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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"
#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: $Format:%ai$ */
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