--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/encauth/chachapoly/chacha20poly1305_setiv_rfc7905.c	Fri Feb 09 21:44:05 2018 +0800
@@ -0,0 +1,40 @@
+/* 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"
+
+#ifdef LTC_CHACHA20POLY1305_MODE
+
+/**
+  Set IV + counter data (with RFC7905-magic) to the ChaCha20Poly1305 state and reset the context
+  @param st     The ChaCha20Poly1305 state
+  @param iv     The IV data to add
+  @param ivlen  The length of the IV (must be 12 or 8)
+  @param sequence_number   64bit sequence number which is incorporated into IV as described in RFC7905
+  @return CRYPT_OK on success
+ */
+int chacha20poly1305_setiv_rfc7905(chacha20poly1305_state *st, const unsigned char *iv, unsigned long ivlen, ulong64 sequence_number)
+{
+   int i;
+   unsigned char combined_iv[12] = { 0 };
+
+   LTC_ARGCHK(st != NULL);
+   LTC_ARGCHK(iv != NULL);
+   LTC_ARGCHK(ivlen == 12);
+
+   STORE64L(sequence_number, combined_iv + 4);
+   for (i = 0; i < 12; i++) combined_iv[i] = iv[i] ^ combined_iv[i];
+   return chacha20poly1305_setiv(st, combined_iv, 12);
+}
+
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */