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Data confidentiality in the Cloud Computing is a very challenging task. Encryption is one of the most secure methods ensuring this task, and searchable encryption techniques are used to search on encrypted data without the need for decryption. But, despite this secure measure some leaks may appear when searching over data. In this article, we propose to improve confidentiality of outsourced data. We are particularly interested in reinforcing the access control on the search result, when the search is performed over encrypted data. The property behind this aspect of security is known as ACAS (Access Control Aware Search) principle. We present a hybridization of Searchable Encryption and Attribute Based Encryption techniques in order to satisfy the ACAS property. The proposed model supports a personalized and secure multi-user access to outsourced data, presenting high search performance. It deals with multi-keywords searches and is designed to speed up the search time by taking advantage of High Performance Computing, which is widely used in Cloud Computing. Two Attribute Based Encryption techniques are considered on the side of the Cloud and some conducted experiments show the efficiency of the proposed method.

With rapid development of cloud computing, more and more enterprises will outsource their sensitive data for sharing in a cloud. To keep the shared data confidential against untrusted cloud service providers (CSPs), a natural way is to store only the encrypted data in a cloud. The key problems of this approach include establishing access control for the encrypted data, and revoking the access rights from users when they are no longer authorized to access the encrypted data. This paper aims to solve both problems. First, we propose a hierarchical attribute-based encryption scheme (HABE) by combining a hierarchical identity-based encryption (HIBE) system and a ciphertext-policy attribute-based encryption (CP-ABE) system, so as to provide not only fine-grained access control, but also full delegation and high performance. Then, we propose a scalable revocation scheme by applying proxy re-encryption (PRE) and lazy re-encryption (LRE) to the HABE scheme, so as to efficiently revoke access rights from users.

Designers and users of encryption algorithms used in cipher systems need a systematic approach in examining their ciphers prior to use, to ensure that they are safe from cryptanalytic attack. This paper describes a computer package used for assessing the security of newly-developed encryption algorithms.

Few controls available to information security professionals today are more potentially powerful than is encryption. Among the many important benefits of encryption are data confidentiality, integrity of data and system files, protection against repudiation in business and other transactions, assurance of individuals' identity, protection against cheating in voting and contract signing, and others. Security professionals are required to know at least the basics of cryptography to pass professional certification tests such as the CISSP exam; they must often know much more to be able to be proficient on the job. A number of vendors have produced impressive encryption products for desktop encryption, authentication methods, virtual private networks (VPNs), and digital signatures. Significant advances in cryptography and cryptanalysis research have also occurred over the years.

This paper serves two purposes: we present some generalizations of the Data Encryption Standard (DES), and explain how to efficiently implement DES and its generalization in software. By preserving the macro structure of DES, but by allowing the user to choose (1) 16 x 48 independent key bits instead of generating them all using only 56 key bits, (2) arbitrary substitutions S"1,...,S"8, (3) arbitrary permutations IP and P, and (4) an arbitrary expanding permutation E, we obtain a very general and presumably much stronger cipher called generalized DES (G-DES). A cipher having the first three extensions is called G-DES with non-arbitrary E. We choose, in an unorthodox way, from some well known equivalent representations of G-DES and some well suited table combinations and implementations. Concatenations of substitutions and permutations are precomputed and tabulated. Since direct tabulation of, for example, a permutations of 32 bits requires 2^3^2 entries of 4 bytes each, which clearly exceeds today's main memories, the big table is split into smaller ones that permute disjoint and compact parts of the input bits at the appropriate positions. To compute an entry in the big table, the corresponding entries in the smaller tables are ORed. For some specific expanding permutations (including the original E in DES), the expense of this permutation can be reduced drastically: only copy, rotate and AND with a mask stored in a register is necesarry if the bits in the register and the tables of the substitutions are ordered appropriately. Since this is the only way we know of to achieve better performance for DES than for G-DES, it does not seem to make sense to implement anything more narrow in software than G-DES with non-arbitrary E. Using these techniques, we get by far the fastest software implementations of DES (more specifically G-DES with non-arbitrary E) and G-DES known to us. The same DES and G-DES implementations, partly in MC68000 assembler language, achieve 100 and 80 kbits/s on an Apple Macintosh Classic (MC68000, 7.83 MHz, 150 ns RAM), 1109 and 789 kbits/s on an Apple Macintosh IIfx (MC68030, 40 MHz, 32 Kbyte cache board, 80 ns RAM) in EBC and CBC modes using less than 110 and 430 Kbytes main memory. OFB(64) mode is between 12% and 234% faster because we can save IP, except for the first time. Conversely, if CBC mode is used for authentication, we can save IP^-^1 except for the last block. This increases speed by between 6% and 24%. To avoid unnecessary IP and IP^-^1 executions, and to enable multiple encryption in all modes of operation, our implementation supports multiple encryption. Our table implementation makes it possible to save key EORing (Exclusive OR=bitwise addition mod 2) in each round by precomputing a key-specific table for every (or in some cases only every second) round. Memory requirements can be reduced by not copying bits which are input to one combined S-box.

The Data Encryption Standard (DES) has been the subject of multiple attempts at breaking. As of this date no one has announced a method that will break DES with certainty. In this paper we do not consider a method but develop another machine. Many such machines have been proposed over the years (see [14]). Our machine makes use of current high-speed encryption chips in combination with hardware fuzzy comparers to automate the breaking process.

An implementation of a technique, based on the Data Encryption Standard (DES), is described for user-controlled encryption of files. The user supplies a privately selected character string as a key and also the desired number of DES iterations. The actual encryption key and initial chaining value for block-chaining are derived from this private key for encryption of the user file. The implementation is adaptible for use on both time-sharing systems and personal computer systems.

Encryption for considentiality and cryptographic techniques for message authentication are usually treated as separate techniques that may or may not be applied to protect message contents. In many cases there is a need for both confidentiality and message authentication. If treated as separate functions this may lead to doubling of cryptographic algorithms and key management. Some encryption functions may, however, give also good protection against message manipulations, while others do less well. The paper investigates how different encryption functions behave in this respect. The redundancy needed in the plain-text for detecting message manipulations is primarily supposed to be of the common error checksum type, rather than specially designed manipulation detection codes. The conclusion is that several encryption schemes will protect well against active attacks with these ''natural'' redundancy controls. Other schemes are found not to be recommendable. By choosing the right encryption scheme, message authentication may in many situations be had for free.

Encryption is a very useful method for data protection, but its use is often made unnecessarily difficult by products which are not adjusted to common situations in the real world. Products should be highly modularized, with encryption/decryption, key management and protocol-dependent adjustments clearly kept apart. Then products can be further refined to meet specific customer demands on physical security, encrypted communications between ''dumb'' and ''intelligent'' terminals and nodes, true end-to-end encryption in complicated networks, etc. All this is necessary if encryption is ever to be of real use in the computer world.

No longer prohibitively expensive, encryption of data in motion and at rest is a new potentially cost-effective thread in the fabric of controls appropriate for many medium-to-high-risk applications of computers and communications. This paper looks at recent and probable developments in commercially available encryption products, and sets forth application oriented ways in which these products are expected to be used. The reasons why and why not to use encryption are also provided.