Internet of Things connects lots of small constrained devices to the Internet. As in any other environment, communication security is important and cryptographic algorithms are one of many elements that we use in order to keep messages secure. It is necessary to use algorithms that do not require high computational power, lightweight ciphers are therefore an ideal candidate for this purpose. Since these devices work in various environments, it is necessary to test security of implementations of cryptographic algorithms. In this paper, we explore a possibility of attacking an ultralightweight cipher PRESENT by using a multiple fault attack. Utilizing the Differential Fault Analysis technique, we were able to recover the secret key with two faulty encryptions and an exhaustive search of 216 remaining key bits. Our attack aims at four nibbles in the penultimate round of the cipher, causing faulty output in all nibbles of the output. We also provide a practical attack scenario by exploiting Hardware Trojan (HT) technique for the proposed fault injection in a Xilinx Spartan-6 FPGA.
@cite_22 presented two DFA attacks on PRESENT, the first one attacks a single bit and the second one attacks a single nibble of the intermediate state. They were able to recover the secret key with 18 faulty cipher texts on average, using the second attack.
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PRESENT is a hardware-optimized 64-bit lightweight block cipher which supports 80-and 128-bit secret keys. In this paper, we propose a differential fault analysis DFA on PRESENT-80 128. The proposed attack is based on a 2-byte random fault model. In detail, by inducing several 2-byte random faults in input registers after 28 rounds, our attack recovers the secret key of the target algorithm. From simulation results, our attacks on PRESENT-80 128 can recover the secret key by inducing only two and three 2-byte random faults, respectively. These are superior to known DFA results on them. In this paper, we present two differential fault analyses on PRESENT-80 which is a lightweight block cipher. The first attack is a basic attack which induces a fault on only one bit of intermediate states, and we can obtain the last subkey of the block cipher, given 48 faulty cipher texts on average. The second attack can retrieve the master key of the block cipher, given 18 faulty cipher texts on average. In the latter attack, we assume that we can induce faults on a single nibble of intermediate states. Given those faulty cipher texts, the computational complexity of attacks is negligible. This article proposes an enhanced differential fault analysis (DFA) method named as fault-propagation pattern-based DFA (FPP-DFA). The main idea of FPP-DFA is using the FPP of the ciphertext difference to predict the fault location and the fault-propagation path. It shows that FPP-DFA is very effective on SPN structure block ciphers using bitwise permutation, which is applied to two block ciphers. The first is PRESENT with the substitution-permutation sequence. With the fault model of injecting one nibble fault into the r-2nd round, on average 8 and 16 faults can reduce the key search space of PRESENT-80 128 to 214.7 and 221.1, respectively. The second is PRINTcipher with the permutation-substitution sequence. For the first time, it shows that although the permutation of PRINTcipher is secret key dependent, FPP-DFA still works well on it. With the fault model of injecting one nibble fault into the r-2nd round, 12 and 24 effective faults can reduce the key search space of PRINTcipher-48 96 to 213.7 and 222.8, respectively. PRESENT is a lightweight block cipher designed by A. in 2007 for extremely constrained environments such as RFID tags and sensor networks, where the AES is not suitable for. In this paper, the strength of PRESENT against the differential fault attack on the key schedule is explored. Our attack adopts the nibble oriented model of random faults and assumes that the attacker can induce a single nibble fault on the round key. The attack can efficiently recover the secret key with the computational complexity of @math , and sixty-four pairs of correct and faulty cipher texts on average. The best known cryptanalytic attack on McEliece's public-key cryptosystem based on algebraic coding theory is to repeatedly select k bits at random from an n-bit ciphertext vector, which is corrupted by at most t errors, in hope that none of the selected k bits are in error until the cryptanalyst recovers the correct message. The method of determining whether the recovered message is the correct one has not been throughly investigated. In this paper, we suggest a systematic method of checking, and describe a generalized version of the cryptanalytic attack which reduces the work factor sigdicantly (factor of 211 for the commonly used example of n=1024 Goppa code case). Some more improvements are also given. We also note that these cryptanalytic algorithms can be viewed as generalized probabilistic decoding algorithms for any linear error correcting codes. In 2010, Tao Xie and Dengguo Feng [XF10] constructed the rst single-block collision for MD5 consisting of two 64-byte messages that have the same MD5 hash. Details of their attack, developed using what they call an evolutionary approach, has not been disclosed security reasons". Instead they have posted a challenge to the cryptology community to nd a new dierent single-block collision attack for MD5. This paper answers that challenge by presenting a single-block collision attack based on other message dierences together with an example colliding message pair. The attack is based on a new collision nding algorithm that exploits the low number of bitconditions in the rst round. It uses a new way to choose message blocks that satisfy bitconditions up to step 22 and additionally uses three known tunnels to correct bitconditions up to step 25. The attack has an average runtime complexity equivalent to 2 49:8 calls to MD5’s compression function. Challenging the conventional wisdom that users cannot remember cryptographically-strong secrets, we test the hypothesis that users can learn randomly-assigned 56- bit codes (encoded as either 6 words or 12 characters) through spaced repetition. We asked remote research participants to perform a distractor task that required logging into a website 90 times, over up to two weeks, with a password of their choosing. After they entered their chosen password correctly we displayed a short code (4 letters or 2 words, 18.8 bits) that we required them to type. For subsequent logins we added an increasing delay prior to displaying the code, which participants could avoid by typing the code from memory. As participants learned, we added two more codes to comprise a 56.4- bit secret. Overall, 94 of participants eventually typed their entire secret from memory, learning it after a median of 36 logins. The learning component of our system added a median delay of just 6.9 s per login and a total of less than 12 minutes over an average of ten days. 88 were able to recall their codes exactly when asked at least three days later, with only 21 reporting having written their secret down. As one participant wrote with surprise, "the words are branded into my brain." Lattice-based signature schemes following the Goldreich–Goldwasser–Halevi (GGH) design have the unusual property that each signature leaks information on the signer’s secret key, but this does not necessarily imply that such schemes are insecure. At Eurocrypt ’03, Szydlo proposed a potential attack by showing that the leakage reduces the key-recovery problem to that of distinguishing integral quadratic forms. He proposed a heuristic method to solve the latter problem, but it was unclear whether his method could attack real-life parameters of GGH and NTRUSign. Here, we propose an alternative method to attack signature schemes a la GGH by studying the following learning problem: given many random points uniformly distributed over an unknown n-dimensional parallelepiped, recover the parallelepiped or an approximation thereof. We transform this problem into a multivariate optimization problem that can provably be solved by a gradient descent. Our approach is very effective in practice: we present the first successful key-recovery experiments on NTRUSign-251 without perturbation, as proposed in half of the parameter choices in NTRU standards under consideration by IEEE P1363.1. Experimentally, 400 signatures are sufficient to recover the NTRUSign-251 secret key, thanks to symmetries in NTRU lattices. We are also able to recover the secret key in the signature analogue of all the GGH encryption challenges. We apply the Flush+Reload side-channel attack based on cache hits misses to extract a small amount of data from OpenSSL ECDSA signature requests. We then apply a "standard" lattice technique to extract the private key, but unlike previous attacks we are able to make use of the side-channel information from almost all of the observed executions. This means we obtain private key recovery by observing a relatively small number of executions, and by expending a relatively small amount of post-processing via lattice reduction. We demonstrate our analysis via experiments using the curve secp256k1 used in the Bitcoin protocol. In particular we show that with as little as 200 signatures we are able to achieve a reasonable level of success in recovering the secret key for a 256-bit curve. This is significantly better than prior methods of applying lattice reduction techniques to similar side channel information. In this paper we address the problem of solving substitution ciphers using a beam search approach. We present a conceptually consistent and easy to implement method that improves the current state of the art for decipherment of substitution ciphers and is able to use high ordern-gram language models. We show experiments with 1:1 substitution ciphers in which the guaranteed optimal solution for 3-gram language models has 38.6 decipherment error, while our approach achieves 4.13 decipherment error in a fraction of time by using a 6-gram language model. We also apply our approach to the famous Zodiac-408 cipher and obtain slightly better (and near to optimal) results than previously published. Unlike the previous state-of-the-art approach that uses additional word lists to evaluate possible decipherments, our approach only uses a letterbased 6-gram language model. Furthermore we use our algorithm to solve large vocabulary substitution ciphers and improve the best published decipherment error rate based on the Gigaword corpus of 7.8 to 6.0 error rate. We consider the scenario where Alice wants to send a secret (classical) @math -bit message to Bob using a classical key, and where only one-way transmission from Alice to Bob is possible. In this case, quantum communication cannot help to obtain perfect secrecy with key length smaller then @math . We study the question of whether there might still be fundamental differences between the case where quantum as opposed to classical communication is used. In this direction, we show that there exist ciphers with perfect security producing quantum ciphertext where, even if an adversary knows the plaintext and applies an optimal measurement on the ciphertext, his Shannon uncertainty about the key used is almost maximal. This is in contrast to the classical case where the adversary always learns @math bits of information on the key in a known plaintext attack. We also show that there is a limit to how different the classical and quantum cases can be: the most probable key, given matching plain- and ciphertexts, has the same probability in both the quantum and the classical cases. We suggest an application of our results in the case where only a short secret key is available and the message is much longer. Several standard cryptographic hash functions were broken in 2005. Some essential building blocks of these attacks lend themselves well to automation by encoding them as CNF formulas, which are within reach of modern SAT solvers. In this paper we demonstrate effectiveness of this approach. In particular, we are able to generate full collisions for MD4 and MD5 given only the differential path and applying a (minimally modified) off-the-shelf SAT solver. To the best of our knowledge, this is the first example of a SAT-solver-aided cryptanalysis of a non-trivial cryptographic primitive. We expect SAT solvers to find new applications as a validation and testing tool of practicing cryptanalysts. The ideas of completeness and the avalanche effect were first introduced by Kam and Davida [1] and Feistel [2], respectively. If a cryptographic transformation is complete, then each ciphertext bit must depend on all of the plaintext bits. Thus, if it were possible to find the simplest Boolean expression for each ciphertext bit in terms of the plaintext bits, each of those expressions would have to contain all of the plaintext bits if the function was complete. Alternatively, if there is at least one pair of n-bit plaintext vectors X and Xi that differ only in bit i, and f(X) and f(Xi) differ at least in bit j for all @math then the function f must be complete. We present complexity results for the verification of security protocols. Since the perfect cryptography assumption is unrealistic for cryptographic primitives with visible algebraic properties, we extend the classical Dolev-Yao model by permitting the intruder to exploit these properties. More precisely, we are interested in theories such as Exclusive or and Abelian groups in combination with the homomorphism axiom. We show that the intruder deduction problem is in PTIME in both cases, improving the EXPTIME complexity results of Lafourcade, Lugiez and Treinen. iez, R. Treinen, Intruder deduction for AC-like equational theories with homomorphisms, in: Proc. 16th Internat. Conf. Rewriting Techniques and Applications (RTA'05), Nara, Japan, Lecture Notes in Comput. Sci., vol. 3467, Springer, Berlin, 2005, pp. 308-322]. We investigate a general class of quantum key distribution (QKD) protocols using one-way classical communication. We show that full security can be proven by considering only collective attacks. We derive computable lower and upper bounds on the secret-key rate of those QKD protocols involving only entropies of two-qubit density operators. As an illustration of our results, we determine new bounds for the Bennett-Brassard 1984, the 6-state, and the Bennett 1992 protocols. We show that in all these cases the first classical processing that the legitimate partners should apply consists in adding noise. Side channel attacks on cryptographic systems exploit information gained from physical implementations rather than theoretical weaknesses of a scheme. In recent years, major achievements were made for the class of so called access-driven cache attacks. Such attacks exploit the leakage of the memory locations accessed by a victim process. In this paper we consider the AES block cipher and present an attack which is capable of recovering the full secret key in almost real time for AES-128, requiring only a very limited number of observed encryptions. Unlike previous attacks, we do not require any information about the plaintext (such as its distribution, etc.). Moreover, for the first time, we also show how the plaintext can be recovered without having access to the cipher text at all. It is the first working attack on AES implementations using compressed tables. There, no efficient techniques to identify the beginning of AES rounds is known, which is the fundamental assumption underlying previous attacks. We have a fully working implementation of our attack which is able to recover AES keys after observing as little as 100 encryptions. It works against the OpenS SL 0.9.8n implementation of AES on Linux systems. Our spy process does not require any special privileges beyond those of a standard Linux user. A contribution of probably independent interest is a denial of service attack on the task scheduler of current Linux systems (CFS), which allows one to observe (on average) every single memory access of a victim process. Cache attacks are known to be sophisticated attacks against cryptographic implementations on desktop computers. Recently, investigations of such attacks on specific testbeds with processors that are employed in mobile devices have been done. In this work we investigate the applicability of Bernstein’s [2] timing attack and the cache-collision attack by Bogdanov ( ) [4] in real environments on three state-of-the-art mobile devices: an Acer Iconia A510, a Google Nexus S, and a Samsung Galaxy SIII. We show that T-table based implementations of the Advanced Encryption Standard (AES) leak enough timing information on these devices in order to recover parts of the used secret key using Bernstein’s timing attack. We also show that systems with a cache-line size larger than 32 bytes exacerbate the cache-collision attack of Bogdanov ( ) [4]. We present a new methodology for realizing Ciphertext-Policy Attribute Encryption (CP-ABE) under concrete and noninteractive cryptographic assumptions in the standard model. Our solutions allow any encryptor to specify access control in terms of any access formula over the attributes in the system. In our most efficient system, ciphertext size, encryption, and decryption time scales linearly with the complexity of the access formula. The only previous work to achieve these parameters was limited to a proof in the generic group model. We present three constructions within our framework. Our first system is proven selectively secure under a assumption that we call the decisional Parallel Bilinear Diffie-Hellman Exponent (PBDHE) assumption which can be viewed as a generalization of the BDHE assumption. Our next two constructions provide performance tradeoffs to achieve provable security respectively under the (weaker) decisional Bilinear-Diffie-Hellman Exponent and decisional Bilinear Diffie-Hellman assumptions. In this paper, we propose an algorithm for constructing guess-and-determine attacks on keystream generators and apply it to the cryptanalysis of the alternating step generator (ASG) and two its modifications (MASG and MASG0). In a guess-and-determine attack, we first “guess” some part of an initial state and then apply some procedure to determine, if the guess was correct and we can use the guessed information to solve the problem, thus performing an exhaustive search over all possible assignments of bits forming a chosen part of an initial state. We propose to use in the “determine” part the algorithms for solving Boolean satisfiability problem (SAT). It allows us to consider sets of bits with nontrivial structure. For each such set it is possible to estimate the runtime of a corresponding guess-and-determine attack via the Monte-Carlo method, so we can search for a set of bits yielding the best attack via a black-box optimization algorithm augmented with several SAT-specific features. We constructed and implemented such attacks on ASG, MASG, and MASG0 to prove that the constructed runtime estimations are reliable. We show, that the constructed attacks are better than the trivial ones, which imply exhaustive search over all possible states of the control register, and present the results of experiments on cryptanalysis of ASG and MASG MASG0 with total registers length of 72 and 96, which have not been previously published in the literature. In this paper, we examine the potential of using a thermal camera to recover codes typed into keypads in a variety of scenarios. This attack has the advantage over using a conventional camera that the codes do not need to be captured while they are being typed and can instead be recovered for a short period afterwards. To get the broadest sense of how effective such an attack might be, we consider a number of variables: the material of the keypad, the user entering the code, the distance from the camera to the keypad, and the possible methods used to analyze the data. First, we present code recovery results from human review of our test data set; this provides us with a baseline for the overall effectiveness of thermal camera-based attacks. Second, using techniques from computer vision we automatically extract the code from raw camera data, thus demonstrating that this attack has the potential to scale well in practice. As we will see, both human and automated attacks are by and large successful in recovering the keys present in the code, even a full minute after they have been pressed; both methods are also able to determine the exact code (i.e., including the order in which the keys were pressed) for a smaller fraction of codes. Even without ordering, however, the search space of possible keys is still vastly reduced by knowing the keys pressed; for example, the search space is reduced from 10,000 possible codes to approximately 24 for a 4-digit code. In large-scale attacks involving many unique codes, such as on ATM PINs, our success rate indicates that an adversary can correctly recover enough codes to make such an attack economically viable.