--- /dev/null
+/* 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: $Format:%ai$ */