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Crypt::DH(3pm) User Contributed Perl Documentation Crypt::DH(3pm)
NAME
Crypt::DH - Diffie-Hellman key exchange system
SYNOPSIS
use Crypt::DH;
my $dh = Crypt::DH->new;
$dh->g($g);
$dh->p($p);
## Generate public and private keys.
$dh->generate_keys;
$my_pub_key = $dh->pub_key;
## Send $my_pub_key to "other" party, and receive "other"
## public key in return.
## Now compute shared secret from "other" public key.
my $shared_secret = $dh->compute_secret( $other_pub_key );
DESCRIPTION
Crypt::DH is a Perl implementation of the Diffie-Hellman key exchange system. Diffie-Hell-
man is an algorithm by which two parties can agree on a shared secret key, known only to
them. The secret is negotiated over an insecure network without the two parties ever
passing the actual shared secret, or their private keys, between them.
THE ALGORITHM
The algorithm generally works as follows: Party A and Party B choose a property p and a
property g; these properties are shared by both parties. Each party then computes a random
private key integer priv_key, where the length of priv_key is at most (number of bits in
p) - 1. Each party then computes a public key based on g, priv_key, and p; the exact value
is
g ^ priv_key mod p
The parties exchange these public keys.
The shared secret key is generated based on the exchanged public key, the private key, and
p. If the public key of Party B is denoted pub_key_B, then the shared secret is equal to
pub_key_B ^ priv_key mod p
The mathematical principles involved insure that both parties will generate the same
shared secret key.
More information can be found in PKCS #3 (Diffie-Hellman Key Agreement Standard):
http://www.rsasecurity.com/rsalabs/pkcs/pkcs-3/
USAGE
Crypt::DH implements the core routines needed to use Diffie-Hellman key exchange. To actu-
ally use the algorithm, you'll need to start with values for p and g; p is a large prime,
and g is a base which must be larger than 0 and less than p.
Crypt::DH uses Math::BigInt internally for big-integer calculations. All accessor methods
(p, g, priv_key, and pub_key) thus return Math::BigInt objects, as does the compute_secret
method. The accessors, however, allow setting with a scalar decimal string, hex string
(^0x), Math::BigInt object, or Math::Pari object (for backwards compatibility).
$dh = Crypt::DH->new([ %param ]).
Constructs a new Crypt::DH object and returns the object. %param may include none, some,
or all of the keys p, g, and priv_key.
$dh->p([ $p ])
Given an argument $p, sets the p parameter (large prime) for this Crypt::DH object.
Returns the current value of p. (as a Math::BigInt object)
$dh->g([ $g ])
Given an argument $g, sets the g parameter (base) for this Crypt::DH object.
Returns the current value of g.
$dh->generate_keys
Generates the public and private key portions of the Crypt::DH object, assuming that
you've already filled p and g with appropriate values.
If you've provided a priv_key, it's used, otherwise a random priv_key is created using
either Crypt::Random (if already loaded), or /dev/urandom, or Perl's rand, in that order.
$dh->compute_secret( $public_key )
Given the public key $public_key of Party B (the party with which you're performing key
negotiation and exchange), computes the shared secret key, based on that public key, your
own private key, and your own large prime value (p).
The historical method name "compute_key" is aliased to this for compatibility.
$dh->priv_key([ $priv_key ])
Returns the private key. Given an argument $priv_key, sets the priv_key parameter for
this Crypt::DH object.
$dh->pub_key
Returns the public key.
AUTHOR & COPYRIGHT
Benjamin Trott, ben AT rhumba.com
Brad Fitzpatrick, brad AT danga.com
Except where otherwise noted, Crypt::DH is Copyright 2001 Benjamin Trott. All rights
reserved. Crypt::DH is free software; you may redistribute it and/or modify it under the
same terms as Perl itself.
perl v5.8.8 2007-10-23 Crypt::DH(3pm)
Generated by $Id: phpMan.php,v 4.49 2006/02/26 13:18:18 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
2012-05-22 18:22 @38.107.179.236 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)