1Crypt::OpenSSL::DSA(3)User Contributed Perl DocumentationCrypt::OpenSSL::DSA(3)
2
6 Crypt::OpenSSL::DSA - Digital Signature Algorithm using OpenSSL
7
9 use Crypt::OpenSSL::DSA;
10 # generate keys and write out to PEM files
12 my $dsa = Crypt::OpenSSL::DSA->generate_parameters( 512 );
13 $dsa->generate_key;
14 $dsa->write_pub_key( $filename );
15 $dsa->write_priv_key( $filename );
16 # using keys from PEM files
18 my $dsa_priv = Crypt::OpenSSL::DSA->read_priv_key( $filename );
19 my $sig = $dsa_priv->sign($message);
20 my $dsa_pub = Crypt::OpenSSL::DSA->read_pub_key( $filename );
21 my $valid = $dsa_pub->verify($message, $sig);
22 # using keys from PEM strings
24 my $dsa_priv = Crypt::OpenSSL::DSA->read_priv_key_str( $key_string );
25 my $sig = $dsa_priv->sign($message);
26 my $dsa_pub = Crypt::OpenSSL::DSA->read_pub_key_str( $key_string );
27 my $valid = $dsa_pub->verify($message, $sig);
28
30 Crypt::OpenSSL::DSA implements the DSA (Digital Signature Algorithm)
31 signature verification system.
32 It is a thin XS wrapper to the DSA functions contained in the OpenSSL
34 crypto library, located at http://www.openssl.org
35
37 $dsa = Crypt::OpenSSL::DSA->generate_parameters( $bits, $seed );
38 Returns a new DSA object and generates the p, q and g parameters
39 necessary to generate keys.
40 bits is the length of the prime to be generated; the DSS allows a
42 maximum of 1024 bits.
43 $dsa = Crypt::OpenSSL::DSA->read_params( $filename );
45 Reads in a parameter PEM file and returns a new DSA object with the
46 p, q and g parameters necessary to generate keys.
47 $dsa = Crypt::OpenSSL::DSA->read_pub_key( $filename );
49 Reads in a public key PEM file and returns a new DSA object that
50 can be used to verify DSA signatures.
51 $dsa = Crypt::OpenSSL::DSA->read_priv_key( $filename );
53 Reads in a private key PEM file and returns a new DSA object that
54 can be used to sign messages.
55 $dsa = Crypt::OpenSSL::DSA->read_pub_key_str( $key_string );
57 Reads in a public key PEM string and returns a new DSA object that
58 can be used to verify DSA signatures. The string should include
59 the -----BEGIN...----- and -----END...----- lines.
60 $dsa = Crypt::OpenSSL::DSA->read_priv_key_str( $key_string );
62 Reads in a private key PEM string and returns a new DSA object that
63 can be used to sign messages. The string should include the
64 -----BEGIN...----- and -----END...----- lines.
65
67 $dsa->generate_key;
68 Generates private and public keys, assuming that $dsa is the return
69 value of generate_parameters.
70 $sig_size = $dsa->get_sig_size( );
72 Returns the maximum size of an ASN.1 encoded DSA signature for key
73 dsa in bytes.
74 512-bit keys = 48
76 1024-bit keys = 48
77 2024-bit keys = 72
78 3072-bit keys = 72
79 ASN.1 dsa signatures consist of:
81 Sequence 1-byte (0x30) Length 1-byte Integer 1-byte (0x02)
83 Length 1-byte (0x14) = 20 r 20-bytes or 21-bytes Integer
84 1-byte (0x02) Length 1-byte (0x14) = 20 s 20-bytes or
85 21-bytes
86 30 2C 02 14
88 6C.70.50.7C.93.A8.B5.EC.1E.A1.5E.C5.73.AA.0F.EA.4D.BE.42.7A 02 14
89 4E.AD.E6.BB.72.54.92.30.2B.03.AB.53.5D.3D.6E.88.B8.AA.D6.30
90 Note that the above signature is 46 bytes long - the extra two
92 bytes are used only when r and/or s are larger than or equal to
93 2^159. The extra bytes are used to distinguish positive from
94 negative values.
95 All that to say if you are using get_sig_size() to determine the
97 size of r + s depending on the size of the key you can subtract 8
98 bytes for the ASN.1 overhead.
99 $sig = $dsa->sign( $message );
101 Signs $message, returning the signature. Note that $meesage cannot
102 exceed 20 characters in length.
103 $dsa is the signer's private key.
105 $sig_obj = $dsa->do_sign( $message );
107 Similar to "sign", but returns a Crypt::OpenSSL::DSA::Signature
108 object.
109 $valid = $dsa->verify( $message, $sig );
111 Verifies that the $sig signature for $message is valid.
112 $dsa is the signer's public key.
114 Note: it croaks if the underlying library call returns error (-1).
116 $valid = $dsa->do_verify( $message, $sig_obj );
118 Similar to "verify", but uses a Crypt::OpenSSL::DSA::Signature
119 object.
120 Note: it croaks if the underlying library call returns error (-1).
122 $dsa->write_params( $filename );
124 Writes the parameters into a PEM file.
125 $dsa->write_pub_key( $filename );
127 Writes the public key into a PEM file.
128 $dsa->write_priv_key( $filename );
130 Writes the private key into a PEM file.
131 $p = $dsa->get_p, $dsa->set_p($p)
133 Gets/sets the prime number in binary format.
134 $q = $dsa->get_q, $dsa->set_q($q)
136 Gets/sets the subprime number (q | p-1) in binary format.
137 $g = $dsa->get_g, $dsa->set_g($g)
139 Gets/sets the generator of subgroup in binary format.
140 $pub_key = $dsa->get_pub_key, $dsa->set_pub_key($pub_key)
142 Gets/sets the public key (y = g^x) in binary format.
143 $priv_key = $dsa->get_priv_key, $dsa->set_priv_key($priv_key)
145 Gets/sets the private key in binary format.
146
148 Crpyt::DSA is a more mature Perl DSA module, but can be difficult to
149 install, because of the Math::Pari requirement.
150 Comments, suggestions, and patches welcome.
152
154 T.J. Mather, <tjmather@maxmind.com>
155
157 Copyright (c) 2002 T.J. Mather. Crypt::OpenSSL::DSA is free software;
158 you may redistribute it and/or modify it under the same terms as Perl
159 itself.
160 Paid support is available directly from the author of this package.
162 Please see <http://www.maxmind.com/app/opensourceservices> for more
163 details.
164
166 Crypt::OpenSSL::DSA::Signature
167 Crypt::DSA, Crypt::OpenSSL::RSA
169 Net::DNS::SEC
171perl v5.36.0 2022-07-22 Crypt::OpenSSL::DSA(3)