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Man Pages

Manual Reference Pages  -  DIGEST::SV1 (3)

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Digest::SV1 - Cryptosleazically strong message digest format



  $sv1  = Digest::SV1->new();

  $sv1->add( $data, ... );

  $sv1->addfile( $io_handle );



So, you chose a hashing algorithm as recommended by the leading security experts of yesteryear, it got hacked, and now some mysterious 15 year old cracker 0wns your toaster because of it.

Fight back! This hash algorithm is designed to infuriate the Mathematicians and Cryptographers out there, who will swear us lowly software engineers are missing the point of all this digest stuff.

Put simply, if one hashing algorithm won’t do the job satisfactorily, then why not use several.

The main algorithm in this module forms the authorative definition of how the SV1 digest format is to operate.

See Digest for a detailed description of the Digest API.

<B>WarningB>: some of the constructed and artificial mathematical formulae may have some kind of constructed and artificial legislation, documentation, papers, et cetera that some group of people acting as a constructed and artificial construct known as a ‘legal person’ that exploited the person who came up with the idea might maintain has some kind of constructed and artificial power to restrict your freedom as recognised by some constructed and artificial social structure. You are strongly advised to just not give a smeg.


<B>Why such a small hash size?B> Because the reasons that a cryptographer extends the hash size differ from the reasons that a software engineer does.
<B>What’s the effective hash entropy?B> Dunno. Let’s say that SHA1 is 160 bits, but has a ‘difficulty’ of 2^50 to crack. We’re using MD5 and Haval-256 as well, and say that they have respective ‘difficulties’ of 2^32 and 2^60 as well.

Assuming that the algorithms are diverse enough to not share a common flaw, then you could safely add the exponents of these difficulties to get a rough estimate of the safety of the algorithm.

But then, I am not a cryptographer. The real reason is that md5 hashes are long enough, already! Heck, there’s no sense into lulling you into a false sense of large hash size cryptonirvana, when the algorithm might be picked apart by some 8 year old prodigy in Russia and those extra 384 bits per checksum only added a complexity of about 4 to a would-be attacker.

If you really want to keep your data safe, simply don’t harbour karmic terrorists.


This module is nothing other than a convention. There are more lines of documentation than real code.

The real heroes are;
Gisle Aas Excellent Digest::base module and related utilities, and the Digest::MD5 implementation. Oh, and help with the SHA-1 interface.
Neil Winton The original MD5 interface author.
Peter C. Gutmann Co-author of Digest::SHA1
Uwe Hollerbach Co-author of Digest::SHA1
Julius C. Duque Author of Digest::Haval-256
Ron Rivest Inventor of the MD5 and SHA1 digest formats. He was working for RSA for the former, and our good friends the NSA for SHA-1.
Yuliang Zheng, Josef Pieprzyk, and Jennifer Seberry. Designers of the Haval-256 digest format.
Last, and in order of actual code contributed, least:

  Sam Vilain, <>

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perl v5.20.3 DIGEST::SV1 (3) 2016-03-17

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