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

Debra L.  Cook; Moti Yung; Angelos Keromytis

Paper 2008/496

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

Debra L. Cook, Moti Yung, and Angelos Keromytis

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.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Published elsewhere. shorter version will appear in Inscrypt 2008
Keywords: (strong) PRPs block ciphers variable-length PRPs
Contact author(s): dcook @ cs columbia edu
History: 2008-12-02: received
Short URL: https://ia.cr/2008/496
License: CC BY

BibTeX

@misc{cryptoeprint:2008/496,
      author = {Debra L.  Cook and Moti Yung and Angelos Keromytis},
      title = {Constructing Variable-Length {PRPs} and {SPRPs} from Fixed-Length {PRPs}},
      howpublished = {Cryptology {ePrint} Archive, Paper 2008/496},
      year = {2008},
      url = {https://eprint.iacr.org/2008/496}
}