Giuseppe Scotti

Leakage Power Analysis Attacks: A Novel Class of Attacks to Nanometer Cryptographic Circuits

In this paper, a novel class of power analysis attacks to cryptographic circuits is presented. These attacks aim at recovering the secret key of a cryptographic core from measurements of its static (leakage) power. These attacks exploit the dependence of the leakage current of CMOS integrated circuits on their inputs (including the secret key of the cryptographic algorithm that they implement), as opposite to traditional power analysis attacks that are focused on the dynamic power. For this reason, this novel class of attacks is named ¿leakage power analysis¿ (LPA). Since the leakage power increases much faster than the dynamic power at each new technology generation, LPA attacks are a serious threat to the information security of cryptographic circuits in sub-100-nm technologies. For the first time in the literature, a well-defined procedure to perform LPA attacks that is based on a solid theoretical background is presented. Advantages and measurement issues are also analyzed in comparison with traditional power analysis attacks based on dynamic power measurements. Examples are provided for various circuits, and an experimental attack to a register is performed for the first time. An analytical model of the LPA attack result is also provided to better understand the effectiveness of this technique. The impact of technology scaling is explicitly addressed by means of a simple analytical model and Monte Carlo simulations. Simulations on a 65- and 90-nm technology and experimental results are presented to justify the assumptions and validate the leakage power models that are adopted.

Effectiveness of Leakage Power Analysis Attacks on DPA-Resistant Logic Styles Under Process Variations

This paper extends the analysis of the effectiveness of Leakage Power Analysis (LPA) attacks to cryptographic VLSI circuits on which circuit level countermeasures against Differential Power Analysis (DPA) are adopted. Security metrics used for assessing the DPA-resistance of crypto core implementations, such as the minimum number to disclosure (MTD) and the asymptotic correlation coefficient, have been extended to the case of LPA. The LPA-resistance has been evaluated in terms of MTD as a function of the on chip noise. Noise variances up to 10000 times greater than the signal variance have been taken into account and LPA attacks have been successfully executed for all the logic styles under analysis using less than 100000 measurements. Moreover the role of process variations has been investigated through extensive Monte Carlo simulations in order to evaluate their impact on the leakage model for the logic styles under analysis. Results show that LPA attacks can be successfully carried out on the different anti-DPA logic styles even in presence of process variations. To the best of our knowledge, this work proves for the first time the effectiveness of LPA attacks in a real scenario where on chip noise and process variations are taken into account.

A novel yield optimization technique for digital CMOS circuits design by means of process parameters run-time estimation and body bias active control

This work presents a novel approach to optimize digital integrated circuits yield referring to speed, dynamic power and leakage power constraints. The method is based on process parameter estimation circuits and active control of body bias performed by an on-chip digital controller. The associated design flow allows us to quantitatively predict the impact of the method on the expected yield in a specific design. We present the architecture scheme, the theoretical foundation, the estimation circuits used, and two application case studies, referring to an industrial 0.13-/spl mu/m CMOS process data. The approach results to be remarkably effective at high operating temperature. In the presented case study, initial yields below 14% are improved to 86% by using a single controller and a single set of estimation circuits per die.

Linearization Technique for Source-Degenerated CMOS Differential Transconductors

A supplementary linearization technique for CMOS differential pairs with resistive source degeneration is proposed. The approach exploits an auxiliary (degenerated) differential pair to drive the bulk terminals of the main pair. Transistor-level simulations on a design using a 0.25-mum process and powered with 2.5 V and 1 mA, show that total harmonic distortion (THD) in the voltage-to-current conversion is decreased by 10 dB (for an input differential signal with a peak amplitude of 0.5 V and for frequencies up to 100 MHz) compared to the traditional source-degenerated transconductor. This THD improvement is achieved with a negligible increase in power consumption.

A novel low-voltage low-power fully differential voltage and current gained CCII for floating impedance simulations

In this paper we present a new current-mode basic building block that we named voltage and current gained second generation current conveyor (VCG-CCII). The proposed active block allows to control and tune both the CCII current gain and the voltage gain through external control voltages. It has been designed, at transistor level in a standard CMOS technology (AMS 0.35@mm), with a low single supply voltage (2V), as a fully differential active block. The proposed integrated solution, having both low-voltage (LV) and low-power (LP) characteristics, can be applied with success in suitable IC applications such as floating capacitance multipliers and floating inductance simulators, utilizing a minimum number of active components (one and two, respectively). Simulation results, related to floating impedance simulators, are in good agreement with the theoretical expectations.

Design Solutions for Sample-and-Hold Circuits in CMOS Nanometer Technologies

Solutions for the design of low-voltage sample-and-hold (S/H) circuits in CMOS nanometer technologies are presented. As a design example, a 0.8-V supply S/H is designed and simulated using a 130-nm CMOS process. It dissipates 0.5 mW at dc and provides almost a rail-to-rail signal swing. When clocked at 40 MS/s and with a 1.4- VPP differential input signal, the simulated spurious-free dynamic range, signal-to-noise ratio, and total harmonic distortion are 57, 67, and -56 dB (9 equivalent bits), respectively, with low sensitivity to supply, temperature, process, and mismatch variations. The proposed solution employs a three-stage low-voltage amplifier without a tail current source in the differential pair and a switch topology, which combines clock voltage doubling and dummy switches.

Delay-Based Dual-Rail Precharge Logic

This paper investigates the design of a dual-rail precharge logic family whose power consumption is insensitive to unbalanced load conditions thus allowing adopting a semi-custom design flow (automatic place and route) without any constraint on the routing of the complementary wires. The proposed logic is based on a novel encoding concept where the information is represented in the time domain rather than in the spatial domain as in a standard dual-rail logic. In this work, a logic family which exploits the proposed concept has been implemented. Implementation details and simulation results are reported which show a power consumption independent of the sequence of processed data and routing capacitances. An improvement in the energy consumption balancing up to 50 times and an area reduction up to 60% with respect to the state of the art have been obtained.

Analysis of data dependence of leakage current in CMOS cryptographic hardware

A novel power analysis technique for CMOS cryptographic hardware based on leakage power consumption measurements is presented. Algorithms and models to predict the input vector for maximum and minimum leakage currentallin CMOS gates are reviewed. Extensive transistor level simulations on a simple CMOS crypto core are presented. Leakage current measurements carried out on an ASIC for cryptographic applications implemented in a 0.13 um CMOS technology are reported. The results of this work show that leakage current can be exploited as a side channel by an attacker to extract information about the secret key in cryptographic hardware implemented in short channel CMOS technologies.

Low Voltage CMOS Current and Voltage References without Resistors

The authors describe low voltage current and voltage references which only use MOSFETs in strong inversion and pnp substrate transistors; both the references exhibit very good performance in terms of power supply rejection and do not require compensation capacitances; the minimum supply voltage is about 0.8V for the current reference and 1.2V for the voltage reference.

Side channel analysis resistant design flow

The threat of side-channel attacks (SCA) is of crucial importance when designing systems with cryptographic hardware or software. The FP6-funded project SCARD enhances the typical micro-chip design flow in order to provide a means for designing side-channel resistant circuits and systems. Appropriate SCA-simulation tools and SCA analysis for the designer of secure systems are part of the project goals. We consider these enhancements for traditional design flows of micro-chips as necessary in order to enable the design for the next generation of secure and dependable devices. SCARD is in its final phase, the final result a SCARD chip designed by using the developed design flow is currently implemented