750 research outputs found
Fast algebraic immunity of Boolean functions and LCD codes
Nowadays, the resistance against algebraic attacks and fast algebraic attacks
are considered as an important cryptographic property for Boolean functions
used in stream ciphers. Both attacks are very powerful analysis concepts and
can be applied to symmetric cryptographic algorithms used in stream ciphers.
The notion of algebraic immunity has received wide attention since it is a
powerful tool to measure the resistance of a Boolean function to standard
algebraic attacks. Nevertheless, an algebraic tool to handle the resistance to
fast algebraic attacks is not clearly identified in the literature. In the
current paper, we propose a new parameter to measure the resistance of a
Boolean function to fast algebraic attack. We also introduce the notion of fast
immunity profile and show that it informs both on the resistance to standard
and fast algebraic attacks. Further, we evaluate our parameter for two
secondary constructions of Boolean functions. Moreover, A coding-theory
approach to the characterization of perfect algebraic immune functions is
presented. Via this characterization, infinite families of binary linear
complementary dual codes (or LCD codes for short) are obtained from perfect
algebraic immune functions. The binary LCD codes presented in this paper have
applications in armoring implementations against so-called side-channel attacks
(SCA) and fault non-invasive attacks, in addition to their applications in
communication and data storage systems
Algorithm 959: VBF: A Library of C plus plus Classes for Vector Boolean Functions in Cryptography
VBF is a collection of C++ classes designed for analyzing vector Boolean functions (functions that map a Boolean vector to another Boolean vector) from a cryptographic perspective. This implementation uses the NTL library from Victor Shoup, adding new modules that call NTL functions and complement the existing ones, making it better suited to cryptography. The class representing a vector Boolean function can be initialized by several alternative types of data structures such as Truth Table, Trace Representation, and Algebraic Normal Form (ANF), among others. The most relevant cryptographic criteria for both block and stream ciphers as well as for hash functions can be evaluated with VBF: it obtains the nonlinearity, linearity distance, algebraic degree, linear structures, and frequency distribution of the absolute values of the Walsh Spectrum or the Autocorrelation Spectrum, among others. In addition, operations such as equality testing, composition, inversion, sum, direct sum, bricklayering (parallel application of vector Boolean functions as employed in Rijndael cipher), and adding coordinate functions of two vector Boolean functions are presented. Finally, three real applications of the library are described: the first one analyzes the KASUMI block cipher, the second one analyzes the Mini-AES cipher, and the third one finds Boolean functions with very high nonlinearity, a key property for robustness against linear attacks
Implementing Symmetric Cryptography Using Sequence of Semi-Bent Functions
Symmetric cryptography is a cornerstone of everyday digital security, where two parties must share a common key to communicate. The most common primitives in symmetric cryptography are stream ciphers and block ciphers that guarantee confidentiality of communications and hash functions for integrity. Thus, for securing our everyday life communication, it is necessary to be convinced by the security level provided by all the symmetric-key cryptographic primitives. The most important part of a stream cipher is the key stream generator, which provides the overall security for stream ciphers. Nonlinear Boolean functions were preferred for a long time to construct the key stream generator. In order to resist several known attacks, many requirements have been proposed on the Boolean functions. Attacks against the cryptosystems have forced deep research on Boolean function to allow us a more secure encryption. In this work we describe all main requirements for constructing of cryptographically significant Boolean functions. Moreover, we provide a construction of Boolean functions (semi-bent Boolean functions) which can be used in the construction of orthogonal variable spreading factor codes used in code division multiple access (CDMA) systems as well as in certain cryptographic applications
New Family of Stream Ciphers as Physically Clone-Resistant VLSI-Structures
A new large class of possible stream ciphers as keystream
generators KSGs, is presented. The sample cipher-structure-concept is based on
randomly selecting a set of 16 maximum-period Nonlinear Feedback Shift
Registers (NLFSRs). A non-linear combining function is merging the 16 selected
sequences. All resulting stream ciphers with a total state-size of 223 bits are
designed to result with the same security level and have a linear complexity
exceeding and a period exceeding . A Secret Unknown Cipher
(SUC) is created randomly by selecting one cipher from that class of
ciphers. SUC concept was presented recently as a physical security anchor to
overcome the drawbacks of the traditional analog Physically Unclonable
Functions (PUFs). Such unknown ciphers may be permanently self-created within
System-on-Chip SoC non-volatile FPGA devices to serve as a digital
clone-resistant structure. Moreover, a lightweight identification protocol is
presented in open networks for physically identifying such SUC structures in
FPGA-devices. The proposed new family may serve for lightweight realization of
clone-resistant identities in future self-reconfiguring SoC non-volatile FPGAs.
Such self-reconfiguring FPGAs are expected to be emerging in the near future
smart VLSI systems. The security analysis and hardware complexities of the
resulting clone-resistant structures are evaluated and shown to exhibit
scalable security levels even for post-quantum cryptography.Comment: 24 pages, 7 Figures, 3 Table
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