SHACAL

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{{Infobox block cipher

| name = SHACAL

| image = Image:SHACAL.png

| caption =

| designers = Helena Handschuh, David Naccache

| publish date =

| derived from = SHA-1, SHA-256

| derived to =

| related to = Crab

| certification = NESSIE (SHACAL-2)

| key size = 128 to 512 bits

| block size = 160 bits (SHACAL-1),
256 bits (SHACAL-2)

| structure = Cryptographic hash function

| rounds = 80

| cryptanalysis =

}}

SHACAL-1 (originally simply SHACAL) is a 160-bit block cipher based on SHA-1, and supports keys from 128-bit to 512-bit. SHACAL-2 is a 256-bit block cipher based upon the larger hash function SHA-256.

Both SHACAL-1 and SHACAL-2 were selected for the second phase of the NESSIE project. However, in 2003, SHACAL-1 was not recommended for the NESSIE portfolio because of concerns about its key schedule, while SHACAL-2 was finally selected as one of the 17 NESSIE finalists.

Design

SHACAL-1 is based on the following observation of SHA-1:

The hash function SHA-1 is designed around a compression function. This function takes as input a 160-bit state and a 512-bit data word and outputs a new 160-bit state after 80 rounds. The hash function works by repeatedly calling this compression function with successive 512-bit data blocks and each time updating the state accordingly. This compression function is easily invertible if the data block is known, i.e. given the data block on which it acted and the output of the compression function, one can compute that state that went in.

SHACAL-1 turns the SHA-1 compression function into a block cipher by using the state input as the data block and using the data input as the key input. In other words, SHACAL-1 views the SHA-1 compression function as an 80-round, 160-bit block cipher with a 512-bit key. Keys shorter than 512 bits are supported by padding them with zeros. SHACAL-1 is not intended to be used with keys shorter than 128 bits.

Security of SHACAL-1

In the paper "Related-key rectangle attack on the full SHACAL-1", 2006, Orr Dunkelman, Nathan Keller and Jongsung Kim presented a related-key rectangle attack on the full 80 rounds of SHACAL-1.

In the paper "Differential and Rectangle Attacks on Reduced-Round SHACAL-1", Jiqiang Lu, Jongsung Kim, Nathan Keller and Orr Dunkelman presented rectangle attacks on the first 51 rounds and a series of 52 inner rounds of SHACAL-1 and presented differential attacks on the first 49 rounds and a series of 55 inner rounds of SHACAL-1. These are the best currently known cryptanalytic results on SHACAL-1 in a single key attack scenario.

Security of SHACAL-2

In the paper "Related-Key Rectangle Attack on 42-Round SHACAL-2", Jiqiang Lu, Jongsung Kim, Nathan Keller, Orr Dunkelman presented a related-key rectangle attack on 42-round SHACAL-2.

In 2008 Lu and Kim presented a related-key rectangle attack on 44-round SHACAL-2. This is the best currently known cryptanalytic result on SHACAL-2.

References

{{cite conference

|author = Eli Biham, Orr Dunkelman, Nathan Keller

|title = Rectangle Attacks on 49-Round SHACAL-1

|conference = 10th International Workshop on Fast Software Encryption (FSE '03)

|pages = 22–35

|publisher = Springer-Verlag

|date = February 2003

|location = Lund

|url = http://vipe.technion.ac.il/~orrd/crypt/shacal.pdf

|access-date = 2007-07-02

|url-status = dead

|archive-url = https://web.archive.org/web/20070926201253/http://vipe.technion.ac.il/~orrd/crypt/shacal.pdf

|archive-date = 2007-09-26

}}

{{cite conference

| author = Helena Handschuh, Lars R. Knudsen, Matthew J. B. Robshaw

| title = Analysis of SHA-1 in Encryption Mode

| conference = CT-RSA 2001, The Cryptographer's Track at RSA Conference 2001

| pages = 70–83

| publisher = Springer-Verlag

| date = April 2001

| location = San Francisco, California

| url = http://citeseer.ist.psu.edu/693913.html

| format = PDF/PostScript

| access-date = 2007-07-02 }}

{{cite conference

| conference = 4th International Conference on Cryptology in India (INDOCRYPT 2003)

| pages = 97–106

| publisher = Springer-Verlag

| date = December 2003

| location = New Delhi }}

{{cite conference

| conference = INDOCRYPT 2004

| pages = 175–190

| publisher = Springer-Verlag

| date = December 2004

| location = Chennai

| url = https://www.researchgate.net/publication/239578679}}

{{cite conference

| conference = 9th Australasian Conference on Information Security and Privacy (ACISP 2004)

| pages= 123–136

| publisher = Springer-Verlag

| date = July 2004

| location = Sydney }}

{{cite conference

| conference = ASIACRYPT 2002

| pages = 243–253

| publisher = Springer-Verlag

| date = December 2002

| location = Queenstown, New Zealand }}

{{cite conference

|author = Markku-Juhani Olavi Saarinen

|title = Cryptanalysis of Block Ciphers Based on SHA-1 and MD5

|conference = FSE '03

|pages = 36–44

|publisher = Springer-Verlag

|date = February 2003

|location = Lund

|url = http://www.m-js.com/doc/saarinen_sha_md5.pdf

|access-date = 2007-07-02

|url-status = dead

|archive-url = https://web.archive.org/web/20061224183009/http://www.m-js.com/doc/saarinen_sha_md5.pdf

|archive-date = 2006-12-24

}}

{{cite conference

| conference = ACISP 2004

| pages = 110–122

| publisher = Springer-Verlag

| date = July 2004

| location = Sydney }}

{{cite conference

|author1 = Jiqiang Lu

|author2 = Jongsung Kim

|author3 = Nathan Keller

|author4 = Orr Dunkelman

|title = Related-Key Rectangle Attack on 42-Round SHACAL-2

|conference = Information Security, 9th International Conference (ISC 2006)

|pages = 85–100

|publisher = Springer-Verlag

|year = 2006

|location = Samos

|url = http://www.isg.rhul.ac.uk/~jiqiang/Papers/ISC2006.pdf

|access-date = 2007-07-02

|url-status = dead

|archive-url = https://web.archive.org/web/20060925104142/http://www.isg.rhul.ac.uk/~jiqiang/Papers/ISC2006.pdf

|archive-date = 2006-09-25

}}

{{cite conference

| conference = INDOCRYPT 2006

| pages = 17–31

| publisher = Springer-Verlag

| date = December 2006

| location = Kolkata

| url = http://homes.esat.kuleuven.be/~kjongsun/papers/indocrypt2006.pdf

| access-date = 2007-07-02 }}

{{cite conference

|author1=O. Dunkelman |author2=N. Keller |author3=J. Kim | title = Related-key rectangle attack on the full SHACAL-1

| conference = Selected Areas in Cryptography (SAC 2006), to appear

| pages = 16 pages

| publisher = Springer-Verlag

| date = August 2006

| location = Montreal

| url = http://www.cosic.esat.kuleuven.be/publications/article-852.ps

| format = PostScript

| access-date = 2007-07-02 }}

{{cite journal

|author1=Jiqiang Lu |author2=Jongsung Kim |title= Attacking 44 Rounds of the SHACAL-2 Block Cipher Using Related-Key Rectangle Cryptanalysis

| journal=IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences

| pages = 2599–2596

| publisher = IEICE

| date = September 2008

| url = https://sites.google.com/site/jiqiang/IEICE91A.pdf

| access-date = 2012-01-30 }}

External links

[https://web.archive.org/web/20080604000934/http://www.ma.huji.ac.il/~nkeller/ Nathan Keller's homepage]

Category:Block ciphers