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Posted 11 Apr 2003

ReHash - A console-based hash calculator

, 11 Apr 2003
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A console-based hash calculator. Supported algorithms: CRC-16, CRC-16-CCITT, CRC-32, FCS-16, FCS-32, GHash-32-3, GHash-32-5, GOST-Hash, HAVAL-5-256, MD2, MD4, MD5, SHA-1, SHA-256, SHA-384, SHA-512, Tiger.
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ReHash is a free, open source console-based hash calculator.

You can disable hash algorithms selectively per command-line if you don't need or like them, you can choose if you want to use recursive directory scanning or not.

This tool is ideal for webmasters who wish to provide their users hash values of their (downloadable) files. The complete hashing process can be automated by using a shell/batch script. No additional user interaction is needed (i.e. the program won't ask for anything, it's just using the command-line).

ReHash is distributed under the terms of the GNU General Public License v2.

Supported algorithms

The current version of ReHash supports the following hash algorithms:

Hash Digest Size
16 bits
16 bits
CRC-32ANSI X3.66, FIPS PUB 71 
32 bits
16 bits
32 bits
GHash (GHash-32-3, GHash-32-5)--
32 bits
GOST-HashR 34.11-94 
256 bits
HAVAL (5 passes, 256 bits) Zheng, Pieprzyk,
256 bits
MD2RFC 1319Rivest
128 bits
MD4RFC 1320Rivest
128 bits
MD5RFC 1321Rivest
128 bits
160 bits
256/384/512 bits
32 bits
Tiger Anderson, Biham
192 bits


rehash.exe [options] filespec [> outputfile]

The command-line is parsed from the left to the right. So if you execute ReHash like this:
rehash.exe -all -none *.*
it will output nothing, because you first activate all algorithms and then deactivate them all.

Some usage examples:

Hash all INI files in C:\Windows (including subdirectories) using all hash algorithms:
rehash.exe C:\Windows\*.ini

Hash all INI files in C:\Windows (excluding subdirectories) using all hash algorithms:
rehash.exe -norecur C:\Windows

Hash all BAT files on C:\ (including subdirectories) using only MD5 and SHA-1 (remember command-line is parsed from the left to the right):
rehash.exe -none -md5 -sha1 C:\*.bat

Hash all files in C:\Temp (excluding subdirectories) using only the GOST algorithm:
rehash.exe -norecur -none -gost C:\Temp\*

Hash all ZIP files in C:\homepage (including subdirectories) using only the MD5 algorithm and output the hashes to C:\homepage\downloads\hashes.txt:
rehash.exe -none -md5 C:\homepage\*.zip > C:\homepage\downloads\hashes.txt

All options:

-help / -h / -?/
-version / -v
Print some information about ReHash.
-fullpath / -fOutput the full paths of hashed files.
-nopathJust output the filenames of hashed files, not the full paths to the files.
-rcrsv / -recur / -rRecursive scanning. Scan all files in the specified path including files in subdirectories.
-norcrsv / -norecurDisable recursive scanning. Scan only the files in the specified path not including subdirectories.
-all / -aEnable all algorithms.
-none / -nDisable all algorithms.
-crc16 / -nocrc16Enable/disable the CRC-16 algorithm.
-crc16c / -nocrc16cEnable/disable the CRC-16-CCITT algorithm.
-crc32 / -nocrc32Enable/disable the CRC-32 algorithm.
-fcs16 / -nofcs16Enable/disable the FCS-16 algorithm.
-fcs32 / -nofcs32Enable/disable the FCS-32 algorithm.
-ghash3 / -noghash3Enable/disable the GHash-3 algorithm.
-ghash5 / -noghash5Enable/disable the GHash-5 algorithm.
-gost / -nogostEnable/disable the GOST-Hash algorithm.
-haval / -nohavalEnable/disable the HAVAL-5-256 algorithm.
-md2 / -nomd2Enable/disable the MD2 algorithm.
-md4 / -nomd4Enable/disable the MD4 algorithm.
-md5 / -nomd5Enable/disable the MD5 algorithm.
-sha1 / -nosha1Enable/disable the SHA-1 algorithm.
-sha256 / -nosha256Enable/disable the SHA-256 algorithm.
-sha384 / -nosha384Enable/disable the SHA-384 algorithm.
-sha512 / -nosha512Enable/disable the SHA-512 algorithm.
-size32 / -nosize32Enable/disable the Size-32 algorithm (simply the byte-count of the message).
-tiger / -notigerEnable/disable the TIGER algorithm.

Thanks / acknowledgements

Thanks to (no particular order):
  • Markku-Juhani O. Saarinen - GOST-Hash implementation
  • Yuliang Zheng - HAVAL implementation
  • Wei Dai - implementations of various algorithms
  • Dr Brian Gladman - SHA-1/SHA-2 implementation
  • Tom St Denis - Tiger implementation


  • 12 April 2003 - v1.0
    First public release


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Dominik Reichl
Software Developer
Germany Germany
Dominik started programming in Omikron Basic, a programming language for the good old Atari ST. After this, there was some short period of QBasic programming on the PC, but soon he began learning C++, which is his favorite language up to now.

Today, his programming experience includes C / C++ / [Visual] C++ [MFC], C#/.NET, Java, JavaScript, PHP and HTML and the basics of pure assembler.

He is interested in almost everything that has to do with computing, his special interests are security and data compression.

You can find his latest freeware, open-source projects and all articles on his homepage:

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Comments and Discussions

Generalprova0 Pin
ocean06-May-03 3:04
memberocean06-May-03 3:04 
GeneralCRC algorithms Pin
Tim Smith13-Apr-03 7:09
memberTim Smith13-Apr-03 7:09 
GeneralRe: CRC algorithms Pin
jacques_freedom31-Mar-04 23:10
memberjacques_freedom31-Mar-04 23:10 
GeneralRe: CRC algorithms Pin
Dominik Reichl1-Apr-04 1:19
memberDominik Reichl1-Apr-04 1:19 
I have a question about CRC and MD5 algorithms:
Is it easy to generate the same int or long value with different strings?

For CRC: CRC has been designed to detect random transmission errors, so you can easily verify corrupted downloads or something like this. BUT you can easily find strings that hash to the same CRC value. In other words: CRCs aren't resistant against attacks, but are fine to quickly check for transmission errors.

For MD5: MD5 is cryptographically secure. This means that it is computationally infeasible ( = it's not impossible but currently nobody can do it) to find two strings that hash to the same MD5 value. MD5 is a 128-bit hash, so compared to a CRC-32 it should also be more collision-resistant.

So, to sum it up: if you need a secure hash then use MD5. If you just want to quickly check if a downloaded file isn't corrupted then use CRC.

Best regards,

_outp(0x64, 0xAD);
__asm mov al, 0xAD __asm out 0x64, al
do the same... but what do they do?? Wink | ;)
(doesn't work on NT)

GeneralRe: CRC algorithms Pin
Panic2k324-Jan-05 14:34
memberPanic2k324-Jan-05 14:34 
Generalcould be cool but... Pin
Jim Crafton13-Apr-03 6:01
memberJim Crafton13-Apr-03 6:01 
GeneralRe: could be cool but... Pin
Chris Losinger13-Apr-03 7:50
memberChris Losinger13-Apr-03 7:50 
GeneralRe: could be cool but... Pin
Jim Crafton13-Apr-03 12:05
memberJim Crafton13-Apr-03 12:05 
GeneralRe: could be cool but... Pin
Tim Smith14-Apr-03 6:11
memberTim Smith14-Apr-03 6:11 
GeneralUseful... but would like to see a managed code version :-) Pin
Jabes12-Apr-03 6:53
memberJabes12-Apr-03 6:53 

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