Rodrigo Possamai Bastos  Frank Sill Torres On-Chip Current Sensors for Reliable, Secure, and Low-Power Integrated Circuits On-Chip Current Sensors for Reliable, Secure, and Low-Power Integrated Circuits Rodrigo Possamai Bastos • Frank Sill Torres On-Chip Current Sensors for Reliable, Secure, and Low-Power Integrated Circuits 123 RodrigoPossamaiBastos FrankSillTorres Univ.GrenobleAlpes,CNRS DFKIGmbH/Cyber-PhysicalSystems GrenobleINP,TIMALaboratory Bremen,Germany Grenoble,France ISBN978-3-030-29352-9 ISBN978-3-030-29353-6 (eBook) https://doi.org/10.1007/978-3-030-29353-6 ©SpringerNatureSwitzerlandAG2020 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof thematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation, broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformation storageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilarmethodology nowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthors,andtheeditorsaresafetoassumethattheadviceandinformationinthisbook arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor theeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinorforany errorsoromissionsthatmayhavebeenmade.Thepublisherremainsneutralwithregardtojurisdictional claimsinpublishedmapsandinstitutionalaffiliations. ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG. Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland Preface Many types of new-generation electronics systems surround nowadays our lives, providingsolutions,utilities,andconvenienceswehadneverexperimentedbefore. Biomedical, agricultural, industrial, commercial, service, entertainment, home, automobile,aeronautical,space,andtelecommunicationapplianceshelpustosolve quotidian problems related, for instance, to the health of living beings, transport over short and long distances, satellite TV broadcast, weather forecast, and com- munication between computers and people [181]. In this context in which billions of electronics and devices harvest data from tens of billions of sensors, dealing with reliability, security, and power issues becomes more and more important for integratedcircuit(IC)systemapplications. Intheadventofself-adaptivesystemslikegeolocationsatellites,aircraft,drones, autonomous cars, nuclear power plant robots, and in-body-implanted medical devices—which are all applications of high risk in case of failure—embedded ICs must be sufficiently reliable, safely operating within a specified range of low- powerperformanceeveninharshenvironments.Furthermore,ICsembeddedinsuch safety-critical applications must also be conveniently secure, hiding confidential data, restricting access to private information, and defending themselves from intentionalattacksthataimtohackintosystemsformaliciouslycarryingoutillegal actionsorinducingcatastrophicsituations. Thisbookisspecificallyinterestedtodealwiththreeimportantissuesrelatedto thereliability,security,andpowerofintegratedcircuit(IC)systemsincomplemen- tarymetal-oxide-semiconductor(CMOS)technologies: (a) Transient faults, as voltage glitches induced by particle radiation [86] or malicious sources [11, 30, 62, 93] of perturbation, can provoke bit flips in memory elements—i.e., soft errors that may lead entire systems to fail, com- promisingsafety-criticalapplicationsorevenprovidingrelevantinformationfor cryptanalysismethodsthatexploitresultsoffaultinjectionattacksoversecure circuits. (b) HardwareTrojans,whicharemaliciousslightlayoutalterationsorfurtivemech- anisms [228] included in outsourced IC design, fabrication, or manufacturing v vi Preface phasesbythird-partysupplierswillingtohack,disturb,orintentionallydisable, atruntime,theTrojan-infectedcircuits. (c) Transistor threshold voltage (V ) alterations—induced by aging, radiation th effects,process,voltage,andtemperature(PVT)variationsaswellasbybody biasmodifications—areablenotonlytoslowdowngatesofcircuits,violating criticaltimingconstraints,butalsospeedthemupattheexpenseofstaticpower consumptionincrease[60,231]. Efficiently making IC systems low-power, secure, and reliable against transient faults, hardware Trojans, and V alterations requires the inclusion of dedicated th hardware-level techniques, incurring extra costs in terms of area, power, or delay. Fordetectingtransientfaults,run-timetestingmechanisms[5,22,45,139,155,158, 159,174,193,217]needtobeembeddedinthesystemsfordynamicallymonitoring illegalvoltageglitches.FordetectinghardwareTrojans,otherwise,post-fabrication testingschemes[1,3,28,31,82,147,157,167,245,255]havetobeimplemented for seeking malicious hardware modifications in the IC under test. And for com- pensating V alterations, adaptive body bias generators [16,60,71,84,130,231] th can be added to intelligently tune V of transistors in function of aging and PVT th variations. Exploiting the body terminals of transistors in IC systems, this book demon- strates and discusses the design and application of on-chip (i.e., built-in) current sensors as techniques of (a) run-time test for detecting transient faults, (b) post- fabrication test for detecting hardware Trojans, and (c) adaptive body bias for IC systemstargetingadaptivecompensationofV alterationsbutalsooptimizationof th poweranddelay. Chapter1ofthisbookdiscussestheeffectsoftransientfaultsinICs—underenvi- ronment perturbations or intentional perturbations—analyzing their main harmful and harmless effects at electrical and logical levels for giving the fundamentals to understandrelatedsofterrorsandfailuresinICsystems. State-of-the-art run-time testing mechanisms for detecting transient faults have been evaluated by using a simulation-based method that is detailed in Chap.2. Results provide a rank in terms of their effectivenesses in detecting transient faults, revealing the BBICS as the most effective solution. BBICS integrates the highconcurrentfaultdetectioneffectivenessofcostlytechniques(duplicationwith comparison)withthelowareaandpoweroverheadsoflesseffectiverun-timetesting mechanisms(timeredundancyschemes). Moreover, unlike most existing techniques for detection of transient faults, the BBICS is also able to detect long-duration and multiple (simultaneous) transient faults, which are also a major problem in fault-based attacks targeting to inten- tionally break the security of IC systems. Hence, available BBICS architectures in literature have been studied and compared with regard to their sensitivities in detecting transient faults. Chapter 3 presents such comparison results and the optimal dynamic BBICS architectures with enhanced fault detection sensitivity, negligiblepowerconsumption,andlowerareapenaltythantheirantecedents. Preface vii Chapter 4 presents strategies for improving the characteristics of body built- in sensors. First, the concept of the modular BBICS (mBBICS) is discussed. The principal idea here is the separation of the sensing part of the sensor and the circuitry for generation of a fault flag. It could be shown that this division enables higher flexibility, improved robustness, and lower costs in terms of area and power dissipation. The second part of the chapter focused on three universal architecturalstrategiesforimprovingsensibilityandcostsofbodybuilt-insensors. AllthreestrategieshavebeenappliedexemplarilyforthemodularBBICSinorderto demonstrateitsutilization.Finally,bothsensortypes,i.e.,thestandardmBBICSand theimprovedmBBICS,havebeensubjectedtoextensiveanalysis.Resultsindicate that the modular concept and the presented techniques enable the implementation of body built-in sensors with high sensibility, negligible power dissipation, high robustness,andreasonableareacosts. Chapter 5 presents a study regarding the noise susceptibility of body built-in sensors. The analysis is based on extracted layout data, including the substrate profile and different kinds of generic noise sources. The results for a predictive 90nm technology indicate that noise sources close to the sensors lead to false detections if the root mean square (rms) value of the noise is in the range of 5–9% of V . Further, it could be determined that noise sources with distances DD correspondingtothesizeofmorethan100minimuminverterscanbedisregarded. Furthermore,simulationresultsindicatethatnoisegeneratedbydigitaltestcircuits is lower than the extracted values for false sensor activation. However, given the proximity of the determined values and the potential complexity of the digital circuit,suchnoiseshouldnotbeignored. Chapter 6 of this book shows a single and compact body built-in cell that integratesallBBICSfeaturesbutalsoafunctionthatismandatorytodynamically adapt the body bias of small subcircuits: a level shifter. In fact, partitioning IC systems into subcircuits (having single N-well or P-well regions) allows better controllingVthvariations,power,anddelay,inadditiontoindividuallymanagepart oftheICsystematruntime. In Chap.7, a flow for automatic integration of BBICS into common designs is demonstrated.ResultsobtainedforastudyonmodularBBICSsensorsindicatethat itisrecommendedtousemBBICSheadcellsthatcombinesensorsforNMOSand PMOSdevices.AnadditionalinterestingresultisthatmBBICSheadcellsshouldbe abletomonitoratleast100minimum-sizedinvertersinordertoachieveareasonable areacosts.Thesecondpartofthechapterintroducedahigh-levelapproachthatuses theindicationsoftransientfaultsbyBBICSsensorstoreturnasystem,inthiscase alight-weightRISCprocessor,toasecurestate. ThisbookshowsalsoanotherfunctionfortheBBICS:thedetectionofhardware Trojans.Chapter8detailsapost-fabricationtestingtechniquethattakesadvantage of the BBICS as an offline-testing mechanism for detecting hardware Trojans. As thistypeofsensormonitorsbodyterminalsofsystemsubcircuits,thetechniqueis capable to identify any slight hardware Trojan-induced variations on the electrical impedanceofsubcircuitsbysimplyinjectingashorttrainofcurrentpulsesintobody terminalsandanalyzingdigitalsignaturesprovidedbytheBBICS.Atruntime,the viii Preface sameBBICSoperatesasanonline-testingmechanismfordetectingtransientfaults. Thistechniquehasaddedanewcategorytotheclassicaltaxonomyofside-channel analysis-basedtechniquesfordetectionhardwareTrojans;itisindeedthefirstwork that analyzes as a side channel the digital signatures related to the impedance of N-wellandP-wellregionsofsubcircuits. AuthorshighlightthattheBBICSapplicationonICsystemdesignsbringsseveral othercomplementarybenefitsinadditiontotheclassicalBBICSabilityindetecting particleradiation-inducedtransients.TheintegrationincommercialICdesignflows is feasible by simply replacing standard filler cells [68]. The reuse of the filler cell areas reduces the inherent costs associated with any type of fault tolerance technique. Furthermore, BBICS-based recomputing techniques are applicable for recoveringprocessorsfromtheeffectsoftransientfaults[108,112,182,187].And unlike mostexistingfaulttolerance techniques, BBICSareabletodetectshort-to- long-durationandmultiple(simultaneous)transientfaults[112,239,240]induced byparticleradiation,laser-inducedtransientssuchasfault-basedattacks[189],and hardwareTrojans[66]thatmaybemaliciouslyimplantedinICs.Complementarily, BBICS can operate to dynamically and adaptively bias the body terminals of subcircuitsforbalancingpoweranddelay[56]. IntheadventofadvancedICfabricationprocesses—suchastheUTBBFD-SOI technologywithwhichdifferentbodyvoltagesareallowedformanagingICsystem poweranddelay[176,177]—theICdesignspacebecomesevenwiderwiththetriple function of the on-chip current sensors discussed herein. In other words, the body built-in cells have the ability to (1) locally bias IC system subcircuits, (2) detect theoccurrenceoftransientfaultsinICs,and(3)testICsforhardwareTrojans.All features represent important contents for the design of more reliable, secure, and low-powerICsystemsinmoderntechnologies. Grenoble,France RodrigoPossamaiBastos Bremen,Germany FrankSillTorres Acknowledgments Thisbooksummarizesourresearchactivitiesoveraperiodofmorethan10years, andmanyofthefindingsandobtainedresultswouldnothavebeenpossiblewithout thededicatedworkofourcollaboratorsandcolleaguestowhomwewanttoexpress ourprofoundgratitude. The author Rodrigo Possamai Bastos would like to thank his former Ph.D. studentsLeonelA.Guimarães,ThiagoF.P.Leite,andRaphaelA.C.Vieraforall their huge efforts, excellent works, smart brainstorms, and technical contributions thatdefinitivelyhavebeenessentialfortheconstructionofthisbook. Rodrigo especially dedicates this book to his girlfriend Munique who has been patient,adorable,andlovelyoverthislast7years,supportinghisworkandfollowing allstepsofcreationandpreparationofthisbook,evenduringmanyweekendsand nights. Finally, He dedicates this book also to his parents Melita and Fernando, his sister Fernanda, his nephew João Fernando, and his aunt Elba, who have all beenencouraginghislongstudyjourney,sincehischildhoodinBrazil—givinghim plentyofLEGO(cid:2)R bricks—untilhisdoctoratethesisinFrance. TheauthorFrankSillTorreswantstothankespeciallyhisformerstudentsJoão Guilherme M. Melo, Mário V. Guimarães, Rafael K. V. Maeda, and Raphael O. Rocha for their excellent work, creativity, and enthusiasm. Furthermore, he would liketothankhiscolleaguesDaviesW.deLimaMonteiro,OmarP.V.Neto,andRolf Drechslerfortheirsubstantialsupportandthemanyenlighteningdiscussions. FrankdedicatesthisbooktohislovelydaughtersAmandaandAmélieaswellas hisadorableandwonderfulwifeLorena,whoishispillarofstrengthandsourceof inspiration.Finally,hededicatesthisbookalsotohisparentsKatharinaandHans- Dieter;hisbrothersAndreas,Stefan,andThomas;aswellashisgrandparentsHans- JürgenandIlse,whoallencouragedhiminhispassionforscience. ix Abstract Ubiquitousintegratedcircuit(IC)applicationshelpthehumanitytorapidlyevolve by supporting electronics systems that are more and more assuming autonomous functions and decisions of important responsibility for the society. In this context, dealing with reliability, security, and power issues of integrated circuits is funda- mentaltoensuretheoperationofsystemswithinreasonablelevelsofsafety,privacy, andenergyconsumption. The key contribution of this book is revealing that compact and effective on- chip (i.e., built-in) current sensors—monitoring body terminals rather than source terminals of transistors like classical current sensors do—can be applied on IC systemsubcircuitsforgatheringandenhancingreliability,security,andlow-power aspects of their applications. The book demonstrates and discusses the design and applicationofon-chipcurrentsensorsastechniquesof(a)run-timetestfordetecting transient faults induced by particle radiation or malicious fault injection (laser irradiation-basedattack),(b)post-fabricationtestfordetectingmaliciouscircuitries (hardware Trojans), and (c) adaptive body bias for IC systems targeting adaptive compensation of transistor threshold voltage alterations but also optimization of poweranddelay. xi