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Digest::SHA(3perl) Perl Programmers Reference Guide Digest::SHA(3perl)
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 $filename will be the
same when computed on different operating systems. It accomplishes this by internally
translating all newlines in text files to UNIX format before calculating the digest;
on the other hand, binary files are read in raw mode with no translation whatsoever.
For a fuller discussion of newline formats, refer to CPAN module
File::LocalizeNewlines. Its "universal line separator" regex forms the basis of
addfile's portable mode processing.
dump($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>
The Keyed-Hash Message Authentication Code (HMAC):
<http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf>
AUTHOR
Mark Shelor <mshelor AT cpan.org>
ACKNOWLEDGMENTS
The author is particularly grateful to
Gisle Aas
Chris Carey
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) 2003-2007 Mark Shelor
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
perlartistic
perl v5.10.0 2011-06-30 Digest::SHA(3perl)
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