Abstract: Searchable (symmetric) encryption allows encryption while still enabling search for keywords. Its immediate application is cloud storage where a client outsources its files while the (cloud) service provider should search and selectively retrieve those. Searchable encryption is an active area of research and a number of schemes with different efficiency and security characteristics have been proposed in the literature. Any scheme for practical adoption should be efficient -- i.e. have sub-linear search time --, dynamic -- i.e. allow updates -- and semantically secure to the most possible extent. Unfortunately, efficient, dynamic searchable encryption schemes suffer from various drawbacks. Either they deteriorate from semantic security to the security of deterministic encryption under updates, they require to store information on the client and for deleted files and keywords or they have very large index sizes. All of this is a problem, since we can expect the majority of data to be later added or changed. Since these schemes are also less efficient than deterministic encryption, they are currently an unfavorable choice for encryption in the cloud. In this paper we present the first searchable encryption scheme whose updates leak no more information than the access pattern, that still has asymptotically optimal search time, linear, very small and asymptotically optimal index size and can be implemented without storage on the client (except the key). Our construction is based on the novel idea of learning the index for efficient access from the access pattern itself. Furthermore, we implement our system and show that it is highly efficient for cloud storage.

Abstract: Motivated by revelations concerning population-wide surveillance of encrypted communications, we formalize and investigate the resistance of symmetric encryption schemes to mass surveillance. The focus is on algorithm-substitution attacks (ASAs), where a subverted encryption algorithm replaces the real one. We assume that the goal of “big brother” is undetectable subversion, meaning that ciphertexts produced by the subverted encryption algorithm should reveal plaintexts to big brother yet be indistinguishable to users from those produced by the real encryption scheme. We formalize security notions to capture this goal and then offer both attacks and defenses. In the first category we show that successful (from the point of view of big brother) ASAs may be mounted on a large class of common symmetric encryption schemes. In the second category we show how to design symmetric encryption schemes that avoid such attacks and meet our notion of security. The lesson that emerges is the danger of choice: randomized, stateless schemes are subject to attack while deterministic, stateful ones are not.

Abstract: Order-preserving encryption enables performing many classes of queries -- including range queries -- on encrypted databases. Popa et al. recently presented an ideal-secure order-preserving encryption (or encoding) scheme, but their cost of insertions (encryption) is very high. In this paper we present an also ideal-secure, but significantly more efficient order-preserving encryption scheme. Our scheme is inspired by Reed's referenced work on the average height of random binary search trees. We show that our scheme improves the average communication complexity from O(n log n) to O(n) under uniform distribution. Our scheme also integrates efficiently with adjustable encryption as used in CryptDB. In our experiments for database inserts we achieve a performance increase of up to 81% in LANs and 95% in WANs.

Abstract: We propose a mediated certificateless encryption scheme without pairing operations for securely sharing sensitive information in public clouds. Mediated certificateless public key encryption (mCL-PKE) solves the key escrow problem in identity based encryption and certificate revocation problem in public key cryptography. However, existing mCL-PKE schemes are either inefficient because of the use of expensive pairing operations or vulnerable against partial decryption attacks. In order to address the performance and security issues, in this paper, we first propose a mCL-PKE scheme without using pairing operations. We apply our mCL-PKE scheme to construct a practical solution to the problem of sharing sensitive information in public clouds. The cloud is employed as a secure storage as well as a key generation center. In our system, the data owner encrypts the sensitive data using the cloud generated users' public keys based on its access control policies and uploads the encrypted data to the cloud. Upon successful authorization, the cloud partially decrypts the encrypted data for the users. The users subsequently fully decrypt the partially decrypted data using their private keys. The confidentiality of the content and the keys is preserved with respect to the cloud, because the cloud cannot fully decrypt the information. We also propose an extension to the above approach to improve the efficiency of encryption at the data owner. We implement our mCL-PKE scheme and the overall cloud based system, and evaluate its security and performance. Our results show that our schemes are efficient and practical.

Abstract: Large-scale cloud storage systems often attempt to achieve two seemingly conflicting goals: (1) the systems need to reduce the copies of redundant data to save space, a process called deduplication; and (2) users demand encryption of their data to ensure privacy. Conventional encryption makes deduplication on ciphertexts ineffective, as it destroys data redundancy. A line of work, originated from Convergent Encryption [27], and evolved into Message Locked Encryption [13] and the latest DupLESS architecture [12], strives to solve this problem. DupLESS relies on a key server to help the clients generate encryption keys that result in convergent ciphertexts. In this paper, we first introduce a new security notion appropriate for the setting of deduplication and show that it is strictly stronger than all relevant notions. We then provide a rigorous proof of security against this notion, in the random oracle model, for the DupLESS architecture which is lacking in the original paper. Our proof shows that using additional secret, other than the data itself, for generating encryption keys achieves the best possible security under current deduplication paradigm. We also introduce a distributed protocol that eliminates the need for the key server. This not only provides better protection but also allows less managed systems such as P2P systems to enjoy the high security level. Implementation and evaluation show that the scheme is both robust and practical.

Abstract: Cipher text Policy Attribute-Based Encryption (CP-ABE) is an extremely powerful asymmetric encryption mechanism, but its complexity and its overhead cannot be neglected in an Internet of Things environment. Indeed, Internet of Things, by its heterogeneous nature, may contains highly resource-constrained devices that are not able to support the heavy overhead due to CP-ABE. Further, constrained devices, like sensors, often need to encrypt data as they are usually led to send sensitive data they collect to more powerful devices like storage servers. This paper proposes a novel approach for employing CP-ABE on highly resource-constrained sensor nodes in the IoT environments. The proposed approach exploits collaboration between heterogeneous nodes, to make feasible the implementation of CP-ABE in an IoT environment, by delegating costly operations to a set of assisting nodes. An analysis is conducted to verify that the proposed solution accomplishes safely and efficiently its objective.

Abstract: Motivated by privacy and usability requirements in various scenarios where existing cryptographic tools (like secure multi-party computation and functional encryption) are not adequate, we introduce a new cryptographic tool called Controlled Functional Encryption (C-FE). As in functional encryption, C-FE allows a user (client) to learn only certain functions of encrypted data, using keys obtained from an authority. However, we allow (and require) the client to send a fresh key request to the authority every time it wants to evaluate a function on a ciphertext. We obtain efficient solutions by carefully combining CCA2 secure public-key encryption (or rerandomizable RCCA secure public-key encryption, depending on the nature of security desired) with Yao's garbled circuit. Our main contributions in this work include developing and for- mally defining the notion of C-FE; designing theoretical and practical constructions of C-FE schemes achieving these definitions for specific and general classes of functions; and evaluating the performance of our constructions on various application scenarios.

Abstract: With the break of RSA and ECC cryptosystems in an era of quantum computing, asymmetric code-based cryptography is an established alternative that can be a potential replacement. A major drawback are large keys in the range between 50kByte to several MByte that prevented real-world applications of code-based cryptosystems so far. A recent proposal by Misoczki et al. showed that quasi-cyclic moderate density parity-check (QC-MDPC) codes can be used in McEliece encryption -- reducing the public key to just 0.6 kByte to achieve a 80-bit security level. Despite of reasonably small key sizes that could also enable small designs, previous work only report high-performance implementations with high resource consumptions of more than 13,000 slices on a large Xilinx Virtex-6 FPGA for a combined en-/decryption unit. In this work we focus on lightweight implementations of code-based cryptography and demonstrate that McEliece encryption using QC-MDPC codes can be implemented with a significantly smaller resource footprint -- still achieving reasonable performance sufficient for many applications, e.g., challenge-response protocols or hybrid firmware encryption. More precisely, our design requires just 68 slices for the encryption and around 150 slices for the decryption unit and is able to en-/decrypt an input block in 2.2ms and 13.4 ms, respectively.

Abstract: Attribute-based encryption (ABE) is an advanced encryption technology where the privacy of receivers is protected by a set of attributes. An encryptor can ensure that only the receivers who match the restrictions on predefined attribute values associated with the ciphertext can decrypt the ciphertext. However, maintaining the correctness of all users’ attributes will take huge cost because it is necessary to renew the users’ private keys whenever a user joins, leaves the group, or updates the value of any of her/his attributes. Since user joining, leaving, and attribute updating may occur frequently in real situations, membership management will become a quite important issue in an ABE system. In this paper, we will present an ABE scheme which is the first ABE scheme that aims at dynamic membership management with arbitrary states, not binary states only, for every attribute. Our work also keeps high flexibility of the constraints on attributes and makes users be able to dynamically join, leave, and update their attributes. It is unnecessary for those users who do not change their attribute statuses to renew their private keys when some user updates the values of her/his attributes. Finally, we also formally prove the security of the proposed scheme without using random oracles.

Abstract: Information security has become an important issue in data communications. One method to ensure the security of data is to use cryptographic method. Cryptography is a method to encode the information to keep the information from being hacked by the other party. The implementation of cryptography is used a significant amount of computer resources. Various range application of blowfish algorithm can be implemented for data encryption sent from an Internet of Things physical network which have IP-based data. In this research, blowfish algorithm is implemented on FPGA using VHDL programming language, and monitored the number of FPGA resource that is used. The blowfish algorithm is analyzed by computing certain metrics performances such as security, encryption time, avalanche effect, and throughput from multiple testing scenarios for system reliability. The testing showed that blowfish algorithm gave a good performance when implemented in FPGA and show a good alternative to proposed as network security on Internet of Things.

Abstract: In this contribution, we implement two techniques to reinforce optical encryption, which we restrict in particular to the QR codes, but could be applied in a general encoding situation. To our knowledge, we present the first experimental-positional optical scrambling merged with an optical encryption procedure. The inclusion of an experimental scrambling technique in an optical encryption protocol, in particular dealing with a QR code "container", adds more protection to the encoding proposal. Additionally, a nonlinear normalization technique is applied to reduce the noise over the recovered images besides increasing the security against attacks. The opto-digital techniques employ an interferometric arrangement and a joint transform correlator encrypting architecture. The experimental results demonstrate the capability of the methods to accomplish the task.

Abstract: In the ciphertext-policy attribute based encryption (CPABE) scheme, a private key holder is related with a set of attributes while the data is encrypted under an access structure defined by the data provider. In most proposed schemes, the characteristics of the attributes are treated as same level. While in the real world circumstance, the attributes are always in the different levels. In this paper, In this paper, a scheme is proposed under a different hierarchy of attributes with the name of ciphertext-policy hierarchical attribute based encryption. The CP-HABE scheme is proved to be secure under the decisional q-parallel bilinear Diffie-Hellman exponent assumption, which can be considered as the generalization of the traditional CP-ABE.

Abstract: With the development of cloud computing, data sharing has a new effective method, i.e., outsourced to cloud platform. In this case, since the outsourced data may contain privacy, they only allow to be accessed by the authorized users. Encrypting the data before outsourcing is a commonly used approach, where the data owners only need to send the corresponding encryption key to the authorized users. However, in such approach it is difficult to use the data since the encrypted data obsoletes comprehensive search functionalities of plaintext keyword search. In this paper, we leverage the secure k-nearest neighbor to propose a secure dynamic searchable symmetric encryption scheme. Our scheme can achieve two important security features, i.e., forward privacy and backward privacy which are very challenging in Dynamic Searchable Symmetric Encryption (DSSE) area. In addition, we evaluate the performance of our proposed scheme compared with other DSSE schemes. The comparison results demonstrate the efficiency of our proposed scheme in terms of the storage, search and update complexity.

Abstract: Advances in digital content transmission have increased in the past few years. Security of multimedia data is an imperative issue because of fast evolution of digital data exchanges over an unsecured network Multimedia data security is achieved by methods of cryptography, which deals with encryption of data Standard symmetric encryption algorithms provide better security for the multimedia data, but applying symmetric key encryption algorithm on more complex multimedia data, problem of computational overhead might be faced Over the last few years, several encryption algorithms have applied to secure video transmission. While a large number of multimedia encryption schemes have been proposed in the literature and some have been used in real time applications, cryptanalytic work has shown the existence of security problems and other weaknesses in most of the proposed multimedia encryption schemes. Encryption is a common technique to uphold multimedia security. MPEG video stream is quite different from traditional textual data because interframe dependencies exist in MPEG video. Special MPEG video encryption algorithms are required because of their special characteristics, such as coding structure, large amount of data and real-time constraints. Image and video encryption have applications in various fields including internet communication, multimedia systems, medical imaging, and military communication. The Advanced Encryption Standard (AES) algorithm is used and modified it, to reduce the calculation of the algorithm and for improving the encryption performance.

Abstract: Public key encryption with keyword search is a novel cryptographic primitive enabling one to search on the encrypted data directly. In the known schemes, once getting a trapdoor, the server can search associated data without any restrictions. However, in reality, it is sometimes essential to prevent the server from searching the data all the time because the server is not fully trusted. In this paper, we propose the notion of public key encryption with revocable keyword search to address the issue. We also develop a concrete construction by dividing the whole life of the system into distinct times to achieve our goals. The proposed scheme achieves the properties of the indistinguishability of ciphertexts against an adaptive chosen keywords attack security under the co-decisional bilinear Diffie-Hellman assumption in our security model. Compared with two somewhat schemes, ours offers much better performance in terms of computational cost. Copyright © 2013 John Wiley & Sons, Ltd.

Abstract: As more and more data is outsourced to cloud which is assumed to be a semi-trusted server, it is necessary to encrypt the sensitive data stored in the cloud. However, it brings a series of problems, such as: How to search over the encrypted data efficiently and securely? How should a data owner grant search capabilities to the data users? To solve these problems, we propose two attribute-based keyword search and data access control schemes based on public-key searchable encryption and attribute based encryption. Our solutions allow a data owner to control the access policy and grant the search policy to any data user who wants to retrieve the encrypted data efficiently.

Abstract: a lot of advancements are being carried out in the field of wireless sensor networks in recent years. The wireless sensor networks are employed in a variety of fields such as military, health care, industry etc. Due to the increasing acceptance of this technology leads us to consider more about the security aspects of the WSNs. To ensure the integrity and to protect data from unauthorised accesses some method of cryptographic technologies must be employed. The symmetric and asymmetric encryption techniques can be employed in the WSN architecture to provide security. The asymmetric key encryption techniques may provide a higher level of security but compared to the symmetric key encryption it causes more overheads to the sensor nodes. Another method of location based encryption which can be used along with these technologies provides an extra layer of security by restricting the cipher text to be decrypted only at a specified location. A review of all these systems is described in this paper.

Abstract: Since the first notions of fully homomorphic encryption more than 30 years ago, there has been numerous attempts to develop such a system. Finally, in 2009 Craig Gentry succeeded. Homomorphic encryption brings great advantages but it seems that, at least for now, it also brings many practical difficulties. Furthermore, in the last couple of years, several other fully homomorphic systems arose where each has its one advantages and drawbacks. However, with the developments in cloud computing, we need it more than ever to become practical for real-world usages. In this paper we are discussing the strengths and weaknesses of homomorphic encryption and we give a brief description of several promising fully homomorphic encryption systems. Next, we give a special attention to the homomorphic encryption systems for cloud computing. Finally, we discuss some recent developments by IBM and their open-source library for homomorphic encryption.

Abstract: In this age of explosive growth in information exchanges, there is indeed no time at which security does not matter. One of the symmetric encryption algorithms, DES, has kept its dominant position in the area of data encryption over the last few decades. However, with a rapid development in the field of computer hardware, DES has already been proved insecure. It takes a short time to translate the ciphertext to its corresponding plaintext using brute-force method at a reasonable cost. This is mainly due to the small key size DES employed. Given these issues, the objective of this article is to suggest an alternative on DES to obtain higher security and better execution efficiency by increasing the key size and updating the iteration technique. Comparisons were conducted with both DES and the advanced DES named triple DES (3DES). The results have demonstrated that the proposed algorithm outperforms both previous algorithms.

Abstract: The notion of comparable encryption is introduced in Esorics 2013 [18] which overcomes the weakness of order-preserving encryption OPE. While an OPE enables to compare the numerical order of numbers from their corresponding ciphertexts alone, the comparable encryption enables to compare the numerical order of the pair of numbers from their ciphertexts if either of the ciphertexts is accompanied with the corresponding token. Hence, it significantly reduces the amount of disclosed knowledge with respect to encrypted numbers from their ciphertexts. Since an OPE is considered to be a key primitive for encrypted databases such as CryptDB [31] and Monomi [36], a comparable encryption has a potential to enhance the security of these applications. However, the previous comparable encryption requires large ciphertext length, which so severely spoils the performance of encrypted databases that it is no longer practical. We propose in this paper, a very short comparable encryption. While each bit is encrypted into a string of security parameter length, say 160 bits, in the previous works, ours encrypts each bit into 3-ary. This is even shorter than the ciphertext length of OPEs.

Abstract: An encryption key management system and method implements enterprise managed encryption key for an enterprise using encryption for cloud-based services. In some embodiments, the enterprise deploys a key agent on the enterprise data network to distribute encryption key material to the network intermediary on a periodic basis. The network intermediary receives the encryption key material from the enterprise and stores the encryption key material in temporary storage and uses the received encryption key material to derive a data encryption key to perform the encryption of the enterprise's data. In this manner, the enterprise can be provided with the added security assurance of maintaining and managing its own encryption key while using cloud-based data storage services. The encryption key management system and method can be applied to ensure that the enterprise's one or more encryption keys do not leave the enterprise's premises.

Abstract: Public key cryptanalysis.- Identity-based encryption.- Key derivation and quantum computing.- Secret-key analysis and implementations.- Obfuscation and multi linear maps.- Authenticated encryption.- Symmetric encryption.- Multi-party encryption.- Side-channel attacks.- Signatures and public-key encryption.- Functional encryption.- Foundations.- Multi-party computation.

Abstract: Encryption schemes where the ciphertext must abide by a specified format have diverse applications, ranging from in-place encryption in databases to per-message encryption of network traffic for censorship circumvention. Despite this, a unifying framework for deploying such encryption schemes has not been developed. One consequence of this is that current schemes are ad-hoc; another is a requirement for expert knowledge that can disuade one from using encryption at all. We present a general-purpose library (called libfte) that aids engineers in the development and deployment of format-preserving encryption (FPE) and format-transforming encryption (FTE) schemes. It incorporates a new algorithmic approach for performing FPE/FTE using the nondeterministic finite-state automata (NFA) representation of a regular expression when specifying formats. This approach was previously considered unworkable, and our approach closes this open problem. We evaluate libfte and show that, compared to other encryption solutions, it introduces negligible latency overhead, and can decrease diskspace usage by as much as 62.5% when used for simultaneous encryption and compression in a PostgreSQL database (both relative to conventional encryption mechanisms). In the censorship circumvention setting we show that, using regular-expression formats lifted from the Snort IDS, libfte can reduce client/server memory requirements by as much as 30%.

Abstract: We study homomorphic authenticated encryption, where privacy and authenticity of data are protected simultaneously. We define homomorphic versions of various security notions for privacy and authenticity, and investigate relations between them. In particular, we show that it is possible to give a natural definition of IND-CCA for homomorphic authenticated encryption, unlike the case of homomorphic encryption. Also, we construct a simple homomorphic authenticated encryption scheme supporting arithmetic circuits, which is chosen-ciphertext secure both for privacy and authenticity. Our scheme is based on the error-free approximate GCD assumption.

Abstract: Fully homomorphic encryption is faced with two problems now One is candidate fully homomorphic encryption schemes are few Another is that the efficiency of fully homomorphic encryption is a big question In this paper, we propose a fully homomorphic encryption scheme based on LWE, which has better key size Our main contributions are: (1) According to the binary-LWE recently, we choose secret key from binary set and modify the basic encryption scheme proposed in Linder and Peikert in 2010 We propose a fully homomorphic encryption scheme based on the new basic encryption scheme We analyze the correctness and give the proof of the security of our scheme The public key, evaluation keys and tensored ciphertext have better size in our scheme (2) Estimating parameters for fully homomorphic encryption scheme is an important work We estimate the concert parameters for our scheme We compare these parameters between our scheme and Bra12 scheme Our scheme have public key and private key that smaller by a factor of about logq than in Bra12 scheme Tensored ciphertext in our scheme is smaller by a factor of about log2q than in Bra12 scheme Key switching matrix in our scheme is smaller by a factor of about log3q than in Bra12 scheme