/* 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

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