Import code from previous AssetBuilder version

thirdparty/libtomcrypt/modes/xts/xts_encrypt.c

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+/* 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:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */