Methods for Linear and Differential Cryptanalysis of Elastic Block Ciphers
ACISP '08 Proceedings of the 13th Australasian conference on Information Security and Privacy
A note on Cook's elastic block cipher
Proceedings of the 4th International Symposium on Information, Computer, and Communications Security
Constructing Variable-Length PRPs and SPRPs from Fixed-Length PRPs
Information Security and Cryptology
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We analyze the security of elastic block ciphers against key-recovery attacks. An elastic version of a fixed-length block cipher is a variable-length block cipher that supports any block size in the range of one to two times the length of the original block. Our method for creating an elastic block cipher involves inserting the round function of the original cipher into a substitution-permutation network. In this paper, we form a polynomial-time reduction between the elastic and original versions of the cipher by exploiting the underlying network structure. We prove that the elastic version of a cipher is secure against a given key-recovery attack if the original cipher is secure against such an attack. Our analysis is based on the general structure of elastic block ciphers (i.e., the network's structure, the composition methods between rounds in the network and the keying methodology) and is independent of the specific cipher.