. Common group signature schemes offer the verification phase that needs some pairing operations and employs a long revocation list. Generally, the revocation list grows until scheme parameters and keys are recomputed. However, the reinitialization of all keys and parameters is not practical in large-scale communication systems. By applying the optimization techniques on the group signature scheme, the verification phase becomes more efficient, and the expiration of group member secret keys naturally reduces the length of a revocation list. In addition to the full cryptographic description, we implement the proposed protocol and outline the performance results. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]