Mercurial > dropbear

annotate src/encauth/gcm/gcm_init.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_init.c
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14 GCM implementation, initialize 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 Initialize a GCM state
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22 @param gcm The GCM state to initialize
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23 @param cipher The index of the cipher to use
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24 @param key The secret key
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25 @param keylen The length of the secret key
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26 @return CRYPT_OK on success
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27 */
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28 int gcm_init(gcm_state *gcm, int cipher,
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29 const unsigned char *key, int keylen)
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30 {
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31 int err;
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32 unsigned char B[16];
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33 #ifdef GCM_TABLES
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34 int x, y;
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35 #endif
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36
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37 LTC_ARGCHK(gcm != NULL);
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38 LTC_ARGCHK(key != NULL);
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39
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40 #ifdef LTC_FAST
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41 if (16 % sizeof(LTC_FAST_TYPE)) {
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42 return CRYPT_INVALID_ARG;
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43 }
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44 #endif
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45
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46 /* is cipher valid? */
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47 if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
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48 return err;
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49 }
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50 if (cipher_descriptor[cipher].block_length != 16) {
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51 return CRYPT_INVALID_CIPHER;
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52 }
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53
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54 /* schedule key */
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55 if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &gcm->K)) != CRYPT_OK) {
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56 return err;
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57 }
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58
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59 /* H = E(0) */
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60 zeromem(B, 16);
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61 cipher_descriptor[cipher].ecb_encrypt(B, gcm->H, &gcm->K);
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62
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63 /* setup state */
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64 zeromem(gcm->buf, sizeof(gcm->buf));
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65 zeromem(gcm->X, sizeof(gcm->X));
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66 gcm->cipher = cipher;
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67 gcm->mode = GCM_MODE_IV;
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68 gcm->ivmode = 0;
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69 gcm->buflen = 0;
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70 gcm->totlen = 0;
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71 gcm->pttotlen = 0;
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72
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73 #ifdef GCM_TABLES
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74 /* setup tables */
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75 zeromem(B, 16);
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76 for (x = 0; x < 16; x++) {
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77 for (y = 0; y < 256; y++) {
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78 B[x] = y;
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79 gcm_gf_mult(gcm->H, B, &gcm->PC[x][y][0]);
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80 }
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81 B[x] = 0;
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82 }
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83 #endif
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84
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85 return CRYPT_OK;
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86 }
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87
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88 #endif