SHA1(3pm)

NAME

Digest::SHA1 - Perl interface to the SHA-1 algorithm

SYNOPSIS

# 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;

DESCRIPTION

The "Digest::SHA1" module allows you to use the NIST SHA-1 message
digest algorithm from within Perl programs. The algorithm takes as
input a message of arbitrary length and produces as output a 160-bit
"fingerprint" or "message digest" of the input.

In 2005, security flaws were identified in SHA-1, 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 SHA family.

The "Digest::SHA1" 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.

FUNCTIONS

The following functions can be exported from the "Digest::SHA1" module. No functions are exported by default.

sha1($data,...): This function will concatenate all arguments, calculate the SHA-1
digest of this "message", and return it in binary form. The
returned string will be 20 bytes long.; The result of sha1("a", "b", "c") will be exactly the same as the
result of sha1("abc").
sha1_hex($data,...): Same as sha1(), 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'.
sha1_base64($data,...): Same as sha1(), but will return the digest as a base64 encoded string. The length of the returned string will be 27 and it will
only contain characters from this set: 'A'..'Z', 'a'..'z',
'0'..'9', '+' and '/'.; Note that the base64 encoded string returned is not padded to be a multiple of 4 bytes long. If you want interoperability with other base64 encoded sha1 digests you might want to append the redundant string "=" to the result.
sha1_transform($data): Implements the basic SHA1 transform on a 64 byte block. The $data
argument and the returned $digest are in binary form. This
algorithm is used in NIST FIPS 186-2

METHODS

The object oriented interface to "Digest::SHA1" is described in this
section. After a "Digest::SHA1" 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.

The following methods are provided:

$sha1 = Digest::SHA1->new: The constructor returns a new "Digest::SHA1" object which
encapsulate the state of the SHA-1 message-digest algorithm.; If called as an instance method (i.e. $sha1->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.
$sha1->reset: This is just an alias for $sha1->new.
$sha1->clone: This a copy of the $sha1 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:

my $sha1 = Digest::SHA1->new;
while (<>) {
$sha1->add($_);
print "Line $.: ", $sha1->clone->hexdigest, "\n";

}
$sha1->add($data,...): The $data provided as argument are appended to the message we
calculate the digest for. The return value is the $sha1 object
itself.; All these lines will have the same effect on the state of the $sha1 object:

$sha1->add("a"); $sha1->add("b"); $sha1->add("c");
$sha1->add("a")->add("b")->add("c");
$sha1->add("a", "b", "c");
$sha1->add("abc");
$sha1->addfile($io_handle): The $io_handle will be read until EOF and its content appended to
the message we calculate the digest for. The return value is the
$sha1 object itself.; The addfile() method will croak() if it fails reading data for some reason. If it croaks it is unpredictable what the state of the
$sha1 object will be in. The addfile() method might have been able to read the file partially before it failed. It is probably wise
to discard or reset the $sha1 object if this occurs.; In most cases you want to make sure that the $io_handle is in
"binmode" before you pass it as argument to the addfile() method.
$sha1->add_bits($data, $nbits) $sha1->add_bits($bitstring): This implementation of SHA-1 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 "Digest::SHA" module instead.
The add_bits() method is provided here for compatibility with other digest implementations. See Digest for description of the
arguments that add_bits() take.
$sha1->digest: Return the binary digest for the message. The returned string will be 20 bytes long.; Note that the "digest" operation is effectively a destructive,
read-once operation. Once it has been performed, the "Digest::SHA1" object is automatically "reset" and can be used to calculate
another digest value. Call $sha1->clone->digest if you want to
calculate the digest without reseting the digest state.
$sha1->hexdigest: Same as $sha1->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'.
$sha1->b64digest: Same as $sha1->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 '/'.; The base64 encoded string returned is not padded to be a multiple
of 4 bytes long. If you want interoperability with other base64
encoded SHA-1 digests you might want to append the string "=" to
the result.

COPYRIGHT

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.: Copyright 1999-2004 Gisle Aas.
Copyright 1997 Uwe Hollerbach.

AUTHORS

Peter C. Gutmann, Uwe Hollerbach <uh@alumni.caltech.edu>, Gisle Aas
<gisle@aas.no>

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