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The consequences of regular expression hashing as a means of finite state automaton reduction is explored, based on variations of Brzozowski's algorithm. In this approach, each hash collision results in the merging of the automaton's states, and it is subsequently shown that a super-automaton will always be constructed, regardless of the hash function used. Since direct adaptation of the classical Brzozowski algorithm leads to a non-deterministic super-automaton, a new algorithm is put forward for constructing a deterministic FA. Approaches are proposed for measuring the quality of a hash function.

These ideas are empirically tested on a large sample of relatively small regular expressions and their associated automata, as well as on a small sample of relatively large regular expressions. Differences in the quality of tested hash functions are observed. Possible reasons for this are mentioned, but future empirical work is required to investigate the matter.

In this paper, we specify a class of mathematical problems, which we refer to as “Function Density Problems” (FDPs, in short), and point out novel connections of FDPs to the following two cryptographic topics; theoretical security evaluations of keyless hash functions (such as SHA-1), and constructions of provably secure pseudorandom generators (PRGs) with some enhanced security property introduced by Dubrov and Ishai (STOC 2006). Our argument aims at proposing new theoretical frameworks for these topics (especially for the former) based on FDPs, rather than providing some concrete and practical results on the topics. We also give some examples of mathematical discussions on FDPs, which would be of independent interest from mathematical viewpoints. Finally, we discuss possible directions of future research on other crypto-graphic applications of FDPs and on mathematical studies on FDPs themselves.

Recently, a secure two-factor user authentication scheme for wireless sensor networks (WSN) was proposed by Das. The proposed scheme can resist many logged in users with the same login identity, stolen-verifier, guessing, impersonation and replay threats. In this paper we study the two-factor user authentication scheme for WSN and find that the scheme is insecure against the masquerade attacks. With our masquerade attacks, an attacker can masquerade as any legal user to login the gateway node without knowing the user's password or can masquerade as a gateway node to communicate with the legal user at anytime.

In this paper, we propose an algorithm for one-way hash function construction based on the chaotic look-up table with changeable parameter. First, the original message with padding is divided into block messages as groups and then further broken into sub-block messages, which are translated into corresponding ASCII codes by groups. Then the group ASCII codes are successively inputted into the chaotic look-up table updated by changeable parameter to permute corresponding values. Finally, based on the calculation of the values, 128-bit hash value is generated. Performance analysis indicates that our proposed algorithm satisfies sensitive requirements and can resist all kinds of attacks.

An efficient $(t,n)$ threshold quantum secret sharing (QSS) scheme is proposed. In our scheme, the Hash function is used to check the eavesdropping, and no particles need to be published. So the utilization efficiency of the particles is real 100%. No entanglement is used in our scheme. The dealer uses the single particles to encode the secret information, and the participants get the secret through measuring the single particles. Compared to the existing schemes, our scheme is simpler and more efficient.

Cryptographic hash functions are at the heart of many information security applications like message authentication codes (MACs), digital signatures and other forms of authentication. One of the methods to ensure information integrity is the use of hash functions, which generates a stream of bytes (hash) that must be unique. But most functions can no longer prevent malicious attacks and ensure that the information have just a hash. Because of the weakening of the widely used SHA-1 hash algorithm and concerns over the similarly-structured algorithms of the SHA-2 family, the US National Institute of Standards and Technology (NIST) has initiated the SHA-3 contest in order to select a suitable drop-in replacement. KECCAK hash function has been submitted to SHA-3 competition and it belongs to the final five candidate functions. In this paper, we present the implementation details of the hash function’s KECCAK algorithm, moreover, the proposed KECCAK design has been implemented on XILINX FPGAs. Its area, frequency, throughput and efficiency have been derived and compared and it is shown that the proposed design allows a trade-off between the maximum frequency and the area implementation.

High-throughput designs of hash functions are strongly demanded due to the need for security in every transmitted packet of worldwide e-transactions. Thus, optimized and non-optimized pipelined architectures have been proposed raising, however, important questions. Which is the optimum number of the pipeline stages? Is it worth to develop optimized designs or could the same results be achieved by increasing only the pipeline stages of the non-optimized designs? The paper answers the above questions studying extensively many pipelined architectures of SHA-1 and SHA-256 hashes, implemented in FPGAs, in terms of throughput/area (T/A) factor. Also, guides for developing efficient security schemes designs are provided.

The cache system dissipates a significant amount of energy compared to the other memory components. This will be intensified if a cache is designed with a set-associative structure to improve the system performance because the parallel accesses to the entries of a set for tag comparisons lead to even more energy consumption. In this paper, a novel method is proposed as a combination of a counting Bloom filter and partial tags to mitigate the energy consumption of set-associative caches. This new hybrid method noticeably decreases the cache energy consumption especially in highly-associative instruction caches. In fact, it uses an enhanced counting Bloom filter to predict cache misses with a high accuracy as well as partial tags to decrease the overall cache size. This way, unnecessary tag comparisons can be prevented and therefore, the cache energy consumption is considerably reduced. Based on the simulation results, the proposed method provides the energy reduction from 22% to 31% for 4-way–32-way set-associative L1 caches bigger than 16kB running the MiBench programs. The improvements are attained with a negligible system performance degradation compared to the traditional cache system.

Wireless sensor networks (WSNs) have attracted a lot of interests over last years in security to ensure integrity, authenticity and data confidentiality. WSN applications are numerous, which range from smart home in indoor deployment offices to smart agriculture in outdoor deployments. Due to the deployment of nodes in remote areas, the solution brought to the wireless sensor network to increase the information security consists in protecting the messages exchanged between nodes. In the paper, modifications in the key management scheme are presented. Due to resource constraints in the sensor nodes, the proposed scheme ensures a distribution of the secured keys between nodes. New session keys transmitted between sensor nodes are defined during the discovery and path key phases. The experimental results prove that the proposed scheme is adapted to the WSN applications in terms of connectivity and resiliency.

In this paper, a chaos-based cryptographic hash function is proposed for message authentication where a fixed length message digest can be generated from any messages with arbitrary length. The compression function in-use is developed according to the diffusion and confusion properties of a novel high-dimensional discrete chaotic map. A symmetric key structure can also be easily embedded based on the high sensitivity to initial conditions and system parameters of the map. As demonstrated in experiments, the throughput of the proposed scheme is about 1.5 times of that with MD5, and the hash value appears randomly without any correlation with the message or the key.

As a basic and crucial security requirement for Wireless Sensor Networks (WSNs), authentication is generally used to prevent various communication attacks such as Denial-of-Service (DoS) attack. A novel broadcast authentication framework is proposed in this paper, where an Identity-Based Signature scheme by using the Extended Chaotic Maps (ECM-IBS) is designed to authenticate all broadcast messages and specifically, a chaos-based hash function is used for message authentication in the WSNs. It is implemented using a WSN hardware device of CC2530 and its performance is analyzed under various methods. Performance analysis and experimental results show that the proposed ECM-IBS scheme has a quick signature generation speed, low energy consumption and short verification delay, and can be applied to WSN applications.

The inherent random-like behavior and one-way property of iteration in chaotic systems provide a good basis for designing Hash function. In the era of big data, due to the increasing data capacity in applications, fast Hash functions with parallel mode are highly desirable when authenticating data integrity. We analyze the issue of how to parallelize Hash function with iterative structure. Some security requirements on parallel Hash function are presented. In addition, using chaotic map and block cipher, we construct a keyed parallel Hash function. The message blocks are firstly processed in parallel by a DM-like structure. Furthermore, a tree mode with chaotic map is utilized to combine the outputs of the hash round function in parallel. The proposed Hash function is analyzed by theory and tested by computer simulations. The test results show that the proposed scheme can resist the various common attacks against Hash functions. It satisfies the secure performance requirements of Hash function. Owing to the usage of the parallel mode to process messages, the proposed chaos-based Hash function possess high efficiency and has high potential in applications to guarantee data integrity on a parallel computing platform.

This paper proposes an image encryption technique which is fast and secure. The encryption scheme is designed for secure transmission of video surveillance data (keyframes) over insecure network. The image encryption technique employs 1D Sine–Sine system with better chaotic properties than its seed map and faster than higher-dimensional chaotic systems. Further, design of encryption scheme is based on two permutation rounds, which employs pixel swapping operation and diffusion operation which is simple and provides required security against plaintext, differential and various other attacks. Three separate chaotic sequences are generated using 1D Sine–Sine system which enhances the key space of the encryption scheme. Secret keys are updated dynamically with SHA-256 hash value obtained from plain image. Hash values of plain image are efficiently used without loss of any hash value information. This makes the encryption scheme plaintext sensitive and secure against plaintext attacks. Performance and security aspects of encryption scheme is analyzed both quantitatively using predefined security metrics and qualitatively by scrutinizing the internal working of encryption scheme. Computational complexity of encrypting a plain image of size $(rows\times columns)$ is ${𝒪}(rows\times columns)$ and is suitable for encrypting keyframes of video for secure surveillance applications.

As blockchain technology and smart contracts develop, computer technology is constantly integrating with smart chemical plants. Due to the continuous development of intelligent chemical plants, their systems have gradually become large and dispersed, posing a threat to safety management. In order to improve the performance of intelligent security management systems, the study first explores the principles of blockchain and smart contract technology, and then combined with the requirements of intelligent chemical plant security management systems, designs an intelligent security management system based on blockchain and smart contract technology. The experimental results showed that compared to systems without smart contract support, the communication success rate between nodes was lower. The error rates of blockchain-based encryption systems, deep learning-based encryption systems and improved data encryption systems proposed in the study were 0.22, 0.07 and 0.09, respectively. The packet loss rates were 0.13, 0.04 and 0.05, respectively. The lower the bit error rate and packet loss rate of the encryption system, the clearer the illegal eavesdropping information. The experimental results indicate that the intelligent security management system designed in this study has good encryption performance and a higher communication success rate. The results have certain reference value in security management application in intelligent chemical plants.

In a recent paper, an improvement of quantum sealed-bid auction protocol is proposed by introducing hash function. However, in this comment, it is shown that the improvement brings in other problems which would not complete the task of a sealed-bid auction fairly.

Traditional hash functions are designed to protect against even the slightest modification of a message. Thus, one bit changed in a message would result in a totally different message digest when a hash function is applied. This feature is not suitable for applications whose message spaces admit a certain fuzziness, such as multimedia communications or biometric authentication applications. In these applications, approximate hash functions must be designed so that the distance between messages are proportionally reflected in the distance between message digests. Most of the previous designs of approximate hash functions employ traditional hash functions. In an ingenious approximate message authentication scheme for an N-ary alphabet recently proposed by Ge, Arce and Crescenzo, the approximate hash functions are based on the majority selection function. This scheme is suitable for N-ary messages with arbitrary alphabet size N. In this paper, we show a hidden property of the majority selection function, which allows us to successfully break this scheme. We show that an adversary, by observing just one message and digest pair, without any knowledge of the secret information, can generate N - 1 new valid message and digest pairs. In order to resist the attack, we propose some modifications to the original design. The corrected scheme is as efficient as the original scheme and it is secure against the attack. By a new combinatorial approach, we calculate explicitly the security parameters of the corrected scheme.

Watermarking technology is widely used in secret communications, in which the security factor is crucial. Existing watermarks protect themselves from being hacked mainly depending on watermarking algorithms. Once hackers obtained the information carriers and figured out the algorithm, secret information embedded in them would be exposed. In this paper, we introduced a Run-length Slotting approach to map information into distributed interrelated images with a hash function. Then we discussed the selection of hash function to avoid information exposure strictly, and gave an algorithm to achieve our goal. Further more, a distributed watermarking model is introduced to improve the security of watermarks.