|
3
|
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, [email protected], http://libtomcrypt.org |
|
|
10 */ |
|
|
11 |
|
|
12 /* RSA Code by Tom St Denis */ |
|
|
13 #include "mycrypt.h" |
|
|
14 |
|
|
15 #ifdef MRSA |
|
|
16 |
|
|
17 int rsa_exptmod(const unsigned char *in, unsigned long inlen, |
|
|
18 unsigned char *out, unsigned long *outlen, int which, |
|
|
19 rsa_key *key) |
|
|
20 { |
|
|
21 mp_int tmp, tmpa, tmpb; |
|
|
22 unsigned long x; |
|
|
23 int err; |
|
|
24 |
|
|
25 _ARGCHK(in != NULL); |
|
|
26 _ARGCHK(out != NULL); |
|
|
27 _ARGCHK(outlen != NULL); |
|
|
28 _ARGCHK(key != NULL); |
|
|
29 |
|
|
30 if (which == PK_PRIVATE && (key->type != PK_PRIVATE && key->type != PK_PRIVATE_OPTIMIZED)) { |
|
|
31 return CRYPT_PK_NOT_PRIVATE; |
|
|
32 } |
|
|
33 |
|
|
34 /* must be a private or public operation */ |
|
|
35 if (which != PK_PRIVATE && which != PK_PUBLIC) { |
|
|
36 return CRYPT_PK_INVALID_TYPE; |
|
|
37 } |
|
|
38 |
|
|
39 /* init and copy into tmp */ |
|
|
40 if ((err = mp_init_multi(&tmp, &tmpa, &tmpb, NULL)) != MP_OKAY) { goto error; } |
|
|
41 if ((err = mp_read_unsigned_bin(&tmp, (unsigned char *)in, (int)inlen)) != MP_OKAY) { goto error; } |
|
|
42 |
|
|
43 /* sanity check on the input */ |
|
|
44 if (mp_cmp(&key->N, &tmp) == MP_LT) { |
|
|
45 err = CRYPT_PK_INVALID_SIZE; |
|
|
46 goto done; |
|
|
47 } |
|
|
48 |
|
|
49 /* are we using the private exponent and is the key optimized? */ |
|
|
50 if (which == PK_PRIVATE && key->type == PK_PRIVATE_OPTIMIZED) { |
|
|
51 /* tmpa = tmp^dP mod p */ |
|
|
52 if ((err = mp_exptmod(&tmp, &key->dP, &key->p, &tmpa)) != MP_OKAY) { goto error; } |
|
|
53 |
|
|
54 /* tmpb = tmp^dQ mod q */ |
|
|
55 if ((err = mp_exptmod(&tmp, &key->dQ, &key->q, &tmpb)) != MP_OKAY) { goto error; } |
|
|
56 |
|
|
57 /* tmp = tmpa*qP + tmpb*pQ mod N */ |
|
|
58 if ((err = mp_mul(&tmpa, &key->qP, &tmpa)) != MP_OKAY) { goto error; } |
|
|
59 if ((err = mp_mul(&tmpb, &key->pQ, &tmpb)) != MP_OKAY) { goto error; } |
|
|
60 if ((err = mp_addmod(&tmpa, &tmpb, &key->N, &tmp)) != MP_OKAY) { goto error; } |
|
|
61 } else { |
|
|
62 /* exptmod it */ |
|
|
63 if ((err = mp_exptmod(&tmp, which==PK_PRIVATE?&key->d:&key->e, &key->N, &tmp)) != MP_OKAY) { goto error; } |
|
|
64 } |
|
|
65 |
|
|
66 /* read it back */ |
|
|
67 x = (unsigned long)mp_unsigned_bin_size(&tmp); |
|
|
68 if (x > *outlen) { |
|
|
69 err = CRYPT_BUFFER_OVERFLOW; |
|
|
70 goto done; |
|
|
71 } |
|
|
72 *outlen = x; |
|
|
73 |
|
|
74 /* convert it */ |
|
|
75 if ((err = mp_to_unsigned_bin(&tmp, out)) != MP_OKAY) { goto error; } |
|
|
76 |
|
|
77 /* clean up and return */ |
|
|
78 err = CRYPT_OK; |
|
|
79 goto done; |
|
|
80 error: |
|
|
81 err = mpi_to_ltc_error(err); |
|
|
82 done: |
|
|
83 mp_clear_multi(&tmp, &tmpa, &tmpb, NULL); |
|
|
84 return err; |
|
|
85 } |
|
|
86 |
|
|
87 #endif |
