Constructing Variable-Length PRPs and SPRPs from Fixed-Length PRPs

Debra L Cook,Angelos Keromytis,Moti Yung

doi:10.1007/978-3-642-01440-6_14

Constructing Variable-Length PRPs and SPRPs from Fixed-Length PRPs

Debra L Cook, Angelos Keromytis + Show 1 more

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https://doi.org/10.1007/978-3-642-01440-6_14

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Publication Date: Jan 1, 2009

Citations: 8

Affiliation: Columbia University, Google (United States)

#Pseudorandom Permutations #Strong Pseudorandom Permutations + Show 8 more

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Abstract

We create variable-length pseudorandom permutations (PRPs) and strong PRPs (SPRPs) accepting any input length chosen from the range of b to 2b bits from fixed-length, b -bit PRPs. We utilize the elastic network that underlies the recently introduced concrete design of elastic block ciphers, exploiting it as a network of PRPs. We prove that three and four-round elastic networks are variable-length PRPs and five-round elastic networks are variable-length SPRPs, accepting any input length that is fixed in the range of b to 2b bits, when the round functions are independently chosen fixed-length PRPs on b bits. We also prove that these are the minimum number of rounds required.

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