digest::sha.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "Digest::SHA 3"
.TH Digest::SHA 3 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Digest::SHA \- Perl extension for SHA\-1/224/256/384/512
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
In programs:
.PP
.Vb 1
\&                # 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;
.Ve
.PP
From the command line:
.PP
.Vb 1
\&        $ shasum files
\&
\&        $ shasum \-\-help
.Ve
.SH "SYNOPSIS (HMAC-SHA)"
.IX Header "SYNOPSIS (HMAC-SHA)"
.Vb 1
\&                # 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);
.Ve
.SH "ABSTRACT"
.IX Header "ABSTRACT"
Digest::SHA is a complete implementation of the \s-1NIST\s0 Secure Hash
Standard.  It gives Perl programmers a convenient way to calculate
\&\s-1SHA\-1\s0, \s-1SHA\-224\s0, \s-1SHA\-256\s0, \s-1SHA\-384\s0, and \s-1SHA\-512\s0 message digests.
The module can handle all types of input, including partial-byte
data.
.SH "DESCRIPTION"
.IX Header "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.
.PP
The programming interface is easy to use: it's the same one found
in \s-1CPAN\s0's Digest module.  So, if your applications currently
use Digest::MD5 and you'd prefer the stronger security of \s-1SHA\s0,
it's a simple matter to convert them.
.PP
The interface provides two ways to calculate digests:  all-at-once,
or in stages.  To illustrate, the following short program computes
the \s-1SHA\-256\s0 digest of \*(L"hello world\*(R" using each approach:
.PP
.Vb 1
\&        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!\en" : "oops!\en";
.Ve
.PP
To calculate the digest of an n\-bit message where \fIn\fR is not a
multiple of 8, use the \fI\fIadd_bits()\fI\fR method.  For example, consider
the 446\-bit message consisting of the bit-string \*(L"110\*(R" repeated
148 times, followed by \*(L"11\*(R".  Here's how to display its \s-1SHA\-1\s0
digest:
.PP
.Vb 4
\&        use Digest::SHA;
\&        $bits = "110" x 148 . "11";
\&        $sha = Digest::SHA\->new(1)\->add_bits($bits);
\&        print $sha\->hexdigest, "\en";
.Ve
.PP
Note that for larger bit-strings, it's more efficient to use the
two-argument version \fIadd_bits($data, \f(CI$nbits\fI)\fR, where \fI\f(CI$data\fI\fR is
in the customary packed binary format used for Perl strings.
.PP
The module also lets you save intermediate \s-1SHA\s0 states to disk, or
display them on standard output.  The \fI\fIdump()\fI\fR method generates
portable, human-readable text describing the current state of
computation.  You can subsequently retrieve the file with \fI\fIload()\fI\fR
to resume where the calculation left off.
.PP
To see what a state description looks like, just run the following:
.PP
.Vb 2
\&        use Digest::SHA;
\&        Digest::SHA\->new\->add("Shaw" x 1962)\->dump;
.Ve
.PP
As an added convenience, the Digest::SHA module offers routines to
calculate keyed hashes using the \s-1HMAC\-SHA\-1/224/256/384/512\s0
algorithms.  These services exist in functional form only, and
mimic the style and behavior of the \fI\fIsha()\fI\fR, \fI\fIsha_hex()\fI\fR, and
\&\fI\fIsha_base64()\fI\fR functions.
.PP
.Vb 1
\&        # 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), "\en";
.Ve
.SH "NIST STATEMENT ON SHA\-1"
.IX Header "NIST STATEMENT ON SHA-1"
\&\fI\s-1NIST\s0 was recently informed that researchers had discovered a way
to \*(L"break\*(R" the current Federal Information Processing Standard \s-1SHA\-1\s0
algorithm, which has been in effect since 1994. The researchers
have not yet published their complete results, so \s-1NIST\s0 has not
confirmed these findings. However, the researchers are a reputable
research team with expertise in this area.\fR
.PP
\&\fIDue to advances in computing power, \s-1NIST\s0 already planned to phase
out \s-1SHA\-1\s0 in favor of the larger and stronger hash functions (\s-1SHA\-224\s0,
\&\s-1SHA\-256\s0, \s-1SHA\-384\s0 and \s-1SHA\-512\s0) by 2010. New developments should use
the larger and stronger hash functions.\fR
.PP
ref. <http://www.csrc.nist.gov/pki/HashWorkshop/NIST%20Statement/Burr_Mar2005.html>
.SH "PADDING OF BASE64 DIGESTS"
.IX Header "PADDING OF BASE64 DIGESTS"
By convention, \s-1CPAN\s0 Digest modules do \fBnot\fR pad their Base64 output.
Problems can occur when feeding such digests to other software that
expects properly padded Base64 encodings.
.PP
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 \*(L"=\*(R" characters to the end
of the digest until it is:
.PP
.Vb 3
\&        while (length($b64_digest) % 4) {
\&                $b64_digest .= \*(Aq=\*(Aq;
\&        }
.Ve
.PP
To illustrate, \fIsha256_base64(\*(L"abc\*(R")\fR is computed to be
.PP
.Vb 1
\&        ungWv48Bz+pBQUDeXa4iI7ADYaOWF3qctBD/YfIAFa0
.Ve
.PP
which has a length of 43.  So, the properly padded version is
.PP
.Vb 1
\&        ungWv48Bz+pBQUDeXa4iI7ADYaOWF3qctBD/YfIAFa0=
.Ve
.SH "EXPORT"