International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Elisabeth Oswald

Publications

Year
Venue
Title
2022
EUROCRYPT
A Novel Completeness Test for Leakage Models and its Application to Side Channel Attacks and Responsibly Engineered Simulators 📺
Si Gao Elisabeth Oswald
Today’sdside channel attack targets are often complex devices in which instructions are processed in parallel and work on 32-bit datae words. Consedsquently, the state that is involved in producing leakage in these modern devices is large, and basing evaluations (i.e. worst case attacks) and simulators, and on a potentially incomplete state can lead to wrong conclusions. We put forward a novel notion for the “completeness” of an assumed state, together with an efficient statistical test that is based on “collapsed models”. Our novel test can be used to recover a state that contains multiple 32-bit variables in a grey box setting. We illustrate how our novel test can help to guide side channel attacks and we reveal new attack vectors for existing implementations. We then demonstrate the application of this test in the context of leakage modelling for leakage simulators and confirm that even the most recent leakage simulators do not capture all available leakage of their respective target devices. Our new test enables finding nominal models that capture all available leakage but do not give a helping hand to adversaries. Thereby we make a first step towards leakage simulators that are responsibly engineered.
2022
EUROCRYPT
Towards Micro-Architectural Leakage Simulators: Reverse Engineering Micro-Architectural Leakage Features is Practical 📺
Si Gao Elisabeth Oswald Dan Page
Leakage simulators offer the tantalising promise of easy and quick testing of software with respect to the presence of side channel leakage. The quality of their build in leakage models is therefore crucial, this includes the faithful inclusion of micro-architectural leakage. Microarchitectural leakage is a reality even on low- to mid-range commercial processors, such as the ARM Cortex M series. Dealing with it seems initially infeasible in a grey box setting: how should we describe it if micro-architectural elements are not publicly known? We demonstrate, for the first time, that it is feasible, using a recent leakage modelling technique, to reverse engineer significant elements of the micro-architectural leakage of a commercial processor. Our approach first recovers the micro-architectural leakage of each stage in the pipeline, and the leakage of elements that are known to produce glitches. Using the reverse engineered leakage features we build an enhanced version of the popular leakage simulator ELMO.
2019
TCHES
Share-slicing: Friend or Foe? 📺
Si Gao Ben Marshall Daniel Page Elisabeth Oswald
Masking is a well loved and widely deployed countermeasure against side channel attacks, in particular in software. Under certain assumptions (w.r.t. independence and noise level), masking provably prevents attacks up to a certain security order and leads to a predictable increase in the number of required leakages for successful attacks beyond this order. The noise level in typical processors where software masking is used may not be very high, thus low masking orders are not sufficient for real world security. Higher order masking however comes at a great cost, and therefore a number techniques have been published over the years that make such implementations more efficient via parallelisation in the form of bit or share slicing. We take two highly regarded schemes (ISW and Barthe et al.), and some corresponding open source implementations that make use of share slicing, and discuss their true security on an ARM Cortex-M0 and an ARM Cortex-M3 processor (both from the LPC series). We show that micro-architectural features of the M0 and M3 undermine the independence assumptions made in masking proofs and thus their theoretical guarantees do not translate into practice (even worse it seems unpredictable at which order leaks can be expected). Our results demonstrate how difficult it is to link theoretical security proofs to practical real-world security guarantees.
2019
ASIACRYPT
A Critical Analysis of ISO 17825 (‘Testing Methods for the Mitigation of Non-invasive Attack Classes Against Cryptographic Modules’)
Carolyn Whitnall Elisabeth Oswald
The ISO standardisation of ‘Testing methods for the mitigation of non-invasive attack classes against cryptographic modules’ (ISO/IEC 17825:2016) specifies the use of the Test Vector Leakage Assessment (TVLA) framework as the sole measure to assess whether or not an implementation of (symmetric) cryptography is vulnerable to differential side-channel attacks. It is the only publicly available standard of this kind, and the first side-channel assessment regime to exclusively rely on a TVLA instantiation.TVLA essentially specifies statistical leakage detection tests with the aim of removing the burden of having to test against an ever increasing number of attack vectors. It offers the tantalising prospect of ‘conformance testing’: if a device passes TVLA, then, one is led to hope, the device would be secure against all (first-order) differential side-channel attacks.In this paper we provide a statistical assessment of the specific instantiation of TVLA in this standard. This task leads us to inquire whether (or not) it is possible to assess the side-channel security of a device via leakage detection (TVLA) only. We find a number of grave issues in the standard and its adaptation of the original TVLA guidelines. We propose some innovations on existing methodologies and finish by giving recommendations for best practice and the responsible reporting of outcomes.
2017
ASIACRYPT
2016
ASIACRYPT
2015
ASIACRYPT
2015
CHES
2014
ASIACRYPT
2014
ASIACRYPT
2013
CHES
2013
ASIACRYPT
2013
FSE
2012
CHES
2011
CRYPTO
2010
ASIACRYPT
2006
FSE
2005
CHES
2005
FSE
2003
CHES
2002
CHES
2001
CHES

Program Committees

CHES 2022
Eurocrypt 2021
Crypto 2020
Asiacrypt 2018
CHES 2018
Crypto 2017
FSE 2017
CHES 2016
Asiacrypt 2016
Eurocrypt 2015 (Program chair)
Eurocrypt 2014 (Program chair)
FSE 2014
FSE 2013
CHES 2012
FSE 2012
FSE 2011
Eurocrypt 2011
CHES 2011
CHES 2010
Asiacrypt 2010
FSE 2010
Asiacrypt 2009
CHES 2009
FSE 2008
CHES 2008 (Program chair)
Asiacrypt 2007
FSE 2007
CHES 2006
FSE 2006
CHES 2005