+
−/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+
− *
+
− * LibTomCrypt is a library that provides various cryptographic
+
− * algorithms in a highly modular and flexible manner.
+
− *
+
− * The library is free for all purposes without any express
+
− * guarantee it works.
+
− *
+
− * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
+
− */
+
−
+
−/**
+
−   @file gcm_process.c
+
−   GCM implementation, process message data, by Tom St Denis
+
−*/
+
−#include "tomcrypt.h"
+
−
+
−#ifdef GCM_MODE
+
−
+
−/** 
+
−  Process plaintext/ciphertext through GCM
+
−  @param gcm       The GCM state 
+
−  @param pt        The plaintext
+
−  @param ptlen     The plaintext length (ciphertext length is the same)
+
−  @param ct        The ciphertext
+
−  @param direction Encrypt or Decrypt mode (GCM_ENCRYPT or GCM_DECRYPT)
+
−  @return CRYPT_OK on success
+
− */
+
−int gcm_process(gcm_state *gcm,
+
−                     unsigned char *pt,     unsigned long ptlen,
+
−                     unsigned char *ct,
+
−                     int direction)
+
−{
+
−   unsigned long x;
+
−   int           y, err;
+
−   unsigned char b;
+
−
+
−   LTC_ARGCHK(gcm != NULL);
+
−   if (ptlen > 0) {
+
−      LTC_ARGCHK(pt  != NULL);
+
−      LTC_ARGCHK(ct  != NULL);
+
−   }
+
−
+
−   if (gcm->buflen > 16 || gcm->buflen < 0) {
+
−      return CRYPT_INVALID_ARG;
+
−   }
+
− 
+
−   if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
+
−      return err;
+
−   }
+
−
+
−   /* in AAD mode? */
+
−   if (gcm->mode == GCM_MODE_AAD) {
+
−      /* let's process the AAD */
+
−      if (gcm->buflen) {
+
−         gcm->totlen += gcm->buflen * CONST64(8);
+
−         gcm_mult_h(gcm, gcm->X);
+
−      }
+
−
+
−      /* increment counter */
+
−      for (y = 15; y >= 12; y--) {
+
−          if (++gcm->Y[y] & 255) { break; }
+
−      }
+
−      /* encrypt the counter */
+
−      if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
+
−         return err;
+
−      }
+
−
+
−      gcm->buflen = 0;
+
−      gcm->mode   = GCM_MODE_TEXT;
+
−   }
+
−
+
−   if (gcm->mode != GCM_MODE_TEXT) {
+
−      return CRYPT_INVALID_ARG;
+
−   }
+
−
+
−   x = 0;
+
−#ifdef LTC_FAST
+
−   if (gcm->buflen == 0) {
+
−      if (direction == GCM_ENCRYPT) { 
+
−         for (x = 0; x < (ptlen & ~15); x += 16) {
+
−             /* ctr encrypt */
+
−             for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
+
−                 *((LTC_FAST_TYPE*)(&ct[x + y])) = *((LTC_FAST_TYPE*)(&pt[x+y])) ^ *((LTC_FAST_TYPE*)(&gcm->buf[y]));
+
−                 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&ct[x+y]));
+
−             }
+
−             /* GMAC it */
+
−             gcm->pttotlen += 128;
+
−             gcm_mult_h(gcm, gcm->X);
+
−             /* increment counter */
+
−             for (y = 15; y >= 12; y--) {
+
−                 if (++gcm->Y[y] & 255) { break; }
+
−             }
+
−             if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
+
−                return err;
+
−             }
+
−         }
+
−      } else {
+
−         for (x = 0; x < (ptlen & ~15); x += 16) {
+
−             /* ctr encrypt */
+
−             for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
+
−                 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&ct[x+y]));
+
−                 *((LTC_FAST_TYPE*)(&pt[x + y])) = *((LTC_FAST_TYPE*)(&ct[x+y])) ^ *((LTC_FAST_TYPE*)(&gcm->buf[y]));
+
−             }
+
−             /* GMAC it */
+
−             gcm->pttotlen += 128;
+
−             gcm_mult_h(gcm, gcm->X);
+
−             /* increment counter */
+
−             for (y = 15; y >= 12; y--) {
+
−                 if (++gcm->Y[y] & 255) { break; }
+
−             }
+
−             if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
+
−                return err;
+
−             }
+
−         }
+
−     }
+
−   }
+
−#endif        
+
−
+
−   /* process text */
+
−   for (; x < ptlen; x++) {
+
−       if (gcm->buflen == 16) {
+
−          gcm->pttotlen += 128;
+
−          gcm_mult_h(gcm, gcm->X);
+
−          
+
−          /* increment counter */
+
−          for (y = 15; y >= 12; y--) {
+
−              if (++gcm->Y[y] & 255) { break; }
+
−          }
+
−          if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) {
+
−             return err;
+
−          }
+
−          gcm->buflen = 0;
+
−       }
+
−
+
−       if (direction == GCM_ENCRYPT) {
+
−          b = ct[x] = pt[x] ^ gcm->buf[gcm->buflen]; 
+
−       } else {
+
−          b = ct[x];
+
−          pt[x] = ct[x] ^ gcm->buf[gcm->buflen];
+
−       }
+
−       gcm->X[gcm->buflen++] ^= b;          
+
−   }
+
−
+
−   return CRYPT_OK;
+
−}
+
−
+
−#endif
+
−
+
−/* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_process.c,v $ */
+
−/* $Revision: 1.14 $ */
+
−/* $Date: 2006/11/19 19:33:36 $ */