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comparison libtomcrypt/src/pk/dsa/dsa_shared_secret.c @ 382:0cbe8f6dbf9e

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propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 2af22fb4e878750b88f80f90d439b316d229796f) to branch 'au.asn.ucc.matt.dropbear' (head 02c413252c90e9de8e03d91e9939dde3029f5c0a)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 02:41:05 +0000
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children f849a5ca2efc
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379:b66a00272a90 382:0cbe8f6dbf9e
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.com
10 */
11 #include "tomcrypt.h"
12
13 /**
14 @file dsa_shared_secret.c
15 DSA Crypto, Tom St Denis
16 */
17
18 #ifdef MDSA
19
20 /**
21 Create a DSA shared secret between two keys
22 @param private_key The private DSA key (the exponent)
23 @param base The base of the exponentiation (allows this to be used for both encrypt and decrypt)
24 @param public_key The public key
25 @param out [out] Destination of the shared secret
26 @param outlen [in/out] The max size and resulting size of the shared secret
27 @return CRYPT_OK if successful
28 */
29 int dsa_shared_secret(void *private_key, void *base,
30 dsa_key *public_key,
31 unsigned char *out, unsigned long *outlen)
32 {
33 unsigned long x;
34 void *res;
35 int err;
36
37 LTC_ARGCHK(private_key != NULL);
38 LTC_ARGCHK(public_key != NULL);
39 LTC_ARGCHK(out != NULL);
40 LTC_ARGCHK(outlen != NULL);
41
42 /* make new point */
43 if ((err = mp_init(&res)) != CRYPT_OK) {
44 return err;
45 }
46
47 if ((err = mp_exptmod(base, private_key, public_key->p, res)) != CRYPT_OK) {
48 mp_clear(res);
49 return err;
50 }
51
52 x = (unsigned long)mp_unsigned_bin_size(res);
53 if (*outlen < x) {
54 *outlen = x;
55 err = CRYPT_BUFFER_OVERFLOW;
56 goto done;
57 }
58 zeromem(out, x);
59 if ((err = mp_to_unsigned_bin(res, out + (x - mp_unsigned_bin_size(res)))) != CRYPT_OK) { goto done; }
60
61 err = CRYPT_OK;
62 *outlen = x;
63 done:
64 mp_clear(res);
65 return err;
66 }
67
68 #endif
69 /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_shared_secret.c,v $ */
70 /* $Revision: 1.7 $ */
71 /* $Date: 2006/12/04 03:18:43 $ */
72