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.

Crypto microprocessor that executes enciphered programs

Abstract: A microprocessor for executing computer programs which are stored in cipher to prevent software piracy. Such a crypto-microprocessor deciphers the enciphered program piecemeal as it executes it, so that a large enciphered program can be securely executed without disclosing the deciphered program or associated data to persons who have access to the wiring of the computer in which the crypto-microprocessor is a component. Such a device may process valuable proprietary programs and data files which are distributed in cipher on videodiscs, semiconductor memory, or other media without risk of software piracy. Various methods of encryption may be used including methods which result in the cipher of a byte being a complicated function of the byte's address in memory. Each crypto-microprocessor chip may use a unique cipher key or tables for deciphering the program, so that a program that can be executed in one chip cannot be run in any other microprocessor.

The Simeck Family of Lightweight Block Ciphers

Abstract: Two lightweight block cipher families, Simon and Speck, have been proposed by researchers from the NSA recently. In this paper, we introduce Simeck, a new family of lightweight block ciphers that combines the good design components from both Simon and Speck, in order to devise even more compact and efficient block ciphers. For Simeck32/64, we can achieve 505 GEs (before the Place and Route phase) and 549 GEs (after the Place and Route phase), with the power consumption of 0.417 \(\mu W\) in CMOS 130 nm ASIC, and 454 GEs (before the Place and Route phase) and 488 GEs (after the Place and Route phase), with the power consumption of 1.292 \(\mu W\) in CMOS 65 nm ASIC. Furthermore, all of the instances of Simeck are smaller than the ones of hardware-optimized cipher Simon in terms of area and power consumption in both CMOS 130 nm and CMOS 65 nm techniques. In addition, we also give the security evaluation of Simeck with respect to many traditional cryptanalysis methods, including differential attacks, linear attacks, impossible differential attacks, meet-in-the-middle attacks, and slide attacks. Overall, all of the instances of Simeck can satisfy the area, power, and throughput requirements in passive RFID tags.

On the Classification of 4 Bit S-Boxes

Abstract: In this paper we classify all optimal 4 bit S-boxes. Remarkably, up to affine equivalence, there are only 16 different optimal S-boxes. This observation can be used to efficiently generate optimal S-boxes fulfilling additional criteria. One result is that an S-box which is optimal against differential and linear attacks is always optimal with respect to algebraic attacks as well. We also classify all optimal S-boxes up to the so called CCZ equivalence. We furthermore generated all S-boxes fulfilling the conditions on nonlinearity and uniformity for S-boxes used in the block cipher Serpent. Up to a slightly modified notion of equivalence, there are only 14 different S-boxes. Due to this small number it is not surprising that some of the S-boxes of the Serpent cipher are linear equivalent. Another advantage of our characterization is that it eases the highly non-trivial task of choosing good S-boxes for hardware dedicated ciphers a lot.

Ciphers with Arbitrary Finite Domains

Abstract: We explore the problem of enciphering members of a finite set M where k = |M| is arbitrary (in particular, it need not be a power of two). We want to achieve this goal starting from a block cipher (which requires a message space of size N = 2n, for some n). We look at a few solutions to this problem, focusing on the case when M= [O, k - 1]. We see ciphers with arbitrary domains as a worthwhile primitive in its own right, and as a potentially useful one for making higher-level protocols.

Attacks on the RC4 stream cipher

Abstract: In this article we present some weaknesses in the RC4 cipher and their cryptographic applications. Especially we improve the attack described by Fluhrer, Mantin, Shamir (In: Selected Areas in Cryptography, 2001) in such a way, that it will work, if the weak keys described in that paper are avoided. A further attack will work even if the first 256 Byte of the output remain unused. Finally we show that variants of the RC4 algorithm like NGG and RC4A are also vulnerable by these techniques.