dsa.pod revision 325337 
1=pod
2
3=head1 NAME
4
5openssl-dsa,
6dsa - DSA key processing
7
8=head1 SYNOPSIS
9
10B<openssl> B<dsa>
11[B<-inform PEM|DER>]
12[B<-outform PEM|DER>]
13[B<-in filename>]
14[B<-passin arg>]
15[B<-out filename>]
16[B<-passout arg>]
17[B<-aes128>]
18[B<-aes192>]
19[B<-aes256>]
20[B<-camellia128>]
21[B<-camellia192>]
22[B<-camellia256>]
23[B<-des>]
24[B<-des3>]
25[B<-idea>]
26[B<-text>]
27[B<-noout>]
28[B<-modulus>]
29[B<-pubin>]
30[B<-pubout>]
31[B<-engine id>]
32
33=head1 DESCRIPTION
34
35The B<dsa> command processes DSA keys. They can be converted between various
36forms and their components printed out. B<Note> This command uses the
37traditional SSLeay compatible format for private key encryption: newer
38applications should use the more secure PKCS#8 format using the B<pkcs8>
39
40=head1 COMMAND OPTIONS
41
42=over 4
43
44=item B<-inform DER|PEM>
45
46This specifies the input format. The B<DER> option with a private key uses
47an ASN1 DER encoded form of an ASN.1 SEQUENCE consisting of the values of
48version (currently zero), p, q, g, the public and private key components
49respectively as ASN.1 INTEGERs. When used with a public key it uses a
50SubjectPublicKeyInfo structure: it is an error if the key is not DSA.
51
52The B<PEM> form is the default format: it consists of the B<DER> format base64
53encoded with additional header and footer lines. In the case of a private key
54PKCS#8 format is also accepted.
55
56=item B<-outform DER|PEM>
57
58This specifies the output format, the options have the same meaning as the 
59B<-inform> option.
60
61=item B<-in filename>
62
63This specifies the input filename to read a key from or standard input if this
64option is not specified. If the key is encrypted a pass phrase will be
65prompted for.
66
67=item B<-passin arg>
68
69the input file password source. For more information about the format of B<arg>
70see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
71
72=item B<-out filename>
73
74This specifies the output filename to write a key to or standard output by
75is not specified. If any encryption options are set then a pass phrase will be
76prompted for. The output filename should B<not> be the same as the input
77filename.
78
79=item B<-passout arg>
80
81the output file password source. For more information about the format of B<arg>
82see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
83
84=item B<-aes128|-aes192|-aes256|-camellia128|-camellia192|-camellia256|-des|-des3|-idea>
85
86These options encrypt the private key with the specified
87cipher before outputting it. A pass phrase is prompted for.
88If none of these options is specified the key is written in plain text. This
89means that using the B<dsa> utility to read in an encrypted key with no
90encryption option can be used to remove the pass phrase from a key, or by
91setting the encryption options it can be use to add or change the pass phrase.
92These options can only be used with PEM format output files.
93
94=item B<-text>
95
96prints out the public, private key components and parameters.
97
98=item B<-noout>
99
100this option prevents output of the encoded version of the key.
101
102=item B<-modulus>
103
104this option prints out the value of the public key component of the key.
105
106=item B<-pubin>
107
108by default a private key is read from the input file: with this option a
109public key is read instead.
110
111=item B<-pubout>
112
113by default a private key is output. With this option a public
114key will be output instead. This option is automatically set if the input is
115a public key.
116
117=item B<-engine id>
118
119specifying an engine (by its unique B<id> string) will cause B<dsa>
120to attempt to obtain a functional reference to the specified engine,
121thus initialising it if needed. The engine will then be set as the default
122for all available algorithms.
123
124=back
125
126=head1 NOTES
127
128The PEM private key format uses the header and footer lines:
129
130 -----BEGIN DSA PRIVATE KEY-----
131 -----END DSA PRIVATE KEY-----
132
133The PEM public key format uses the header and footer lines:
134
135 -----BEGIN PUBLIC KEY-----
136 -----END PUBLIC KEY-----
137
138=head1 EXAMPLES
139
140To remove the pass phrase on a DSA private key:
141
142 openssl dsa -in key.pem -out keyout.pem
143
144To encrypt a private key using triple DES:
145
146 openssl dsa -in key.pem -des3 -out keyout.pem
147
148To convert a private key from PEM to DER format: 
149
150 openssl dsa -in key.pem -outform DER -out keyout.der
151
152To print out the components of a private key to standard output:
153
154 openssl dsa -in key.pem -text -noout
155
156To just output the public part of a private key:
157
158 openssl dsa -in key.pem -pubout -out pubkey.pem
159
160=head1 SEE ALSO
161
162L<dsaparam(1)|dsaparam(1)>, L<gendsa(1)|gendsa(1)>, L<rsa(1)|rsa(1)>,
163L<genrsa(1)|genrsa(1)>
164
165=cut
166