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See detailAlgorithms for Switching between Boolean and Arithmetic Masking of Second Order
Vadnala, Praveen Kumar UL; Groszschädl, Johann UL

in Gierlichs, Benedikt; Guilley, Sylvain; Mukhopadhyay, Debdeep (Eds.) Security, Privacy, and Applied Cryptography Engineering - Third International Conference, SPACE 2013, Kharagpur, India, October 19-23, 2013. Proceedings (2013, October)

Masking is a widely-used countermeasure to thwart Differential Power Analysis (DPA) attacks, which, depending on the involved operations, can be either Boolean, arithmetic, or multiplicative. When used to ... [more ▼]

Masking is a widely-used countermeasure to thwart Differential Power Analysis (DPA) attacks, which, depending on the involved operations, can be either Boolean, arithmetic, or multiplicative. When used to protect a cryptographic algorithm that performs both Boolean and arithmetic operations, it is necessary to change the masks from one form to the other in order to be able to unmask the secret value at the end of the algorithm. To date, known techniques for conversion between Boolean and arithmetic masking can only resist first-order DPA. This paper presents the first solution to the problem of converting between Boolean and arithmetic masking of second order. To set the context, we show that a straightforward extension of first-order conversion schemes to second order is not possible. Then, we introduce two algorithms to convert from Boolean to arithmetic masking based on the second-order provably secure S-box output computation method proposed by Rivain et al (FSE 2008). The same can be used to obtain second-order secure arithmetic to Boolean masking. We prove the security of our conversion algorithms using similar arguments as Rivain et al. Finally, we provide implementation results of the algorithms on three different platforms. [less ▲]

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See detailTwisted Edwards-Form Elliptic Curve Cryptography for 8-bit AVR-based Sensor Nodes
Chu, Dalin; Groszschädl, Johann UL; Liu, Zhe UL et al

in Chen, Kefei; Xie, Qi; Qiu, Weidong (Eds.) et al Proceedings of the first ACM Workshop on Asia Public-Key Cryptography (ASIAPKC 2013) (2013, May)

Wireless Sensor Networks (WSNs) pose a number of unique security challenges that demand innovation in several areas including the design of cryptographic primitives and protocols. Despite recent progress ... [more ▼]

Wireless Sensor Networks (WSNs) pose a number of unique security challenges that demand innovation in several areas including the design of cryptographic primitives and protocols. Despite recent progress, the efficient implementation of Elliptic Curve Cryptography (ECC) for WSNs is still a very active research topic and techniques to further reduce the time and energy cost of ECC are eagerly sought. This paper presents an optimized ECC implementation that we developed from scratch to comply with the severe resource constraints of 8-bit sensor nodes such as the MICAz and IRIS motes. Our ECC software uses Optimal Prime Fields (OPFs) as underlying algebraic structure and supports two different families of elliptic curves, namely Weierstraß-form and twisted Edwards-form curves. Due to the combination of efficient field arithmetic and fast group operations, we achieve an execution time of 5.8*10^6 clock cycles for a full 158-bit scalar multiplication on an 8-bit ATmega128 microcontroller, which is 2.78 times faster than the widely-used TinyECC library. Our implementation also shows that the energy cost of scalar multiplication on a MICAz (or IRIS) mote amounts to just 19 mJ when using a twisted Edwards curve over a 160-bit OPF. This result compares fairly well with the energy figures of two recently-presented hardware designs of ECC based on twisted Edwards curves. [less ▲]

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See detailCryptanalysis of the Full AES Using GPU-Like Special-Purpose Hardware
Biryukov, Alex UL; Groszschädl, Johann UL

in Fundamenta Informaticae (2012), 114(3-4), 221-237

The block cipher Rijndael has undergone more than ten years of extensive cryptanalysis since its submission as a candidate for the Advanced Encryption Standard (AES) in April 1998. To date, most of the ... [more ▼]

The block cipher Rijndael has undergone more than ten years of extensive cryptanalysis since its submission as a candidate for the Advanced Encryption Standard (AES) in April 1998. To date, most of the publicly-known cryptanalytic results are based on reduced-round variants of the AES (respectively Rijndael) algorithm. Among the few exceptions that target the full AES are the Related-Key Cryptanalysis (RKC) introduced at ASIACRYPT 2009 and attacks exploiting Time-Memory-Key (TMK) trade-offs such as demonstrated at SAC 2005. However, all these attacks are generally considered infeasible in practice due to their high complexity (i.e. 2^99.5 AES operations for RKC, 2^80 for TMK). In this paper, we evaluate the cost of cryptanalytic attacks on the full AES when using special-purpose hardware in the form of multi-core AES processors that are designed in a similar way as modern Graphics Processing Units (GPUs) such as the NVIDIA GT200b. Using today's VLSI technology would allow for the implementation of a GPU-like processor reaching a throughput of up to 10^12 AES operations per second. An organization able to spend one trillion US$ for designing and building a supercomputer based on such processors could theoretically break the full AES in a time frame of as little as one year when using RKC, or in merely one month when performing a TMK attack. We also analyze different time-cost trade-offs and assess the implications of progress in VLSI technology under the assumption that Moore's law will continue to hold for the next ten years. These assessments raise some concerns about the long-term security of the AES. [less ▲]

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