diff options
Diffstat (limited to 'libtomcrypt/src/encauth/gcm/gcm_process.c')
| -rw-r--r-- | libtomcrypt/src/encauth/gcm/gcm_process.c | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/libtomcrypt/src/encauth/gcm/gcm_process.c b/libtomcrypt/src/encauth/gcm/gcm_process.c new file mode 100644 index 0000000..f4d21d3 --- /dev/null +++ b/libtomcrypt/src/encauth/gcm/gcm_process.c @@ -0,0 +1,152 @@ +/* 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 $ */ |