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1 | /* -*-c-*- |
2 | * |
3 | * $Id: rsa-gen.c,v 1.1 1999/12/22 15:50:45 mdw Exp $ |
4 | * |
5 | * RSA parameter generation |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: rsa-gen.c,v $ |
33 | * Revision 1.1 1999/12/22 15:50:45 mdw |
34 | * Initial RSA support. |
35 | * |
36 | */ |
37 | |
38 | /*----- Header files ------------------------------------------------------*/ |
39 | |
40 | #include <mLib/dstr.h> |
41 | |
42 | #include "grand.h" |
43 | #include "mp.h" |
44 | #include "pgen.h" |
45 | #include "rsa.h" |
46 | #include "strongprime.h" |
47 | |
48 | /*----- Main code ---------------------------------------------------------*/ |
49 | |
50 | /* --- @rsa_gen@ --- * |
51 | * |
52 | * Arguments: @rsa_param *rp@ = pointer to block to be filled in |
53 | * @unsigned nbits@ = required modulus size in bits |
54 | * @grand *r@ = random number source |
55 | * @unsigned n@ = number of attempts to make |
56 | * @pgen_proc *event@ = event handler function |
57 | * @void *ectx@ = argument for the event handler |
58 | * |
59 | * Returns: Zero if all went well, nonzero otherwise. |
60 | * |
61 | * Use: Constructs a pair of strong RSA primes and other useful RSA |
62 | * parameters. A small encryption exponent is chosen if |
63 | * possible. |
64 | */ |
65 | |
66 | int rsa_gen(rsa_param *rp, unsigned nbits, grand *r, unsigned n, |
67 | pgen_proc *event, void *ectx) |
68 | { |
69 | mp *phi; |
70 | int i; |
71 | mp *g; |
72 | |
73 | /* --- Generate strong primes %$p$% and %$q$% --- */ |
74 | |
75 | if ((rp->p = strongprime("p", MP_NEW, nbits/2, r, n, event, ectx)) == 0) |
76 | goto fail_p; |
77 | if ((rp->q = strongprime("q", MP_NEW, nbits/2, r, n, event, ectx)) == 0) |
78 | goto fail_q; |
79 | |
80 | /* --- Work out the modulus and the CRT coefficient --- */ |
81 | |
82 | rp->n = mp_mul(MP_NEW, rp->p, rp->q); |
83 | rp->q_inv = MP_NEW; mp_gcd(0, 0, &rp->q_inv, rp->p, rp->q); |
84 | |
85 | /* --- Work out %$\varphi(n) = (p - 1)(q - 1)$% --- * |
86 | * |
87 | * Save on further multiplications by noting that %$n = pq$% is known and |
88 | * that %$(p - 1)(q - 1) = pq - p - q + 1$%. |
89 | */ |
90 | |
91 | phi = mp_sub(MP_NEW, rp->n, rp->p); |
92 | phi = mp_sub(phi, phi, rp->q); |
93 | phi = mp_add(phi, phi, MP_ONE); |
94 | |
95 | /* --- Decide on a public exponent --- * |
96 | * |
97 | * Simultaneously compute the private exponent. |
98 | */ |
99 | |
100 | rp->e = mp_create(1); |
101 | rp->d = MP_NEW; |
102 | g = MP_NEW; |
103 | for (i = 1; i < NPRIME; i++) { |
104 | rp->e->v[0] = primetab[i]; |
105 | mp_gcd(&g, 0, &rp->d, phi, rp->e); |
106 | if (MP_CMP(g, ==, MP_ONE)) |
107 | goto good_e; |
108 | } |
109 | goto fail_e; |
110 | |
111 | /* --- Work out exponent residues --- */ |
112 | |
113 | good_e: |
114 | rp->dp = MP_NEW; phi = mp_sub(phi, rp->p, MP_ONE); |
115 | mp_div(0, &rp->dp, rp->d, phi); |
116 | |
117 | rp->dq = MP_NEW; phi = mp_sub(phi, rp->q, MP_ONE); |
118 | mp_div(0, &rp->dq, rp->d, phi); |
119 | |
120 | /* --- Done --- */ |
121 | |
122 | mp_drop(phi); |
123 | mp_drop(g); |
124 | return (0); |
125 | |
126 | /* --- Tidy up when something goes wrong --- */ |
127 | |
128 | fail_e: |
129 | mp_drop(g); |
130 | mp_drop(phi); |
131 | mp_drop(rp->n); |
132 | mp_drop(rp->q_inv); |
133 | mp_drop(rp->q); |
134 | fail_q: |
135 | mp_drop(rp->p); |
136 | fail_p: |
137 | return (-1); |
138 | } |
139 | |
140 | /*----- That's all, folks -------------------------------------------------*/ |