1,253 research outputs found
Doubly Perfect Nonlinear Boolean Permutations
Due to implementation constraints the XOR operation is widely used in order
to combine plaintext and key bit-strings in secret-key block ciphers. This
choice directly induces the classical version of the differential attack by the
use of XOR-kind differences. While very natural, there are many alternatives to
the XOR. Each of them inducing a new form for its corresponding differential
attack (using the appropriate notion of difference) and therefore block-ciphers
need to use S-boxes that are resistant against these nonstandard differential
cryptanalysis. In this contribution we study the functions that offer the best
resistance against a differential attack based on a finite field
multiplication. We also show that in some particular cases, there are robust
permutations which offers the best resistant against both multiplication and
exponentiation base differential attacks. We call them doubly perfect nonlinear
permutations
Steganography from weak cryptography
We introduce a problem setting which we call ``the freedom fighters'
problem''. It subtly differs from the prisoners' problem. We propose a
steganographic method that allows Alice and Bob to fool Wendy the warden in
this setting. Their messages are hidden in encryption keys. The recipient has
no prior knowledge of these keys, and has to cryptanalyze ciphertexts in order
to recover them. We show an example of the protocol and give a partial security
analysis
Group theory in cryptography
This paper is a guide for the pure mathematician who would like to know more
about cryptography based on group theory. The paper gives a brief overview of
the subject, and provides pointers to good textbooks, key research papers and
recent survey papers in the area.Comment: 25 pages References updated, and a few extra references added. Minor
typographical changes. To appear in Proceedings of Groups St Andrews 2009 in
Bath, U
Error Function Attack of chaos synchronization based encryption schemes
Different chaos synchronization based encryption schemes are reviewed and
compared from the practical point of view. As an efficient cryptanalysis tool
for chaos encryption, a proposal based on the Error Function Attack is
presented systematically and used to evaluate system security. We define a
quantitative measure (Quality Factor) of the effective applicability of a chaos
encryption scheme, which takes into account the security, the encryption speed,
and the robustness against channel noise. A comparison is made of several
encryption schemes and it is found that a scheme based on one-way coupled
chaotic map lattices performs outstandingly well, as judged from Quality
Factor
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