NAME

       Crypt::GCrypt::MPI - Perl interface to multi-precision integers from the GNU Cryptographic
       library

SYNOPSIS

         use Crypt::GCrypt::MPI;

         my $mpi = Crypt::GCrypt::MPI->new();

ABSTRACT

       Crypt::GCrypt::MPI provides an object interface to multi-precision integers from the C
       libgcrypt library.

BASIC OPERATIONS

   new()
       Create a new multi-precision integer.

         my $mpi = Crypt::GCrypt::MPI::new(
           secure => 1,
           value => 20,
         );

       No parameters are required.  If only one parameter is given, it is treated as the "value"
       parameter.  Available parameters:

       value
           The initial value of the MPI.  This can be an integer, a string, or another
           Crypt::GCrypt::MPI.  (It would also be nice to be able to initialize it with a
           Math::Int).

       secure
           If this parameter evaluates to non-zero, initialize the MPI using secure memory, if
           possible.

       format
           If the value is a string, the format parameter suggests how to convert the string.
           See CONVERSION FORMATS for the available formats.  Defaults to
           Crypt::GCrypt::MPI::FMT_STD.

   set()
       Copies the value of the other Crypt::GCrypt::MPI object.

         $mpi->set($othermpi);

   swap()
       Exchanges the value with the value of another Crypt::GCrpyt::MPI object:

         $mpi->swap($othermpi);

   is_secure()
       Returns true if the Crypt::GCrypt::MPI uses secure memory, where possible.

   cmp($other)
       Compares this object against another Crypt::GCrypt::MPI object, returning 0 if the two
       values are equal, positive if this value is greater, negative if $other is greater.

   mutually_prime($other)
       Compares this object against another Crypt::GCrypt::MPI object, returning true only if the
       two values share no factors in common other than 1.

   copy()
       Returns a new Crypt::GCrypt::MPI object, with the contents identical to this one.  This is
       different from using the assignment operator (=), which just makes two references to the
       same object.  For example:

        $b = new Crypt::GCrypt::MPI(15);
        $a = $b;
        $b->add(1); # $a points to the same object,
                    # so both $a and $b contain 16.

        $a = $b->copy(); # $a and $b are both 16, but
                         # different objects; no risk of
                         # double-free.
        $b->add(1); # $a == 16, $b == 17

       If $b is a Crypt::GCrypt::MPI object, then "$a = $b->copy();" is identical to "$a =
       Crypt::GCrypt::MPI->new($b);"

CALCULATIONS

       All calculation operations modify the object they are called on, and return the same
       object, so you can chain them like this:

        $g->addm($a, $m)->mulm($b, $m)->gcd($x);

       If you don't want an operation to affect the initial object, use the copy() operator:

        $h = $g->copy()->addm($a, $m)->mulm($b, $m)->gcd($x);

   add($other)
       Adds the value of $other to this MPI.

   addm($other, $modulus)
       Adds the value of $other to this MPI, modulo the value of $modulus.

   sub($other)
       Subtracts the value of $other from this MPI.

   subm($other, $modulus)
       Subtracts the value of $other from this MPI, modulo the value of $modulus.

   mul($other)
       Multiply this MPI by the value of $other.

   mulm($other, $modulus)
       Multiply this MPI by the value of $other, modulo the value of $modulus.

   mul_2exp($e)
       Multiply this MPI by 2 raised to the power of $e (this is a leftward bitshift)

   div($other)
       Divide this MPI by the value of $other, leaving the integer quotient.  (This is integer
       division)

   mod($other)
       Divide this MPI by the value of $other, leaving the integer remainder.  (This is the
       modulus operation)

   powm($other, $modulus)
       Raise this MPI to the power of $other, modulo the value of $modulus.

   invm($modulus)
       Find the multiplicative inverse of this MPI, modulo $modulus.

   gcd($other)
       Find the greatest common divisor of this MPI and $other.

OUTPUT AND DEBUGGING

   dump()
       Send the MPI to the libgcrypt debugging stream.

   print($format)
       Return a string with the data of this MPI, in a given format.  See CONVERSION FORMATS for
       the available formats.

CONVERSION FORMATS

       The available printing and scanning formats are all in the Crypt::GCrypt::MPI namespace,
       and have the same meanings as in gcrypt.

   FMT_STD
       Two's complement representation.

   FMT_PGP
       Same as FMT_STD, but with two-byte length header, as used in OpenPGP.  (Only works for
       non-negative values)

   FMT_SSH
       Same as FMT_STD, but with four-byte length header, as used by OpenSSH.

   FMT_HEX
       Hexadecimal string in ASCII.

   FMT_USG
       Simple unsigned integer.

BUGS AND FEEDBACK

       Crypt::GCrypt::MPI does not currently auto-convert to and from Math::BigInt objects, even
       though it should.

       Other than that, here are no known bugs. You are very welcome to write mail to the
       maintainer (aar@cpan.org) with your contributions, comments, suggestions, bug reports or
       complaints.

AUTHORS AND CONTRIBUTORS

       Daniel Kahn Gillmor <dkg@fifthhorseman.net>

       Alessandro Ranellucci <aar@cpan.org>

COPYRIGHT AND LICENSE

       Copyright © Daniel Kahn Gillmor.  Crypt::GCrypt::MPI is free software, you may
       redistribute it and/or modify it under the same terms as Perl itself.

ACKNOWLEDGEMENTS

       This module was initially inspired by the GCrypt.pm bindings made by Robert Bihlmeyer in
       2002. Thanks to users who give feedback and submit patches (see Changelog).

DISCLAIMER

       This software is provided by the copyright holders and contributors ``as is'' and any
       express or implied warranties, including, but not limited to, the implied warranties of
       merchantability and fitness for a particular purpose are disclaimed. In no event shall the
       regents or contributors be liable for any direct, indirect, incidental, special,
       exemplary, or consequential damages (including, but not limited to, procurement of
       substitute goods or services; loss of use, data, or profits; or business interruption)
       however caused and on any theory of liability, whether in contract, strict liability, or
       tort (including negligence or otherwise) arising in any way out of the use of this
       software, even if advised of the possibility of such damage.