1Crypt::DSA(3)         User Contributed Perl Documentation        Crypt::DSA(3)
2
3
4

NAME

6       Crypt::DSA - DSA Signatures and Key Generation
7

SYNOPSIS

9           use Crypt::DSA;
10           my $dsa = Crypt::DSA->new;
11
12           my $key = $dsa->keygen(
13                          Size      => 512,
14                          Seed      => $seed,
15                          Verbosity => 1
16                     );
17
18           my $sig = $dsa->sign(
19                          Message   => "foo bar",
20                          Key       => $key
21                     );
22
23           my $verified = $dsa->verify(
24                          Message   => "foo bar",
25                          Signature => $sig,
26                          Key       => $key,
27                     );
28

DESCRIPTION

30       Crypt::DSA is an implementation of the DSA (Digital Signature
31       Algorithm) signature verification system. The implementation itself is
32       pure Perl, although the heavy-duty mathematics underneath are provided
33       by the Math::Pari library.
34
35       This package provides DSA signing, signature verification, and key
36       generation.
37

USAGE

39       The Crypt::DSA public interface is similar to that of Crypt::RSA. This
40       was done intentionally.
41
42   Crypt::DSA->new
43       Constructs a new Crypt::DSA object. At the moment this isn't
44       particularly useful in itself, other than being the object you need to
45       do much else in the system.
46
47       Returns the new object.
48
49   $key = $dsa->keygen(%arg)
50       Generates a new set of DSA keys, including both the public and private
51       portions of the key.
52
53       %arg can contain:
54
55       ·   Size
56
57           The size in bits of the p value to generate. The q and g values are
58           always 160 bits each.
59
60           This argument is mandatory.
61
62       ·   Seed
63
64           A seed with which q generation will begin. If this seed does not
65           lead to a suitable prime, it will be discarded, and a new random
66           seed chosen in its place, until a suitable prime can be found.
67
68           This is entirely optional, and if not provided a random seed will
69           be generated automatically.
70
71       ·   Verbosity
72
73           Should be either 0 or 1. A value of 1 will give you a progress
74           meter during p and q generation--this can be useful, since the
75           process can be relatively long.
76
77           The default is 0.
78
79   $signature = $dsa->sign(%arg)
80       Signs a message (or the digest of a message) using the private portion
81       of the DSA key and returns the signature.
82
83       The return value--the signature--is a Crypt::DSA::Signature object.
84
85       %arg can include:
86
87       ·   Digest
88
89           A digest to be signed. The digest should be 20 bytes in length or
90           less.
91
92           You must provide either this argument or Message (see below).
93
94       ·   Key
95
96           The Crypt::DSA::Key object with which the signature will be
97           generated. Should contain a private key attribute (priv_key).
98
99           This argument is required.
100
101       ·   Message
102
103           A plaintext message to be signed. If you provide this argument,
104           sign will first produce a SHA1 digest of the plaintext, then use
105           that as the digest to sign. Thus writing
106
107               my $sign = $dsa->sign(Message => $message, ... );
108
109           is a shorter way of writing
110
111               use Digest::SHA1 qw( sha1 );
112               my $sig = $dsa->sign(Digest => sha1( $message ), ... );
113
114   $verified = $dsa->verify(%arg)
115       Verifies a signature generated with sign. Returns a true value on
116       success and false on failure.
117
118       %arg can contain:
119
120       ·   Key
121
122           Key of the signer of the message; a Crypt::DSA::Key object.  The
123           public portion of the key is used to verify the signature.
124
125           This argument is required.
126
127       ·   Signature
128
129           The signature itself. Should be in the same format as returned from
130           sign, a Crypt::DSA::Signature object.
131
132           This argument is required.
133
134       ·   Digest
135
136           The original signed digest whose length is less than or equal to 20
137           bytes.
138
139           Either this argument or Message (see below) must be present.
140
141       ·   Message
142
143           As above in sign, the plaintext message that was signed, a string
144           of arbitrary length. A SHA1 digest of this message will be created
145           and used in the verification process.
146

TODO

148       Add ability to munge format of keys. For example, read/write keys
149       from/to key files (SSH key files, etc.), and also write them in other
150       formats.
151

SUPPORT

153       Bugs should be reported via the CPAN bug tracker at
154
155       http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Crypt-DSA
156       <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Crypt-DSA>
157
158       For other issues, contact the author.
159

AUTHOR

161       Benjamin Trott <ben@sixapart.com>
162

COPYRIGHT

164       Except where otherwise noted, Crypt::DSA is Copyright 2006 - 2009
165       Benjamin Trott.
166
167       Crypt::DSA is free software; you may redistribute it and/or modify it
168       under the same terms as Perl itself.
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172perl v5.12.0                      2009-09-11                     Crypt::DSA(3)