1Crypt::DH::GMP(3) User Contributed Perl Documentation Crypt::DH::GMP(3)
2
6 Crypt::DH::GMP - Crypt::DH Using GMP Directly
7
9 use Crypt::DH::GMP;
10 my $dh = Crypt::DH::GMP->new(p => $p, g => $g);
12 my $val = $dh->compute_secret();
13 # If you want compatibility with Crypt::DH (it uses Math::BigInt)
15 # then use this flag
16 # You /think/ you're using Crypt::DH, but...
17 use Crypt::DH::GMP qw(-compat);
18 my $dh = Crypt::DH->new(p => $p, g => $g);
20 my $val = $dh->compute_secret();
21
23 Crypt::DH::GMP is a (somewhat) portable replacement to Crypt::DH,
24 implemented mostly in C.
25
27 In the beginning, there was "Crypt::DH". However, "Crypt::DH" suffers
28 from a couple of problems:
29 GMP/Pari libraries are almost always required
31 "Crypt::DH" works with a plain "Math::BigInt", but if you want to
32 use it in production, you almost always need to install
33 "Math::BigInt::GMP" or "Math::BigInt::Pari" because without them,
34 the computation that is required by "Crypt::DH" makes the module
35 pretty much unusable.
36 Because of this, "Crypt::DH" might as well make "Math::BigInt::GMP"
38 a hard requirement.
39 Crypt::DH suffers from having Math::BigInt in between GMP
41 With or without "Math::BigInt::GMP" or "Math::BigInt::Pari",
42 "Crypt::DH" makes several round trip conversions between Perl
43 scalars, Math::BigInt objects, and finally its C representation (if
44 GMP/Pari are installed).
45 Instantiating an object comes with a relatively high cost, and if
47 you make many computations in one go, your program will suffer
48 dramatically because of this.
49 These problems quickly become apparent when you use modules such as
51 "Net::OpenID::Consumer", which requires to make a few calls to
52 "Crypt::DH".
53 "Crypt::DH::GMP" attempts to alleviate these problems by providing a
55 "Crypt::DH"-compatible layer, which, instead of doing calculations via
56 Math::BigInt, directly works with libgmp in C.
57 This means that we've essentially eliminated 2 call stacks worth of
59 expensive Perl method calls and we also only load 1 (Crypt::DH::GMP)
60 module instead of 3 (Crypt::DH + Math::BigInt + Math::BigInt::GMP).
61 These add up to a fairly significant increase in performance.
63
65 Crypt::DH::GMP absolutely refuses to consider using anything other than
66 strings as its parameters and/or return values therefore if you would
67 like to use Math::BigInt objects as your return values, you can not use
68 Crypt::DH::GMP directly. Instead, you need to be explicit about it:
69 use Crypt::DH;
71 use Crypt::DH::GMP qw(-compat); # must be loaded AFTER Crypt::DH
72 Specifying -compat invokes a very nasty hack that overwrites
74 Crypt::DH's symbol table -- this then forces Crypt::DH users to use
75 Crypt::DH::GMP instead, even if you are writing
76 my $dh = Crypt::DH->new(...);
78 $dh->compute_key();
79
81 By NO MEANS is this an exhaustive benchmark, but here's what I get on
82 my MacBook (OS X 10.5.8, 2.4 GHz Core 2 Duo, 4GB RAM)
83 Benchmarking instatiation cost...
85 Rate pp gmp
86 pp 9488/s -- -79%
87 gmp 45455/s 379% --
88 Benchmarking key generation cost...
90 Rate gmp pp
91 gmp 6.46/s -- -0%
92 pp 6.46/s 0% --
93 Benchmarking compute_key cost...
95 Rate pp gmp
96 pp 12925/s -- -96%
97 gmp 365854/s 2730% --
98
100 new
101 p
102 g
103 compute_key
104 compute_secret
105 generate_keys
106 pub_key
107 priv_key
108 compute_key_twoc
109 Computes the key, and returns a string that is byte-padded two's
110 compliment in binary form.
111 pub_key_twoc
113 Returns the pub_key as a string that is byte-padded two's compliment in
114 binary form.
115 clone
118 Daisuke Maki "<daisuke@endeworks.jp>"
119
121 This program is free software; you can redistribute it and/or modify it
122 under the same terms as Perl itself.
123 See http://www.perl.com/perl/misc/Artistic.html
125perl v5.32.1 2021-01-27 Crypt::DH::GMP(3)