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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_CCM_MODE
/**
Initialize a CCM state
@param ccm The CCM state to initialize
@param cipher The index of the cipher to use
@param key The secret key
@param keylen The length of the secret key
@param ptlen The length of the plain/cipher text that will be processed
@param taglen The max length of the MAC tag
@param aadlen The length of the AAD
@return CRYPT_OK on success
*/
int ccm_init(ccm_state *ccm, int cipher,
const unsigned char *key, int keylen, int ptlen, int taglen, int aadlen)
{
int err;
LTC_ARGCHK(ccm != NULL);
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(taglen != 0);
XMEMSET(ccm, 0, sizeof(ccm_state));
/* check cipher input */
if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
return err;
}
if (cipher_descriptor[cipher].block_length != 16) {
return CRYPT_INVALID_CIPHER;
}
/* make sure the taglen is even and <= 16 */
ccm->taglen = taglen;
ccm->taglen &= ~1;
if (ccm->taglen > 16) {
ccm->taglen = 16;
}
/* can't use < 4 */
if (ccm->taglen < 4) {
return CRYPT_INVALID_ARG;
}
/* schedule key */
if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ccm->K)) != CRYPT_OK) {
return err;
}
ccm->cipher = cipher;
/* let's get the L value */
ccm->ptlen = ptlen;
ccm->L = 0;
while (ptlen) {
++ccm->L;
ptlen >>= 8;
}
if (ccm->L <= 1) {
ccm->L = 2;
}
ccm->aadlen = aadlen;
return CRYPT_OK;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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