Security in random number generation for cryptography is closely related to the entropy rate at the generator output. This rate has to be evaluated using an appropriate stochastic model. The stochastic model proposed in this paper is dedicated to the transition effect ring oscillator (TERO)-based true random number generator (TRNG) proposed by Varchola and Drutarovsky (in: Cryptographic hardware and embedded systems (CHES), 2010, Springer, 2010 ). The advantage and originality of this model are that it is derived from a physical model based on a detailed study and on the precise electrical description of the noisy physical phenomena that contribute to the generation of random numbers. We compare the proposed electrical description with data generated in two different technologies: TERO TRNG implementations in 40 and 28 nm CMOS ASICs. Our experimental results are in very good agreement with those obtained with both the physical model of TERO’s noisy behavior and the stochastic model of the TERO TRNG, which we also confirmed using the AIS 31 test suites.

In the past few years, much research on watermarking has been focused on improving robustness to attacks. The starting point of the present study is an R&D algorithm which was not optimised for still images, but offered a good trade-off in terms of capacity, visibility and robustness, and worked in a full blind manner. We have focused on adapting it to video and on optimising it to the world of embedded terminals, such as digital still cameras, digital television and wireless terminals, where the computing power and storage resources of a Pentium are not available. Results of our adaptations are shown in the form of execution times versus platform capabilities. This work is the result of a close collaboration between the Eurecom research institute and STMicroelectronics.