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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, 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 2_1_. 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

                   "0"     use BITS mode

           The "p" mode 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.

           The BITS mode ("0") interprets the contents of $filename as a logical stream of bits, where each
           ASCII '0' or '1' character represents a 0 or 1 bit, respectively.  All other characters are
           ignored.  This provides a convenient way to calculate the digest values of partial-byte data by
           using files, rather than having to write programs using the add_bits method.

       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
               Thomas Drugeon
               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) 2003-2012 Mark Shelor

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

       perlartistic



perl v5.16.2                                     2012-10-25                                 Digest::SHA(3pm)