International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

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

Authors:
Debra L. Cook
Moti Yung
Angelos Keromytis
Download:
URL: http://eprint.iacr.org/2008/496
Search ePrint
Search Google
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.
BibTeX
@misc{eprint-2008-18055,
  title={Constructing Variable-Length PRPs and SPRPs from Fixed-Length PRPs},
  booktitle={IACR Eprint archive},
  keywords={secret-key cryptography / (strong) PRPs, block ciphers, variable-length PRPs},
  url={http://eprint.iacr.org/2008/496},
  note={shorter version will appear in Inscrypt 2008 dcook@cs.columbia.edu 14209 received 25 Nov 2008},
  author={Debra L. Cook and Moti Yung and Angelos Keromytis},
  year=2008
}