Digest-Hashcash/Hashcash.pm

=head1 NAME

Digest::Hashcash - generate Hashcashes (http://www.hashcash.org)

=head1 SYNOPSIS

 use Digest::Hashcash;

=head1 DESCRIPTION

This module implements the hashcash hash (or digest, although it's
not clearly a digest). For all your information needs please visit
http://www.hashcash.org.

One thing to note about this module is that it requires ISO C99 support,
both in your compiler and your standard library.  If you don't have a
compiler that supports ISO C, get gcc at http://gcc.gnu.org/ :)

=over 4

=cut

package Digest::Hashcash;

use Time::Local;
use Time::HiRes;

no warnings;

BEGIN {
   our $VERSION = 1.1;

   require XSLoader;
   XSLoader::load Digest::Hashcash, $VERSION;
}

=item $secs = estimate_time $size

Estimate the average time necessary to calculate a token of the given
size.

See also C<estimate_size>.

=item $size = estimate_size $time[, $min]

Estimate the size that can be calculated in the given time (which is an
upper bound). The function will not return a size less then C<min>.

Estimating the time to be used can go wrong by as much as 50% (but is
usually quite accurate), and the estimation itself can take as much as a
second on slower (<pentium) machines, but faster machines (1Ghz P3 for
example) usually handle it within a hundredth of a second or so.

The estimation will be done only once, so you can call this function as
often as you like without incuring the overhead everytime.

=cut

my $rounds;

sub _rounds() {
   $rounds ||= _estimate_rounds
}

sub estimate_time($) {
   my ($size) = @_;

   2**$size / _rounds
}

sub estimate_size($$) {
   my ($time, $min) = @_;

   $time = (log $time * _rounds) / log 2;
   $time < $min ? $min : int $time
}

=item $cipher = new Digest::Hashcash [param => value...]

=over 4

=item size => 18

The number of collisions, in bits. Every bit increases the time to create
the token (and thus the cash) by two.

=item uid => ""

A string used to make the token more unique (e.g. the senders address)
and reduce token collisions. The string must only contain characters
valid for the trial part of the token, e.g. uuencoded, base64 or
e-mail-address-parts are useful here.

=item extrarand => 0

The extra bytes of randomness to add to the token in addition to the
standard amount. Each byte adds a little bit over 6 bit of randomness to
the token.

The standard amount of randomness is 8 (> 51 bits of randomness).

=item timestamp => 0

The timestamp to use. A value of 0 (the default) means to use the current
time.

=back

=item $token = $cipher->hash ($data [, param => value...])

Creates and returns a new token. This can take some time.

Any additional parameters are interpreted the same way as arguments to
C<new>.

=item $prefix = $cipher->verify ($token [, param => value...]))

Checks the given token and returns true if the token has the minimum
number of prefix bits, or false otherwise.  The value returned is actually
the number of collisions, so to find the number of collisions bits specify
C<< collisions => 0 >>.

Any additional parameters are interpreted the same way as arguments to
C<new>.

=item $resource = $cipher->resource ($token)

Returns the resource part, or C<undef>.

=item $tstamp = $ciper->timestamp ($token)

Returns the timestamp part (in the same format as perl's C<time>), or
C<undef>.

=back

=cut

sub new {
   my $class = shift;

   bless { @_ }, $class;
}

sub hash {
   my $self = shift;
   my %arg = (%$self, resource => @_);

   &_gentoken (@arg{qw(size timestamp resource uid extrarand)})
}

sub verify {
   my ($self, $token) = (shift, shift);
   my %arg = (%$self, @_);

   my $prefix = _prefixlen $token;

   $prefix < $arg{size}
      ? undef
      : $prefix
}

sub resource {
   my ($self, $token) = @_;

   $token =~ /^\d+:\d*:(.*):/
      or return undef;

   $1
}

sub timestamp {
   my ($self, $token) = @_;

   $token =~ /^\d+:(\d*):.*:/
      or return undef;

   my ($y, $m, $d, $H, $M, $S);
   local $_ = $1;
   $y = /\G(\d\d)/gc ? $1 : return undef;
   $m = /\G(\d\d)/gc ? $1 : 1;
   $d = /\G(\d\d)/gc ? $1 : 1;
   $H = /\G(\d\d)/gc ? $1 : 0;
   $M = /\G(\d\d)/gc ? $1 : 0;
   $S = /\G(\d\d)/gc ? $1 : 0;

   timegm $S, $M, $H, $d, $m - 1, $y
}

=head1 SEE ALSO

L<http://www.hashcash.org>.

=head1 SUPPORT FOR THE PERL MULTICORE SPECIFICATION

This module supports the perl multicore specification
(<http://perlmulticore.schmorp.de/>) for token generation of any length
and size.

=head1 BUGS

 * There is a y2k+100 problem, as I always assume the same as Time::Local.
   This is a problem with the hashcash specification, which specifies
   years as 2 digits :(

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de

=cut

1;

Revision:	1.8
Committed:	Wed Jul 22 12:09:48 2015 UTC (8 years, 9 months ago) by root
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.7:	+20 -17 lines
Log Message:	* empty log message *
#	Content
1	=head1 NAME
2
3	Digest::Hashcash - generate Hashcashes (http://www.hashcash.org)
4
5	=head1 SYNOPSIS
6
7	use Digest::Hashcash;
8
9	=head1 DESCRIPTION
10
11	This module implements the hashcash hash (or digest, although it's
12	not clearly a digest). For all your information needs please visit
13	http://www.hashcash.org.
14
15	One thing to note about this module is that it requires ISO C99 support,
16	both in your compiler and your standard library. If you don't have a
17	compiler that supports ISO C, get gcc at http://gcc.gnu.org/ :)
18
19	=over 4
20
21	=cut
22
23	package Digest::Hashcash;
24
25	use Time::Local;
26	use Time::HiRes;
27
28	no warnings;
29
30	BEGIN {
31	our $VERSION = 1.1;
32
33	require XSLoader;
34	XSLoader::load Digest::Hashcash, $VERSION;
35	}
36
37	=item $secs = estimate_time $size
38
39	Estimate the average time necessary to calculate a token of the given
40	size.
41
42	See also C<estimate_size>.
43
44	=item $size = estimate_size $time[, $min]
45
46	Estimate the size that can be calculated in the given time (which is an
47	upper bound). The function will not return a size less then C<min>.
48
49	Estimating the time to be used can go wrong by as much as 50% (but is
50	usually quite accurate), and the estimation itself can take as much as a
51	second on slower (<pentium) machines, but faster machines (1Ghz P3 for
52	example) usually handle it within a hundredth of a second or so.
53
54	The estimation will be done only once, so you can call this function as
55	often as you like without incuring the overhead everytime.
56
57	=cut
58
59	my $rounds;
60
61	sub _rounds() {
62	$rounds \|\|= _estimate_rounds
63	}
64
65	sub estimate_time($) {
66	my ($size) = @_;
67
68	2**$size / _rounds
69	}
70
71	sub estimate_size($$) {
72	my ($time, $min) = @_;
73
74	$time = (log $time * _rounds) / log 2;
75	$time < $min ? $min : int $time
76	}
77
78	=item $cipher = new Digest::Hashcash [param => value...]
79
80	=over 4
81
82	=item size => 18
83
84	The number of collisions, in bits. Every bit increases the time to create
85	the token (and thus the cash) by two.
86
87	=item uid => ""
88
89	A string used to make the token more unique (e.g. the senders address)
90	and reduce token collisions. The string must only contain characters
91	valid for the trial part of the token, e.g. uuencoded, base64 or
92	e-mail-address-parts are useful here.
93
94	=item extrarand => 0
95
96	The extra bytes of randomness to add to the token in addition to the
97	standard amount. Each byte adds a little bit over 6 bit of randomness to
98	the token.
99
100	The standard amount of randomness is 8 (> 51 bits of randomness).
101
102	=item timestamp => 0
103
104	The timestamp to use. A value of 0 (the default) means to use the current
105	time.
106
107	=back
108
109	=item $token = $cipher->hash ($data [, param => value...])
110
111	Creates and returns a new token. This can take some time.
112
113	Any additional parameters are interpreted the same way as arguments to
114	C<new>.
115
116	=item $prefix = $cipher->verify ($token [, param => value...]))
117
118	Checks the given token and returns true if the token has the minimum
119	number of prefix bits, or false otherwise. The value returned is actually
120	the number of collisions, so to find the number of collisions bits specify
121	C<< collisions => 0 >>.
122
123	Any additional parameters are interpreted the same way as arguments to
124	C<new>.
125
126	=item $resource = $cipher->resource ($token)
127
128	Returns the resource part, or C<undef>.
129
130	=item $tstamp = $ciper->timestamp ($token)
131
132	Returns the timestamp part (in the same format as perl's C<time>), or
133	C<undef>.
134
135	=back
136
137	=cut
138
139	sub new {
140	my $class = shift;
141
142	bless { @_ }, $class;
143	}
144
145	sub hash {
146	my $self = shift;
147	my %arg = (%$self, resource => @_);
148
149	&_gentoken (@arg{qw(size timestamp resource uid extrarand)})
150	}
151
152	sub verify {
153	my ($self, $token) = (shift, shift);
154	my %arg = (%$self, @_);
155
156	my $prefix = _prefixlen $token;
157
158	$prefix < $arg{size}
159	? undef
160	: $prefix
161	}
162
163	sub resource {
164	my ($self, $token) = @_;
165
166	$token =~ /^\d+:\d:(.):/
167	or return undef;
168
169	$1
170	}
171
172	sub timestamp {
173	my ($self, $token) = @_;
174
175	$token =~ /^\d+:(\d):.:/
176	or return undef;
177
178	my ($y, $m, $d, $H, $M, $S);
179	local $_ = $1;
180	$y = /\G(\d\d)/gc ? $1 : return undef;
181	$m = /\G(\d\d)/gc ? $1 : 1;
182	$d = /\G(\d\d)/gc ? $1 : 1;
183	$H = /\G(\d\d)/gc ? $1 : 0;
184	$M = /\G(\d\d)/gc ? $1 : 0;
185	$S = /\G(\d\d)/gc ? $1 : 0;
186
187	timegm $S, $M, $H, $d, $m - 1, $y
188	}
189
190	=head1 SEE ALSO
191
192	L<http://www.hashcash.org>.
193
194	=head1 SUPPORT FOR THE PERL MULTICORE SPECIFICATION
195
196	This module supports the perl multicore specification
197	(<http://perlmulticore.schmorp.de/>) for token generation of any length
198	and size.
199
200	=head1 BUGS
201
202	* There is a y2k+100 problem, as I always assume the same as Time::Local.
203	This is a problem with the hashcash specification, which specifies
204	years as 2 digits :(
205
206	=head1 AUTHOR
207
208	Marc Lehmann <schmorp@schmorp.de>
209	http://home.schmorp.de
210
211	=cut
212
213	1;
214