1 .TH DSA 3
2 .SH NAME
3 dsagen, dsasign, dsaverify, dsapuballoc, dsapubfree, dsaprivalloc, dsaprivfree, dsasigalloc, dsasigfree, dsaprivtopub - digital signature algorithm
4 .SH SYNOPSIS
5 .B #include <u.h>
6 .br
7 .B #include <libc.h>
8 .br
9 .B #include <mp.h>
10 .br
11 .B #include <libsec.h>
12 .PP
13 .B
14 DSApriv*	dsagen(DSApub *opub)
15 .PP
16 .B
17 DSAsig*	dsasign(DSApriv *k, mpint *m)
18 .PP
19 .B
20 int		dsaverify(DSApub *k, DSAsig *sig, mpint *m)
21 .PP
22 .B
23 DSApub*	dsapuballoc(void)
24 .PP
25 .B
26 void		dsapubfree(DSApub*)
27 .PP
28 .B
29 DSApriv*	dsaprivalloc(void)
30 .PP
31 .B
32 void		dsaprivfree(DSApriv*)
33 .PP
34 .B
35 DSAsig*	dsasigalloc(void)
36 .PP
37 .B
38 void		dsasigfree(DSAsig*)
39 .PP
40 .B
41 DSApub*	dsaprivtopub(DSApriv*)
42 .SH DESCRIPTION
43 .PP
44 DSA is the NIST approved digital signature algorithm.  The owner of a key publishes
45 the public part of the key:
46 .EX
47 	struct DSApub
48 	{
49 		mpint	*p;	// modulus
50 		mpint	*q;	// group order, q divides p-1
51 		mpint	*alpha;	// group generator
52 		mpint	*key;	// alpha**secret mod p
53 	};
54 .EE
55 This part can be used for verifying signatures (with
56 .IR dsaverify )
57 created by the owner.
58 The owner signs (with
59 .IR dsasign )
60 using his private key:
61 .EX
62 	struct DSApriv
63 	{
64 		DSApub	pub;
65 		mpint	*secret; // (decryption key)
66 	};
67 .EE
68 .PP
69 Keys are generated using
70 .IR dsagen .
71 If
72 .IR dsagen 's
73 argument
74 .I opub
75 is
76 .BR nil ,
77 a key is created using a new
78 .B p
79 and
80 .B q
81 generated by
82 .IR DSAprimes (3).
83 Otherwise,
84 .B p
85 and
86 .B q
87 are copied from the old key.
88 .PP
89 .I Dsaprivtopub
90 returns a newly allocated copy of the public key
91 corresponding to the private key.
92 .PP
93 The routines
94 .IR dsapuballoc ,
95 .IR dsapubfree ,
96 .IR dsaprivalloc ,
97 and
98 .I dsaprivfree
99 are provided to manage key storage.
100 .PP
101 .I Dsasign
102 signs message
103 .I m
104 using a private key
105 .I k
106 yielding a
107 .EX
108 	struct DSAsig
109 	{
110 		mpint	*r, *s;
111 	};
112 .EE
113 .I Dsaverify
114 returns 0 if the signature is valid and \-1 if not.
115 .PP
116 The routines
117 .I dsasigalloc
118 and
119 .I dsasigfree
120 are provided to manage signature storage.
121 .SH SOURCE
122 .B /usr/local/plan9/src/libsec
123 .SH SEE ALSO
124 .IR mp (3),
125 .IR aes (3),
126 .IR blowfish (3),
127 .IR des (3),
128 .IR rc4 (3),
129 .IR rsa (3),
130 .IR sechash (3),
131 .IR prime (3),
132 .IR rand (3)