A Novel Luby-Rackoff Based Cipher in a NewFeistel-Network Based LPRKES for Smart Cards

摘要

The RKES (Remotely Keyed Encryption Schemes) are greatly useful in solving the vital problem of how to do bulk encryption and decryption for high-bandwidth applications (like multimedia and video encryption) in a way that takes advantage of both the superior power of the host and the superior security of the smart card. In this way, we propose a novel length preserving (LP) RKES by using a proposed general view of Feistel-Network (FN) in which we use only two rounds in an efficient way. The proposed LPRKES needs a strong pseudorandom permutation (PRP) as its basic building block, so we introduce a new symmetric-key block cipher, with variable block and key lengths, referred to as NLMSFC (Nonlinear Matrix Structure Based Feistel Cipher), appropriate for hardware and software implementations. NLMSFC is a 3-round Luby-Rackoff construction. In this structure, robust pseudorandom functions (PF) are used to obtain a pseudorandom permutation (PRP). NLMSFC makes use of a novel PR keyed-subfunction in a matrix like structure. Extensive statistical tests are conducted upon NLMSFC and its round function in order to demonstrate their competitive diffusion, confusion and pseudorandomness characteristics. In addition NLMSFC is provably secure. At the end of this paper, we show how we can apply NLMSFC as a strong PRP in the suggested LPKES to be used for cryptographic smart cards.