Biblio

Entropy sources are designed to provide unpredictable random numbers for cryptographic systems. As an assessment of the sources, Shannon entropy is usually adopted to quantitatively measure the unpredictability of the outputs. In several related works about the entropy evaluation of ring oscillator-based (RO-based) entropy sources, authors evaluated the unpredictability with the average conditional Shannon entropy (ACE) of the source, moreover provided a lower bound of the ACE (LBoACE). However, in this paper, we have demonstrated that when the adversaries have access to the history outputs of the entropy source, for example, by some intrusive attacks, the LBoACE may overestimate the actual unpredictability of the next output for the adversaries. In this situation, we suggest to adopt the specific conditional Shannon entropy (SCE) which exactly measures the unpredictability of the future output with the knowledge of previous output sequences and so is more consistent with the reality than the ACE. In particular, to be conservative, we propose to take the lower bound of the SCE (LBoSCE) as an estimation of the worst-case entropy of the sources. We put forward a detailed method to estimate this worst-case entropy of RO-based entropy sources, which we have also verified by experiment on an FPGA device. We recommend to adopt this method to provide a conservative assessment of the unpredictability when the entropy source works in a vulnerable environment and the adversaries might obtain the previous outputs.

Embedded electronic devices and sensors such as smartphones, smart watches, medical implants, and Wireless Sensor Nodes (WSN) are making the “Internet of Things” (IoT) a reality. Such devices often require cryptographic services such as authentication, integrity and non-repudiation, which are provided by Public-Key Cryptography (PKC). As these devices are severely resource-constrained, choosing a suitable cryptographic system is challenging. Pairing Based Cryptography (PBC) is among the best candidates to implement PKC in lightweight devices. In this research, we present a fast and energy efficient implementation of PBC based on Barreto-Naehrig (BN) curves and optimal Ate pairing using hardware/software co-design. Our solution consists of a hardware-based Montgomery multiplier, and pairing software running on an ARM Cortex A9 processor in a Zynq-7020 System-on-Chip (SoC). The multiplier is protected against simple power analysis (SPA) and differential power analysis (DPA), and can be instantiated with a variable number of processing elements (PE). Our solution improves performance (in terms of latency) over an open-source software PBC implementation by factors of 2.34 and 2.02, for 256- and 160-bit field sizes, respectively, as measured in the Zynq-7020 SoC.

Random numbers represent one of the most sensible part of a cryptographic system, since the cryptographic keys must be entirely based on them. The security of a communication relies on the key that had been established between two users. If an attacker is able to deduce that key, the communication is compromised. This is why key generation must completely rely on random number generators, so that nobody can deduce the. This paper will describe a set of public and free Random Number Generators (RNG) within Android-based Smartphones by exploiting different sensors, along with the way of achieving this scope. Moreover, this paper will present some conclusive tests and results over them.