1/* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
10 */
11#include "tomcrypt.h"
12
13/**
14  @file katja_make_key.c
15  Katja key generation, Tom St Denis
16*/
17
18#ifdef MKAT
19
20/**
21   Create a Katja key
22   @param prng     An active PRNG state
23   @param wprng    The index of the PRNG desired
24   @param size     The size of the modulus (key size) desired (octets)
25   @param key      [out] Destination of a newly created private key pair
26   @return CRYPT_OK if successful, upon error all allocated ram is freed
27*/
28int katja_make_key(prng_state *prng, int wprng, int size, katja_key *key)
29{
30   void *p, *q, *tmp1, *tmp2;
31   int    err;
32
33   LTC_ARGCHK(key != NULL);
34   LTC_ARGCHK(ltc_mp.name != NULL);
35
36   if ((size < (MIN_KAT_SIZE/8)) || (size > (MAX_KAT_SIZE/8))) {
37      return CRYPT_INVALID_KEYSIZE;
38   }
39
40   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
41      return err;
42   }
43
44   if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, NULL)) != CRYPT_OK) {
45      return err;
46   }
47
48   /* divide size by three  */
49   size   = (((size << 3) / 3) + 7) >> 3;
50
51   /* make prime "q" (we negate size to make q == 3 mod 4) */
52   if ((err = rand_prime(q, -size, prng, wprng)) != CRYPT_OK)      { goto done; }
53   if ((err = mp_sub_d(q, 1, tmp1)) != CRYPT_OK)                   { goto done; }
54
55   /* make prime "p" */
56   do {
57      if ((err = rand_prime(p, size+1, prng, wprng)) != CRYPT_OK)  { goto done; }
58      if ((err = mp_gcd(p, tmp1, tmp2)) != CRYPT_OK)               { goto done; }
59   } while (mp_cmp_d(tmp2, 1) != LTC_MP_EQ);
60
61   /* make key */
62   if ((err = mp_init_multi(&key->d, &key->N, &key->dQ, &key->dP,
63                     &key->qP, &key->p, &key->q, &key->pq, NULL)) != CRYPT_OK) {
64      goto error;
65   }
66
67   /* n=p^2q and 1/n mod pq */
68   if ((err = mp_copy( p,  key->p)) != CRYPT_OK)                       { goto error2; }
69   if ((err = mp_copy( q,  key->q)) != CRYPT_OK)                       { goto error2; }
70   if ((err = mp_mul(key->p, key->q, key->pq)) != CRYPT_OK)            { goto error2; } /* tmp1 = pq  */
71   if ((err = mp_mul(key->pq, key->p, key->N)) != CRYPT_OK)            { goto error2; } /* N = p^2q   */
72   if ((err = mp_sub_d( p, 1,  tmp1)) != CRYPT_OK)                     { goto error2; } /* tmp1 = q-1 */
73   if ((err = mp_sub_d( q, 1,  tmp2)) != CRYPT_OK)                     { goto error2; } /* tmp2 = p-1 */
74   if ((err = mp_lcm(tmp1, tmp2, key->d)) != CRYPT_OK)                 { goto error2; } /* tmp1 = lcd(p-1,q-1) */
75   if ((err = mp_invmod( key->N,  key->d,  key->d)) != CRYPT_OK)       { goto error2; } /* key->d = 1/N mod pq */
76
77   /* optimize for CRT now */
78   /* find d mod q-1 and d mod p-1 */
79   if ((err = mp_mod( key->d,  tmp1,  key->dP)) != CRYPT_OK)           { goto error2; } /* dP = d mod p-1 */
80   if ((err = mp_mod( key->d,  tmp2,  key->dQ)) != CRYPT_OK)           { goto error2; } /* dQ = d mod q-1 */
81   if ((err = mp_invmod( q,  p,  key->qP)) != CRYPT_OK)                { goto error2; } /* qP = 1/q mod p */
82
83   /* set key type (in this case it's CRT optimized) */
84   key->type = PK_PRIVATE;
85
86   /* return ok and free temps */
87   err       = CRYPT_OK;
88   goto done;
89error2:
90   mp_clear_multi( key->d,  key->N,  key->dQ,  key->dP,  key->qP,  key->p,  key->q, key->pq, NULL);
91error:
92done:
93   mp_clear_multi( tmp2,  tmp1,  p,  q, NULL);
94   return err;
95}
96
97#endif
98
99/* $Source: /cvs/libtom/libtomcrypt/src/pk/katja/katja_make_key.c,v $ */
100/* $Revision: 1.10 $ */
101/* $Date: 2006/03/31 14:15:35 $ */
102