Building Secure and Fast Cryptographic Hash Functions Using Programmable Cellular Automata

Cryptographic hash functions have recently brought an exceptional research interest. With the increasing number of attacks against the widely used functions as MD5, SHA-1 and RIPEMD, the need to consider new hash functions design and conception strategies becomes crucial. In this paper, we propose a fast and efficient hash function using programmable cellular automata that are very suitable for cryptographic applications due to their chaotic and complex behavior derived from simple rules interaction. The proposed function is evaluated using several statistical tests, while obtained results demonstrate very admissible cryptographic properties such as confusion/diffusion capability and high sensitivity to input changes. Furthermore, the hashing scheme can be easily implemented through software or hardware, so it provides very competitive running performances

Construction of an NP Problem with an Exponential Lower Bound

In this paper we present a Hashed-Path Traveling Salesperson Problem (HPTSP), a new type of problem which has the interesting property of having no polynomial time solutions. Next we show that HPTSP is in the class NP by demonstrating that local information about sub-routes is insufficient to compute the complete value of each route. As a consequence, via Ladner's theorem, we show that the class NPI is non-empty

Slender PUF Protocol: A lightweight, robust, and secure authentication by substring matching

We introduce Slender PUF protocol, an efficient and secure method to authenticate the responses generated from a Strong Physical Unclonable Function (PUF). The new method is lightweight, and suitable for energy constrained platforms such as ultra-low power embedded systems for use in identification and authentication applications. The proposed protocol does not follow the classic paradigm of exposing the full PUF responses (or a transformation of the full string of responses) on the communication channel. Instead, random subsets of the responses are revealed and sent for authentication. The response patterns are used for authenticating the prover device with a very high probability.We perform a thorough analysis of the method’s resiliency to various attacks which guides adjustment of our protocol parameters for an efficient and secure implementation. We demonstrate that Slender PUF protocol, if carefully designed, will be resilient against all known machine learning attacks. In addition, it has the great advantage of an inbuilt PUF error tolerance. Thus, Slender PUF protocol is lightweight and does not require costly additional error correction, fuzzy extractors, and hash modules suggested in most previously known PUF-based robust authentication techniques. The low overhead and practicality of the protocol are confirmed by a set of hardware implementation and evaluations

Preimages for SHA-1

This research explores the problem of finding a preimage — an input that, when passed through a particular function, will result in a pre-specified output — for the compression function of the SHA-1 cryptographic hash. This problem is much more difficult than the problem of finding a collision for a hash function, and preimage attacks for very few popular hash functions are known. The research begins by introducing the field and giving an overview of the existing work in the area. A thorough analysis of the compression function is made, resulting in alternative formulations for both parts of the function, and both statistical and theoretical tools to determine the difficulty of the SHA-1 preimage problem. Different representations (And- Inverter Graph, Binary Decision Diagram, Conjunctive Normal Form, Constraint Satisfaction form, and Disjunctive Normal Form) and associated tools to manipulate and/or analyse these representations are then applied and explored, and results are collected and interpreted. In conclusion, the SHA-1 preimage problem remains unsolved and insoluble for the foreseeable future. The primary issue is one of efficient representation; despite a promising theoretical difficulty, both the diffusion characteristics and the depth of the tree stand in the way of efficient search. Despite this, the research served to confirm and quantify the difficulty of the problem both theoretically, using Schaefer's Theorem, and practically, in the context of different representations

An enhanced Blowfish Algorithm based on cylindrical coordinate system and dynamic permutation box

The Blowfish Algorithm (BA) is a symmetric block cipher that uses Feistel network to iterate simple encryption and decryption functions. BA key varies from 32 to 448 bits to ensure a high level of security. However, the substitution box (S-Box) in BA occupies a high percentage of memory and has problems in security, specifically in randomness of output with text and image files that have large strings of identical bytes. Thus, the objective of this research is to enhance the BA to overcome these problems. The research involved three phases, algorithm design, implementation, and evaluation. In the design phase, a dynamic 3D S-Box, a dynamic permutation box (P-Box), and a Feistal Function (F-Function) were improved. The improvement involved integrating Cylindrical Coordinate System (CCS) and dynamic P-Box. The enhanced BA is known as Ramlan Ashwak Faudziah (RAF) algorithm. The implementation phase involved performing key expansion, data encryption, and data decryption. The evaluation phase involved measuring the algorithm in terms of memory and security. In terms of memory, the results showed that the RAF occupied 256 bytes, which is less than the BA (4096 bytes). In terms of randomness of text and image files that have large strings of identical bytes, the average rate of randomness for 188 statistical tests obtained values of more than 96%. This means that the RAF has high randomness indicating that it is more secured. Thus, the results showed that the RAF algorithm that integrates the CCS and dynamic P-Box serves as an effective approach that can consume less memory and strengthen security

Statistical Analysis of Reduced Round Compression Functions of SHA-3 Second Round Candidates

National Institute of Standards and Technology announced a competition in 2008, of which the winner will be acknowledged as the new hash standard SHA-3. There are 14 second round candidates which are selected among 51 first round algorithms. In this paper, we apply statistical analysis to the second round candidate algorithms by using two different methods, and observe how conservative the algorithms are in terms of randomness. The first method evaluates 256-bit outputs, obtained from reduced round versions of the algorithms, through statistical randomness tests. On the other hand, the second method evaluates the randomness of the reduced round compression functions based on certain cryptographic properties. This analysis gives a rough idea on the security factor of the compression functions

Multi-shape symmetric encryption mechanism for nongeneric attacks mitigation

Static cyphers use static transformations for encryption and decryption. Therefore, the attacker will have some knowledge that can be exploited to construct assaults since the transformations are static. The class of attacks which target a specific cypher design are called Non-Generic Attacks. Whereby, dynamic cyphers can be utilised to mitigate non-generic attacks. Dynamic cyphers aim at mitigating non-generic attacks by changing how the cyphers work according to the value of the encryption key. However, existing dynamic cyphers either degrade the performance or decrease the cypher’s actual security. Hence, this thesis introduces a Multi-Shape Symmetric Encryption Mechanism (MSSEM) which is capable of mitigating non-generic attacks by eliminating the opponents’ leverage of accessing the exact operation details. The base cyphers that have been applied in the proposed MSSEM are the Advanced Encryption Standard (AES) competition finalists, namely Rijndael, Serpent, MARS, Twofish, and RC6. These cyphers satisfy three essential criteria, such as security, performance, and expert input. Moreover, the modes of operation used by the MSSEM are the secure modes suggested by the National Institute of Standards and Technology, namely, Cipher Block Chaining (CBC), Cipher Feedback Mode (CFB), Output Feedback Mode (OFB), and Counter (CTR). For the proposed MSSEM implementation, the sender initially generates a random key using a pseudorandom number generator such as Blum Blum Shub (BBS) or a Linear Congruential Generator (LCG). Subsequently, the sender securely shares the key with the legitimate receiver. Besides that, the proposed MSSEM has an entity called the operation table that includes sixty different cypher suites. Each cypher suite has a specific cypher and mode of operation. During the run-time, one cypher suite is randomly selected from the operation table, and a new key is extracted from the master key with the assistance of SHA-256. The suite, as well as the new key, is allowed to encrypt one message. While each of the messages produces a new key and cypher suite. Thus, no one except communicating parties can access the encryption keys or the cypher suites. Furthermore, the security of MSSEM has been evaluated and mathematically proven to resist known and unknown attacks. As a result, the proposed MSSEM successfully mitigates unknown non-generic attacks by a factor of 2−6. In addition, the proposed MSSEM performance is better than MODEM since MODEM generates 4650 milliseconds to encrypt approximately 1000 bytes, whereas MSSEM needs only 0.14 milliseconds. Finally, a banking system simulation has been tested with the proposed MSSEM in order to secure inbound and outbound system traffic

Avalanche Effect in Improperly Initialized CAESAR Candidates

Cryptoprimitives rely on thorough theoretical background, but often lack basic usability features making them prone to unintentional misuse by developers. We argue that this is true even for the state-of-the-art designs. Analyzing 52 candidates of the current CAESAR competition has shown none of them have an avalanche effect in authentication tag strong enough to work properly when partially misconfigured. Although not directly decreasing their security profile, this hints at their security usability being less than perfect. Paper details available at crcs.cz/papers/memics201