Reflection ciphers

Reflection Ciphers ( Extended abstract )

This paper investigates ciphers where the set of encryption functions is identical to the set of decryption functions, which we call reflection ciphers. Equivalently, there exists a permutation P , named the coupling permutation, such that decryption under k corresponds to encryption under P (k). We show that this coupling permutation must be an involution without fixed points. Special care has...

Reflection Attacks on Product Ciphers

In this paper we describe a novel attack method on product ciphers, the reflection attack. The attack method exploits certain similarities among round functions which have not been utilized in previous self similarity attacks. We give practical examples illustrating the power of the reflection attack on several ciphers such as GOST, DEAL and some variants of DES and Magenta. Many interesting an...

Length-Doubling Ciphers and Tweakable Ciphers

We motivate and describe a mode of operation HEM (resp., THEM) that turns a n-bit blockcipher into a variable-input-length cipher (resp., tweakable cipher) that acts on strings of [n..2n − 1] bits. Both HEM and THEM are simple and intuitive and use only two blockcipher calls, while prior work at least takes three. We prove them secure in the sense of strong PRP and tweakable strong PRP, assumin...

Stream ciphers

Stream ciphers and the eSTREAM project

Stream ciphers are an important class of symmetric cryptographic algorithms. The eSTREAM project contributed significantly to the recent increase of activity in this field. In this paper, we present a survey of the eSTREAM project. We also review recent time/memory/data and time/memory/key trade-offs relevant for the generic attacks on stream ciphers.