Whirlpool (hash function)

In computer science and cryptography, Whirlpool (sometimes styled WHIRLPOOL) is a cryptographic hash function. It was designed by Vincent Rijmen (co-creator of the Advanced Encryption Standard) and Paulo S. L. M. Barreto, who first described it in 2000.

The hash has been recommended by the NESSIE project. It has also been adopted by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) as part of the joint ISO/IEC 10118-3 international standard.

DesignersVincent Rijmen, Paulo S. L. M. Barreto
First published2000, 2001, 2003
Derived fromSquare, AES
Digest sizes512 bits
Security claimsLarge hashsum size
Best public cryptanalysis
In 2009, a rebound attack was announced that presents full collisions against 4.5 rounds of Whirlpool in 2120 operations, semi-free-start collisions against 5.5 rounds in 2120 time and semi-free-start near-collisions against 7.5 rounds in 2128 time.[1]

Design features

Messier51 sRGB
The Whirlpool Galaxy (M51), which inspired the name of the algorithm.[2]

Whirlpool is a hash designed after the Square block cipher, and is considered to be in that family of block cipher functions.

Whirlpool is a Miyaguchi-Preneel construction based on a substantially modified Advanced Encryption Standard (AES).

Whirlpool takes a message of any length less than 2256 bits and returns a 512-bit message digest.[3]

The authors have declared that

"WHIRLPOOL is not (and will never be) patented. It may be used free of charge for any purpose."[2]

Version changes

The original Whirlpool will be called Whirlpool-0, the first revision of Whirlpool will be called Whirlpool-T and the latest version will be called Whirlpool in the following test vectors.

  • In the first revision in 2001, the S-box was changed from a randomly generated one with good cryptographic properties to one which has better cryptographic properties and is easier to implement in hardware.
  • In the second revision (2003), a flaw in the diffusion matrix was found that lowered the estimated security of the algorithm below its potential.[4] Changing the 8x8 rotating matrix constants from (1, 1, 3, 1, 5, 8, 9, 5) to (1, 1, 4, 1, 8, 5, 2, 9) solved this issue.

Internal structure

The Whirlpool hash function is a Merkle–Damgård construction based on an AES-like block cipher W in Miyaguchi–Preneel mode.[2]

The block cipher W consists of an 8×8 state matrix of bytes, for a total of 512 bits.

The encryption process consists of updating the state with four round functions over 10 rounds. The four round functions are SubBytes (SB), ShiftColumns (SC), MixRows (MR) and AddRoundKey (AK). During each round the new state is computed as .


The SubBytes operation applies a non-linear permutation (the S-box) to each byte of the state independently. The 8-bit S-box is composed of 3 smaller 4-bit S-boxes.


The ShiftColumns operation cyclically shifts each byte in each column of the state. Column j has its bytes shifted downwards by j positions.


The MixRows operation is a right-multiplication of each row by an 8×8 matrix over . The matrix is chosen such that the branch number (an important property when looking at resistance to differential cryptanalysis) is 9, which is maximal.


The AddRoundKey operation uses bitwise xor to add a key calculated by the key schedule to the current state. The key schedule is identical to the encryption itself, except the AddRoundKey function is replaced by an AddRoundConstant function that adds a predetermined constant in each round.

Whirlpool hashes

The Whirlpool algorithm has undergone two revisions since its original 2000 specification.

People incorporating Whirlpool will most likely use the most recent revision of Whirlpool; while there are no known security weaknesses in earlier versions of Whirlpool, the most recent revision has better hardware implementation efficiency characteristics, and is also likely to be more secure. As mentioned earlier, it is also the version adopted in the ISO/IEC 10118-3 international standard.

The 512-bit (64-byte) Whirlpool hashes (also termed message digests) are typically represented as 128-digit hexadecimal numbers.
The following demonstrates a 43-byte ASCII input (not including quotes) and the corresponding Whirlpool hashes:

Version Input String Computed Hash
Whirlpool-0 "The quick brown fox jumps over the lazy dog"
Whirlpool-T "The quick brown fox jumps over the lazy dog"
Whirlpool "The quick brown fox jumps over the lazy dog"

Even a small change in the message will (with an extremely high probability of ) result in a different hash, which will usually look completely different just like two unrelated random numbers do. The following demonstrates the result of changing the previous input by a single letter (a single bit, even, in ASCII-compatible encodings), replacing d with e:

Version Input String Computed Hash
Whirlpool-0 "The quick brown fox jumps over the lazy eog"
Whirlpool-T "The quick brown fox jumps over the lazy eog"
Whirlpool "The quick brown fox jumps over the lazy eog"

The hash of a zero-length string is:

Version Input String Computed Hash
Whirlpool-0 ""
Whirlpool-T ""
Whirlpool ""


The authors provide reference implementations of the Whirlpool algorithm, including a version written in C and a version written in Java.[2] These reference implementations have been released into the public domain.[2]


Two of the first widely used mainstream cryptographic programs that started using Whirlpool were FreeOTFE, followed by TrueCrypt in 2005.

VeraCrypt (a fork of TrueCrypt) included Whirlpool (the final version) as one of its supported hash algorithms.[5]

See also


  1. ^ Florian Mendel1, Christian Rechberger, Martin Schläffer, Søren S. Thomsen (2009-02-24). The Rebound Attack: Cryptanalysis of Reduced Whirlpool and Grøstl (pdf). Fast Software Encryption: 16th International Workshop.CS1 maint: Multiple names: authors list (link)
  2. ^ a b c d e Paulo S. L. M. Barreto (2008-11-25). "The WHIRLPOOL Hash Function". Archived from the original on 2017-11-29. Retrieved 2018-08-09.
  3. ^ Barreto, Paulo S. L. M. & Rijmen, Vincent (2003-05-24). "The WHIRLPOOL Hashing Function". Archived from the original (ZIP) on 2017-10-26. Retrieved 2018-08-09.
  4. ^ Kyoji, Shibutani & Shirai, Taizo (2003-03-11). "On the diffusion matrix employed in the Whirlpool hashing function" (PDF). Retrieved 2018-08-09.
  5. ^ "Whirlpool". VeraCrypt Documentation. IDRIX. Retrieved 2018-08-09.

External links

AES instruction set

An Advanced Encryption Standard instruction set is now integrated into many processors. The purpose of the instruction set is to improve the speed (as well as the resistance to side-channel attacks) of applications performing encryption and decryption using Advanced Encryption Standard (AES). They are often implemented as instructions implementing a single round of AES along with a special version for the last round which has a slightly different method.

Advanced Encryption Standard

The Advanced Encryption Standard (AES), also known by its original name Rijndael (Dutch pronunciation: [ˈrɛindaːl]), is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology (NIST) in 2001.AES is a subset of the Rijndael block cipher developed by two Belgian cryptographers, Vincent Rijmen and Joan Daemen, who submitted a proposal to NIST during the AES selection process. Rijndael is a family of ciphers with different key and block sizes.

For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.

AES has been adopted by the U.S. government and is now used worldwide. It supersedes the Data Encryption Standard (DES), which was published in 1977. The algorithm described by AES is a symmetric-key algorithm, meaning the same key is used for both encrypting and decrypting the data.

In the United States, AES was announced by the NIST as U.S. FIPS PUB 197 (FIPS 197) on November 26, 2001. This announcement followed a five-year standardization process in which fifteen competing designs were presented and evaluated, before the Rijndael cipher was selected as the most suitable (see Advanced Encryption Standard process for more details).

AES became effective as a federal government standard on May 26, 2002, after approval by the Secretary of Commerce. AES is included in the ISO/IEC 18033-3 standard. AES is available in many different encryption packages, and is the first (and only) publicly accessible cipher approved by the National Security Agency (NSA) for top secret information when used in an NSA approved cryptographic module (see Security of AES, below).

List of cryptographers

List of cryptographers.

Paulo S. L. M. Barreto

Paulo S. L. M. Barreto (born 1965) is a Brazilian cryptographer and one of the designers of the Whirlpool hash function and the block ciphers Anubis and KHAZAD, together with Vincent Rijmen. He has also co-authored a number of research works on elliptic curve cryptography and pairing-based cryptography, including the eta pairing technique,identity-based cryptographic protocols,

and the family of Barreto-Naehrig (BN) pairing-friendly elliptic curves.

More recently he has been focusing his research on post-quantum cryptography, being one of the discoverers of quasi-dyadic codes

and quasi-cyclic moderate-density parity-check (QC-MDPC) codes

to instantiate the McEliece and Niederreiter cryptosystems and related schemes.

His paper "Efficient Algorithms for Pairing-Based Cryptosystems", jointly written with Hae Y. Kim, Ben Lynn and Mike Scott and presented at the Crypto 2002 conference, has been identified in March 2005 as a "Hot Paper", and in December 2005 as "Fast Breaking Paper", by Thomson ISI's Essential Science Indicators (now Science Watch), by virtue of being among the top one-tenth of one percent (0.1%) most cited papers and by having the largest percentage increase in citations in the Computer Science category.Barreto was born in Salvador, capital of the northeastern state of Bahia, Brazil. In 1987, he graduated in Physics at the University of São Paulo. He subsequently worked at Unisys Brazil Ltd and Scopus Tecnologia S/A as a software developer and then as chief cryptographer. Barreto received his Ph.D. degree in 2003. He has been awarded the SFI E. T. S. Walton Award 2008-2009. He was associate professor at the Department of Computer and Digital Systems Engineering, Escola Politécnica, University of São Paulo. He is currently a professor at the Institute of Technology of the University of Washington Tacoma.

Rebound attack

The rebound attack is a tool in the cryptanalysis of cryptographic hash functions. The attack was first published in 2009 by Florian Mendel, Christian Rechberger, Martin Schläffer and Søren Thomsen. It was conceived to attack AES like functions such as Whirlpool and Grøstl, but was later shown to also be applicable to other designs such as Keccak, JH and Skein.


Streebog is a cryptographic hash function defined in the Russian national standard GOST R 34.11-2012 Information Technology – Cryptographic Information Security – Hash Function. It was created to replace an obsolete GOST hash function defined in the old standard GOST R 34.11-94, and as an asymmetric reply to SHA-3 competition by the US National Institute of Standards and Technology. The function is also described in RFC 6986.

ISO standards by standard number

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