Please use this identifier to cite or link to this item: https://hdl.handle.net/10356/81487
Title: Analysis and Improvements of the Full Spritz Stream Cipher
Authors: Banik, Subhadeep
Isobe, Takanori
Morii, Masakatu
Keywords: RC4
Spritz
Issue Date: 2017
Source: Banik, S., Isobe, T., & Morii, M. (2017). Analysis and Improvements of the Full Spritz Stream Cipher. IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, E100.A(6), 1296-1305.
Series/Report no.: IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
Abstract: Spritz is a stream cipher proposed by Rivest and Schuldt at the rump session of CRYPTO 2014. It is intended to be a replacement of the popular RC4 stream cipher. In this paper we propose distinguishing attacks on the full Spritz, based on a short-term bias in the first two bytes of a keystream and a long-term bias in the first two bytes of every cycle of N keystream bytes, where N is the size of the internal permutation. Our attacks are able to distinguish a keystream of the full Spritz from a random sequence with samples of first two bytes produced by 244.8 multiple key-IV pairs or 260.8 keystream bytes produced by a single key-IV pair. These biases are also useful in the event of plaintext recovery in a broadcast attack. In the second part of the paper, we look at a state recovery attack on Spritz, in a special situation when the cipher enters a class of weak states. We determine the probability of encountering such a state, and demonstrate a state recovery algorithm that betters the 21400 step algorithm of Ankele et al. at Latincrypt 2015. Finally we propose a simple fix that removes the bias in the first two keystream bytes. The countermeasure requires only one additional memory access and hence does not diminish software performance substantially, and in fact the loss in software speed is only around 1.5%.
URI: https://hdl.handle.net/10356/81487
http://hdl.handle.net/10220/43486
ISSN: 0916-8508
DOI: 10.1587/transfun.E100.A.1296
Rights: © 2017 Institute of Electronics, Information and Communication Engineers (IEICE). This paper was published in IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences and is made available as an electronic reprint (preprint) with permission of Institute of Electronics, Information and Communication Engineers (IEICE). The published version is available at: [http://dx.doi.org/10.1587/transfun.E100.A.1296]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:TL Journal Articles

Files in This Item:
File Description SizeFormat 
Analysis and Improvements of the Full Spritz Stream Cipher.pdf870.23 kBAdobe PDFThumbnail
View/Open

SCOPUSTM   
Citations 20

1
checked on Aug 31, 2020

WEB OF SCIENCETM
Citations

1
checked on Oct 17, 2020

Page view(s)

153
checked on Oct 21, 2020

Download(s)

96
checked on Oct 21, 2020

Google ScholarTM

Check

Altmetric


Plumx

Items in DR-NTU are protected by copyright, with all rights reserved, unless otherwise indicated.