--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/stream/chacha/chacha_ivctr64.c	Fri Feb 09 21:44:05 2018 +0800
@@ -0,0 +1,47 @@
+/* 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.
+ */
+
+/* The implementation is based on:
+ * chacha-ref.c version 20080118
+ * Public domain from D. J. Bernstein
+ */
+
+#include "tomcrypt.h"
+
+#ifdef LTC_CHACHA
+
+/**
+  Set IV + counter data to the ChaCha state
+  @param st      The ChaCha20 state
+  @param iv      The IV data to add
+  @param ivlen   The length of the IV (must be 8)
+  @param counter 64bit (unsigned) initial counter value
+  @return CRYPT_OK on success
+ */
+int chacha_ivctr64(chacha_state *st, const unsigned char *iv, unsigned long ivlen, ulong64 counter)
+{
+   LTC_ARGCHK(st != NULL);
+   LTC_ARGCHK(iv != NULL);
+   /* 64bit IV + 64bit counter */
+   LTC_ARGCHK(ivlen == 8);
+
+   st->input[12] = (ulong32)(counter & 0xFFFFFFFF);
+   st->input[13] = (ulong32)(counter >> 32);
+   LOAD32L(st->input[14], iv + 0);
+   LOAD32L(st->input[15], iv + 4);
+   st->ksleft = 0;
+   st->ivlen = ivlen;
+   return CRYPT_OK;
+}
+
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */