Improved Differential Fault Analysis on AES Key Schedule

Literature on Differential Fault Analysis (DFA) on AES-128 shows that it is more difficult to attack AES when the fault is induced in the key schedule, than when it is injected in the intermediate states. Recent research shows that DFA on AES key schedule still requires two faulty cipher texts, while it requires only one faulty cipher text and a brute-force search of $2^8$ AES-128 keys when the fault is injected inside the round of AES. The present paper proposes a DFA on AES-128 key schedule which requires only one single byte fault and a brute-force search of $2^8$ keys, showing that a DFA on AES key schedule is equally dangerous as a fault analysis when the fault is injected in the intermediate state of AES. Further, the fault model of the present attack is a single byte fault. This is more realistic than the existing fault model of injecting three byte faults in a column of the AES key which has a less chance of success. To the best of our knowledge the proposed attack is the best known DFA on AES key schedule and requires minimum number of faulty cipher text. The simulated attack, running on 3GHz Intel Core 2 Duo desktop machine with 2GB RAM, takes around 35 minutes to reveal the secret key.

Side channel analysis(SCA) focuses on attacking cryptographic algorithm implementations by collecting leaked information and analyzing the correlation between the leaked and key information in the cryptographic system. Currently, SCA is the main threat to cryptographic implementations, with DPA (differential power analysis) and DFA (differential fault analysis) being two of the most threatening types of SCA. However, the existing countermeasures against DPA and DFA have shortcomings and can hardly protect cipher designs perfectly. Based on a comprehensive analysis of DPA and DFA, this paper proposes a new idea of using an evolutionary cipher (EVOC) against DPAs based on the model proposed by Kocher, and several different new types of DFAs. In fact, an EVOC is a kind of dynamic cipher designing method. Moreover, combined with intelligent searching algorithms and cryptography design policies, EVOCs utilize the dynamic and unpredictable properties of TRNG (a truly random number generator) to ensure cipher design at a high level of security. Therefore, with an EVOC we could design cryptography algorithms with high security to resist mathematical analysis as well as DPAs and DFAs. This paper analyzes and proves the security, efficiency, cost, and original features of EVOCs against DPA and DFA both theoretically and experimentally. Compared with existing countermeasures against SCAs, EVOCs use dynamic non-linear operations to destroy the bases of DPA and DFA. At the algorithm level, EVOCs are more efficient than other resistance methods. Based on the theory and experiments, this paper proposes certain modifications to the EVOC in the AES (advanced encryption standard) algorithm, which can be referenced by other dynamic designs of cryptographic algorithms.

The development of differential fault analysis (DFA) techniques and mechanisms to inject faults into cryptographic circuits brings with it the need to use protection mechanisms that guarantee the expected level of security. The AES cipher, as a standard, has been the target of numerous DFA techniques, where its security has been compromised through different formulations and types of fault injections. These attacks have shown vulnerabilities of different AES implementations and building blocks. Consequently, several solutions have been proposed that provide additional protection to cover the identified vulnerabilities. In this paper, an extensive analysis has been carried out covering the existing fault injection techniques, the types of faults, and the requirements needed to apply DFA. Additionally, an analysis of the countermeasures reported in the literature is also presented, considering the protection provided, the type of faults considered, and the coverage against fault attacks. The eight different types of fault that allow us to perform DFAs on the AES cipher have been differentiated, as well as the vulnerabilities of the cipher. On the other hand, two comparisons have been made considering frequency penalty vs. area and fault coverage vs. area and frequency overhead. A metric has been proposed to compare the fault coverage of all the proposed solutions. To conclude, a final analysis is presented discussing the key aspects when choosing a particular solution and the possible development of new countermeasures to provide further protection against DFA.

In this paper we describe several fault attacks on the Ad- vanced Encryption Standard (AES). First, using optical/eddy current fault induction attacks as recently publicly presented by Skorobogatov, Anderson and Quisquater, Samyde (SA,QS), we present an implemen- tation independent fault attack on AES. This attack is able to deter- mine the complete 128-bit secret key of a sealed tamper-proof smart- card by generating 128 faulty cipher texts. Second, we present several implementation-dependent fault attacks on AES. These attacks rely on the observation that due to the AES's known timing analysis vulnera- bility (as pointed out by Koeune and Quisquater (KQ)), any implemen- tation of the AES must ensure a data independent timing behavior for the so called AES's xtime operation. We present fault attacks on AES based on various timing analysis resistant implementations of the xtime- operation. Our strongest attack in this direction uses a very liberal fault model and requires only 256 faulty encryptions to determine a 128-bit key.

Fault injection attacks are powerful cryptanalysis techniques against the Advanced Encryption Standard (AES) algorithm. These attacks are based on injecting faults into the structure of the AES to obtain confidential information. To protect the AES implementation against these attacks, a number of countermeasures have been proposed. In this paper, we proposed a fault detection scheme, based on the information redundancy, for the AES. We discuss the strengths and the weaknesses of this scheme against the fault attacks. Moreover, we conduct a comparative study between fault detection schemes from the literature in terms of fault detection capabilities and implementation cost. The simulation results show that the fault coverage achieves 99.998% for the proposed scheme. Moreover, the proposed detection scheme has been implemented on Xilinx Virtex-5 FPGA. Its fault coverage, area overhead, throughput and frequency degradation have been compared and it is shown that the proposed scheme allows a trade-off between the hardware overhead and the security of the AES.

This paper proposes a fault analysis technique on LED by combining algebraic cryptanalysis and differential fault analysis (DFA). The technique is called algebraic differential fault analysis (ADFA). In ADFA on LED, we use DFA to deduce the possible fault differences of the correct and faulty S-Box input in the last round, and convert them into algebraic equations. We then combine the equation set of LED with the injected fault and use the CryptoMiniSat solver to recover the secret key. Our experiments show that, on a common PC, ADFA can succeed on LED under the nibble-based fault model within three minutes and with only one fault injection, which is more efficient than previous DFA work. To evaluate DFA on LED, we first propose an improved evaluation algorithm of DFA, then provide a modified ADFA approach to compute the solutions for the secret key. The results are more accurate than previous work. We also successfully extend ADFA on LED to other fault models using a single fault injection, where traditional DFAs are difficult to launch.

In 2013, the US National Security Agency proposed two new families of lightweight block ciphers: SIMON and SPECK. Currently, linear and differential cryptanalytic results for SIMON are available in the literature but no fault attacks have been reported so far on these two cipher families. In this paper, we show that these families of ciphers are vulnerable to differential fault attacks. Specifically, we demonstrate two fault attacks on SIMON and one fault attack on SPECK. The first attack on SIMON assumes a bit-flip fault model and recovers the n-bit last round key of SIMON using n/2 bit faults. The second attack on SIMON uses a more practical, random byte fault model and requires n/8 faults on average to retrieve the last round key. The attack presented on SPECK also assumes a bit-flip fault model and recovers the n-bit last round key of SPECK using n/3 bit faults on average.

An active attacker can induce errors during the computation of the cryptographic algorithm and exploit the faulty results to extract information about the secret key in embedded systems. We call this kind of attack a fault attack. Fault attacks can break an unprotected system more quickly than any other kind of side-channel attack such as simple power analysis (SPA), differential power analysis (DPA), or electromagnetic analysis (EMA). For example, the attacker can break RSA-CRT (RSA with Chinese Remainder Theorem) with one faulty result, and Data Encryption Standard (DES) and Advanced Encryption Standard (AES) with two. Furthermore, the protection of fault attacks is more costly in terms of chip area. Here, we survey fault injection methods, types of faults, and fault attack models.

Aiming to protect cryptographic circuits against physical attacks, researchers have proposed a variety of mature and effective countermeasures. However, most of these defensive technologies are used for specific and single attack, thus it is hard to thwart combined attack, such as combined power and fault attacks. In this paper, we propose a dual complementary infection countermeasure for Advanced Encryption Standard (AES) cryptographic circuit to defend against both power and fault attacks. According to the target AES circuit, we first design and construct a dual complementary AES circuit to defend against power attacks, which can balance the power consumption when processing different data. Besides, to defend against fault attacks, in the dual complementary AES circuit, we design an improved random infection mechanism to diffuse the effect of injected faults. Experiment results show that the proposed countermeasure can thwart both power and fault attacks effectively. Compared with those AES circuits which can only defend against single attack, our designed circuit increases greatly the security under extra 83.1% area overhead and 2.1% impacts on the maximum working frequency.

The present paper develops a new fault attack suitable against hardware designs of the Advanced Encryption Standard (AES) cryptosystem. The paper presents a two stage fault based attack of an AES implementation that assumes a random non-zero random byte fault at the input of the eighth round. The paper shows that the fault model is practical, does not assume the location of the byte fault in the state matrix and requires a brute force search of complexity 236. The paper discusses the possibility of the attack on an FPGA implementation of AES by making sudden changes in the frequency of the input clock.

Differential fault analysis on the contracting UFN structure, with application to SMS4 and MacGuffin

Basically, Differential Fault Analysis (DFA) against ciphers consists of two stages: fault induction and fault exploitation. Success rate of the latter strongly depends upon the availability of the required type of some faulty ciphertexts, which typically assumes that adversaries have precise control over the location, timing and/or even the type of the fault induced. In view of this, there seems to be a technical gap between these two stages. In this paper, by amplifying the fault propagation pattern inherent in block ciphers, we propose an algorithmic method to narrow this gap, or to relax the underlying assumption. Our method provides a faulty ciphertext filtering process between two basic stages in DFA. This additional process equips adversaries with the capabilities to deterministically decide whether or not one faulty ciphertext is relevant to a specific DFA, before or without performing DFA itself. We take AES as a concrete case of study and conduct theoretical analysis and simulation experiments as well, the results of which strongly demonstrate the validity and power of our proposed filtering method.

This work analyzes the strength of NIST Lightweight Cryptography (LWC) Round 1 Candidate SIV-Rijndael256 in light of Differential Fault Attacks (DFA). It is observed that SIV-Rijndael256 presents an interesting case for DFA due to its large state-size which has been capitalized in this work to contribute to the state-of-the-art in DFA on AES-like ciphers. We first study the differential properties over three rounds of the cipher and then use it to mount a DFA that uses a classical strategy in conjunction with the properties of the key-schedule. The nonce-misuse property of SIV-Rijndael256 facilitates the use of DFA and is exploited to reduce the key-space from 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">128</sup> to just one using only a single random byte fault in the internal state. Moreover, the support for the release of unverified plaintexts which have been shown in literature as a vulnerability to DFA, makes the decryption also vulnerable to the same attack. Finally, the ability to uniquely retrieve the key using just a single fault makes the attack, reported here, an optimal DFA. To the best of our knowledge, this is the first differential fault analysis of any candidate in the NIST LWC competition.

In this paper we present an improved differential fault attack on the Advanced Encryption Standard (AES) with 256-bit key. We show an improved attack which retrieves the AES-256 key using two pairs of fault free and faulty ciphertexts and a brute-force search of 216 with a time complexity 232. The attack retrieves the secret key within approximately 45 minutes, running on desktop Intel Core TM 2 Duo processor of 3GHz speed. To the best of the knowledge of the authors, this is the most optimized fault attack on AES-256 among reported results requiring only two faulty ciphertexts.

Improved differential fault attack against SIMECK based on two-bit fault model