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 Computer Science , 2012, Abstract: In Europe and North America, the most widely used stream cipher to ensure privacy and confidentiality of conversations in GSM mobile phones is the A5/1. In this paper, we present a new attack on the A5/1 stream cipher with an average time complexity of 2^(48.5), which is much less than the brute-force attack with a complexity of 2^(64). The attack has a 100% success rate and requires about 5.65GB storage. We provide a detailed description of our new attack along with its implementation and results.
 Journal of Networks , 2010, DOI: 10.4304/jnw.5.1.75-87 Abstract: This paper presents a new stream cipher for data security, which is based on permutation of the data and replacement of the data values. Permutation is done by scan patterns generated by the SCAN approach. The replacement of data values using variable ordered recursive cellular automata (CA) substitutions. To achieve this aim, an encryption-specific SCAN technique was firstly developed, 2-D hybrid CA was next built, and then 1st-ordered and 2nd-ordered generalized CA transforms were introduced to build variable ordered recursive CA substitutions. The proposed stream cipher satisfies the properties of confusion and diffusion because of characteristics of the SCAN and the CA substitutions are flexible. Moreover, the characteristics of the proposed stream cipher are loss-less, symmetric private key, very large number of security keys (number of possible security keys is more than 9568 10 ~ 14785 10 - according to the size of the 2-D von Neumann CA), and key-dependent pixel value replacement. Experimental results obtained using some color images clearly demonstrate the strong performance of the proposed stream cipher. This paper also shows the DSP+FPGA implementation of the proposed stream cipher for the real-time image security.
 International Journal of Advanced Computer Sciences and Applications , 2012, Abstract: In this work a new algorithm for encryption image is introduced. This algorithm makes it possible to cipher and decipher images by guaranteeing a maximum security. The algorithm introduced is based on stream cipher with nonlinear filtering function. The Boolean function used in this algorithm is resilient function satisfying all the cryptographic criteria necessary carrying out the best possible compromises. In order to evaluate performance, the proposed algorithm was measured through a series of tests. Experimental results illustrate that the scheme is highly key sensitive, highly resistance to the noises and shows a good resistance against brute-force, Berlekamp-Massey Attack and algebraic attack.
 Computer Science , 2014, Abstract: In a system that performs both encryption and lossy compression, the conventional way is to compress first and then encrypt the compressed data. This separation approach proves to be optimal. In certain applications where sensitive information should be protected as early as possible, it is preferable to perform encryption first and then compress the encrypted data, which leads to the concept of the reversed system. Johnson et al. proposed an achievability scheme for the reversed system that has a modulo-sum encryption followed by a compression using Wyner-Ziv distributed source coding with side information. However, this reversed system performs worse than the conventional system in the sense that it requires more compression rate and secrecy key rate. In this paper, we propose a new achievability scheme for the reverse system where encryption is conducted by a permutation cipher and then the encrypted data is compressed using the optimal rate-distortion code. The proposed scheme can achieve the optimal compression rate and secret key rate, and therefore shows that reversing the order of encryption and compression does not necessarily compromise the performance of an encryption-compression system. The proposed system attains weak secrecy, and we show that the information leakage is mainly contributed by the type information of the sequence, which is not concealed by the permutation cipher. Given the type of the sequence, the rest of the information leakage vanishes exponentially.
 International Journal of Innovative Technology and Exploring Engineering , 2013, Abstract: Stream ciphers are more efficient as compared to block ciphers, when implemented in hardware environment, like Field Programmable Gate Array (FPGA). In this paper a high throughput hardware implementation of ZUC stream cipher is presented. ZUC is a stream cipher that forms the heart of the 3GPP confidentiality algorithm 128-EEA3 and the 3GPP integrity algorithm 128-EIA3. This algorithm offers reliable security services in Long Term Evolution networks (LTE), which is a candidate standard for the 4G network. A detailed hardware implementation is presented in order to reach satisfactory performance results in LTE systems. The design is being coded using VHDL language and for the hardware implementation, a XILINX Virtex-5 FPGA is used [1][2].
 An-Ping Li Computer Science , 2008, Abstract: In this paper, we will propose a new synchronous stream cipher named DICING, which can be viewed as a clock-controlled one but with a new mechanism of altering steps. It has satisfactory performance and there have not been found weakness for the known attacks, the key sizes can be 128bits and 256bits respectively.
 Computer Science , 2001, Abstract: This paper discusses mixing of chaotic systems as a dependable method for secure communication. Distribution of the entropy function for steady state as well as plaintext input sequences are analyzed. It is shown that the mixing of chaotic sequences results in a sequence that does not have any state dependence on the information encrypted by them. The generated output states of such a cipher approach the theoretical maximum for both complexity measures and cycle length. These features are then compared with some popular ciphers.
 Vladimir Anashin Computer Science , 2006, Abstract: The paper develops a novel approach to stream cipher design: Both the state update function and the output function of the corresponding pseudorandom generators are compositions of arithmetic and bitwise logical operations, which are standard instructions of modern microprocessors. Moreover, both the state update function and the output function are being modified dynamically during the encryption. Also, these compositions could be keyed, so the only information available to an attacker is that these functions belong to some exponentially large class. The paper shows that under rather loose conditions the output sequence is uniformly distributed, achieves maximum period length and has high linear complexity and high $\ell$-error linear complexity. Ciphers of this kind are flexible: One could choose a suitable combination of instructions to obtain due performance without affecting the quality of the output sequence. Finally, some evidence is given that a key recovery problem for (reasonably designed) stream ciphers of this kind is intractable up to plausible conjectures.
 Computer Science , 2012, Abstract: Two recent Hill cipher modifications which iteratively use interweaving and interlacing are considered. We show that strength of these ciphers is due to non-linear transformation used in them (bit-level permutations). Impact of number of iterations on the avalanche effect is investigated. We propose two Hill cipher modifications using column swapping and arbitrary permutation with significantly less computational complexity (2 iterations are used versus 16). The proposed modifications decrease encryption time while keeping the strength of the ciphers. Numerical experiments for two proposed ciphers indicate that they can provide a substantial avalanche effect.
 Journal of Software , 2011, DOI: 10.4304/jsw.6.10.1961-1968 Abstract: To solve the problem of traditional stream ciphers can not transmit through the public channel and the construction of high-strength cipher key generator, the paper presents the minimum power clock function driven by a parallel clock-control sequence and chaotic cascade function made of multiple Logistic function, which are used to built the self-reference model and chaotic module; it designs an adapt controller independent of the key generator and encrypt module, achieve controlling encryption and transmission process by multi-threaded code; it makes a high-strength key generator with sure differential transformation and pseudo-random horizontal level disturbance wheel key method of AES and S-box of Camellia, which makes the sub-key and the key generator’s internal station become vogue and uncertain within controlled area that does not depend on the secret channel, the model achieves an exponential growth in the key space and the same application scope of traditional stream cipher model. The new protocol model features can be seen under the actual operation of modifying RC4 and real-time RC5 algorithm.
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