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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
/**
Decrypt bytes of ciphertext with ChaCha20Poly1305
@param st The ChaCha20Poly1305 state
@param in The ciphertext
@param inlen The length of the input (octets)
@param out [out] The plaintext (length inlen)
@return CRYPT_OK if successful
*/
int chacha20poly1305_decrypt(chacha20poly1305_state *st, const unsigned char *in, unsigned long inlen, unsigned char *out)
{
unsigned char padzero[16] = { 0 };
unsigned long padlen;
int err;
if (inlen == 0) return CRYPT_OK; /* nothing to do */
LTC_ARGCHK(st != NULL);
if (st->aadflg) {
padlen = 16 - (unsigned long)(st->aadlen % 16);
if (padlen < 16) {
if ((err = poly1305_process(&st->poly, padzero, padlen)) != CRYPT_OK) return err;
}
st->aadflg = 0; /* no more AAD */
}
if (st->aadflg) st->aadflg = 0; /* no more AAD */
if ((err = poly1305_process(&st->poly, in, inlen)) != CRYPT_OK) return err;
if ((err = chacha_crypt(&st->chacha, in, inlen, out)) != CRYPT_OK) return err;
st->ctlen += (ulong64)inlen;
return CRYPT_OK;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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