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Digest::SHA(3pm)       Perl Programmers Reference Guide       Digest::SHA(3pm)

NAME
       Digest::SHA - Perl extension for SHA-1/224/256/384/512

SYNOPSIS
       In programs:

                       # Functional interface

               use Digest::SHA qw(sha1 sha1_hex sha1_base64 ...);

               $digest = sha1($data);
               $digest = sha1_hex($data);
               $digest = sha1_base64($data);

               $digest = sha256($data);
               $digest = sha384_hex($data);
               $digest = sha512_base64($data);

                       # Object-oriented

               use Digest::SHA;

               $sha = Digest::SHA->new($alg);

               $sha->add($data);               # feed data into stream

               $sha->addfile(*F);
               $sha->addfile($filename);

               $sha->add_bits($bits);
               $sha->add_bits($data, $nbits);

               $sha_copy = $sha->clone;        # if needed, make copy of
               $sha->dump($file);              #       current digest state,
               $sha->load($file);              #       or save it on disk

               $digest = $sha->digest;         # compute digest
               $digest = $sha->hexdigest;
               $digest = $sha->b64digest;

       From the command line:

               $ shasum files

               $ shasum --help

SYNOPSIS (HMAC-SHA)
                       # Functional interface only

               use Digest::SHA qw(hmac_sha1 hmac_sha1_hex ...);

               $digest = hmac_sha1($data, $key);
               $digest = hmac_sha224_hex($data, $key);
               $digest = hmac_sha256_base64($data, $key);

ABSTRACT
       Digest::SHA is a complete implementation of the NIST Secure Hash
       Standard.  It gives Perl programmers a convenient way to calculate
       SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512 message digests.  The
       module can handle all types of input, including partial-byte data.

DESCRIPTION
       Digest::SHA is written in C for speed.  If your platform lacks a C
       compiler, you can install the functionally equivalent (but much slower)
       Digest::SHA::PurePerl module.

       The programming interface is easy to use: it's the same one found in
       CPAN's Digest module.  So, if your applications currently use
       Digest::MD5 and you'd prefer the stronger security of SHA, it's a
       simple matter to convert them.

       The interface provides two ways to calculate digests:  all-at-once, or
       in stages.  To illustrate, the following short program computes the
       SHA-256 digest of "hello world" using each approach:

               use Digest::SHA qw(sha256_hex);

               $data = "hello world";
               @frags = split(//, $data);

               # all-at-once (Functional style)
               $digest1 = sha256_hex($data);

               # in-stages (OOP style)
               $state = Digest::SHA->new(256);
               for (@frags) { $state->add($_) }
               $digest2 = $state->hexdigest;

               print $digest1 eq $digest2 ?
                       "whew!\n" : "oops!\n";

       To calculate the digest of an n-bit message where n is not a multiple
       of 8, use the add_bits() method.  For example, consider the 446-bit
       message consisting of the bit-string "110" repeated 148 times, followed
       by "11".  Here's how to display its SHA-1 digest:

               use Digest::SHA;
               $bits = "110" x 148 . "11";
               $sha = Digest::SHA->new(1)->add_bits($bits);
               print $sha->hexdigest, "\n";

       Note that for larger bit-strings, it's more efficient to use the two-
       argument version add_bits($data, $nbits), where $data is in the
       customary packed binary format used for Perl strings.

       The module also lets you save intermediate SHA states to disk, or
       display them on standard output.  The dump() method generates portable,
       human-readable text describing the current state of computation.  You
       can subsequently retrieve the file with load() to resume where the
       calculation left off.

       To see what a state description looks like, just run the following:

               use Digest::SHA;
               Digest::SHA->new->add("Shaw" x 1962)->dump;

       As an added convenience, the Digest::SHA module offers routines to
       calculate keyed hashes using the HMAC-SHA-1/224/256/384/512 algorithms.
       These services exist in functional form only, and mimic the style and
       behavior of the sha(), sha_hex(), and sha_base64() functions.

               # Test vector from draft-ietf-ipsec-ciph-sha-256-01.txt

               use Digest::SHA qw(hmac_sha256_hex);
               print hmac_sha256_hex("Hi There", chr(0x0b) x 32), "\n";

NIST STATEMENT ON SHA-1
       NIST was recently informed that researchers had discovered a way to
       "break" the current Federal Information Processing Standard SHA-1
       algorithm, which has been in effect since 1994. The researchers have
       not yet published their complete results, so NIST has not confirmed
       these findings. However, the researchers are a reputable research team
       with expertise in this area.

       Due to advances in computing power, NIST already planned to phase out
       SHA-1 in favor of the larger and stronger hash functions (SHA-224,
       SHA-256, SHA-384 and SHA-512) by 2010. New developments should use the
       larger and stronger hash functions.

       ref.
       <http://www.csrc.nist.gov/pki/HashWorkshop/NIST%20Statement/Burr_Mar2005.html>

PADDING OF BASE64 DIGESTS
       By convention, CPAN Digest modules do not pad their Base64 output.
       Problems can occur when feeding such digests to other software that
       expects properly padded Base64 encodings.

       For the time being, any necessary padding must be done by the user.
       Fortunately, this is a simple operation: if the length of a
       Base64-encoded digest isn't a multiple of 4, simply append "="
       characters to the end of the digest until it is:

               while (length($b64_digest) % 4) {
                       $b64_digest .= '=';
               }

       To illustrate, sha256_base64("abc") is computed to be

               ungWv48Bz+pBQUDeXa4iI7ADYaOWF3qctBD/YfIAFa0

       which has a length of 43.  So, the properly padded version is

               ungWv48Bz+pBQUDeXa4iI7ADYaOWF3qctBD/YfIAFa0=

EXPORT
       None by default.

EXPORTABLE FUNCTIONS
       Provided your C compiler supports a 64-bit type (e.g. the long long of
       C99, or __int64 used by Microsoft C/C++), all of these functions will
       be available for use.  Otherwise, you won't be able to perform the
       SHA-384 and SHA-512 transforms, both of which require 64-bit
       operations.

       Functional style

       sha1($data, ...)
       sha224($data, ...)
       sha256($data, ...)
       sha384($data, ...)
       sha512($data, ...)
           Logically joins the arguments into a single string, and returns its
           SHA-1/224/256/384/512 digest encoded as a binary string.

       sha1_hex($data, ...)
       sha224_hex($data, ...)
       sha256_hex($data, ...)
       sha384_hex($data, ...)
       sha512_hex($data, ...)
           Logically joins the arguments into a single string, and returns its
           SHA-1/224/256/384/512 digest encoded as a hexadecimal string.

       sha1_base64($data, ...)
       sha224_base64($data, ...)
       sha256_base64($data, ...)
       sha384_base64($data, ...)
       sha512_base64($data, ...)
           Logically joins the arguments into a single string, and returns its
           SHA-1/224/256/384/512 digest encoded as a Base64 string.

           It's important to note that the resulting string does not contain
           the padding characters typical of Base64 encodings.  This omission
           is deliberate, and is done to maintain compatibility with the
           family of CPAN Digest modules.  See "PADDING OF BASE64 DIGESTS" for
           details.

       OOP style

       new($alg)
           Returns a new Digest::SHA object.  Allowed values for $alg are 1,
           224, 256, 384, or 512.  It's also possible to use common string
           representations of the algorithm (e.g. "sha256", "SHA-384").  If
           the argument is missing, SHA-1 will be used by default.

           Invoking new as an instance method will not create a new object;
           instead, it will simply reset the object to the initial state
           associated with $alg.  If the argument is missing, the object will
           continue using the same algorithm that was selected at creation.

       reset($alg)
           This method has exactly the same effect as new($alg).  In fact,
           reset is just an alias for new.

       hashsize
           Returns the number of digest bits for this object.  The values are
           160, 224, 256, 384, and 512 for SHA-1, SHA-224, SHA-256, SHA-384,
           and SHA-512, respectively.

       algorithm
           Returns the digest algorithm for this object.  The values are 1,
           224, 256, 384, and 512 for SHA-1, SHA-224, SHA-256, SHA-384, and
           SHA-512, respectively.

       clone
           Returns a duplicate copy of the object.

       add($data, ...)
           Logically joins the arguments into a single string, and uses it to
           update the current digest state.  In other words, the following
           statements have the same effect:

                   $sha->add("a"); $sha->add("b"); $sha->add("c");
                   $sha->add("a")->add("b")->add("c");
                   $sha->add("a", "b", "c");
                   $sha->add("abc");

           The return value is the updated object itself.

       add_bits($data, $nbits)
       add_bits($bits)
           Updates the current digest state by appending bits to it.  The
           return value is the updated object itself.

           The first form causes the most-significant $nbits of $data to be
           appended to the stream.  The $data argument is in the customary
           binary format used for Perl strings.

           The second form takes an ASCII string of "0" and "1" characters as
           its argument.  It's equivalent to

                   $sha->add_bits(pack("B*", $bits), length($bits));

           So, the following two statements do the same thing:

                   $sha->add_bits("111100001010");
                   $sha->add_bits("\xF0\xA0", 12);

       addfile(*FILE)
           Reads from FILE until EOF, and appends that data to the current
           state.  The return value is the updated object itself.

       addfile($filename [, $mode])
           Reads the contents of $filename, and appends that data to the
           current state.  The return value is the updated object itself.

           By default, $filename is simply opened and read; no special modes
           or I/O disciplines are used.  To change this, set the optional
           $mode argument to one of the following values:

                   "b"     read file in binary mode

                   "p"     use portable mode

           The "p" mode is handy since it ensures that the digest value of
           $filename will be the same when computed on different operating
           systems.  It accomplishes this by internally translating all
           newlines in text files to UNIX format before calculating the
           digest.  Binary files are read in raw mode with no translation
           whatsoever.

           For a fuller discussion of newline formats, refer to CPAN module
           File::LocalizeNewlines.  Its "universal line separator" regex forms
           the basis of addfile's portable mode processing.

       dump($filename)
           Provides persistent storage of intermediate SHA states by writing a
           portable, human-readable representation of the current state to
           $filename.  If the argument is missing, or equal to the empty
           string, the state information will be written to STDOUT.

       load($filename)
           Returns a Digest::SHA object representing the intermediate SHA
           state that was previously dumped to $filename.  If called as a
           class method, a new object is created; if called as an instance
           method, the object is reset to the state contained in $filename.
           If the argument is missing, or equal to the empty string, the state
           information will be read from STDIN.

       digest
           Returns the digest encoded as a binary string.

           Note that the digest method is a read-once operation. Once it has
           been performed, the Digest::SHA object is automatically reset in
           preparation for calculating another digest value.  Call
           $sha->clone->digest if it's necessary to preserve the original
           digest state.

       hexdigest
           Returns the digest encoded as a hexadecimal string.

           Like digest, this method is a read-once operation.  Call
           $sha->clone->hexdigest if it's necessary to preserve the original
           digest state.

           This method is inherited if Digest::base is installed on your
           system.  Otherwise, a functionally equivalent substitute is used.

       b64digest
           Returns the digest encoded as a Base64 string.

           Like digest, this method is a read-once operation.  Call
           $sha->clone->b64digest if it's necessary to preserve the original
           digest state.

           This method is inherited if Digest::base is installed on your
           system.  Otherwise, a functionally equivalent substitute is used.

           It's important to note that the resulting string does not contain
           the padding characters typical of Base64 encodings.  This omission
           is deliberate, and is done to maintain compatibility with the
           family of CPAN Digest modules.  See "PADDING OF BASE64 DIGESTS" for
           details.

       HMAC-SHA-1/224/256/384/512

       hmac_sha1($data, $key)
       hmac_sha224($data, $key)
       hmac_sha256($data, $key)
       hmac_sha384($data, $key)
       hmac_sha512($data, $key)
           Returns the HMAC-SHA-1/224/256/384/512 digest of $data/$key, with
           the result encoded as a binary string.  Multiple $data arguments
           are allowed, provided that $key is the last argument in the list.

       hmac_sha1_hex($data, $key)
       hmac_sha224_hex($data, $key)
       hmac_sha256_hex($data, $key)
       hmac_sha384_hex($data, $key)
       hmac_sha512_hex($data, $key)
           Returns the HMAC-SHA-1/224/256/384/512 digest of $data/$key, with
           the result encoded as a hexadecimal string.  Multiple $data
           arguments are allowed, provided that $key is the last argument in
           the list.

       hmac_sha1_base64($data, $key)
       hmac_sha224_base64($data, $key)
       hmac_sha256_base64($data, $key)
       hmac_sha384_base64($data, $key)
       hmac_sha512_base64($data, $key)
           Returns the HMAC-SHA-1/224/256/384/512 digest of $data/$key, with
           the result encoded as a Base64 string.  Multiple $data arguments
           are allowed, provided that $key is the last argument in the list.

           It's important to note that the resulting string does not contain
           the padding characters typical of Base64 encodings.  This omission
           is deliberate, and is done to maintain compatibility with the
           family of CPAN Digest modules.  See "PADDING OF BASE64 DIGESTS" for
           details.

SEE ALSO
       Digest, Digest::SHA::PurePerl

       The Secure Hash Standard (FIPS PUB 180-2) can be found at:

       http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf
       <http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf>

       The Keyed-Hash Message Authentication Code (HMAC):

       http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf
       <http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf>

AUTHOR
               Mark Shelor     <mshelor@cpan.org>

ACKNOWLEDGMENTS
       The author is particularly grateful to

               Gisle Aas
               Chris Carey
               Alexandr Ciornii
               Jim Doble
               Julius Duque
               Jeffrey Friedl
               Robert Gilmour
               Brian Gladman
               Adam Kennedy
               Andy Lester
               Alex Muntada
               Steve Peters
               Chris Skiscim
               Martin Thurn
               Gunnar Wolf
               Adam Woodbury

       for their valuable comments and suggestions.

COPYRIGHT AND LICENSE
       Copyright (C) 2003-2008 Mark Shelor

       This library is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

       perlartistic

perl v5.12.1                      2010-04-26                  Digest::SHA(3pm)
 

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