Most cryptosystems are defined over finite algebraic structures where arithmetic operations are performed modulo natural numbers. This applies to private key as well as to public key ciphers. No secure cryptosystems defined over the field of real numbers are known. In this work, we demonstrate the feasibility of constructing secure symmetric key ciphers defined over the field of real numbers. We consider the security of ciphers introduced in a previous work and based on solving linear and non-linear equations numerically. We complement the design of those ciphers to satisfy the requirements of secure systems and, consequently, extend them into composite ciphers with multiple encryptions. We show security enhancements by estimating the uncertainty in finding the keys using a measure based on Shannon's entropy function.
The Hill cipher is a classical symmetric encryption algorithm that succumbs to the know-plaintext attack. Although its vulnerability to cryptanalysis has rendered it unusable in practice, it still serves an important pedagogical role in cryptology and linear algebra. In this paper, a variant of the Hill cipher is introduced that makes the Hill cipher secure while it retains the efficiency. The proposed scheme includes a ciphering core for which a cryptographic protocol is introduced.
We follow two main objectives in this article. On the one hand, we introduce a security model called LORBACPA$^+$ for self-synchronized stream ciphers which is stronger than the blockwise LOR-IND-CPA, where we show that standard constructions as delayed CBC or similar existing self-synchronized modes of operation are not secure in this stronger model. Then, on the other hand, following contributions of G.~Millérioux et.al., we introduce a new self-synchronized stream cipher and prove its security in LORBACPA$^+$ model.
We consider the problem of constructing an unconditionally secure cipher for the case when the key length is less than the length of the encrypted message. (Unconditional security means that a computationally unbounded adversary cannot obtain information about the encrypted message without the key.) In this article, we propose data compression and randomization techniques combined with entropically-secure encryption. The resulting cipher can be used for encryption in such a way that the key length does not depend on the entropy or the length of the encrypted message; instead, it is determined …
This paper explains the recent developments in security and encryption. The Butterfly cipher and quantum cryptography are reviewed and compared. Examples of their relative uses are discussed and suggestions for future developments considered. In addition application to network security together with a substantial review of classification of encryption systems and a summary of security weaknesses are considered.
Caesar cipher is an ancient, elementary method of encrypting plain text message to protect it from adversaries. However, with the advent of powerful computers there is a need for increasing the complexity of such algorithms. In this paper, we contribute in the area of classical cryptography by providing a modified approach and expanded version for Caesar cipher using knowledge of mathematics and computer science. To increase the strength of this classical encryption technique we use the concepts of affine ciphers, transposition ciphers and randomized substitution techniques to create a cipher …
This paper develops a new algorithm to improve the security of RC4. Given that RC4 cipher is widely used in the wireless communication and has some weaknesses in the security of RC4 cipher, our idea is based on the combination of the RC4 and the poly alphabetic cipher Vigenère to give a new and more secure algorithm which we called VRC4. In this technique the plain text is encrypted using the classic RC4 cipher then re-encrypt the resulted cipher text using Vigenère cipher to be a more secure cipher text. For simplicity, we have implemented our new algorithm in Java Script taking into consider…
Natural phenomena show that many creatures form large social groups and move in regular patterns. Previous In this paper, we first propose an efficient distributed mining algorithm to jointly identify a group of moving objects and discover their movement patterns in wireless sensor networks. Afterward, we propose a compression algorithm, called 2P2D, which exploits the obtained group movement patterns to reduce the amount of delivered data. The compression algorithm includes a sequence merge and an entropy reduction phases. we formulate a Hit Item Replacement (HIR) problem and propose a Replac…
In 2002, Russell and Wang proposed a definition of entropically security that was developed within the framework of secret key cryptography. An entropically-secure system is unconditionally secure, that is, unbreakable, regardless of the enemy's computing power. In 2004, Dodis and Smith developed the results of Russell and Wang and, in particular, stated that the concept of an entropy-protected symmetric encryption scheme is extremely important for cryptography, since it is possible to construct entropy-protected symmetric encryption schemes with keys much shorter than the keys. the length of …
The resource-constrained nature of the Internet of Things (IoT) devices, poses a challenge in designing a secure, reliable, and particularly high-performance communication for this family of devices. Although side-channel resistant ciphers (either block cipher or stream cipher) are the well-suited solution to establish a guaranteed secure communication, the energy-intensive nature of these ciphers makes them undesirable for particularly lightweight IoT solutions. In this paper, we introduce ExTru, a novel encrypted communication protocol based on stream ciphers that adds a configurable switchi…
Existing semantically secure public-key searchable encryption schemes take search time linear with the total number of the ciphertexts. This makes retrieval from large-scale databases prohibitive. To alleviate this problem, this paper proposes Searchable Public-Key Ciphertexts with Hidden Structures (SPCHS) for keyword search as fast as possible without sacrificing semantic security of the encrypted keywords. In SPCHS, all keyword-searchable ciphertexts are structured by hidden relations, and with the search trapdoor corresponding to a keyword, the minimum information of therelations is disclo…
We consider the problem of constructing an unconditionally secure cipher with a short key for the case where the probability distribution of encrypted messages is unknown. Note that unconditional security means that an adversary with no computational constraints can obtain only a negligible amount of information ("leakage") about an encrypted message (without knowing the key). Here we consider the case of a priori (partially) unknown message source statistics. More specifically, the message source probability distribution belongs to a given family of distributions. We propose an unconditionall…
In recent years, several protocols for password-based authenticated key exchange have been proposed. These protocols aim to be secure even though the sample space of passwords may be small enough to be enumerated by an off-line adversary. In Eurocrypt 2000, Bellare, Pointcheval and Rogaway (BPR) presented a model and security definition for authenticated key exchange. They claimed that in the ideal-cipher model (random oracles), the two-flow protocol at the core of Encrypted Key Exchange (EKE) is secure. Bellare and Rogaway suggested several instantiations of the ideal cipher in their proposal…
In this paper we consider the description of homomorphic and fully homomorphic ciphers in the $p$-adic model of encryption. This model describes a wide class of ciphers, but certainly not all. Homomorphic and fully homomorphic ciphers are used to ensure the credibility of remote computing, including cloud technology. The model describes all homomorphic ciphers with respect to arithmetic and coordinate-wise logical operations in the ring of $p$-adic integers $Z_p$. We show that there are no fully homomorphic ciphers for each pair of the considered set of arithmetic and coordinate-wise logical o…
A new scheme for transmitting sensitive data is proposed, the proposed scheme depends on partitioning the output of a block encryption module using the Chinese Remainder Theorem among a set of channels. The purpose of using the Chinese Remainder Theorem is to hide the cipher text in order to increase the difficulty of attacking the cipher. The theory, implementation and the security of this scheme are described in this paper.
This paper describes a novel bit level stream cipher based symmetric key cryptographic technique. At first, sender and receiver agree upon a symmetric key. Then the symmetric key is formed using Greatest Common Divisor (G.C.D) of sum of even or odd bit positional weightth even or odd number and a symmetric key value is derived from the symmetric by the sender. The symmetric key value is XORed with the ASCII value of the plain text character to get the cipher text character. This is repeated for the entire plain text file. The symmetric key and the entire cipher text file is sent by the sender …
This paper deals with the merger of the two lightweight stream ciphers: A5by1 and Trivium. The idea is to make the key stream generation more secure and to remove the attacks of the individual algorithms. The bits generated by the Trivium cipher will act as the input of the A5by1 cipher. The registers used in the A5by1 cipher will be filled by the output bits of the Trivium cipher. The three registers will then be connected to generate an output which will be our required key stream.
Reversible data hiding in encrypted images (RDH-EI) has attracted increasing attention, since it can protect the privacy of original images while the embedded data can be exactly extracted. Recently, some RDH-EI schemes with multiple data hiders have been proposed using secret sharing technique. However, these schemes protect the contents of the original images with lightweight security level. In this paper, we propose a high-security RDH-EI scheme with multiple data hiders. First, we introduce a cipher-feedback secret sharing (CFSS) technique. It follows the cryptography standards by introduc…
We describe a novel way in which students can learn the cipher systems without much supervision. In this work we focus on learning symmetric ciphers by altering them using the agile development approach. Two agile approaches the eXtreme Programming (XP) and the closely related Test-Driven Development (TDD) are mentioned or discussed. To facilitate this development we experiment with an approach that is based on refactoring, with JUnit serves as the automatic testing framework. In this work we exemplify our learning approach by test-infecting the Vernam cipher, an aged but still widely used str…
The previous work showed that the Y00 protocol could stay secure with the eavesdropper's guessing probability on the secret keys being strictly less than one under an unlimitedly long known-plaintext attack with quantum memory. However, an assumption that at least a fast correlation attack is completely disabled by irregular mapping. The present study shows that the Y00 protocol can be information-theoretic secure under any quantum-computational crypto-analyses if the Y00 system is well designed. The Y00 protocol directly encrypts messages with short secret keys expanded into pseudo-random run…
This paper proposes to put forward an innovative algorithm for symmetric key block cipher named as "Triple Prime Symmetric Key Block Cipher with Variable Key-Spaces (TPSKBCVK)" that employs triple prime integers as private key-spaces of varying lengths to encrypt data files. Principles of modular arithmetic have been elegantly used in the proposed idea of the cipher. Depending on observations of the results of implementation of the proposed cipher on a set of real data files of several types, all results are registered and analyzed. The strength of the underlying design of the cipher and the l…
The BMR16 circuit garbling scheme introduces gadgets that allow for ciphertext-free modular addition, while the multiplication of private inputs modulo a prime p can be done with 2(p - 1) ciphertexts as described in Malkin, Pastro, and Shelat's An algebraic approach to garbling. By using a residue number system (RNS), we can construct a circuit to handle the squaring and multiplication of inputs modulo a large N via the methods described in Hollman and Gorissen's multi-layer residue number system. We expand on the existing techniques for arithmetic modulo p to develop methods to handle arithme…
Lightweight ciphers are the form of encryption that strictly limited to devices such as tags, RFID, wireless sensor networks applications. Low-resource devices has many limitations in power, energy and memory. In this work, the lightweight block ciphers is implemented on the Atmega128 microprocessor and the results of the energy perspectives and memory were assessed. The results of the evaluation show that the SPECK(64,96) cipher has been the best value of the perspective of energy and is appropriate for wireless sensor networks with the main requirement of energy. If the measure is memory usa…
This paper discusses mixing of chaotic systems as a dependable method for secure communication. Distribution of the entropy function for steady state as well as plaintext input sequences are analyzed. It is shown that the mixing of chaotic sequences results in a sequence that does not have any state dependence on the information encrypted by them. The generated output states of such a cipher approach the theoretical maximum for both complexity measures and cycle length. These features are then compared with some popular ciphers.
This paper presents a novel and robust chaos-based cryptosystem for secure transmitted images and four other versions. In the proposed block encryption/decryption algorithm, a 2D chaotic map is used to shuffle the image pixel positions. Then, substitution (confusion) and permutation (diffusion) operations on every block, with multiple rounds, are combined using two perturbed chaotic PWLCM maps. The perturbing orbit technique improves the statistical properties of encrypted images. The obtained error propagation in various standard cipher block modes demonstrates that the proposed cryptosystem …
The McEliece public-key encryption scheme has become an interesting alternative to cryptosystems based on number-theoretical problems. Differently from RSA and ElGa- mal, McEliece PKC is not known to be broken by a quantum computer. Moreover, even tough McEliece PKC has a relatively big key size, encryption and decryption operations are rather efficient. In spite of all the recent results in coding theory based cryptosystems, to the date, there are no constructions secure against chosen ciphertext attacks in the standard model - the de facto security notion for public-key cryptosystems. In thi…
A novel bit level block cipher based symmetric key cryptographic technique using G.C.D is proposed in this research paper. Entire plain text file is read one character at a time and according to the binary representation of ASCII value of the characters, entire plain text file is divided into n number of 16 bit blocks. Then an agreed-upon symmetric key file is formed by dividing each 16 bit block into two 8 bit sub blocks and by using Greatest Common Divisor (G.C.D) operation among them. The key size is 40 times the number of 16 bit blocks present in the plain text file as each block produces …
A process for the secure transmission of data is presented that has to a certain degree the advantages of the one-time pad (OTP) cipher, that is, simplicity, speed, and information-theoretically security, but overcomes its fundamental weakness, the necessity of securely exchanging a key that is as long as the message. For each transmission, a dedicated one-time pad is generated for encrypting and decrypting the plaintext message. This one-time pad is built from a randomly chosen set of basic keys taken from a public library. Because the basic keys can be chosen and used multiple times, the met…
The linear and grid based Wireless Sensor Networks (WSN) are formed by applications where objects being monitored are either placed in linear or grid based form. E.g. monitoring oil, water or gas pipelines; perimeter surveillance; monitoring traffic level of city streets, goods warehouse monitoring. The security of data is a critical issue for all such applications and as the devices used for the monitoring purpose have several resource constraints (bandwidth, storage capacity, battery life); it is significant to have a lightweight security solution. Therefore, we consider symmetric key based …
In this paper we propose a multi-map orbit hopping chaotic stream cipher that utilizes the idea of spread spectrum mechanism for secure digital communications and fundamental chaos characteristics of mixing, unpredictable, and extremely sensitive to initial conditions. The design, key and subkeys, and detail implementation of the system are addressed. A variable number of well studied chaotic maps form a map bank. And the key determines how the system hops between multiple orbits, and it also determines the number of maps, the number of orbits for each map, and the number of sample points for …
Post-Quantum Security of Block Cipher Constructions
QuICS, University of Maryland/NIST（马里兰大学/美国国家标准与技术研究院量子信息与计算科学中心）；Dept. of Computer Science, Virginia Tech（弗吉尼亚理工大学计算机系）；Dept. of Applied Mathematics and Computer Science, Technical University of Denmark（丹麦技术大学应用数学与计算机科学系）；Dept. of Computer Science, University of Maryland（马里兰大学计算机系）
This paper proposes a new block cipher termed as "Modular Arithmetic based Block Cipher with Varying Key-Spaces (MABCVK)" that uses private key-spaces of varying lengths to encrypt data files. There is a simple but intelligent use of theory of modular arithmetic in the scheme of the cipher. Based on observed implementation of the proposed cipher on a set of real data files of several types, all results are tabulated and analyzed.The schematic strength of the cipher and the freedom of using a long key-space expectedly can make it reasonably nonvulnerable against possible cryptanalytic attacks. …
Security in embedded systems has become a main requirement in modern electronic devices. The demand for low-cost and highly secure cryptographic algorithms is increasingly growing in fields such as mobile telecommunications, handheld devices, etc. In this paper, we analyze and evaluate the development of cheap and relatively fast hardware implementations of the KATAN family of block ciphers. KATAN is a family of six hardware oriented block ciphers. All KATAN ciphers share an 80-bit key and have 32, 48, or 64-bit blocks. We use VHDL under Altera Quartus in conjunction with ModelSim to implement…
The field of lightweight cryptography has been gaining popularity as traditional cryptographic techniques are challenging to implement in resource-limited environments. This research paper presents an approach to utilizing the ESP32 microcontroller as a hardware platform to implement a lightweight cryptographic algorithm. Our approach employs KATAN32, the smallest block cipher of the KATAN family, with an 80-bit key and 32-bit blocks. The algorithm requires less computational power as it employs an 80 unsigned 64-bit integer key for encrypting and decrypting data. During encryption, a data arr…
In this paper we design a stream cipher that uses the algebraic structure of the multiplicative group $\bbbz_p^*$ (where p is a big prime number used in ElGamal algorithm), by defining a quasigroup of order $p-1$ and by doing quasigroup string transformations. The cryptographical strength of the proposed stream cipher is based on the fact that breaking it would be at least as hard as solving systems of multivariate polynomial equations modulo big prime number $p$ which is NP-hard problem and there are no known fast randomized or deterministic algorithms for solving it. Unlikely the speed of kn…
Recent years have shown that more than ever governments and intelligence agencies try to control and bypass the cryptographic means used for the protection of data. Backdooring encryption algorithms is considered as the best way to enforce cryptographic control. Until now, only implementation backdoors (at the protocol/implementation/management level) are generally considered. In this paper we propose to address the most critical issue of backdoors: mathematical backdoors or by-design backdoors, which are put directly at the mathematical design of the encryption algorithm. While the algorithm …
In e-healthcare record systems (EHRS), attribute-based encryption (ABE) appears as a natural way to achieve fine-grained access control on health records. Some proposals exploit key-policy ABE (KP-ABE) to protect privacy in such a way that all users are associated with specific access policies and only the ciphertexts matching the users' access policies can be decrypted. An issue with KP-ABE is that it requires an a priori formulation of access policies during key generation, which is not always practicable in EHRS because the policies to access health records are sometimes determined after ke…
Evolutionary Approach to S-box Generation: Optimizing Nonlinear Substitutions in Symmetric Ciphers
eCampus University（伊坎普斯大学）；V. N. Karazin Kharkiv National University（哈尔科夫国立大学）；University of Macerata（马切拉塔大学）；Central Ukrainian National Technical University（乌克兰中部国立技术大学）
Large-scale quantum computing is a significant threat to classical public-key cryptography. In strong "quantum access" security models, numerous symmetric-key cryptosystems are also vulnerable. We consider classical encryption in a model which grants the adversary quantum oracle access to encryption and decryption, but where the latter is restricted to non-adaptive (i.e., pre-challenge) queries only. We define this model formally using appropriate notions of ciphertext indistinguishability and semantic security (which are equivalent by standard arguments) and call it QCCA1 in analogy to the cl…
Vigenere Cipher is one of the classic cryptographic algorithms and included into symmetric key cryptography algorithm, where to encryption and decryption process use the same key. Vigenere Cipher has the disadvantage that if key length is not equal to the length of the plaintext, then the key will be repeated until equal to the plaintext length, it course allows cryptanalysts to make the process of cryptanalysis. And weaknesses of the symmetric key cryptographic algorithm is the safety of key distribution factor, if the key is known by others, then the function of cryptography itself become us…
It has been established that quantum algorithms can solve several key cryptographic problems more efficiently than classical computers. As progress continues in the field of quantum computing it is important to understand the risks they pose to deployed cryptographic systems. Here we focus on one of these risks - quantum key-recovery attacks against ideal ciphers. Specifically, we seek to model the risk posed by an economically motivated quantum attacker who will choose to run a quantum key-recovery attack against an ideal cipher if the cost to recover the secret key is less than the value of …
Chosen-ciphertext security, which guarantees confidentiality of encrypted messages even in the presence of a decryption oracle, has become the defacto notion of security for public-key encryption under active attack. In this manuscript, for the first time, we propose a new approach for constructing post-quantum cryptosystems secure against adaptive chosen ciphertext attack (CCA2-secure) in the standard model using the knapsack problem. The computational version of the knapsack problem is NP-hard. Thus, this problem is expected to be difficult to solve using quantum computers. Our construction …
Braid group is a very important non-commutative group. It is also an important tool of quantum field theory, and has good topological properties. This paper focuses on the provable security research of cryptosystem over braid group, which consists of two aspects: One, we proved that the Ko's cryptosystem based on braid group is secure against chosen-plaintext-attack(CPA) which proposed in CRYPTO2000, while it dose not resist active attack. The other is to propose a new public key cryptosystem over braid group which is secure against adaptive chosen-ciphertext-attack(CCA2). Our proofs are based…
In this paper, we report the first quantum key-recovery attack on a symmetric block cipher design, using classical queries only, with a more than quadratic time speedup compared to the best classical attack. We study the 2XOR-Cascade construction of Gaži and Tessaro (EUROCRYPT~2012). It is a key length extension technique which provides an n-bit block cipher with 5n/2 bits of security out of an n-bit block cipher with 2n bits of key, with a security proof in the ideal model. We show that the offline-Simon algorithm of Bonnetain et al. (ASIACRYPT~2019) can be extended to, in particular, attack …
Public key encryption with equality test (PKEET) supports to check whether two ciphertexts encrypted under different public keys contain the same message or not. PKEET has many interesting applications such as keyword search on encrypted data, encrypted data partitioning for efficient encrypted data management, personal health record systems, spam filtering in encrypted email systems and so on. However, the PKEET scheme lacks an authorization mechanism for a user to control the comparison of its ciphertexts with others. In 2015, Ma et al. introduce the notion of PKEET with flexible authorizati…
In this paper, we introduce a symmetric-key Latin square image cipher (LSIC) for grayscale and color images. Our contributions to the image encryption community include 1) we develop new Latin square image encryption primitives including Latin Square Whitening, Latin Square S-box and Latin Square P-box ; 2) we provide a new way of integrating probabilistic encryption in image encryption by embedding random noise in the least significant image bit-plane; and 3) we construct LSIC with these Latin square image encryption primitives all on one keyed Latin square in a new loom-like substitution-per…
We initiate the provable related-key security treatment for models of practical Feistel ciphers. In detail, we consider Feistel networks with four whitening keys $w_i(k)$ ($i=0,1,2,3$) and round-functions of the form $f(γ_i(k)\oplus X)$, where $k$ is the main-key, $w_i$ and $γ_i$ are efficient transformations, and $f$ is a public ideal function or permutation that the adversary is allowed to query. We investigate conditions on the key-schedules that are sufficient for security against XOR-induced related-key attacks up to $2^{n/2}$ adversarial queries. When the key-schedules are non-linear, we…
