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Paper Abstract and Keywords
Presentation 2006-07-20 16:35
Possibility of the Key Recovery Attack against Py
Takanori Isobe, Toshihiro Ohigashi, Hidenori Kuwakado, Masakatu Morii (Kobe Univ.)
Abstract (in Japanese) (See Japanese page) 
(in English) Biham and Seberry have submitted the stream cipher Py to the ECRYPT
Stream Cipher Project (eSTREAM).
In this paper, we present two useful methods for the key recovery
attack against Py.
First, we show the method for finding a secret key from a part of
the initial state of Py.
In this method, the required data size of the initial state is
one fifth or less compared with the method proposed by
Kogiso, Shimoyama, and Chao.
And, the required data size of the initial state by our method
is almost equal to that of the secret key.
Additionally, we show the relation between the required data size of
the initial state and the rate of the recoverable keys by our method.
Second, we show the method to guess a part of the initial state
from other part of the initial state with high probability.
This method can reduce the computational time for reconstructing the
initial state from the keystream.
Keyword (in Japanese) (See Japanese page) 
(in English) stream cipher / Py / key recovery attack / key scheduling algorithm / / / /  
Reference Info. IEICE Tech. Rep., vol. 106, no. 175, ISEC2006-28, pp. 141-148, July 2006.
Paper # ISEC2006-28 
Date of Issue 2006-07-13 (ISEC, SITE) 
ISSN Print edition: ISSN 0913-5685
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Conference Information
Committee ISEC SITE IPSJ-CSEC  
Conference Date 2006-07-20 - 2006-07-21 
Place (in Japanese) (See Japanese page) 
Place (in English) Okayama Univ. 
Topics (in Japanese) (See Japanese page) 
Topics (in English)  
Paper Information
Registration To ISEC 
Conference Code 2006-07-ISEC-SITE-IPSJ-CSEC 
Language Japanese 
Title (in Japanese) (See Japanese page) 
Sub Title (in Japanese) (See Japanese page) 
Title (in English) Possibility of the Key Recovery Attack against Py 
Sub Title (in English)  
Keyword(1) stream cipher  
Keyword(2) Py  
Keyword(3) key recovery attack  
Keyword(4) key scheduling algorithm  
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Keyword(6)  
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Keyword(8)  
1st Author's Name Takanori Isobe  
1st Author's Affiliation Kobe University (Kobe Univ.)
2nd Author's Name Toshihiro Ohigashi  
2nd Author's Affiliation Kobe University (Kobe Univ.)
3rd Author's Name Hidenori Kuwakado  
3rd Author's Affiliation Kobe University (Kobe Univ.)
4th Author's Name Masakatu Morii  
4th Author's Affiliation Kobe University (Kobe Univ.)
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Speaker Author-1 
Date Time 2006-07-20 16:35:00 
Presentation Time 25 minutes 
Registration for ISEC 
Paper # ISEC2006-28, SITE2006-25 
Volume (vol) vol.106 
Number (no) no.175(ISEC), no.174(SITE) 
Page pp.141-148 
#Pages
Date of Issue 2006-07-13 (ISEC, SITE) 


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