SHA1(3) 						User Contributed Perl Documentation						   SHA1(3)

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, "
";
	       }

       $sha1->add($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.

SEE ALSO

       Digest, Digest::HMAC_SHA1, Digest::SHA, Digest::MD5

       http://www.itl.nist.gov/fipspubs/fip180-1.htm

       http://en.wikipedia.org/wiki/SHA_hash_functions

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>

perl v5.18.2							    2010-07-03								   SHA1(3)