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Provably Secure Masking of AES
 In SAC
, 2004
"... A general method to secure cryptographic algorithm implementations against sidechannel attacks is the use of randomization techniques and, in particular, masking. ..."
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A general method to secure cryptographic algorithm implementations against sidechannel attacks is the use of randomization techniques and, in particular, masking.
Hardware countermeasures against DPA ? A statistical analysis of their effectiveness
 Topics in Cryptology  CTRSA 2004, volume 2964 of LNCS
, 2004
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Algebraic SideChannel Attacks on the AES: Why Time also Matters in DPA
"... Algebraic sidechannel attacks have been recently introduced as a powerful cryptanalysis technique against block ciphers. These attacks represent both a target algorithm and its physical information leakages as an overdefined system of equations that the adversary tries to solve. They were first ap ..."
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Cited by 28 (3 self)
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Algebraic sidechannel attacks have been recently introduced as a powerful cryptanalysis technique against block ciphers. These attacks represent both a target algorithm and its physical information leakages as an overdefined system of equations that the adversary tries to solve. They were first applied to PRESENT because of its simple algebraic structure. In this paper, we investigate the extent to which they can be exploited against the AES Rijndael and discuss their practical specificities. We show experimentally that most of the intuitions that hold for PRESENT can also be observed for an unprotected implementation of Rijndael in an 8bit controller. Namely, algebraic sidechannel attacks can recover the AES master key with the observation of a single encrypted plaintext and they easily deal with unknown plaintexts/ciphertexts in this context. Because these attacks can take advantage of the physical information corresponding to all the cipher rounds, they imply that one cannot trade speed for code size (or gate count) without affecting the physical security of a leaking device. In other words, more intermediate computations inevitably leads to more exploitable leakages. We analyze the consequences of this observation on two different masking schemes and discuss its impact on other countermeasures. Our results exhibit that algebraic techniques lead to a new understanding of implementation weaknesses that is different than classical sidechannel attacks.
Differential Fault Analysis on AES Key Schedule and Some Countermeasures
 in Proc. ACISP, v. 2727 of LNCS, 2003
"... Abstract. This paper describes a DFA attack on the AES key schedule. This fault model assumes that the attacker can induce a single byte fault on the round key. It efficiently finds the key of AES128 with feasible computation and less than thirty pairs of correct and faulty ciphertexts. Several cou ..."
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Abstract. This paper describes a DFA attack on the AES key schedule. This fault model assumes that the attacker can induce a single byte fault on the round key. It efficiently finds the key of AES128 with feasible computation and less than thirty pairs of correct and faulty ciphertexts. Several countermeasures are also proposed. This weakness can be resolved without modifying the structure of the AES algorithm and without decreasing the efficiency.
Algebraic SideChannel Analysis in the Presence of Errors
"... Abstract. Measurement errors make power analysis attacks difficult to mount when only a single power trace is available: the statistical methods that make DPA attacks so successful are not applicable since they require many (typically thousands) of traces. Recently it was suggested by [18] to use al ..."
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Abstract. Measurement errors make power analysis attacks difficult to mount when only a single power trace is available: the statistical methods that make DPA attacks so successful are not applicable since they require many (typically thousands) of traces. Recently it was suggested by [18] to use algebraic methods for the singletrace scenario, converting the key recovery problem into a Boolean satisfiability (SAT) problem, then using a SAT solver. However, this approach is extremely sensitive to noise (allowing an error rate of well under 1 % at most), and the question of its practicality remained open. In this work we show how a singletrace sidechannel analysis problem can be transformed into a pseudoBoolean optimization (PBOPT) problem, which takes errors into consideration. The PBOPT instance can then be solved using a suitable optimization problem solver. The PBOPT syntax provides for a more expressive input specification which allows a very natural representation of measurement errors. Most importantly, we show that using our approach we are able to mount successful and efficient singletrace attacks even in the presence of realistic error rates of 10%–20%. We call our new attack methodology Tolerant Algebraic SideChannel Analysis (TASCA). We show practical attacks on two real ciphers: Keeloq and AES.
Algebraic SideChannel Attacks
, 2009
"... In 2002, algebraic attacks using overdefined systems of equations have been proposed as a potentially very powerful cryptanalysis technique against block ciphers. However, although a number of convincing experiments have been performed against certain reduced algorithms, it is not clear wether thes ..."
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Cited by 15 (2 self)
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In 2002, algebraic attacks using overdefined systems of equations have been proposed as a potentially very powerful cryptanalysis technique against block ciphers. However, although a number of convincing experiments have been performed against certain reduced algorithms, it is not clear wether these attacks can be successfully applied in general and to a large class of ciphers. In this paper, we show that algebraic techniques can be combined with sidechannel attacks in a very effective and natural fashion. As an illustration, we apply them to the block cipher PRESENT that is a stimulating first target, due to its simple algebraic structure. The proposed attacks have a number of interesting features: (1) they exploit the information leakages of all the cipher rounds, (2) in common implementation contexts (e.g. assuming a Hamming weight leakage model), they recover the block cipher keys after the observation of a single encryption, (3) these attacks can succeed in an unknownplaintext/ciphertext adversarial scenario and (4) they directly defeat countermeasures such as boolean masking. Eventually, we argue that algebraic sidechannel attacks can take advantage of any kind of physical leakage, leading to a new tradeoff between the robustness and informativeness of the sidechannel information extraction.
F.: Fresh Rekeying: Security against SideChannel and Fault Attacks for LowCost Devices
, 2010
"... Abstract. The market for RFID technology has grown rapidly over the past few years. Going along with the proliferation of RFID technology is an increasing demand for secure and privacypreserving applications. In this context, RFID tags need to be protected against physical attacks such as Different ..."
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Abstract. The market for RFID technology has grown rapidly over the past few years. Going along with the proliferation of RFID technology is an increasing demand for secure and privacypreserving applications. In this context, RFID tags need to be protected against physical attacks such as Differential Power Analysis (DPA) and fault attacks. The main obstacles towards secure RFID are the extreme constraints of passive tags in terms of power consumption and silicon area, which makes the integration of countermeasures against physical attacks even more difficult than for other types of embedded systems. In this paper we propose a fresh rekeying scheme that is especially suited for challengeresponse protocols such as used to authenticate tags. We evaluate the resistance of our scheme against fault and sidechannel analysis, and introduce a simple architecture for VLSI implementation on RFID tags. In addition, we estimate the cost of our scheme in terms of area and execution time for various security/performance tradeoffs. Our experimental results show that the proposed rekeying scheme provides better security (and does so at less cost) than other stateoftheart countermeasures. 1
Algebraic SideChannel Attacks Beyond the Hamming Weight Leakage Model
"... Abstract. Algebraic sidechannel attacks (ASCA) are a method of cryptanalysis which allow performing key recoveries with very low data complexity. In an ASCA, the sidechannel leaks of a device under test (DUT) are represented as a system of equations, and a machine solver is used to find a key whic ..."
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Abstract. Algebraic sidechannel attacks (ASCA) are a method of cryptanalysis which allow performing key recoveries with very low data complexity. In an ASCA, the sidechannel leaks of a device under test (DUT) are represented as a system of equations, and a machine solver is used to find a key which satisfies these equations. A primary limitation of the ASCA method is the way it tolerates errors. If the correct key is excluded from the system of equations due to noise in the measurements, the attack will fail. On the other hand, if the DUT is described in a more robust manner to better tolerate errors, the loss of information may make computation time intractable. In this paper, we first show how this robustnessinformation tradeoff can be simplified by using an optimizer, which exploits the probability data output by a sidechannel decoder, instead of a standard SAT solver. For this purpose, we describe a way of representing the leak equations as vectors of aposteriori probabilities, enabling a natural integration of template attacks and ASCA. Next, we put forward the applicability of ASCA against devices which does not conform to simple leakage models (e.g. based on the Hamming weight of the manipulated data). We finally report on various experiments that illustrate the strengths and weaknesses of standard and optimizing solvers in various settings, hence demonstrating the versatility of ASCA. 1
Tolerant algebraic sidechannel analysis of AES,” Cryptology ePrint Archive, Report 2012/092
, 2012
"... Abstract. We report on a Tolerant Algebraic SideChannel Analysis (TASCA) attack on an AES implementation, using an optimizing pseudoBoolean solver to recover the secret key from a vector of Hamming weights corresponding to a single encryption. We first develop a boundary on the maximum error rate ..."
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Abstract. We report on a Tolerant Algebraic SideChannel Analysis (TASCA) attack on an AES implementation, using an optimizing pseudoBoolean solver to recover the secret key from a vector of Hamming weights corresponding to a single encryption. We first develop a boundary on the maximum error rate that can be tolerated as a function of the set size output by the decoder and the number of measurements. Then, we show that the TASCA approach is capable of recovering the secret key from errored traces in a reasonable time for error rates approaching this theoretical boundary – specifically, the key was recovered in 10 hours on average from 100 measurements with error rates of up to 20%. We discovered that, perhaps counterintuitively, there are strong incentives for the attacker to use as few leaks as possible to recover the key. We describe the equation setup, the experiment setup and discuss the results.
Pragmatism vs. Elegance: comparing two approaches to Simple Power Attacks on AES
"... Abstract. Simple sidechannel attacks trade off data complexity (i.e. the number of sidechannel observations needed for a successful attack) with computational complexity (i.e. the number of operations applied to the sidechannel traces). In the specific example of Simple Power Analysis (SPA) atta ..."
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Abstract. Simple sidechannel attacks trade off data complexity (i.e. the number of sidechannel observations needed for a successful attack) with computational complexity (i.e. the number of operations applied to the sidechannel traces). In the specific example of Simple Power Analysis (SPA) attacks on the Advanced Encryption Standard (AES), two approaches can be found in the literature, one which is a pragmatic approach that involves basic techniques such as efficient enumeration of key candidates, and one that is seemingly more elegant and uses algebraic techniques. Both of these different techniques have been used in complementary settings: the pragmatic attacks were solely applied to the key schedule whereas the more elegant methods were only applied to the encryption rounds. In this article, we investigate how these methods compare in what we consider to be a more practical setting in which adversaries gain access to erroneous information about both key schedule and encryption rounds. We conclude that the pragmatic enumeration technique better copes with erroneous information which makes it more interesting in practice. 1