Mercurial > dropbear

annotate libtomcrypt/src/pk/dsa/dsa_shared_secret.c @ 556:ccdc4c6183c0

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- Payload length doesn't include macsize.
author Matt Johnston <matt@ucc.asn.au>
date Sun, 26 Jul 2009 16:11:27 +0000
parents 0cbe8f6dbf9e
children f849a5ca2efc
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
382
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diff changeset
1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 *
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9 * Tom St Denis, [email protected], http://libtomcrypt.com
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10 */
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11 #include "tomcrypt.h"
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12
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13 /**
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14 @file dsa_shared_secret.c
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15 DSA Crypto, Tom St Denis
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16 */
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17
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18 #ifdef MDSA
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19
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20 /**
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21 Create a DSA shared secret between two keys
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22 @param private_key The private DSA key (the exponent)
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23 @param base The base of the exponentiation (allows this to be used for both encrypt and decrypt)
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24 @param public_key The public key
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25 @param out [out] Destination of the shared secret
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26 @param outlen [in/out] The max size and resulting size of the shared secret
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27 @return CRYPT_OK if successful
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28 */
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29 int dsa_shared_secret(void *private_key, void *base,
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30 dsa_key *public_key,
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31 unsigned char *out, unsigned long *outlen)
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32 {
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33 unsigned long x;
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34 void *res;
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35 int err;
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36
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37 LTC_ARGCHK(private_key != NULL);
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38 LTC_ARGCHK(public_key != NULL);
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39 LTC_ARGCHK(out != NULL);
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40 LTC_ARGCHK(outlen != NULL);
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41
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42 /* make new point */
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43 if ((err = mp_init(&res)) != CRYPT_OK) {
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44 return err;
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45 }
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46
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47 if ((err = mp_exptmod(base, private_key, public_key->p, res)) != CRYPT_OK) {
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48 mp_clear(res);
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49 return err;
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50 }
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51
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52 x = (unsigned long)mp_unsigned_bin_size(res);
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53 if (*outlen < x) {
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54 *outlen = x;
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55 err = CRYPT_BUFFER_OVERFLOW;
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56 goto done;
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57 }
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58 zeromem(out, x);
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59 if ((err = mp_to_unsigned_bin(res, out + (x - mp_unsigned_bin_size(res)))) != CRYPT_OK) { goto done; }
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60
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61 err = CRYPT_OK;
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62 *outlen = x;
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63 done:
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64 mp_clear(res);
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65 return err;
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66 }
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67
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68 #endif
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69 /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_shared_secret.c,v $ */
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70 /* $Revision: 1.7 $ */
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71 /* $Date: 2006/12/04 03:18:43 $ */
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72