A MAC Mode for Lightweight Block Ciphers

status: accepte

Mixing Additive and Multiplicative Masking for Probing Secure Polynomial Evaluation Methods

International audienceMasking is a sound countermeasure to protect implementations of block-cipher algorithms against Side Channel Analysis (SCA). Currently, the most efficient masking schemes use Lagrange's Interpolation Theorem in order to represent any S-box by a polynomial function over a binary finite field. Masking the processing of an S-box is then achieved by masking every operation involved in the evaluation of its polynomial representation. While the common approach requires to use the well-known Ishai-Sahai-Wagner (ISW) scheme in order to secure this processing, there exist alternatives. In the particular case of power functions, Genelle, Prouff and Quisquater proposed an efficient masking scheme (GPQ). However, no generalization has been suggested for polynomial functions so far. In this paper, we solve the open problem of extending GPQ for polynomials, and we also solve the open problem of proving that both the original scheme and its variants for polynomials satisfy the t-SNI security definition. Our approach to extend GPQ is based on the cyclotomic method and results in an alternate cyclotomic method which is three times faster in practice than the original proposal in almost all scenarios we address. The best-known method for polynomial evaluation is currently CRV which requires to use the cyclotomic method for one of its step. We also show how to plug our alternate cyclo-tomic approach into CRV and again provide an alternate approach that outperforms the original in almost all scenarios. We consider the masking of n-bit S-boxes for n ∈ [4; 8] and we get in practice 35% improvement of efficiency for S-boxes with dimension n ∈ {5, 7, 8} and 25% for 6-bit S-boxes

Higher-Order Threshold Implementation of the AES S-Box

In this paper we present a threshold implementation of the Advanced Encryption Standard’s S-box which is secure against first- and second-order power analysis attacks. This security guarantee holds even in the presence of glitches, and includes resistance against bivariate attacks. The design requires an area of 7849 Gate Equivalents and 126 bits of randomness per S-box execution. The implementation is tested on an FPGA platform and its security claim is supported by practical leakage detection tests

Cryptanalysis of Reduced Round SPEEDY

SPEEDY is a family of ultra low latency block ciphers proposed by Leander, Moos, Moradi and Rasoolzadeh at TCHES 2021. Although the designers gave some differential/linear distinguishers for reduced rounds, a concrete cryptanalysis considering key recovery attacks on SPEEDY was completely missing. The latter is crucial to understand the security margin of designs like SPEEDY which typically use low number of rounds to have low latency. In this work, we present the first third-party cryptanalysis of SPEEDY-$r$-192, where $r \in \{5, 6, 7\}$ is the number of rounds and 192 is block and key size in bits. We identify cube distinguishers for 2 rounds with data complexities $2^{14}$ and $2^{13}$, while the differential/linear distinguishers provided by designers has a complexity of $2^{39}$. Notably, we show that there are several such cube distinguishers, and thus, we then provide a generic description of them. We also investigate the structural properties of 13-dimensional cubes and give experimental evidence that the partial algebraic normal form of certain state bits after two rounds is always the same. Next, we utilize the 2 rounds distinguishers to mount a key recovery attack on 3 rounds SPEEDY. Our attack require $2^{17.6}$ data, $2^{25.5}$ bits of memory and $2^{52.5}$ time. Our results show that the practical variant of SPEEDY, i.e., SPEEDY-5-192 has a security margin of only 2 rounds. We believe our work will bring new insights in understanding the security of SPEEDY

The Security of SIMON-like Ciphers Against Linear Cryptanalysis

In the present paper, we analyze the security of SIMON-like ciphers against linear cryptanalysis. First, an upper bound is derived on the squared correlation of SIMON-like round function. It is shown that the upper bound on the squared correlation of SIMON-like round function decreases with the Hamming weight of output mask increasing. Based on this, we derive an upper bound on the squared correlation of linear trails for SIMON and SIMECK, which is $2^{-2R+2}$ for any $R$-round linear trail. We also extend this upper bound to SIMON-like ciphers. Meanwhile, an automatic search algorithm is proposed, which can find the optimal linear trails in SIMON-like ciphers under the Markov assumption. With the proposed algorithm, we find the provably optimal linear trails for $12$, $16$, $19$, $28$ and $37$ rounds of SIMON$32/48/64/96/128$. To the best of our knowledge, it is the first time that the provably optimal linear trails for SIMON$64$, SIMON$96$ and SIMON$128$ are reported. The provably optimal linear trails for $13$, $19$ and $25$ rounds of SIMECK$32/48/64$ are also found respectively. Besides the optimal linear trails, we also find the $23$, $31$ and $41$-round linear hulls for SIMON$64/96/128$, and $13$, $21$ and $27$-round linear hulls for SIMECK$32/48/64$. As far as we know, these are the best linear hull distinguishers for SIMON and SIMECK so far. Compared with the approach based on SAT/SMT solvers in \cite{KolblLT15}, our search algorithm is more efficient and practical to evaluate the security against linear cryptanalysis in the design of SIMON-like ciphers

Tradeoff Attacks on Symmetric Ciphers

Tradeoff attacks on symmetric ciphers can be considered as the generalization of the exhaustive search. Their main objective is reducing the time complexity by exploiting the memory after preparing very large tables at a cost of exhaustively searching all the space during the precomputation phase. It is possible to utilize data (plaintext/ciphertext pairs) in some cases like the internal state recovery attacks for stream ciphers to speed up further both online and offline phases. However, how to take advantage of data in a tradeoff attack against block ciphers for single key recovery cases is still unknown. We briefly assess the state of art of tradeoff attacks on symmetric ciphers, introduce some open problems and discuss the security criterion on state sizes. We discuss the strict lower bound for the internal state size of keystream generators and propose more practical and fair bound along with our reasoning. The adoption of our new criterion can break a fresh ground in boosting the security analysis of small keystream generators and in designing ultra-lightweight stream ciphers with short internal states for their usage in specially low source devices such as IoT devices, wireless sensors or RFID tags

NaCl on 8-Bit AVR Microcontrollers

This paper presents first results of the Networking and Cryptography library (NaCl) on the 8-bit AVR family of microcontrollers. We show that NaCl, which has so far been optimized mainly for different desktop and server platforms, is feasible on resource-constrained devices while being very fast and memory efficient. Our implementation shows that encryption using Salsa20 requires 268 cycles/byte, authentication using Poly1305 needs 195 cycles/byte, a Curve25519 scalar multiplication needs 22,791,579 cycles, signing of data using Ed25519 needs 23,216,241 cycles, and verification can be done within 32,634,713 cycles. All implemented primitives provide at least 128-bit security, run in constant time, do not use secret-data-dependent branch conditions, and are open to the public domain (no usage restrictions)

Pushing the Limits of SHA-3 Hardware Implementations to Fit on RFID

There exists a broad range of RFID protocols in literature that propose hash functions as cryptographic primitives. Since Keccak has been selected as the winner of the NIST SHA-3 competition in 2012, there is the question of how far we can push the limits of Keccak to fulfill the stringent requirements of passive low-cost RFID. In this paper, we address this question by presenting a hardware implementation of Keccak that aims for lowest power and lowest area. Our smallest (full-state) design requires only 2\,927 GEs (for designs with external memory available) and 5\,522 GEs (total size including memory). It has a power consumption of $12.5\,\mu$W at 1\,MHz on a low leakage 130\,nm CMOS process technology. As a result, we provide a design that needs 40\,\% less resources than related work. Our design is even smaller than the smallest SHA-1 and SHA-2 implementations

Fault Attacks In Symmetric Key Cryptosystems

Fault attacks are among the well-studied topics in the area of cryptography. These attacks constitute a powerful tool to recover the secret key used in the encryption process. Fault attacks work by forcing a device to work under non-ideal environmental conditions (such as high temperature) or external disturbances (such as glitch in the power supply) while performing a cryptographic operation. The recent trend shows that the amount of research in this direction; which ranges from attacking a particular primitive, proposing a fault countermeasure, to attacking countermeasures; has grown up substantially and going to stay as an active research interest for a foreseeable future. Hence, it becomes apparent to have a comprehensive yet compact study of the (major) works. This work, which covers a wide spectrum in the present day research on fault attacks that fall under the purview of the symmetric key cryptography, aims at fulfilling the absence of an up-to-date survey. We present mostly all aspects of the topic in a way which is not only understandable for a non-expert reader, but also helpful for an expert as a reference

Threshold Implementation in Software - Case Study of PRESENT

Masking is one of the predominantly deployed countermeasures in order to prevent side-channel analysis (SCA) attacks. Over the years, various masking schemes have been proposed. However, the implementation of Boolean masking schemes has proven to be difficult in particular for embedded devices due to undisclosed architecture details and device internals. In this article, we investigate the application of Threshold Implementation (TI) in terms of Boolean masking in software using the PRESENT cipher as a case study. Since TI has proven to be a proper solution in order to implement Boolean masking for hardware circuits, we apply the same concept for software implementations and compare it to classical first- and second-order Boolean masking schemes. Eventually, our practical security evaluations reveal that amongst all our considered implementation variants only the TI can provide first-order security while all others still exhibit detectable first-order leakage