--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/encauth/chachapoly/chacha20poly1305_setiv.c	Fri Feb 09 23:49:22 2018 +0800
@@ -0,0 +1,68 @@
+/* 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 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)
+  @return CRYPT_OK on success
+ */
+int chacha20poly1305_setiv(chacha20poly1305_state *st, const unsigned char *iv, unsigned long ivlen)
+{
+   chacha_state tmp_st;
+   int i, err;
+   unsigned char polykey[32];
+
+   LTC_ARGCHK(st != NULL);
+   LTC_ARGCHK(iv != NULL);
+   LTC_ARGCHK(ivlen == 12 || ivlen == 8);
+
+   /* set IV for chacha20 */
+   if (ivlen == 12) {
+      /* IV 96bit */
+      if ((err = chacha_ivctr32(&st->chacha, iv, ivlen, 1)) != CRYPT_OK) return err;
+   }
+   else {
+      /* IV 64bit */
+      if ((err = chacha_ivctr64(&st->chacha, iv, ivlen, 1)) != CRYPT_OK) return err;
+   }
+
+   /* copy chacha20 key to temporary state */
+   for(i = 0; i < 12; i++) tmp_st.input[i] = st->chacha.input[i];
+   tmp_st.rounds = 20;
+   /* set IV */
+   if (ivlen == 12) {
+      /* IV 32bit */
+      if ((err = chacha_ivctr32(&tmp_st, iv, ivlen, 0)) != CRYPT_OK) return err;
+   }
+   else {
+      /* IV 64bit */
+      if ((err = chacha_ivctr64(&tmp_st, iv, ivlen, 0)) != CRYPT_OK) return err;
+   }
+   /* (re)generate new poly1305 key */
+   if ((err = chacha_keystream(&tmp_st, polykey, 32)) != CRYPT_OK) return err;
+   /* (re)initialise poly1305 */
+   if ((err = poly1305_init(&st->poly, polykey, 32)) != CRYPT_OK) return err;
+   st->ctlen  = 0;
+   st->aadlen = 0;
+   st->aadflg = 1;
+
+   return CRYPT_OK;
+}
+
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */