Some Observations on HC-128

Subhamoy Maitra; Goutam Paul; Shashwat Raizada

Paper 2008/499

Some Observations on HC-128

Subhamoy Maitra, Goutam Paul, and Shashwat Raizada

Abstract

In this paper, we use linear approximations of the addition modulo $2^n$ of three $n$-bit integers to identify linear approximations of $g_1, g_2$, the feedback functions of HC-128. This, in turn, shows that the process of keystream output generation of HC-128 can be well approximated by linear functions. In this direction, we show that the ``least significant bit" based distinguisher (presented by the designer himself) of HC-128 works for the complete 32-bit word. In a different note, in the line of Dunkelman's observation, we also study how HC-128 keystream words leak secret state information of the cipher due to the properties of the functions $h_1, h_2$ and present improved results.

Note: Publication information added

Metadata

Available format(s): PDF
Publication info: Published elsewhere. WCC 2009 (extended version in DCC 2011)
Keywords: Bias Cryptography Distinguishing Attack eStream Keystream Linear Approximation Stream Cipher.
Contact author(s): subho @ isical ac in
History: 2011-11-16: last of 2 revisions; 2008-12-02: received; See all versions
Short URL: https://ia.cr/2008/499
License: CC BY

BibTeX

@misc{cryptoeprint:2008/499,
      author = {Subhamoy Maitra and Goutam Paul and Shashwat Raizada},
      title = {Some Observations on {HC}-128},
      howpublished = {Cryptology {ePrint} Archive, Paper 2008/499},
      year = {2008},
      url = {https://eprint.iacr.org/2008/499}
}