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