Cipher

About: Cipher is a research topic. Over the lifetime, 9409 publications have been published within this topic receiving 110309 citations. The topic is also known as: cypher & cryptographic algorithm.

Practical Algebraic Attacks on the Hitag2 Stream Cipher

Abstract: Hitag2 is a stream cipher that is widely used in RFID car locks in the automobile industry. It can be seen as a (much) more secure version of the [in]famous Crypto-1 cipher that is used in MiFare Classic RFID products [14,20,15]. Recently, a specification of Hitag2 was circulated on the Internet [29]. Is this cipher secure w.r.t. the recent algebraic attacks [8,17,1,25] that allowed to break with success several LFSR-based stream ciphers? After running some computer simulations we saw that the Algebraic Immunity [25] is at least 4 and we see no hope to get a very efficient attack of this type. However, there are other algebraic attacks that rely on experimentation but nevertheless work. For example Faugere and Ars have discovered that many simple stream ciphers can be broken experimentally with Grobner bases, given an extremely small quantity of keystream, see [17]. Similarly reduced-round versions of DES [9] and KeeLoq [11,12] were broken using SAT solvers, that actually seem to outperform Grobner basis techniques. Thus, we have implemented a generic experimental algebraic attack with conversion and SAT solvers,[10,9]. As a result we are able to break Hitag2 quite easily, the full key can be recovered in a few hours on a PC. In addition, given the specific protocol in which Hitag2 cipher is used in cars, some of our attacks are practical.

System for translating encrypted data

Abstract: A system translates a first group of cipher blocks based on a first encryption key to a second group of respective cipher blocks based on a second encryption key. Respective cipher blocks of the first and second groups represent the same data. The system comprises decryption hardware for sequentially decrypting the cipher blocks of the first group based on the first key. Encryption hardware is coupled to receive decrypted blocks output from the decryption hardware and sequentially encrypts the decrypted blocks into respective cipher blocks of the second group based on the second encryption key. A control unit controls the encryption hardware to encrypt the decrypted blocks into the respective cipher blocks of the second group while the decryption hardware decrypts cipher blocks of the first group. Consequently, decryption and encryption operations occur in parallel and the translation process is expedited.

A Novel Image Encryption Algorithm Based on Improved 3D Chaotic Cat Map

Abstract: In this paper, an image encryption algorithm based on improved 3D cat map is proposed. The new algorithm employs Henon map chaotic sequence to generate control parameters of shuffling and uses improved 2D Logistic map sequence to substitute grey values. It cannot only effectively encrypt images, but also can resist cipher analyzers' attack by periodicity of cat map. Experimental results and security analysis show that the algorithm can be easily implemented and its encryption effect is satisfactory. Moreover, the algorithm possesses high security in terms of the resistance to exhaustive attack, statistical attack and cipher-text-only attack..

Hardware stream cipher with controllable chaos generator for colour image encryption

Abstract: This study presents hardware realisation of chaos-based stream cipher utilised for image encryption applications. A third-order chaotic system with signum non-linearity is implemented and a new post processing technique is proposed to eliminate the bias from the original chaotic sequence. The proposed stream cipher utilises the processed chaotic output to mask and diffuse input pixels through several stages of XORing and bit permutations. The performance of the cipher is tested with several input images and compared with previously reported systems showing superior security and higher hardware efficiency. The system is experimentally verified on XilinxVirtex 4 field programmable gate array (FPGA) achieving small area utilisation and a throughput of 3.62 Gb/s.