Mercurial > dropbear

annotate src/encauth/gcm/gcm_add_iv.c @ 196:704bb050935f libtomcrypt

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makefile fixup for Dropbear
author Matt Johnston <matt@ucc.asn.au>
date Mon, 09 May 2005 12:00:08 +0000
parents 1c15b283127b
children 39d5d58461d6
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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.org
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10 */
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11
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12 /**
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13 @file gcm_add_iv.c
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14 GCM implementation, add IV data to the state, by Tom St Denis
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15 */
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16 #include "tomcrypt.h"
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17
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18 #ifdef GCM_MODE
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19
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20 /**
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21 Add IV data to the GCM state
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22 @param gcm The GCM state
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23 @param IV The initial value data to add
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24 @param IVlen The length of the IV
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25 @return CRYPT_OK on success
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26 */
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27 int gcm_add_iv(gcm_state *gcm,
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28 const unsigned char *IV, unsigned long IVlen)
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29 {
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30 unsigned long x, y;
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31 int err;
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32
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33 LTC_ARGCHK(gcm != NULL);
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34 if (IVlen > 0) {
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35 LTC_ARGCHK(IV != NULL);
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36 }
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37
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38 /* must be in IV mode */
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39 if (gcm->mode != GCM_MODE_IV) {
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40 return CRYPT_INVALID_ARG;
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41 }
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42
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43 if (gcm->buflen >= 16 || gcm->buflen < 0) {
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44 return CRYPT_INVALID_ARG;
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45 }
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46
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47 if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
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48 return err;
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49 }
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50
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51
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52 /* trip the ivmode flag */
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53 if (IVlen + gcm->buflen > 12) {
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54 gcm->ivmode |= 1;
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55 }
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56
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57 x = 0;
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58 #ifdef LTC_FAST
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59 if (gcm->buflen == 0) {
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60 for (x = 0; x < (IVlen & ~15); x += 16) {
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61 for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
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62 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&IV[x + y]));
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63 }
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64 gcm_mult_h(gcm, gcm->X);
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65 gcm->totlen += 128;
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66 }
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67 IV += x;
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68 }
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69 #endif
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70
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71 /* start adding IV data to the state */
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72 for (; x < IVlen; x++) {
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73 gcm->buf[gcm->buflen++] = *IV++;
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74
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75 if (gcm->buflen == 16) {
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76 /* GF mult it */
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77 for (y = 0; y < 16; y++) {
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78 gcm->X[y] ^= gcm->buf[y];
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79 }
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80 gcm_mult_h(gcm, gcm->X);
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81 gcm->buflen = 0;
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82 gcm->totlen += 128;
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83 }
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84 }
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85
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86 return CRYPT_OK;
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87 }
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88
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89 #endif
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90