/* 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. */ #include "tomcrypt.h" /** Source donated by Elliptic Semiconductor Inc (www.ellipticsemi.com) to the LibTom Projects */ #ifdef LTC_XTS_MODE static int _tweak_crypt(const unsigned char *P, unsigned char *C, unsigned char *T, symmetric_xts *xts) { unsigned long x; int err; /* tweak encrypt block i */ #ifdef LTC_FAST for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) { *(LTC_FAST_TYPE_PTR_CAST(&C[x])) = *(LTC_FAST_TYPE_PTR_CAST(&P[x])) ^ *(LTC_FAST_TYPE_PTR_CAST(&T[x])); } #else for (x = 0; x < 16; x++) { C[x] = P[x] ^ T[x]; } #endif if ((err = cipher_descriptor[xts->cipher].ecb_encrypt(C, C, &xts->key1)) != CRYPT_OK) { return err; } #ifdef LTC_FAST for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) { *(LTC_FAST_TYPE_PTR_CAST(&C[x])) ^= *(LTC_FAST_TYPE_PTR_CAST(&T[x])); } #else for (x = 0; x < 16; x++) { C[x] = C[x] ^ T[x]; } #endif /* LFSR the tweak */ xts_mult_x(T); return CRYPT_OK; } /** XTS Encryption @param pt [in] Plaintext @param ptlen Length of plaintext (and ciphertext) @param ct [out] Ciphertext @param tweak [in] The 128--bit encryption tweak (e.g. sector number) @param xts The XTS structure Returns CRYPT_OK upon success */ int xts_encrypt(const unsigned char *pt, unsigned long ptlen, unsigned char *ct, unsigned char *tweak, symmetric_xts *xts) { unsigned char PP[16], CC[16], T[16]; unsigned long i, m, mo, lim; int err; /* check inputs */ LTC_ARGCHK(pt != NULL); LTC_ARGCHK(ct != NULL); LTC_ARGCHK(tweak != NULL); LTC_ARGCHK(xts != NULL); /* check if valid */ if ((err = cipher_is_valid(xts->cipher)) != CRYPT_OK) { return err; } /* get number of blocks */ m = ptlen >> 4; mo = ptlen & 15; /* must have at least one full block */ if (m == 0) { return CRYPT_INVALID_ARG; } if (mo == 0) { lim = m; } else { lim = m - 1; } if (cipher_descriptor[xts->cipher].accel_xts_encrypt && lim > 0) { /* use accelerated encryption for whole blocks */ if ((err = cipher_descriptor[xts->cipher].accel_xts_encrypt(pt, ct, lim, tweak, &xts->key1, &xts->key2)) != CRYPT_OK) { return err; } ct += lim * 16; pt += lim * 16; /* tweak is encrypted on output */ XMEMCPY(T, tweak, sizeof(T)); } else { /* encrypt the tweak */ if ((err = cipher_descriptor[xts->cipher].ecb_encrypt(tweak, T, &xts->key2)) != CRYPT_OK) { return err; } for (i = 0; i < lim; i++) { if ((err = _tweak_crypt(pt, ct, T, xts)) != CRYPT_OK) { return err; } ct += 16; pt += 16; } } /* if ptlen not divide 16 then */ if (mo > 0) { /* CC = tweak encrypt block m-1 */ if ((err = _tweak_crypt(pt, CC, T, xts)) != CRYPT_OK) { return err; } /* Cm = first ptlen % 16 bytes of CC */ for (i = 0; i < mo; i++) { PP[i] = pt[16 + i]; ct[16 + i] = CC[i]; } for (; i < 16; i++) { PP[i] = CC[i]; } /* Cm-1 = Tweak encrypt PP */ if ((err = _tweak_crypt(PP, ct, T, xts)) != CRYPT_OK) { return err; } } /* Decrypt the tweak back */ if ((err = cipher_descriptor[xts->cipher].ecb_decrypt(T, tweak, &xts->key2)) != CRYPT_OK) { return err; } return err; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */