Linking Online Misuse-Resistant Authenticated Encryption and Blockwise Attack Models

This paper presents a lightweight, sponge-based authenticated encryption (AE) family called Beetle. When instantiated with the PHOTON permutation from CRYPTO 2011, Beetle achieves the smallest footprint—consuming only a few more than 600 LUTs on FPGA while maintaining 64-bit security. This figure is significantly smaller than all known lightweight AE candidates which consume more than 1,000 LUTs, including the latest COFB-AES from CHES 2017. In order to realize such small hardware implementation, we equip Beetle with an “extremely tight” bound of security. The trick is to use combined feedback to create a difference between the cipher text block and the rate part of the next feedback (in traditional sponge these two values are the same). Then we are able to show that Beetle is provably secure up to min{ c − log r , b /2, r } bits, where b is the permutation size and r and c are parameters called rate and capacity, respectively. The tight security bound allows us to select the smallest security parameters, which in turn result in the smallest footprint.

When users store their data on a cloud, they may concern on whether their data is stored correctly and can be fully retrieved. Proofs of Retrivability (PoR) is a cryptographic concept that allows users to remotely check the integrity of their data without downloading. This check is usually done by attaching data with message authenticators that contain data integrity information. The existing PoR schemes consider only the retrievability of unencrypted data and their message authenticators are usually deterministic. In this paper, we propose a PoR scheme that is built over homomorphic encryption schemes. Our PoR scheme can prove the retrievability of homomorphically encrypted data by generating probabilistic and homomorphic message authenticators. Moreover, the homomorphically encrypted data can be processed by the cloud directly and our PoR scheme can verify the integrity of such outsourced computations over ciphertexts. A prototype of our scheme is implemented to evaluate its performance.

Background and Objectives: Search protocols are among the main applications of RFID systems. Since a search protocol should be able to locate a certain tag among many tags, not only it should be secure against RFID threats but also it should be affordable. Methods: In this article, an RFID-based search protocol will be presented. We use an encryption technique that is referred to as authenticated encryption in order to boost the security level, which can provide confidentiality and integrity, simultaneously. Results: Furthermore, since the proposed protocol belongs to the lightweight protocols category, it is appropriate for applications that require many tags and costs must be low. In terms of the security, the analysis results give a satisfactory security level and it is robust against different RFID threats like replay, traceability and impersonation attacks. Using Ouafi-Phan model, BAN and AVISPA, we also checked the security correctness of the suggested protocol. Conclusion: In this paper, we presented a scalable lightweight RFID search protocol. We employed an encryption technique called Authenticated Encryption (A.E.) to improve the security level of the suggested protocol.======================================================================================================Copyrights©2018 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.======================================================================================================

Previously, two schemes were proposed to enhance the security of EIGamal encryption. The weakness of the original scheme is improved by adding a message authentication tag to ciphertext. The resultant schemes are non-malleable encryption under chosen ciphertext attack. We observed that the same security goal can be achieved with less computational cost The proposed scheme saves 33% of computing power on average In processing decryption, it can save at most 46% of computations if the technique of multiple simultaneous exponentiations is used.

The Secure Shell (SSH) protocol is one of the most popular cryptographic protocols on the Internet. Unfortunately, the current SSH authenticated encryption mechanism is insecure. In this paper we propose several fixes to the SSH protocol and, using techniques from modern cryptography, we prove that our modified versions of SSH meet strong new chosen-ciphertext privacy and integrity requirements. Furthermore, our proposed fixes will require relatively little modification to the SSH protocol or to SSH implementations. We believe that our new notions of privacy and integrity for encryption schemes with stateful decryption algorithms will be of independent interest.

Cube-attack-like cryptanalysis on round-reduced Keccak was proposed by Dinur et al. at EUROCRYPT 2015. It recovers the key through two phases: the preprocessing phase for precomputing a look-up table and online phase for querying the output and getting the cube sum with which the right key can be retrieved by looking up the precomputed table. It was shown that such attacks are efficient specifically for Keccak-based constructions with small nonce or message block size. In this paper, we provide a mixed integer linear programming (MILP) model for cubeattack- like cryptanalysis on keyed Keccak, which does not impose any unnecessary constraint on cube variables and finds almost optimal cubes by balancing the two phases of cube-attack-like cryptanalysis. Our model is applied to Ketje Jr, Ketje Sr, a Xoodoo-based authenticated encryption and Keccak-MAC-512, all of which have a relatively small nonce or message block size. As a result, time complexities of 5-round attacks on Ketje Jr and 7-round attacks on Ketje Sr can be improved significantly. Meanwhile, 6-round attacks, one more round than the previous best attack, are possible if the key size of Ketje V1 (V2) is reduced to 72 (80) bits. For Xoodoo-based AE in Ketje style, the attack reaches 6 rounds. Additionally, a 7-round attack of Keccak-MAC-512 is achieved. To verify the correctness of our attacks, a 5-round attack on Ketje V1 is implemented and tested practically. It is noted that this work does not threaten the security of any Keccak-based construction.

Cryptographic Primitives that Resist Backdooring and Subversion

Ad hoc wireless networks have emerged as a solution to providing ubiquitous, on-demand connectivity without the need for significant infrastructure deployment. In this thesis we address the privacy problems in two types of emerging wireless ad hoc networks, namely sensor and vehicular networks. Although the content of sensor messages describing “events of interest” may be encrypted to provide confidentiality, the context surrounding these events may also be sensitive and therefore should be protected from eavesdroppers. The source-location privacy problem occurs in sensor networks when adversaries use RF localization techniques to perform hop-by-hop traceback of messages to the source sensor’s location. Our work provides a formal model for this problem and examines the privacy characteristics of different sensor routing protocols. In order to provide efficient and private sensor communications, we devise new techniques to enhance source-location privacy that augment these routing protocols. Similarly, an adversary armed with knowledge of the network deployment, routing algorithms, and the data sink location can infer the temporal patterns and track the spatio-temporal evolution of a sensed event, by monitoring the packet arrivals at the sink. We introduce the temporal privacy problem for delay-tolerant sensor networks, provide an information theoretic formulation and propose adaptive buffering to obfuscate temporal information from the adversary. Sensor networks are also characterized by distinctive traffic patterns, wherein traffic mostly exists when events of interests occur. Due to the direct correlation between the type of event and size of data generated by it, an adversary observing a traffic burst can infer information about the type of event simply from the observed message size. We formulate this traffic privacy problem in terms of information entropy, present a quantifiable means to measure traffic privacy and propose solutions to enhance it. Vehicular ad hoc networks represent a promising new communication paradigm that can facilitate many new forms of automotive applications. We present a robust and efficient security and privacy framework, for such networks, that uses identity-based cryptography. We show that our framework provides authentication, confidentiality, non-repudiation and message-integrity. Further, it supports scalable, user-customizable privacy through short-lived, unforgeable, pseudonyms.

The security of public-key cryptography relies on well-studied hard problems, problems for which we do not have efficient algorithms. Factorization and discrete logarithm are the two most known and used hard problems. Unfortunately, they can be easily solved on a quantum computer by Shor's algorithm. Also, the research area of cryptography demands for crypto-diversity which says that we should offer a range of hard problems for public-key cryptography. If one hard problem proves to be easy, we should be able to provide alternative solutions. Some of the candidates for post-quantum hard problems, i.e. problems which are believed to be hard even on a quantum computer, are the Learning Parity with Noise (LPN), the Learning with Errors (LWE) and the Shortest Vector Problem (SVP). A thorough study of these problems is needed in order to assess their hardness. In this thesis we focus on the algorithmic study of LPN. LPN is a hard problem that is attractive, as it is believed to be post-quantum resistant and suitable for lightweight devices. In practice, it has been employed in several encryption schemes and authentication protocols. At the beginning of this thesis, we take a look at the existing LPN solving algorithms. We provide the theoretical analysis that assesses their complexity. We compare the theoretical results with practice by implementing these algorithms. We study the efficiency of all LPN solving algorithms which allow us to provide secure parameters that can be used in practice. We push further the state of the art by improving the existing algorithms with the help of two new frameworks. In the first framework, we split an LPN solving algorithm into atomic steps. We study their complexity, how they impact the other steps and we construct an algorithm that optimises their use. Given an LPN instance that is characterized by the noise level and the secret size, our algorithm provides the steps to follow in order to solve the instance with optimal complexity. In this way, we can assess if an LPN instance provides the security we require and we show what are the secure instances for the applications that rely on LPN. The second framework handles problems that can be decomposed into steps of equal complexity. Here, we assume that we have an adversary that has access to a finite or infinite number of instances of the same problem. The goal of the adversary is to succeed in just one instance as soon as possible. Our framework provides the strategy that achieves this. We characterize an LPN solving algorithm in this framework and show that we can improve its complexity in the scenario where the adversary is restricted. We show that other problems, like password guessing, can be modeled in the same framework.

Confidentiality and authenticity are two fundamental security requirement of Public key Cryptography. These are achieved by encryption scheme and digital signatures respectively. Wireless sensor networks are commonly used for critical security tasks such as intrusion or tamper detection, and therefore must be protected. The article proposes a provable secure signcryption scheme in Random oracle model for wireless security. It enables nodes to authenticate each other by keeping the information confidential. Also achieve data integrity in the communication. Security of the scheme is based on q-Diffie Hellman Problem. We modify the scheme proposed by Libert et al. and proposed a provably secure scheme with respect to security under assumptions of Strong Diffie-Hellman (SDH) and Diffie-Hellman Inversion (DHI) in the random oracles.

Nowadays, the possibility to communicate securely is crucial for users in the private as well as in the business context. However, to do so they have to face problems regarding mismatching mental models of encryption and bad usability not only concerning the encryption, but also the authentication process. To solve this problem, we evaluate users’ perception on encryption and authentication schemes in order to (1) derive a process, which is more in line with their expectations and (2) use authentication schemes which provide security but also achieve a high acceptance rate from users. We plan to integrate our findings into a prototypical software in order to evaluate users’ acceptance for our technical approach.

Wireless sensor networks are new technologies that are used for various purposes such as environmental monitoring, home security, industrial process monitoring, healthcare programs and etc. Wireless sensor networks are vulnerable to various attacks. Cryptography is one of the methods for secure transmission of information between sensors in wireless sensor networks. A complete and secure encryption system must establish three principles of confidentiality, authentication and integrity. An encryption algorithm alone cannot provide all the principles of encryption. A hybrid encryption algorithm, consisting of symmetric and asymmetric encryption algorithms, provides complete security for a cryptographic system. The papers presented in this area over the last few years, and a new secure algorithm present with regard to the limitations of wireless sensor networks, which establishes three principles of cryptography. The details of the algorithm and basic concepts are presented in such a way that the algorithm can be operational and showed a very high efficiency in compare to the current proposed methods.

Cloud storage is a useful service of cloud computing which allows users to upload their data in the cloud and share it with others. Although, this new service is affordable and practical, but it is associated with several privacy and security challenges. Nowadays, Attribute Based Encryption (ABE) is widely used to provide secure data sharing in the distributed environment such as cloud computing. Unfortunately, most of the existing ABE schemes are not suitable for resource- constraint cloud systems, because they use expensive bilinear pairing operation and thus they cause a very high encryption and decryption computation overhead. In this paper, we propose an efficient no-pairing and revocable ABE data sharing scheme based on Elliptic Curve Cryptography (ECC) for cloud storage systems. Moreover, a comprehensive security and performance analysis shows that our scheme is both secure and efficient.

In this paper, novel selective encryption image schemes based on JPEG2000 are proposed. The first one encrypts only the code-blocks corresponding to some sensitive precincts. In order to improve the security level we introduce the permutation of codeblocks contributing in the selected precincts. The idea of combining permutation and selective encryption is used in order to minimize the amount of processed data encryption while ensuring the best possible degradation through the permutation. Many of proposals format compliant encryption schemes for JPEG2000 that have been made encrypt packet body data, but leave header packet in plaintext. The second approach, combines code-blocks data encryption to a cyclic permutation of all packets headers in the bitstream. Actually, in the JPEG2000 codestream, packet header information is specific to the visual content, and it is can be used as a fingerprint of the codestream. Symmetric encryption AES with CFB mode is used to encrypt in the two schemes. The proposed schemes don't introduce superfluous JPEG2000 markers in the protected codestream, i.e, its format is compliant to JPEG2000 codestream one. It keeps file format and compression ratio unchanged and doesn't degrade the original error robustness. The proposed scheme works with any standard ciphers and introduces negligible computational cost.

Searchable Symmetric Encryption (SSE) allows a client to search over the encrypted database, which protects privacy while maintaining the searchability of the data. Later, Dynamic SSE (DSSE) has been introduced, which supports the update of the encrypted database. However, most existing DSSE schemes either achieve less security level or support single keyword queries only. To tackle this problem, this thesis gives enhanced security definition and introduces several different DSSE schemes with enhanced security and supporting richer queries.