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Wadi and Zainal recently proposed a high definition image encryption algorithm based on a modified AES-128 block cipher in (Wirel Pers Commun 79(2):811---829, 2014). In this paper, we show that the core component of their image encryption algorithm, a modified AES-128 cipher, is insecure against impossible differential attack. The proposed impossible differential attack on the full rounds of the modified AES-128 cipher has a time complexity of around $$2^{88.74}$$288.74 encryptions with $$2^{114.06}$$2114.06 chosen plaintexts and $$2^{99}$$299 bytes of memory, in contrast to the expected security of $$2^{128}$$2128. The existence of such an attack disproves the claims made by the designers that their modified AES-128 cipher improves the security of the AES cipher and that it can subsequently be used to construct a secure image encryption scheme. The root cause of this attack, some other issues with the modified AES cipher and possible solutions are described to serve as important remarks in designing a secure image encryption scheme.

Cloud computing has become a significant computing model in the IT industry. In this emerging model, computing resources such as software, hardware, networking, and storage can be accessed anywhere in the world on a pay-per-use basis. However, storing sensitive data on un-trusted servers is a challenging issue for this model. To guarantee confidentiality and proper access control of outsourced sensitive data, classical encryption techniques are used. However, such access control schemes are not feasible in cloud computing because of their lack of flexibility, scalability, and fine-grained access control. Instead, Attribute-Based Encryption (ABE) techniques are used in the cloud. This paper extensively surveys all ABE schemes and creates a comparison table for the key criteria for these schemes in cloud applications.

Cryptography is a process by which information or messages can be sent from one user to another user which provides several security services such as confidentiality, data integrity or authentication to the wireless communication system. As there is need for secure communication, efficient cryptographic processing is required for good system performance. One of the basic fundamental tools used in information security is known as the signature. Thus, the security for internet banking, account passwords, emails accounts password etc. requires text protection in digital media. This paper presents the security and compression for the data with the advance encryption standard (AES). In our research, we increase the number of rounds (Nr) to 16 for the encryption and decryption process of AES algorithm, which results in more security to the system. Experimental results and Theoretical analysis proved that this AES technique provide high speed as well as less transfer of data over the unsecured channels.

We introduce a new encryption notion called distance-based encryption (DBE) to apply biometrics in identity-based encryption. In this notion, a ciphertext encrypted with a vector and a threshold value can be decrypted with a private key of another vector, if and only if the distance between these two vectors is less than or equal to the threshold value. The adopted distance measurement is called Mahalanobis distance, which is a generalization of Euclidean distance. This novel distance is a useful recognition approach in the pattern recognition and image processing community. The primary application of this new encryption notion is to incorporate biometric identities, such as face, as the public identity in an identity-based encryption. In such an application, usually the input biometric identity associated with a private key will not be exactly the same as the input biometric identity in the encryption phase, even though they are from the same user. The introduced DBE addresses this problem well as the decryption condition does not require identities to be identical but having small distance. The closest encryption notion to DBE is the fuzzy identity-based encryption, but it measures biometric identities using a different distance called an overlap distance (a variant of Hamming distance) that is not widely accepted by the pattern recognition community, due to its long binary representations. In this paper, we study this new encryption notion and its constructions. We show how to generically and efficiently construct such a DBE from an inner product encryption (IPE) with reasonable size of private keys and ciphertexts. We also propose a new IPE scheme with the shortest private key to build DBE, namely, the need for a short private key. Finally, we study the encryption efficiency of DBE by splitting our IPE encryption algorithm into offline and online algorithms.

Broadcast encryption (BE) schemes allow a sender to securely broadcast to any subset of members but require a trusted party to distribute decryption keys. Group key agreement (GKA) protocols enable a group of members to negotiate a common encryption key via open networks so that only the group members can decrypt the ciphertexts encrypted under the shared encryption key, but a sender cannot exclude any particular member from decrypting the ciphertexts. In this paper, we bridge these two notions with a hybrid primitive referred to as contributory broadcast encryption (ConBE). In this new primitive, a group of members negotiate a common public encryption key while each member holds a decryption key. A sender seeing the public group encryption key can limit the decryption to a subset of members of his choice. Following this model, we propose a ConBE scheme with short ciphertexts. The scheme is proven to be fully collusion-resistant under the decision $n$ -Bilinear Diffie-Hellman Exponentiation (BDHE) assumption in the standard model. Of independent interest, we present a new BE scheme that is aggregatable. The aggregatability property is shown to be useful to construct advanced protocols.

We cryptanalyse the new ID-based encryption scheme proposed by Meshram.We find a method to factorize N, where N is the parameter proposed by Meshram.We also give a method to recover the secret master key of Meshram's ID-based encryption scheme.We also pointed out the flaws in the security proof in Theorem 5.1 of Meshram's paper in Section 4 of revised paper. Identity-based (ID-based) cryptography is very useful as it can simplify the certificate management in public key cryptosystem. Since 2001, researchers have introduced various practical and efficient ID-based encryption schemes. Most of them are based on pairings, under the Diffie-Hellman assumptions. Recently, Meshram 1 proposed a new ID-based encryption scheme which was not based on pairing-based cryptography. He proved that his scheme was secure against adaptive chosen plaintext attack, as its security was based on the difficulty of discrete logarithm and integer factorization problems. However, in this paper, we show that this new ID-based encryption scheme is insecure by presenting a method to recover the secret master key.

In order to limit the damage of key exposure for identity-based encryption, we propose a new paradigm called intrusion-resilient identity-based encryption (IRIBE) in this paper. Compared with key-insulated identity-based encryption and forward-secure identity-based encryption, IRIBE can achieve a stronger level of security. In our proposed scheme, the ciphertexts in any other time periods are secure even after arbitrarily many compromises of the base and the user, as long as compromises do not happen simultaneously. Furthermore, the intruder cannot decrypt the ciphertexts pertaining to previous time periods, even if it compromises the base and the user simultaneously. Therefore, our IRIBE scheme can greatly enhance the security of identity-based encryption. We also formalize the definition and the security notions of this paradigm. The proposed scheme is proven secure in the standard model.

In this article, a new algorithm that can encrypt data on TCP data segment by using a novel chaotic random number generator was developed. First of all, dynamic analyses of the chaotic system to be used were made and the original pseudo-random number generator (PRNG) with a new approach was designed. Key series produced by PRNG was tested on NIST and passed all the tests. The chaos-based encryption here was performed on TCP, one of the most fundamental protocols in data communication. Following this, TCP data segments were encrypted by the sender on bit base with key series produced by PRNG, and then they were decrypted by the receiver. Security level of the chaos-based encryption carried out here was tested with histogram, its key length, key sensitivity and entropy method. Memory and time usages were measured in performance analysis. So as to reveal the performance of the encryption, memory usage, encryption and decryption times were analyzed by comparison on different security algorithms. According to tests and analyses results, this chaos-based encryption has a high level of performance and security; and it is an original study that can be used in real-time implementations with TCP protocol. Copyright © 2016 John Wiley & Sons, Ltd.

This paper proposes a scheme for password management by storing password encryptions on a server. The method involves having the encryption key split into a share for the user and one for the server. The user’s share shall be based solely on a selected passphrase. The server’s share shall be generated from the user’s share and the encryption key. The security and trust are achieved by performing both encryption and decryption on the client side. We also address the issue of countering dictionary attack by providing a further enhancement of the scheme.

This paper describes an approach and implementation issues of client-side data encryption for thin client-web browser. Since the service provider may be a competitor of the service user, sensitive parts of data are encrypted and decrypted by the client. Cipher key generation and distribution issues are discussed: although the cipher key is kept in private, the paper shows the way for the key validation by the server side to maintain data consistency.

Recently, a number of extended Proxy Re-Encryptions (PRE), e.g. Conditional (CPRE), identity-based PRE (IPRE) and broadcast PRE (BPRE), have been proposed for flexible applications. By incorporating CPRE, IPRE and BPRE, this paper proposes a versatile primitive referred to as conditional identity-based broadcast PRE (CIBPRE) and formalizes its semantic security. CIBPRE allows a sender to encrypt a message to multiple receivers by specifying these receivers’ identities, and the sender can delegate a re-encryption key to a proxy so that he can convert the initial ciphertext into a new one to a new set of intended receivers. Moreover, the re-encryption key can be associated with a condition such that only the matching ciphertexts can be re-encrypted, which allows the original sender to enforce access control over his remote ciphertexts in a fine-grained manner. We propose an efficient CIBPRE scheme with provable security. In the instantiated scheme, the initial ciphertext, the re-encrypted ciphertext and the re-encryption key are all in constant size, and the parameters to generate a re-encryption key are independent of the original receivers of any initial ciphertext. Finally, we show an application of our CIBPRE to secure cloud email system advantageous over existing secure email systems based on Pretty Good Privacy protocol or identity-based encryption.

With the growth in technology, there is always a need of good encryption method which may provide better security and authenticity with lesser computational complexities. Although there are a lot of symmetric key algorithms which are already been proposed, yet we are going to propose a content based symmetric key algorithm. This algorithm has two rounds and each round uses the ASCII code of characters, round two serves as the heart of this algorithm as XOR operation is performed here. It uses only two operation addition and XOR for encryption process and to generate two sub key, it uses two operation addition and subtraction. The goal of the algorithm is to reduce the correlation between plain text and cipher.

AES a symmetric block cipher is suitable for high speed application. The throughput as one of the bottleneck for huge data size such as image. Another symmetric block cipher MASK, a matrix based encryption technique, also suitable for high speed application with speed eight times that of AES. The proposed work discuses about AES and MASK algorithm and compares in terms of encryption speed, diffusion, confusion and statistical attacks. Based on the analysis a Modified MASK algorithm is designed to overcome the security weakness in MASK algorithm. A hardware implementation of Modified MASK algorithm is done and validated.

Attribute Based Encryption (ABE) is a type of public encryption in decryptor can only decrypt the ciphertext if its attributes of secret key matches the attributes of ciphertext but functionality comes at higher cost. The main idea of this paper is to provide multi authority in attribute based encryption which also allows fast decryption. Multi authority concept allows any polynomial number of independent authorities to monitor attributes, distribute secret keys and decrypt the message. In this paper, a secure multi authority attribute based encryption with fast decryption scheme is design.

It is the first time to integrate identity-based encryption into public key encryption with equality test.It extends identity-based encryption with keyword search to yield a general function: equality test.It is proven to be one-way chosen-ciphertext security against a chosen identity attack as a desirable security.Unlike PEKS or IBEKS, it can be used alone since it contains decryption algorithm besides encryption algorithm. We firstly combine the concepts of public key encryption with equality test (PKEET) and identity-based encryption (IBE) to obtain identity-based encryption with equality test (IBEET). Inheriting the advantage of IBE, IBEET can simplify the certificate management of PKEET with all messages encrypted with the receiver's public identity. In the IBEET scheme, the receiver computes a trapdoor using the secret value for the identity and then sends it to a cloud server for equality test on its ciphertexts with others' ciphertexts. Using this primitive someone with the trapdoor for its identity can delegate out the capability of equality test on its ciphertexts without requiring a central authority to act as a delegator. So it is very suitable for the client with minimal computation resource, e.g, mobile phone. Furthermore, compared with PKEET, it has security improvement since not anyone can perform the test. Therefore, IBEET may have interesting applications in cloud computing, e.g., partition of encrypted emails. We define one-way chosen-ciphertext security against a chosen identity attack (OW-ID-CCA) and propose a construction in bilinear pairing. Finally, extensive security analysis and comparison with related works show that the proposed scheme is proven secure and useful.

In this fast world of networking, secure image transmission of data whether the image having some information or some text, is one of the area focus for security. Here we had tried to implement the proposed technique fuzzy logic based image encryption for confidential data transfer using (2, 2) secret sharing scheme. Using fuzzy logic makes encryption and decryption complex. The (2, 2) secret sharing scheme provides secured and confidential authentication. For image encryption AES algorithm is used for encryption and decryption. The implementation of encryption algorithms can be very complex when we are focusing on rule based share generation.

Attribute-based encryption (ABE) has emerged as a promising solution for access control to diverse set of users in cloud computing systems. Policy can just specify whether (or not) any specific user should be given access to data, but it lacks to provide data owner the privilege to specify (how much) fraction, or (which) specific chunk from that data to be accessed or decrypted. In this paper, we address this issue, and propose a scheme that will give data owner excessive access control, so that he can specify specific chunk out of total data to be accessed by user depending on his attributes. In our scheme, a data owner can encrypt data over attributes specified in a policy, but even if user's attributes satisfy the policy; he can decrypt data (partially or fully) fractionally based on his attributes specified by owner. The owner can also prioritize user's access based on his designation, or hierarchal role in a specific organization. We also address to resolve the issue of attributes repetition, due to which the cost of computations in encryption by owner and ciphertext size is reduced. Furthermore, we achieve it with a single ciphertext over policy for entire data, and proof our scheme to be secure in the generic group and random oracle model. Theoretical comparisons of computations with existing constructions, and performance of the scheme evaluated in the Charm simulator is reasonable enough to be adopted in practice.

We propose two new ciphertext policy attribute-based encryption (CP-ABE) schemes where the access policy is defined by AND-gate with wildcard. In the first scheme, we present a new technique that uses only one group element to represent an attribute, while the existing ABE schemes of the same type need to use three different group elements to represent an attribute for the three possible values (namely, positive, negative, and wildcard). Our new technique leads to a new CP-ABE scheme with constant ciphertext size, which, however, cannot hide the access policy used for encryption. The main contribution of this paper is to propose a new CP-ABE scheme with the property of hidden access policy by extending the technique we used in the construction of our first scheme. In particular, we show a way to bridge ABE based on AND-gate with wildcard with inner product encryption and then use the latter to achieve the goal of hidden access policy. We prove that our second scheme is secure under the standard decisional linear and decisional bilinear Diffie-Hellman assumptions.

WSN (wireless sensor network) has been used in a wide range of applications nowadays. Sensor networks may often relay critical data; thus, security must be a high priority. However, due to their limited computational, energy, and storage resources, sensor nodes are vulnerable to attack. So how to protect sensor nodes from attacks without raising computational capability and energy consumption is a worthwhile issue. A WAC (wireless authentication center) with mixed encryption named “MEWAC” is proposed. MEWAC is based on MCU (Microcontroller Unit) and WiFi (Wireless Fidelity) module and uses RSA, AES (Advanced Encryption Standard), and SHA-1 (Secure Hash Algorithm 1) to provide high performance authentication and data encryption services for sensor nodes. The experimental results show that MEWAC has the advantages of low cost, low power consumption, good performance, and stability; moreover, the authentication protocol improves the security of WSN and reduces the overhead in node authentication.

In this work, we study indistinguishability obfuscation and functional encryption for general circuits: Indistinguishability obfuscation requires that given any two equivalent circuits C0 and C1 of similar size, the obfuscations of C0 and C1 should be computationally indistinguishable. In functional encryption, cipher texts encrypt inputs x and keys are issued for circuits C. Using the key SKC to decrypt a cipher text CTx = Enc(x), yields the value C(x) but does not reveal anything else about x. Furthermore, no collusion of secret key holders should be able to learn anything more than the union of what they can each learn individually. We give constructions for indistinguishability obfuscation and functional encryption that supports all polynomial-size circuits. We accomplish this goal in three steps: - (1) We describe a candidate construction for indistinguishability obfuscation for NC1 circuits. The security of this construction is based on a new algebraic hardness assumption. The candidate and assumption use a simplified variant of multilinear maps, which we call Multilinear Jigsaw Puzzles. (2) We show how to use indistinguishability obfuscation for NC1 together with Fully Homomorphic Encryption (with decryption in NC1) to achieve indistinguishability obfuscation for all circuits. (3) Finally, we show how to use indistinguishability obfuscation for circuits, public-key encryption, and non-interactive zero knowledge to achieve functional encryption for all circuits. The functional encryption scheme we construct also enjoys succinct cipher texts, which enables several other applications.

There are important concerns when trusting sensitive information to the cloud. Health and financial records, for instance, suffer strict legal restrictions to data escrow. Organizations holding such information need to assure end-users and authorities that a third party will never access restricted data. Client-side encryption is a common solution in literature. Most works fail, however, to reason the impact of security solutions on performance and usability. Homomorphic and order preserving encryption systems can mitigate such negative impacts, as they allow the computation of regular searches over encrypted records on the cloud, while preserving information confidentiality and the privacy if end-users.

Electronic Medical Records (EMRs) pose a number of security challenges. Conventional cryptographic solutions have been used to protect the patients EMRs but with one major weakness; in an event where there is an exposure of a secret key, the secrecy of past and future encrypted data is void. This work concentrated on integrating the concept of forward secrecy in the protection of EMRs. In order to come up with the right integration, an experimental simulation has been carried out to evaluate the performance of forward secure and non-forward secure secret key encryption schemes. The study shows that only few cryptographic schemes that have implemented forward secrecy are used in the protection of EMRs, and very few of them use the forward secure secret key encryption scheme (FSSKES). The experiment also shows that the cost of running forward secure symmetric encryption is closely related to that of running non-forward secure symmetric encryption scheme (NFSSKES).

To leverage the power of cloud computing, you can no longer encrypt data the traditional way. However, anyone (including the cloud service itself) can easily read unencrypted data. Fully homomorphic encryption reconciles this dilemma.

Transferring medical images using networks is subjected to a wide variety of security risks. Hence, there is a need of a robust and secure mechanism to exchange medical images over the Internet. The Digital Image and Communication in Medicine (DICOM) standard provides attributes for the header data confidentiality but not for the pixel image data. In this paper, a simple and effective encryption approach for pixel data is provided for multi-frame DICOM medical images. The main goal of the proposed approach is to reduce the encryption and decryption time of these images, using Advanced Encryption Standard (AES) where only one image is encrypted and XOR cipher for encrypting the remaining multi-frame DICOM images. The proposed algorithm is evaluated using computational time, normalized correlation, entropy, Peak-Signal-to-Noise-Ratio (PSNR) and histogram analysis. The results show that the proposed approach can reduce the encryption and decryption time and is able to ensure image confidentiality.

Every Organization uses data encryption for securing their communication. It provides data integrity, confidentiality and authentication. The primary goal of this paper is to combine the reversible data hiding and encryption to get maximum security. There are some areas like military, medical, forensic, bank, etc. which cannot compromise with any security issue. In the above areas both data and image are highly confidential, so no permanent distortion is acceptable. The paper proposes the algorithm reversible data hiding with a novel lightweight software oriented symmetric stream cipher namely A-S algorithm. The reversible data hiding algorithm used here produces maximum data capacity and contrast improved cover image. When applying the A-S encryption algorithm on the reversible data hiding process results a very good amount of security level. This new combined algorithm tested with two different datasets and the result shows a maximum data capacity and enhanced contrast of the cover image. The paper also measures another important metric of performance which results an extra ordinary result.

Disk encryption is frequently used to secure confidential data on mobile devices. However, the high energy cost of disk encryption poses a heavy burden on those devices with limited battery capacity especially when a large amount of data needs to be protected by disk encryption. To address the challenge, we develop a new kernel-level disk encryption software, Populus. Almost 98% of Populus's encryption/decryption computation is not related with the input plaintext/ciphertext, so we accomplish the computation in advance during initialization when a consistent power supply is available. We conduct cryptanalysis on Populus and finally conclude that state-of-the-art cryptanalysis techniques fail to break Populus in reasonable computational complexity. We also conduct energy consumption experiments on Populus and dm-crypt, a famous disk encryption software for Android and Linux mobile devices. The experimental results demonstrate that Populus consumes 50%-70% less energy than dm-crypt.

A chaotic-cipher-based packet body encryption algorithm for JPEG2000 images is proposed in this paper. In order to produce a compliant codestream, a 2-byte block encryption procedure including bit-wise exclusive OR and cyclic rotation operations is investigated. Moreover, a repeatedly encryption process is adopted to eliminate the undesirable marker codes during encryption. The repeatedly encryption process only introduces a negligible computational overhead. Both simulations and analysis show that the proposed algorithm is of high security and simplicity. Therefore, these good properties make the algorithm efficient to process and useful for image applications.

Data security has a major role in the development of communication system, where more randomization in the secret keys increases the security as well as the complexity of the cryptography algorithms. In the recent years network security has become an important concern. Cryptography plays a vital role in the information security system against various attacks. Efficient and newer versions of cryptography techniques can help to reduce this security threat. The Advanced Encryption Standard is a strong symmetric key cryptographic algorithm which uses a number of table look ups to increase its performance. The Cache Timing Attack correlates the timing details for encryption under a known key with an unknown key to infer the unknown key. This paper proposes an extension of a public-key cryptosystem to support a private key cryptosystem which is a combination of Advanced Encryption Standard and ECC. The past results have been computed on the basis of AES key length as 128 bit and no. of iterations as 10.To increase competency and to minimize drawbacks this paper proposes a hybrid encryption scheme. The parameters to be studied will primarily focus on the key length, no. of iterations and the type of side channel attack to be implemented. The key length for this work has been increased to 192 bit and the no. of iterations taken will be 12.

Networked control systems with encrypted sensors measurements is considered. Semi-homomorphic encryption is used so that the controller can perform the required computation on the encrypted data. Specifically, in this paper, the Paillier encryption technique is utilized that allows summation of decrypted data to be performed by multiplication of the encrypted data. Conditions on the parameters of the encryption technique are provided that guarantee the stability of the closed-loop system and ensure certain bounds on the closed-loop performance.

The ultimate goal of private function evaluation is the complete outsourcing of processing tasks to distrusted platforms (such as clouds), so that arbitrary functions can be evaluated without any leakage of secret information. Several successful concepts have been proposed in the past, the most striking one having been fully homomorphic encryption besides the well-known garbled circuits and multiparty computation. In this paper, we look at an idealized model of outsourced computation, which we call a cryptocomputer . This is a (theoretical) machine that works exactly like a real-life computer in the sense of understanding a standard assembly language, but retaining all its internal signals, registers, and memory encrypted at all times. The encryption is assumed under a key that is unknown to the attacker, and taken as secure (in any cryptographically meaningful way), so that no leakage of information from any ciphertext can be expected from programs with reasonable (polynomial) time complexity. Unfortunately, such a cryptocomputer is necessarily insecure, irrespectively of how the encryption looks like. In particular, we explicitly do not assume any specific form of security (chosen-ciphertext or other) or (a)symmetry of encryption; our attack works only on ciphertexts and makes no assumptions whatsoever on the encryption. We prove insecurity of the cryptocomputer by taking the encryption as a black box, and show how to decipher every signal in the computer by pure virtue of submitting proper instructions for execution. Our attack falls into the general category of side-channel attacks, however unlike other related attacks, does neither exploit physical nor any logical characteristics of the underlying platform (besides the execution flow being observable). Somewhat surprisingly, it turns out that although the problem that we consider is cryptographic, it seemingly has no cryptographic solution and apparently calls for an interdisciplinary approach from new directions.

Security is playing a very important role in the field of authentication system,network system and Internet. The main goal of cryptography is to secure the data so that it cannot be accessed by any unauthorized user. Cryptography is an emerging tool, which is important for authentication. The AES is a 128 bit Symmetric block Cipher. This paper include enhancing reliability and security, use modified AES (Advanced Encryption Technique) which will be implemented step by step. For the process of encryption various classical techniques are used. These are substitution technique, rearrangement and transformation technique. Key expansion module is introduced in the encryption and decryption modules, which generates key for all iterations. In each iterative rounds addition of an arithmetic operator and a route transposition cipher is introduced in this modification. To increase the immunity against unauthorized attacks, the Key extended module doubles the number of iterative processing rounds.

The approach described in the paper is similar to the idea of memory organization in a computer. In the computer memory there must be saved not only data workable, but also directions for processing itself. Only in case when with encryption a key appears as a memory: it contains both, information essential in the course of encryption (a key proper), and an instruction on the way of encryption should be carried out (an additional block of information). As a consequence of this the crypto-durability of the whole system increases. At the same time the postulate of used algorithm openness is not broken: in the course of encryption there are used open algorithms only, only a key is secret which bears in itself the block of secret information on an open algorithm superposition.

Nowadays, security and privacy has become one of the primary issues in data storage and transmission. In the age of multimedia, images are widely used in business, advertising and promotions. Therefore the protection of images from unauthorized access is important. Image encryption plays a significant role in the field of information hiding. In this article, we introduce a chaos based image encryption technique using method of shuffled operations. This technique uses 128-bit private key for encryption. Performance of proposed image encryption scheme is compared with the existing inter pixel displacement image encryption scheme. Performance evaluation reveals that proposed scheme performs better than existing scheme in terms of entropy of encrypted image.

Timed-release encryption is a kind of encryption scheme in which a recipient can decrypt only after a specified amount of time T (assuming that we have a moderately precise estimate of his computing power). A revocable timed-release encryption is one where, before the time T is over, the sender can “give back” the timed-release encryption, provably loosing all access to the data. We show that revocable timed-release encryption without trusted parties is possible using quantum cryptography (while trivially impossible classically). Along the way, we develop two proof techniques in the quantum random oracle model that we believe may have applications also for other protocols. Finally, we also develop another new primitive, unknown recipient encryption , which allows us to send a message to an unknown/unspecified recipient over an insecure network in such a way that at most one recipient will get the message.

Identity-based encryption with keyword search (IBEKS) is a useful cryptographic primitive for cloud computing, i.e., it allows a data owner to encrypt and store his data in a cloud storage server, and later the owner can use his/her private key to produce a search trapdoor for searching the encrypted data. Existing IBEKS schemes only focus on supporting efficient and complex queries for the private key holder, while the authority, who is in charge of the generation of the private keys for users, cannot efficiently search the encrypted data. However, some applications might require the authority to efficiently search the encrypted data intended for any user. To address this problem, in this paper, we introduce a new primitive named dual trapdoor identity-based encryption with keyword search (DTIBEKS). In this primitive, the authority can use a peculiar way to produce one more trapdoor, which allows the authority to search any identity's encrypted data. We formally give the definition and security model for DTIBEKS, and then propose a novel DTIBEKS scheme. We further prove the security of our proposed DTIBEKS without random oracles. It is worth noting that our scheme can be easily transformed into identity-based encryption with fuzzy keyword search.

Public-key encryption (PKE) can be used in cloud system to protect data in data sharing, identity authentication, etc. However, the security model of traditional PKE does not capture the “key-leakage attacks” which can leak partial information about the secret key. Also, the adversary can inject fault to tamper with the secret key and observe the output of the public key encryption scheme under this modified key which is called “related-key attack”. In this paper, we present a method to construct public key encryption schemes secure against both weak key-leakage attacks and affine related-key attacks directly from extractable hash proof systems. Specifically, we first add Key Homomorphism and Fingerprinting properties to all-but-one (ABO) extractable hash proofs and construct a key encapsulation mechanism scheme secure against related-key attacks via it and thus public key encryption scheme secure against related-key attacks. Also, we prove that if the based ABO-extractable hash proof with Key Homomorphism and Fingerprinting properties is weak leakage-resilient, then the key encapsulation mechanism scheme constructed from it is weak leakage-resilient and related-key attack secure. Moreover, we propose a public key encryption scheme secure against affine related-key attacks based on lattice.

In the age of big data, border of data security has become increasingly blurred. Our privacy security is facing a new round of test. The multimedia big data especially images often carry many secrets or privacy information. How to ensure safety and the authorization of accessing to confidential data becomes a hot problem of urgency in image information processing and transmission. In this paper, we propose a novel symmetrical image encryption algorithm based on skew tent map. Utilizing a new chaos based Line map, the proposed algorithm is suitable for encryption of any size of image. In order to disrupt the correlations between the R, G, B components of the true color image, these three components are encrypted at bit level and operated at the same time. The proposed algorithm realizes fast encryption and decryption of both gray-scale image and color image. In addition, the algorithm can be implemented parallelly because there is no complex sub-block processing operation. Results of various analyses and numerical simulations show that the new algorithm has high security and is suitable for practical image encryption.

Recently, a novel couple images encryption algorithm based on DNA subsequence operation and chaotic system has been proposed. This paper evaluates the security of this encryption algorithm. The main weakness of the encryption algorithm is that the generated pesudo-random number sequences remain unchanged for encrypting every image. Based on this flaws, the present paper proposed a chosen-plaintext attack to reveal the equivalent keys with some pairs of chosen-plaintext and the corresponding ciphertext. Finally, the experimental results are provided to support the proposed attack.

Data security is the very important part in the network data communication. Avoidance of the information hacking and steeling are very challenging part for network data communication. Now-a-days people are using many encryption and decryption techniques for data security. But all encryption and decryption techniques are having more time occupation or less security for the process. This paper proposed high level security approach to encryption and decryption for data security. Two levels of securities are used in this proposed method. First one is data encryption and the second one is hash value generation. The proposed Weaving based Superior Encryption Standard (WSES) uses a novel weaving based approach. The weaving array generation is done by Elementary Number Theory Notation (ENTN) method. The weaving array has multiple private keys for XOR encryption. After encryption the error value is extracted from the encrypted array and weaving array. This error value is sent to the other side. The novel approach for hash value generation uses the encrypted array. After encryption, the encrypted array is rotated into four degrees and each degree data are converted to vector format and arranged on by one under the vector. Finally a 2D Rotational Encryption Matrix (REM) is obtained. After this process a REM copy is converted to mirror flip and it is need as Flipped Matrix (FM). The FM is concatenated under the REM and converted to vector using the zigzag operation. Finally this process gives two bytes hash value from the vector. This proposed method executes very fast and provide high security. This method is much reliable to small size applications and also used for any type of data security.

This paper analyzes the security of an image encryption algorithm proposed by Ye and Huang [\textit{IEEE MultiMedia}, vol. 23, pp. 64-71, 2016]. The Ye-Huang algorithm uses electrocardiography (ECG) signals to generate the initial key for a chaotic system and applies an autoblocking method to divide a plain image into blocks of certain sizes suitable for subsequent encryption. The designers claimed that the proposed algorithm is "strong and flexible enough for practical applications". In this paper, we perform a thorough analysis of their algorithm from the view point of modern cryptography. We find it is vulnerable to the known plaintext attack: based on one pair of a known plain-image and its corresponding cipher-image, an adversary is able to derive a mask image, which can be used as an equivalent secret key to successfully decrypt other cipher-images encrypted under the same key with a non-negligible probability of 1/256. Using this as a typical counterexample, we summarize security defects in the design of the Ye-Huang algorithm. The lessons are generally applicable to many other image encryption schemes., 8 pages, 6 figures

Wireless devices are characterized by low computational power and memory. Hence security protocols dealing with these devices have to be designed to give minimal computational and memory load. We present an efficient authentication and key exchange protocol for low-end wireless clients and high end servers, which is overall nearly three times as fast as comparable protocols. The basic idea of our protocol is to use symmetric key encryption in place of public key encryption wherever possible. &nbsp

The need for fast and strong image cryptosystems motivates researchers to develop new techniques to apply traditional cryptographic primitives in order to exploit the intrinsic features of digital images. One of the most popular and mature technique is the use of complex ynamic phenomena, including chaotic orbits and quantum walks, to generate the required key stream. In this paper, under the assumption of plaintext attacks we investigate the security of a classic diffusion mechanism (and of its variants) used as the core cryptographic rimitive in some image cryptosystems based on the aforementioned complex dynamic phenomena. We have theoretically found that regardless of the key schedule process, the data complexity for recovering each element of the equivalent secret key from these diffusion mechanisms is only O(1). The proposed analysis is validated by means of numerical examples. Some additional cryptographic applications of our work are also discussed., Comment: 16 pages, 7 figures

Attribute-based Encryption (ABE) is a new and promising public key encryption that allows fine-grained authorization on data based on user attributes. Such property is favorable for multiple applications that require encrypted storage or access control on data, in particular: eHealth applications. However, ABE schemes are known not to be efficient in the encryption phase because ciphertext size and the time required to encrypt grow with the complexity of the access policy. Such drawback is critical in the context of pervasive computing, for instance, in the Internet of Things, where data producers are usually resource-constrained devices, e.g. smart phones or sensing platforms. In this work, we propose OEABE standing for Outsourcing mechanism for the Encryption of Ciphertext-Policy ABE (CP-ABE). We show how a user can offload expensive operations of CP-ABE encryption to a semi-trusted party in a secure manner. Our proposed mechanism requires only one exponentiation on resource-constrained devices. We provide also an informal security analysis of possible attacks from a semi-honest adversary against the proposed solution. To demonstrate the performance gains of our mechanism, we first conducted a performance estimation on an emulated Wismote sensor platform. Then, we implemented our proposal and did comparison to an existing implementation of CP-ABE on a laptop.

Functional encryption supports restricted decryption keys that allow users to learn specific functions of the encrypted messages. Although the vast majority of research on functional encryption has so far focused on the privacy of the encrypted messages, in many realistic scenarios it is crucial to offer privacy also for the functions for which decryption keys are provided. Whereas function privacy is inherently limited in the public-key setting, in the private-key setting it has a tremendous potential. Specifically, one can hope to construct schemes where encryptions of messages $$\mathsf{m}_1, \ldots , \mathsf{m}_T$$ together with decryption keys corresponding to functions $$f_1, \ldots , f_T$$ , reveal essentially no information other than the values $$\{ f_i(\mathsf{m}_j)\}_{i,j\in [T]}$$ . Despite its great potential, the known function-private private-key schemes either support rather limited families of functions (such as inner products) or offer somewhat weak notions of function privacy. We present a generic transformation that yields a function-private functional encryption scheme, starting with any non-function-private scheme for a sufficiently rich function class. Our transformation preserves the message privacy of the underlying scheme and can be instantiated using a variety of existing schemes. Plugging in known constructions of functional encryption schemes, we obtain function-private schemes based either on the learning with errors assumption, on obfuscation assumptions, on simple multilinear-maps assumptions, and even on the existence of any one-way function (offering various trade-offs between security and efficiency).

Indistinguishability obfuscation (IO) is a tremendous notion, powerful enough to give rise to almost any known cryptographic object. Prior candidate IO constructions were based on specific assumptions on algebraic objects called multi-linear graded encodings. We present a generic construction of indistinguishability obfuscation from public-key functional encryption with succinct encryption circuits and subexponential security. This shows the equivalence of indistinguishability obfuscation and public-key functional encryption, a primitive that has previously seemed to be much weaker, lacking the power and the staggering range of applications of indistinguishability obfuscation. Our main construction can be based on functional encryption schemes that support a single functional key , and where the encryption circuit grows sub-linearly in the circuit-size of the function. We further show that sublinear succinctness in circuit-size for single-key schemes can be traded with sublinear succinctness in the number of keys (also known as the collusion-size ) for multi-key schemes. We also show that, under the Learning with Errors assumption, our techniques imply that any indistinguishability obfuscator can be converted into one where the size of obfuscated circuits is twice that of the original circuit plus an additive overhead that is polynomial in its depth, input length, and the security parameter.