Difference between revisions of "Fugue"

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| Type of Analysis || Hash Function Part || Hash Size (n) || Parameters/Variants || Compression Function Calls || Memory Requirements ||  Reference  
 
| Type of Analysis || Hash Function Part || Hash Size (n) || Parameters/Variants || Compression Function Calls || Memory Requirements ||  Reference  
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| observations || hash || 256 ||  (2,5,13)  || -  || - || [http://www2.mat.dtu.dk/pg-projects/Fugue-256-analysis-v1.pdf Gauravaram et al.]
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| meet-in-the-middle preimage || hash || 256 ||  (2,5,13)  || 2<sup>416</sup>  || 2<sup>416</sup> || [http://www2.mat.dtu.dk/pg-projects/Fugue-256-analysis-v1.pdf Gauravaram et al.]
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| distinguisher || output transformation || 256 ||  (2,5,11.5), keyed  || 2<sup>8</sup>  || - || [http://www2.mat.dtu.dk/pg-projects/Fugue-256-analysis-v1.pdf Gauravaram et al.]
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| semi-free-start collision || compression function || 256 || (2,1,5) || example || - || [http://csrc.nist.gov/groups/ST/hash/sha-3/Round2/Aug2010/documents/papers/TURAN_Paper_Erdener.pdf Turan,Uyan]
 
| semi-free-start collision || compression function || 256 || (2,1,5) || example || - || [http://csrc.nist.gov/groups/ST/hash/sha-3/Round2/Aug2010/documents/papers/TURAN_Paper_Erdener.pdf Turan,Uyan]
 
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<sup>(1)</sup>The Fugue team commented on these distinguishers in [http://ehash.iaik.tugraz.at/uploads/d/d7/Fugue_designers_reply_to_AumassonPhan_Distinguisher.txt this note] using [http://ehash.iaik.tugraz.at/uploads/c/c8/Fig7.pdf this figure].
 
<sup>(1)</sup>The Fugue team commented on these distinguishers in [http://ehash.iaik.tugraz.at/uploads/d/d7/Fugue_designers_reply_to_AumassonPhan_Distinguisher.txt this note] using [http://ehash.iaik.tugraz.at/uploads/c/c8/Fig7.pdf this figure].
  
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<bibtex>
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@misc{fugueGKBW11,
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  author = {Praveen Gauravaram and Lars R.Knudsen and Nasour Bagher and Lei Wei},
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  title = {Improved Security Analysis of Fugue-256 (a second round SHA-3 candidate)},
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  howpublished = {Proceedings of ACISP (short paper), 2011},
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  year = {2011},
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  url = {http://www2.mat.dtu.dk/pg-projects/Fugue-256-analysis-v1.pdf},
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  abstract = {Fugue is a cryptographic hash function designed by Halevi, Hall and Jutla and was one of the fourteen hash algorithms of the second round of NIST's SHA3 hash competition. We consider Fugue-256, the 256-bit instance of Fugue. Fugue-256 updates a state of 960 bits with a \textit{round transformation} \textbf{R} parametrized by a 32-bit message word. Twice in every state update, this transform invokes an AES like round function called \textbf{SMIX}. Fugue-256 relies on a \textit{final transformation} \textbf{G} to output digests that look random. \textbf{G} has 18 rounds where each round invokes \textbf{SMIX} twice and finally the 960-bit output of the \textbf{G} transform is mapped with a transform $\tau$ to a 256-bit digest. \\ In this paper, we present some improved as well as new analytical results of Fugue-256 (with length-padding). First we improve Aumasson and Phans' integral distinguisher on the 5.5 rounds of the \textbf{G} transform to 16.5 rounds, thus showing \textit{weak} diffusion in the \textbf{G} transform. Next we improve the designers' meet-in-the-middle preimage attack on Fugue-256 from $2^{480}$ time and memory to $2^{416}$. Next we study the security of Fugue-256 against free-start distinguishers and free-start collisions. In this direction, we use an improved variant of the differential characteristic of the \textbf{G} transform shown by the designers to present an efficient distinguisher for the $\tau(\mathbf{G})(.)$ transform showing another \textit{weak} diffusion property of \textbf{G}. We then extend this distinguisher to some interesting practical free-start distinguishers and free-start collisions for the length padded Fugue-256 in $2^{33}$ complexity. Finally, we show that free-start collision attacks on the length-padded Fugue-256 can be found in just $\mathcal{O}(1)$ \textit{without} relying on the differential properties of the \textbf{G} transform and even \textit{without} inverting it.}
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}
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</bibtex>
  
 
<bibtex>
 
<bibtex>

Latest revision as of 09:05, 12 July 2011

1 The algorithm


Shai Halevi, William E. Hall, Charanjit S. Jutla - The Hash Function Fugue

,2009
http://domino.research.ibm.com/comm/research_projects.nsf/pages/fugue.index.html/$FILE/fugue_09.pdf
Bibtex
Author : Shai Halevi, William E. Hall, Charanjit S. Jutla
Title : The Hash Function Fugue
In : -
Address :
Date : 2009

Shai Halevi, William E. Hall, Charanjit S. Jutla - The Hash Function Fugue

,2008
http://domino.research.ibm.com/comm/research_projects.nsf/pages/fugue.index.html/$FILE/NIST-submission-Oct08-fugue.pdf
Bibtex
Author : Shai Halevi, William E. Hall, Charanjit S. Jutla
Title : The Hash Function Fugue
In : -
Address :
Date : 2008


2 Cryptanalysis

We distinguish between two cases: results on the complete hash function, and results on underlying building blocks.

A description of the tables is given here.

Recommended security parameters: (k,r,t) = (2,5,13) for (n=224,256); (k,r,t) = (3,5,13) for (n=384); (k,r,t) = (4,8,13) for (n=512)

2.1 Hash function

Here we list results on the hash function according to the NIST requirements. The only allowed modification is to change the security parameter.

Type of Analysis Hash Size (n) Parameters Compression Function Calls Memory Requirements Reference


2.2 Building blocks

Here we list results on underlying building blocks, and the hash function modified by other means than the security parameter.

Note that these results assume more direct control or access over some internal variables (aka. free-start, pseudo, compression function, block cipher, or permutation attacks).

Type of Analysis Hash Function Part Hash Size (n) Parameters/Variants Compression Function Calls Memory Requirements Reference
observations hash 256 (2,5,13) - - Gauravaram et al.
meet-in-the-middle preimage hash 256 (2,5,13) 2416 2416 Gauravaram et al.
distinguisher output transformation 256 (2,5,11.5), keyed 28 - Gauravaram et al.
semi-free-start collision compression function 256 (2,1,5) example - Turan,Uyan
semi-free-start near-collision compression function 256 (2,2,10) example - Turan,Uyan
distinguisher(1) output transformation 256 1 - Aumasson,Phan
distinguisher output transformation 256 (2,5,0.5), keyed 28 - Aumasson,Phan
internal collision hash function 256 (2,5,13) 2352 2352 Khovratovich
internal collision hash function 512 (4,8,13) 2480 2480 Khovratovich

(1)The Fugue team commented on these distinguishers in this note using this figure.


Praveen Gauravaram, Lars R.Knudsen, Nasour Bagher, Lei Wei - Improved Security Analysis of Fugue-256 (a second round SHA-3 candidate)

,2011
http://www2.mat.dtu.dk/pg-projects/Fugue-256-analysis-v1.pdf
Bibtex
Author : Praveen Gauravaram, Lars R.Knudsen, Nasour Bagher, Lei Wei
Title : Improved Security Analysis of Fugue-256 (a second round SHA-3 candidate)
In : -
Address :
Date : 2011

Meltem Sönmez Turan, Erdener Uyan - Practical Near-Collisions for Reduced Round Blake, Fugue, Hamsi and JH

,2010
http://csrc.nist.gov/groups/ST/hash/sha-3/Round2/Aug2010/documents/papers/TURAN_Paper_Erdener.pdf
Bibtex
Author : Meltem Sönmez Turan, Erdener Uyan
Title : Practical Near-Collisions for Reduced Round Blake, Fugue, Hamsi and JH
In : -
Address :
Date : 2010

Jean-Philippe Aumasson, Raphael C.-W. Phan - Analysis of Fugue-256

,2010
http://ehash.iaik.tugraz.at/uploads/c/cd/Fugue_path.pdf
Bibtex
Author : Jean-Philippe Aumasson, Raphael C.-W. Phan
Title : Analysis of Fugue-256
In : -
Address :
Date : 2010

Dmitry Khovratovich - Cryptanalysis of hash functions with structures

,2009
http://cryptolux.org/mediawiki/uploads/9/99/Struct2.pdf
Bibtex
Author : Dmitry Khovratovich
Title : Cryptanalysis of hash functions with structures
In : -
Address :
Date : 2009
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