1 .TH ELGAMAL 3
2 .SH NAME
3 eggen, egencrypt, egdecrypt, egsign, egverify, egpuballoc, egpubfree, egprivalloc, egprivfree, egsigalloc, egsigfree, egprivtopub - elgamal encryption
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 EGpriv*	eggen(int nlen, int nrep)
15 .PP
16 .B
17 mpint*	egencrypt(EGpub *k, mpint *in, mpint *out)
18 .PP
19 .B
20 mpint*	egdecrypt(EGpriv *k, mpint *in, mpint *out)
21 .PP
22 .B
23 EGsig*	egsign(EGpriv *k, mpint *m)
24 .PP
25 .B
26 int		egverify(EGpub *k, EGsig *sig, mpint *m)
27 .PP
28 .B
29 EGpub*	egpuballoc(void)
30 .PP
31 .B
32 void		egpubfree(EGpub*)
33 .PP
34 .B
35 EGpriv*	egprivalloc(void)
36 .PP
37 .B
38 void		egprivfree(EGpriv*)
39 .PP
40 .B
41 EGsig*	egsigalloc(void)
42 .PP
43 .B
44 void		egsigfree(EGsig*)
45 .PP
46 .B
47 EGpub*	egprivtopub(EGpriv*)
48 .SH DESCRIPTION
49 .PP
50 Elgamal is a public key encryption and signature algorithm.  The owner of a key publishes
51 the public part of the key:
52 .EX
53 	struct EGpub
54 	{
55 		mpint	*p;	// modulus
56 		mpint	*alpha;	// generator
57 		mpint	*key;	// (encryption key) alpha**secret mod p
58 	};
59 .EE
60 This part can be used for encrypting data (with
61 .IR egencrypt )
62 to be sent to the owner.
63 The owner decrypts (with
64 .IR egdecrypt )
65 using his private key:
66 .EX
67 	struct EGpriv
68 	{
69 		EGpub	pub;
70 		mpint	*secret; // (decryption key)
71 	};
72 .EE
73 .PP
74 Keys are generated using
75 .IR eggen .
76 .I Eggen
77 takes both bit length of the modulus
78 and the number of repetitions of the Miller-Rabin
79 primality test to run.  If the latter is 0, it does the default number
80 of rounds.
81 .I Egprivtopub
82 returns a newly allocated copy of the public key
83 corresponding to the private key.
84 .PP
85 The routines
86 .IR egpuballoc ,
87 .IR egpubfree ,
88 .IR egprivalloc ,
89 and
90 .I egprivfree
91 are provided to manage key storage.
92 .PP
93 .I Egsign
94 signs message
95 .I m
96 using a private key
97 .I k
98 yielding a
99 .EX
100 	struct EGsig
101 	{
102 		mpint	*r, *s;
103 	};
104 .EE
105 .I Egverify
106 returns 0 if the signature is valid and \-1 if not.
107 .PP
108 The routines
109 .I egsigalloc
110 and
111 .I egsigfree
112 are provided to manage signature storage.
113 .SH SOURCE
114 .B \*9/src/libsec
115 .SH SEE ALSO
116 .MR mp (3) ,
117 .MR aes (3) ,
118 .MR blowfish (3) ,
119 .MR des (3) ,
120 .MR dsa (3) ,
121 .MR rc4 (3) ,
122 .MR rsa (3) ,
123 .MR sechash (3) ,
124 .MR prime (3) ,
125 .MR rand (3)