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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, SHA-512,
       SHA-512/224, and SHA-512/256 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($data, ...)
       sha512224($data, ...)
       sha512256($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($data, ...)
       sha512224_hex($data, ...)
       sha512256_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($data, ...)
       sha512224_base64($data, ...)
       sha512256_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, 512,
           512224, or 512256.  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,
           512, 224, and 256 for SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224 and
           SHA-512/256, respectively.

       algorithm
           Returns the digest algorithm for this object.  The values are 1, 224, 256, 384, 512,
           512224, and 512256 for SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, and
           SHA-512/256, 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, $key)
       hmac_sha512224($data, $key)
       hmac_sha512256($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, $key)
       hmac_sha512224_hex($data, $key)
       hmac_sha512256_hex($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, $key)
       hmac_sha512224_base64($data, $key)
       hmac_sha512256_base64($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 (Draft FIPS PUB 180-4) can be found at:

       http://csrc.nist.gov/publications/drafts/fips180-4/Draft-FIPS180-4_Feb2011.pdf
       <http://csrc.nist.gov/publications/drafts/fips180-4/Draft-FIPS180-4_Feb2011.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
               Sean Burke
               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

       "who by trained skill rescued life from such great billows and such thick darkness and
       moored it in so perfect a calm and in so brilliant a light" - Lucretius

COPYRIGHT AND LICENSE

       Copyright (C) 2003-2011 Mark Shelor

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

       perlartistic