Страницы справочника OS X

Эта страница руководства для  версии 10.9 Mac OS X

Читать страницы руководства

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, "\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.

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 v5.12.5                                     2010-07-03                                          SHA1(3)