Ciphertext Block Research Articles

Truncated Differential-Neural Key Recovery Attacks on Round-Reduced HIGHT

Recently, differential-neural cryptanalysis, which integrates deep learning with differential cryptanalysis, has emerged as a powerful and practical cryptanalysis method. It has been particularly applied to lightweight block ciphers, which are characterized by simple structures and operations, and relatively small block and key sizes. In resource-constrained environments, such as Internet of Things (IoT), it is essential to verify the resistance of existing lightweight block ciphers against differential-neural cryptanalysis to ensure security. In differential-neural cryptanalysis, a deep learning model, known as a neural distinguisher, is trained to differentiate a target cipher from others, facilitating key recovery through statistical analysis. For successful differential-neural cryptanalysis, it is crucial to develop a highly accurate neural distinguisher and to optimize the key recovery attack algorithm. In this paper, we introduce a novel neural distinguisher and key recovery attack against the 15-round reduced HIGHT cipher. Our proposed neural distinguisher is capable of distinguishing HIGHT ciphertext by analyzing only a portion of the ciphertext, which we refer to as a truncated neural distinguisher. Notably, our experiments demonstrate that the truncated neural distinguisher achieves performance comparable to existing distinguishers trained on entire ciphertext blocks, while enabling a more efficient key recovery attack through a divide-and-conquer strategy. Furthermore, we observe a significant improvement in key recovery efficiency compared to traditional cryptanalysis methods.

Differential Fault Attacks on Privacy Protocols Friendly Symmetric-Key Primitives: RAIN and HERA

As the practical applications of fully homomorphic encryption (FHE), secure multi-party computation (MPC) and zero-knowledge (ZK) proof continue to increase, so does the need to design and analyze new symmetric-key primitives that can adapt to these privacy-preserving protocols. These designs typically have low multiplicative complexity and depth with the parameter domain adapted to their application protocols, aiming to minimize the cost associated with the number of nonlinear operations or the multiplicative depth of their representation as circuits. In this paper, we propose two differential fault attacks against a one-way function RAIN used for Rainier (CCS 2022), a signature scheme based on the MPC-in-the-head approach and an FHE-friendly cipher HERA used for the RtF framework (Eurocrypt 2022), respectively. We show that our attacks can recover the keys for both ciphers by only injecting a fault into the internal state and requiring only one normal and one faulty ciphertext blocks. Thus, we can use only the practical complexity of 226.6/228.8/230.4 bit operations to break the full-round RAIN with 128/192/256-bit keys. For full-round HERA with 80/128-bit key, our attack is practical with complexity the complexity of 220 encryptions with about 216 memory.

Data Security and Privacy Mechanism Based on Key Exposure Method over Cloud

Recent news reveal a powerful attacker which breaks data confidentiality by acquiring cryptographic keys, by means of coercion or backdoors in cryptographic software. Once the encryption key is exposed, the only viable measure to preserve data confidentiality is to limit the attacker’s access to the ciphertext. This may be achieved, for example, by spreading ciphertext blocks across servers in multiple administrative domains—thus assuming that the adversary cannot compromise all of them. Nevertheless, if data is encrypted with existing schemes, an adversary equipped with the encryption key, can still compromise a single server and decrypt the ciphertext blocks stored therein. In this paper, we study data confidentiality against an adversary which knows the encryption key and has access to a large fraction of the ciphertext blocks. To this end, we propose Bastion, a novel and efficient scheme that guarantees data confidentiality even if the encryption key is leaked and the adversary has access to almost all ciphertext blocks. We analyze the security of Bastion, and we evaluate its performance by means of a prototype implementation. We also discuss practical insights with respect to the integration of Bastion in commercial dispersed storage systems.

Description, Implementation and Performance/Security Analysis of ASCON128

The aim of the report is to introduce detailed description of the functioning of and to provide an efficient implementation (using bit-sliced implementation of S-Box) in C of encryption, decryption and authentication of the lightweight authenticated encryption algorithm ASCON 128 (sponge based SPN network based on Keccak like operations) as per the v 1.2 submitted to NIST. This is achieved using a sponge construction by setting up initialization state and performing 12 rounds of permutations, XORing consecutively the plaintext blocks (encryption) or ciphertext blocks (decryption) with first 64 bits of the state (after 6 rounds of sponge permutations) and after all consecutive operations on ciphertext/plaintext blocks, XORing the last 128 bits of the resultant state with the secret Key (after 12 rounds of final permutation operations) to produce/re-create the tag. Discussions on Key Features, Performance Analysis (comparison of ASCON 128 v/s AES 128 in GCM mode on our own PC), Performance Comparisons with other NIST lightweight cryptography contest finalists on ARM Cortex M3, and discussions on the Security Analysis (side channel attacks: fault injection and power analysis) of ASCON are included in this report.

Cryptanalysis of iterative encryption and image sharing scheme based on the VQ attack

Reversible data hiding in encrypted images (RDHEI) is widely employed to protect privacy in images stored on cloud storage. Recently, Yu et al. [22] proposed an effective image encryption scheme called iterative encryption and image sharing (IEIS), which is highly compatible with RDHEI. In this study, we analyze the characteristics of IEIS and present a cryptanalysis scheme based on vector quantization (VQ) attack. To capture the pixel-changing pattern of an image block, the concept of pixel difference matrix (PDM) is introduced. VQ attack is subsequently utilized to estimate the ciphertext block. Furthermore, we employ a well-trained convolutional neural network (CNN) based discriminator to identify the proper block permutation sequence within the secret key space. Experimental results demonstrate the efficacy of our proposed cryptanalysis scheme. Based on our study, we conclude that the IEIS scheme raises security concerns.

Cryptanalysis of Reversible Data Hiding in Encrypted Images Based on the VQ Attack

Reversible data hiding in encrypted images (RDHEI) is commonly used for privacy protection in images stored on cloud storage. Currently, block permutation and co-modulation (BPCM) encryption is commonly utilized in most existing RDHEI schemes to generate encrypted images. In this paper, we analyze the vulnerabilities of RDHEI based on BPCM encryption and then propose a cryptanalysis method based on the vector quantization (VQ) attack. Unlike the existing cryptanalysis method, our method does not require the help of a plaintext image instead of adopting the symmetric property between the original cover image and the encrypted cover image. To obtain the pixel-changing pattern of a block before and after co-modulation, the concept of a pixel difference block (PDB) is first defined. Then, the VQ technique is used to estimate the content of the ciphertext block. Finally, we propose a sequence recovery method to help obtain the final recovered image based on the premise that the generator is compromised. The experimental results demonstrate that when the block size is 4 × 4, our proposed cryptanalysis method can decrypt the contents of the ciphertext image well. The average similarity can exceed 75% when comparing the edge information of the estimated image and the original image. It is concluded from our study that the BPCM encryption algorithm is not robust enough.

Securing Cloud Data Under Key Exposure

Abstract: Recent news reveal a powerful attacker which breaks data confidentiality by acquiring cryptographic keys, by means of coercion or backdoors in cryptographic software. Once the encryption key is exposed, the only viable measure to preserve data confidentiality is to limit the attacker’s access to the ciphertext. This may be achieved, for example, by spreading ciphertext blocks across servers in multiple administrative domains—thus assuming that the adversary cannot compromise all of them. Nevertheless, if data is encrypted with existing schemes, an adversary equipped with the encryption key, can still compromise a single server and decrypt the ciphertext blocks stored therein. In this paper, we study data confidentiality against an adversary which knows the encryption key and has access to a large fraction of the ciphertext blocks[3]. To this end, we propose Bastion, a novel and efficient scheme that guarantees data confidentiality even if the encryption key is leaked and the adversary has access to almost all ciphertext blocks. We analyze the security of Bastion, and we evaluate its performance by means of a prototype implementation. We also discuss practical insights with respect to the integration of Bastion in commercial dispersed storage systems.

Comparison of the Randomness Analysis of the Modified Rectangle Block Cipher and Original algorithm

In recent years, different encryption lightweight algorithms have been suggested to protect the security of data transferred across the IoT network. The symmetric key ciphers play a significant role in the security of devices, in particular block ciphers. the RECTANGLE algorithm amongst the current lightweight algorithms. Rectangle algorithm does have good encryption efficacy but the characteristics of confusion and diffusion that a cipher needed are lacking from this algorithm. Therefore, by improving the algorithm confusion and diffusion properties, we expanded Rectangle utilizing a 3D cipher and modified the key scheduling algorithm. To assess if these two algorithms are random or not, randomness analysis was done by using the NIST Statistical Test Suite. To create 100 samples for each algorithm, nine distinct data categories were used. These algorithms created ciphertext blocks, which were then concatenated to form a binary sequence. NIST tests carried out under 1% significance level. According to the results of the comparison study, the proposed algorithm's randomness analysis results are gave 27.48% better results than the original algorithm.

Security Framework for Cloud Information under Transparency of a Key

Abstract: The ongoing headlines or broadcast shows the strong goon, that damages the instruction or details secrecy in obtaining cryptographic keys, through pressure in secure communication programming technique When the instruction key or details is open, one major suitable option is to safeguard the privacy of the details. All things considered, assuming that the data is covered with past facilities, a goon spotted with the encoded key, will think twice about disclosing the ciphertext blocks. The major advantage of implementing key transparency in this paper is to information secrecy over a foe which identifies the encryption key and has an aspiration to get over an enormous part of the ciphertext blocks. Keywords: Cloud Storage, Security, Auditing Mechanism, Key Transparency, Data Confidentiality, MySQL.

A NOVEL APPROACH FOR DATA CONFIDENTIALITY UNDER KEY EXPOSURE IN CLOUDS

Recent surveys reveals a powerful attacker which breaks data confidentiality by acquiring cryptographic keys, by means of coercion or backdoors in cryptographic software. Once the encryption key is exposed, the only viable measure to preserve data confidentiality is to limit the attacker’s access to the ciphertext. Nevertheless, if data is encrypted with existing schemes, an adversary equipped with the encryption key, can still compromise a single server and decrypt the ciphertext blocks stored therein. In this paper, we study data confidentiality against an adversary which knows the encryption key and has access to a large fraction of the ciphertext blocks. To this end, we propose Bastion, a novel and efficient scheme that guarantees data confidentiality even if the encryption key is leaked and the adversary has access to almost all ciphertext blocks[8]. Index terms – Data Confidentiality, Key exposure, dispersed storage.

Data Encryption Using Face Antimagic Labeling and Hill Cipher

An approach to encrypt and decrypt messages is obtained by relating the concepts of graph labeling and cryptography. Among the various types of labelings given in [3], our interest is on face antimagic labeling introduced by Mirka Miller in 2003 [1]. Baca [2] defines a connected plane graph <img src=image/13426646_01.gif> with edge set <img src=image/13426646_02.gif> and face set <img src=image/13426646_03.gif> as <img src=image/13426646_04.gif> face antimagic if there exist positive integers <img src=image/13426646_05.gif> and <img src=image/13426646_06.gif> and a bijection <img src=image/13426646_07.gif> such that the induced mapping <img src=image/13426646_08.gif>, where for a face <img src=image/13426646_09.gif>, <img src=image/13426646_10.gif> is the sum of all <img src=image/13426646_11.gif> for all edges <img src=image/13426646_12.gif> surrounding <img src=image/13426646_09.gif> is also a bijection. In cryptography there are many cryptosystems such as affine cipher, Hill cipher, RSA, knapsack and so on. Amongst these, Hill cipher is chosen for our encryption and decryption. In Hill cipher [8], plaintext letters are grouped into two-letter blocks, with a dummy letter X inserted at the end if needed to make all blocks of the same length, and then replace each letter with its respective ordinal number. Each plaintext block <img src=image/13426646_13.gif> is then replaced by a numeric ciphertext block <img src=image/13426646_14.gif>, where <img src=image/13426646_15.gif> and <img src=image/13426646_16.gif> are different linear combinations of <img src=image/13426646_17.gif> and <img src=image/13426646_18.gif> modulo 26: <img src=image/13426646_19.gif> (mod 26) and <img src=image/13426646_20.gif> (mod 26) with condition as <img src=image/13426646_21.gif> is one. Each number is translated into a cipher text letter which results in cipher text. In this paper, face antimagic labeling on double duplication of graphs along with Hill cipher is used to encrypt and decrypt the message.

Text Encoding Using Cipher Block Chaining Algorithm

. Data confidentiality and security are critical in data communication, both for the purpose of shared security, and for individual privacy. Computer users who want their data unknown to unauthorized parties are always trying to work out how to secure the information that will be communicated or that will be stored. Protection against data confidentiality is increasing, one way is by applying cryptographic science. Cipher Block Chaining (CBC), this mode is a feedback mechanism on a block, and in this case the result of the previous block encryption is feedback into the current block encryption. The trick is to block the current plaintext in XOR first with the ciphertext block of the previous encryption result, then the result of this XOR-ing goes into the encryption function. With CBC mode, each ciphertext block is calculated not only on its plaintext block but also on the entire previous plaintext block. The author tries to co-create a text encoding to secure the data with the Cipher Block Chaining (CBC) cryptographic method.

The Oribatida v1.3 Family of Lightweight Authenticated Encryption Schemes

Abstract Permutation-based modes have been established for lightweight authenticated encryption, as can be seen from the high interest in the ongoing NIST lightweight competition. However, their security is upper bounded by O(σ 2/2 c ) bits, where σ are the number of calls and c is the hidden capacity of the state. The development of more schemes that provide higher security bounds led to the CHES’18 proposal Beetle that raised the bound to O(rσ/2 c ), where r is the public rate of the state. While authenticated encryption can be performed in an on-line manner, authenticated decryption assumes that the resulting plaintext is buffered and never released if the corresponding tag is incorrect. Since lightweight devices may lack the resources for buffering, additional robustness guarantees, such as integrity under release of unverified plaintexts (Int-RUP), are desirable. In this stronger setting, the security of the established schemes, including Beetle, is limited by O(qpqd /2 c ), where qd is the maximal number of decryption queries, and qp that of off-line primitive queries, which motivates novel approaches. This work proposes Oribatida, a permutation-based AE scheme that derives s-bit masks from previous permutation outputs to mask ciphertext blocks. Oribatida can provide a security bound of O(rσ 2/ c+s ), which allows smaller permutations for the same level of security. It provides a security level dominated by O ( σ d 2 / 2 c ) O(\sigma_d^2{/2^c}) under Int-RUP adversaries, which eliminates the dependency on primitive queries. We prove its security under nonce-respecting and Int-RUP adversaries. We show that our Int-RUP bound is tight and show general attacks on previous constructions.

A novel image encryption scheme based on conservative hyperchaotic system and closed-loop diffusion between blocks

Dissipative chaotic systems have been widely used in digital image encryption schemes in the past 20 years. However, compared to conservative chaotic systems, the dissipative chaotic systems have attractors thus attacker can reconstruct the chaotic systems by reconstructing the attractors. Therefore, the conservative chaotic systems are more suitable in chaos-based encryption system because they have no attractors thus can avoid the reconstructing attacks. Based on this, an image encryption scheme based on conservative hyper-chaotic system and closed-loop diffusion between blocks is proposed in this paper. On the one hand, the conservative hyperchaotic system has strong pseudo-randomness and anti-reconstruction attack property. On the other hand, different from the existing closed-loop diffusion schemes which change pixel values one by one until the last pixel value is changed, the proposed closed-loop diffusion method cannot only generate the first ciphertext and other ciphertext blocks but also update the first ciphertext block using the other generated ciphertext block information. In addition, the key streams are related to plaintext and ciphertext. Consequently, the key, plaintext and ciphertext form an organic whole to ensure the sensitivity of the encryption system. Moreover, simulation results and analysis show that the encryption scheme has strong security and excellent performance.

Securing Cloud Data Under Key Exposure

Recent news reveal a powerful attacker which breaks data confidentiality by acquiring cryptographic keys, by means of coercion or backdoors in cryptographic software. Once the encryption key is exposed, the only viable measure to preserve data confidentiality is to limit the attacker's access to the ciphertext. This may be achieved, for example, by spreading ciphertext blocks across servers in multiple administrative domains—thus assuming that the adversary cannot compromise all of them. Nevertheless, if data is encrypted with existing schemes, an adversary equipped with the encryption key, can still compromise a single server and decrypt the ciphertext blocks stored therein. In this paper, we study data confidentiality against an adversary which knows the encryption key and has access to a large fraction of the ciphertext blocks. To this end, we propose $\mathrm{Bastion}$ Bastion , a novel and efficient scheme that guarantees data confidentiality even if the encryption key is leaked and the adversary has access to almost all ciphertext blocks. We analyze the security of $\mathrm{Bastion}$ Bastion , and we evaluate its performance by means of a prototype implementation. We also discuss practical insights with respect to the integration of $\mathrm{Bastion}$ Bastion in commercial dispersed storage systems. Our evaluation results suggest that $\mathrm{Bastion}$ Bastion is well-suited for integration in existing systems since it incurs less than 5 percent overhead compared to existing semantically secure encryption modes.

Применение атаки различения на легковесные блочные шифры, основанные на ARX-операциях

Рассмотрено применение атаки различения на ряд легковесных блочных шифров, основанных на ARX-операциях (сложение по модулю, циклический сдвиг и исключающее ИЛИ). Представлены экспериментальные результаты и теоретические оценки устойчивости легковесных шифров Speck, Simon, Simeck, HIGHT, LEA к атаке различения. Вывод, что семейство шифров Simeck не выдерживает эту атаку, сделан на основе прогнозов, полученных путем экстраполяции экспериментальных данных. The distinguishing attack on modern lightweight ARX-based block ciphers was applied. Distinguishing attack is any form of cryptanalysis on data encrypted by a cipher that allows an attacker distinguishing the encrypted data from random data. Purpose. Modern symmetric-key ciphers must be designed to be immune to such an attack. The purpose of the work was to estimate the resistance of lightweight ciphers Speck, Simon, Simeck, HIGHT, and LEA to a distinguishing attack. Methodology. We note that these ciphers are iterated block ciphers. It is means that they transform blocks of plain text into blocks of cipher text by using the cyclically repeated invertible function known as the round function where each iteration is to be referred as a round. We have experimentally found a maximum number of rounds where encrypted data looked like random bit-sequence by using statistical test “Book Stack”. Then we extrapolated the theoretical length required for a successful distinguishing attack on cipher with full-number rounds by a polynomial of a low degree. Note that cryptography attack is considered as successful if the length of the encrypted sequence is less than the length 2K (K — key size). Originality/value. Our experiments and estimations show, that Simeck with 48bit block size and 96-bit key size is not immune to distinguishing attack. We recommended increasing the number of rounds by 15–20% in order to improve the reliability of the Simeck 48/96.

An error-tolerant approach for efficient AES key retrieval in the presence of cacheprefetching – experiments, results, analysis

The challenge in cache-based attacks on cryptographic algorithms is not merely to capture the cache footprints during their execution but to process the obtained information to deduce the secret key. Our principal contribution is to develop a theoretical framework based upon which our AES key retrieval algorithms are not only more efficient in terms of execution time but also require up to 75% fewer blocks of ciphertext compared with previous work. Aggressive hardware prefetching greatly complicates access-driven attacks since they are unable to distinguish between a cache line fetched on demand versus one prefetched and not subsequently used during a run of a victim executing AES. We implement a multi-threaded spy code that reports accesses to the AES tables at the granularity level of a cache block. Since prefetching greatly increases side-channel noise, we develop sophisticated heuristics to “clean up” the input received from the spy threads. Our key retrieval algorithms process the sanitized input to recover the AES key using only about 25 blocks of ciphertext in the presence of prefetching and, stunningly, a mere 2–3 blocks with prefetching disabled. We also derive analytical models that capture the effect of varying false positive and false negative rates on the number of blocks of ciphertext required for key retrieval.

A Strategy of Encryption and Decryption based in a Low Memory Environment

This paper proposes an information encryption and decryption Strategy that can run smoothly in a low memory environment. It divides the information into blocks, which consumes less memory in encryption. And then it adds the identifiers into each block of cipher text. When cipher text is decrypted, it reads identifiers, and divides the cipher text into groups and decrypt it based on the group identifier to obtain the plaintext. In addition, it analyses the root causes of garbled plaintext after decryption, proposes a strategy of increasing cipher text disorder, and provide a method to make a difference between all identifiers and cipher text content. The test results show that the proposed strategy can implement more secure encryption in low memory system than normal strategy, and reduce the memory requirement for encryption and decryption, and increase the complexity of encrypted cipher text. Practices has proved that this strategy can be used in the field of mobile phone encryption and decryption [2], and has certain use value

Deterministic Authenticated Encryption Scheme for Memory Constrained Devices

A technique of authenticated encryption for memory constrained devices called sp-AELM was proposed by Agrawal et al. at ACISP 2015. The sp-ALEM construction utilizes a sponge-based primitive to support online encryption and decryption functionalities. Online encryption in the construction is achieved in the standard manner by processing plaintext blocks as they arrive to produce ciphertext blocks. However, decryption is achieved by storing only one intermediate state and releasing it to the user upon correct verification. This intermediate state allows a legitimate user to generate the plaintext herself. However, the scheme is nonce-respecting, i.e., the scheme is insecure if the nonce is repeated. Implementation of a nonce is non-trivial in practice, and reuse of a nonce in an AE scheme is often devastating. In this paper, we propose a new AE scheme called dAELM, which stands for deterministic authenticated encryption (DAE) scheme for low memory devices. DAE is used in domains such as the key wrap, where the available message entropy omits the overhead of a nonce. For limiting memory usage, our idea is to use a session key to encrypt a message and share the session key with the user depending upon the verification of a tag. We provide the security proof of the proposed construction in the ideal cipher model.

Methods and Algorithms for Pseudo-probabilistic Encryption with Shared Key

As a method for providing security of the messages sent via a public channel in the case of potential coercive attacks there had been proposed algorithms and protocols of deniable encryption. The lasts are divided on the following types: 1) schemes with public key, 2) schemes with shares secret key, and 3) no-key schemes. There are introduced pseudo-probabilistic symmetric ciphers that represent a particular variant of implementing deniable encryption algorithms. It is discussed application of the pseudo-probabilistic encryption for constructing special mechanisms of the information protection including steganographic channels hidden in ciphertexts. There are considered methods for designing stream and block pseudo-probabilistic encryption algorithms that implement simultaneous ciphering fake and secret messages so that the generated ciphertext is computationally indistinguishable from the ciphertext obtained as output of the probabilistic encryption of the fake message. The requirement of the ciphertext indistinguishability from the probabilistic encryption has been used as one of the design criteria. To implement this criterion in the construction scheme of the pseudo-probabilistic ciphers it is included step of bijective mapping pairs of intermediate ciphertext blocks of the fake and secret messages into a single expanded block of the output ciphertext. Implementations of the pseudo-probabilistic block ciphers in which algorithms for recovering the fake and secret messages coincide completely are also considered. There are proposed general approaches to constructing no-key encryption protocols and randomized pseudo-probabilistic block ciphers. Concrete implementations of the cryptoschemes of such types are presented.