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.\" ========================================================================
.\"
.IX Title "SHA1 3"
.TH SHA1 3 "2009-05-23" "perl v5.8.7" "User Contributed Perl Documentation"
.\" 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::SHA1 \- Perl interface to the SHA\-1 algorithm
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& # Functional style
\& use Digest::SHA1  qw(sha1 sha1_hex sha1_base64);
\&
\& $digest = sha1($data);
\& $digest = sha1_hex($data);
\& $digest = sha1_base64($data);
\& $digest = sha1_transform($data);
\&
\&
\& # OO style
\& use Digest::SHA1;
\&
\& $sha1 = Digest::SHA1\->new;
\&
\& $sha1\->add($data);
\& $sha1\->addfile(*FILE);
\&
\& $sha1_copy = $sha1\->clone;
\&
\& $digest = $sha1\->digest;
\& $digest = $sha1\->hexdigest;
\& $digest = $sha1\->b64digest;
\& $digest = $sha1\->transform;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \f(CW\*(C`Digest::SHA1\*(C'\fR module allows you to use the \s-1NIST\s0 \s-1SHA\-1\s0 message
digest algorithm from within Perl programs.  The algorithm takes as
input a message of arbitrary length and produces as output a 160\-bit
\&\*(L"fingerprint\*(R" or \*(L"message digest\*(R" of the input.
.PP
In 2005, security flaws were identified in \s-1SHA\-1\s0, namely that a possible
mathematical weakness might exist, indicating that a stronger hash function
would be desirable.  The Digest::SHA module implements the stronger
algorithms in the \s-1SHA\s0 family.
.PP
The \f(CW\*(C`Digest::SHA1\*(C'\fR module provide a procedural interface for simple
use, as well as an object oriented interface that can handle messages
of arbitrary length and which can read files directly.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
The following functions can be exported from the \f(CW\*(C`Digest::SHA1\*(C'\fR
module.  No functions are exported by default.
.IP "sha1($data,...)" 4
.IX Item "sha1($data,...)"
This function will concatenate all arguments, calculate the \s-1SHA\-1\s0
digest of this \*(L"message\*(R", and return it in binary form.  The returned
string will be 20 bytes long.
.Sp
The result of sha1(\*(L"a\*(R", \*(L"b\*(R", \*(L"c\*(R") will be exactly the same as the
result of sha1(\*(L"abc\*(R").
.IP "sha1_hex($data,...)" 4
.IX Item "sha1_hex($data,...)"
Same as \fIsha1()\fR, but will return the digest in hexadecimal form.  The
length of the returned string will be 40 and it will only contain
characters from this set: '0'..'9' and 'a'..'f'.
.IP "sha1_base64($data,...)" 4
.IX Item "sha1_base64($data,...)"
Same as \fIsha1()\fR, but will return the digest as a base64 encoded string.
The length of the returned string will be 27 and it will only contain
characters from this set: 'A'..'Z', 'a'..'z', '0'..'9', '+' and
\&'/'.
.Sp
Note that the base64 encoded string returned is not padded to be a
multiple of 4 bytes long.  If you want interoperability with other
base64 encoded sha1 digests you might want to append the redundant
string \*(L"=\*(R" to the result.
.IP "sha1_transform($data)" 4
.IX Item "sha1_transform($data)"
Implements the basic \s-1SHA1\s0 transform on a 64 byte block. The \f(CW$data\fR
argument and the returned \f(CW$digest\fR are in binary form. This algorithm
is used in \s-1NIST\s0 \s-1FIPS\s0 186\-2
.SH "METHODS"
.IX Header "METHODS"
The object oriented interface to \f(CW\*(C`Digest::SHA1\*(C'\fR is described in this
section.  After a \f(CW\*(C`Digest::SHA1\*(C'\fR object has been created, you will add
data to it and finally ask for the digest in a suitable format.  A
single object can be used to calculate multiple digests.
.PP
The following methods are provided:
.ie n .IP "$sha1 = Digest::SHA1\->new" 4
.el .IP "\f(CW$sha1\fR = Digest::SHA1\->new" 4
.IX Item "$sha1 = Digest::SHA1->new"
The constructor returns a new \f(CW\*(C`Digest::SHA1\*(C'\fR object which encapsulate
the state of the \s-1SHA\-1\s0 message-digest algorithm.
.Sp
If called as an instance method (i.e. \f(CW$sha1\fR\->new) it will just reset the
state the object to the state of a newly created object.  No new
object is created in this case.
.ie n .IP "$sha1\->reset" 4
.el .IP "\f(CW$sha1\fR\->reset" 4
.IX Item "$sha1->reset"
This is just an alias for \f(CW$sha1\fR\->new.
.ie n .IP "$sha1\->clone" 4
.el .IP "\f(CW$sha1\fR\->clone" 4
.IX Item "$sha1->clone"
This a copy of the \f(CW$sha1\fR object. It is useful when you do not want to
destroy the digests state, but need an intermediate value of the
digest, e.g. when calculating digests iteratively on a continuous data
stream.  Example:
.Sp
.Vb 5
\&    my $sha1 = Digest::SHA1\->new;
\&    while (<>) {
\&        $sha1\->add($_);
\&        print "Line $.: ", $sha1\->clone\->hexdigest, "\en";
\&    }
.Ve
.ie n .IP "$sha1\->add($data,...)" 4
.el .IP "\f(CW$sha1\fR\->add($data,...)" 4
.IX Item "$sha1->add($data,...)"
The \f(CW$data\fR provided as argument are appended to the message we
calculate the digest for.  The return value is the \f(CW$sha1\fR object itself.
.Sp
All these lines will have the same effect on the state of the \f(CW$sha1\fR
object:
.Sp
.Vb 4
\&    $sha1\->add("a"); $sha1\->add("b"); $sha1\->add("c");
\&    $sha1\->add("a")\->add("b")\->add("c");
\&    $sha1\->add("a", "b", "c");
\&    $sha1\->add("abc");
.Ve
.ie n .IP "$sha1\->addfile($io_handle)" 4
.el .IP "\f(CW$sha1\fR\->addfile($io_handle)" 4
.IX Item "$sha1->addfile($io_handle)"
The \f(CW$io_handle\fR will be read until \s-1EOF\s0 and its content appended to the
message we calculate the digest for.  The return value is the \f(CW$sha1\fR
object itself.
.Sp
The \fIaddfile()\fR method will \fIcroak()\fR if it fails reading data for some
reason.  If it croaks it is unpredictable what the state of the \f(CW$sha1\fR
object will be in. The \fIaddfile()\fR method might have been able to read
the file partially before it failed.  It is probably wise to discard
or reset the \f(CW$sha1\fR object if this occurs.
.Sp
In most cases you want to make sure that the \f(CW$io_handle\fR is in
\&\f(CW\*(C`binmode\*(C'\fR before you pass it as argument to the \fIaddfile()\fR method.
.ie n .IP "$sha1\->add_bits($data, $nbits)" 4
.el .IP "\f(CW$sha1\fR\->add_bits($data, \f(CW$nbits\fR)" 4
.IX Item "$sha1->add_bits($data, $nbits)"
.PD 0
.ie n .IP "$sha1\->add_bits($bitstring)" 4
.el .IP "\f(CW$sha1\fR\->add_bits($bitstring)" 4
.IX Item "$sha1->add_bits($bitstring)"
.PD
This implementation of \s-1SHA\-1\s0 only supports byte oriented input so you
might only add bits as multiples of 8.  If you need bit level support
please consider using the \f(CW\*(C`Digest::SHA\*(C'\fR module instead.  The
\&\fIadd_bits()\fR method is provided here for compatibility with other digest
implementations.  See Digest for description of the arguments that
\&\fIadd_bits()\fR take.
.ie n .IP "$sha1\->digest" 4
.el .IP "\f(CW$sha1\fR\->digest" 4
.IX Item "$sha1->digest"
Return the binary digest for the message.  The returned string will be
20 bytes long.
.Sp
Note that the \f(CW\*(C`digest\*(C'\fR operation is effectively a destructive,
read-once operation. Once it has been performed, the \f(CW\*(C`Digest::SHA1\*(C'\fR
object is automatically \f(CW\*(C`reset\*(C'\fR and can be used to calculate another
digest value.  Call \f(CW$sha1\fR\->clone\->digest if you want to calculate the
digest without reseting the digest state.
.ie n .IP "$sha1\->hexdigest" 4
.el .IP "\f(CW$sha1\fR\->hexdigest" 4
.IX Item "$sha1->hexdigest"
Same as \f(CW$sha1\fR\->digest, but will return the digest in hexadecimal
form. The length of the returned string will be 40 and it will only
contain characters from this set: '0'..'9' and 'a'..'f'.
.ie n .IP "$sha1\->b64digest" 4
.el .IP "\f(CW$sha1\fR\->b64digest" 4
.IX Item "$sha1->b64digest"
Same as \f(CW$sha1\fR\->digest, but will return the digest as a base64 encoded
string.  The length of the returned string will be 27 and it will only
contain characters from this set: 'A'..'Z', 'a'..'z', '0'..'9', '+'
and '/'.
.Sp
The base64 encoded string returned is not padded to be a multiple of 4
bytes long.  If you want interoperability with other base64 encoded
\&\s-1SHA\-1\s0 digests you might want to append the string \*(L"=\*(R" to the result.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Digest, Digest::HMAC_SHA1, Digest::SHA, Digest::MD5
.PP
http://www.itl.nist.gov/fipspubs/fip180\-1.htm
.PP
http://en.wikipedia.org/wiki/SHA_hash_functions
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
.PP
.Vb 2
\& Copyright 1999\-2004 Gisle Aas.
\& Copyright 1997 Uwe Hollerbach.
.Ve
.SH "AUTHORS"
.IX Header "AUTHORS"
Peter C. Gutmann,
Uwe Hollerbach <uh@alumni.caltech.edu>,
Gisle Aas <gisle@aas.no>