Universal homophonic coding scheme using differential encoding and interleaving

Abstract

A universal homophonic coding scheme is introduced which combines properties of differential encoding and homophonic symbol interleaving. The use of a uniform random interleaver is discussed and it is argued that asymptotically, when the interleaver length grows to infinity, the homophonic coding scheme generates a sequence of independent and uniformly distributed binary digits. For practical reasons, an interleaver with a complexity that grows linearly with its length is proposed. As a consequence, both the generation and the recovery of the digits produced by the proposed universal homophonic coding scheme are easy to implement. Validation tests for this new universal homophonic coding scheme were performed using the statistical test suite IR 6483 available from the National Institute of Standards and Technology, USA, and the corresponding computer simulation results are presented. The statistical tests demonstrate that the performance of the proposed universal homophonic coding scheme is at least as good as that of other published schemes, however with a significant reduction in plaintext expansion.