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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.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
*/
/**
@file eax_decrypt_verify_memory.c
EAX implementation, decrypt block of memory, by Tom St Denis
*/
#include "tomcrypt.h"
#ifdef EAX_MODE
/**
Decrypt a block of memory and verify the provided MAC tag with EAX
@param cipher The index of the cipher desired
@param key The secret key
@param keylen The length of the key (octets)
@param nonce The nonce data (use once) for the session
@param noncelen The length of the nonce data.
@param header The session header data
@param headerlen The length of the header (octets)
@param ct The ciphertext
@param ctlen The length of the ciphertext (octets)
@param pt [out] The plaintext
@param tag The authentication tag provided by the encoder
@param taglen [in/out] The length of the tag (octets)
@param stat [out] The result of the decryption (1==valid tag, 0==invalid)
@return CRYPT_OK if successful regardless of the resulting tag comparison
*/
int eax_decrypt_verify_memory(int cipher,
const unsigned char *key, unsigned long keylen,
const unsigned char *nonce, unsigned long noncelen,
const unsigned char *header, unsigned long headerlen,
const unsigned char *ct, unsigned long ctlen,
unsigned char *pt,
unsigned char *tag, unsigned long taglen,
int *stat)
{
int err;
eax_state *eax;
unsigned char *buf;
unsigned long buflen;
LTC_ARGCHK(stat != NULL);
LTC_ARGCHK(key != NULL);
LTC_ARGCHK(pt != NULL);
LTC_ARGCHK(ct != NULL);
LTC_ARGCHK(tag != NULL);
/* default to zero */
*stat = 0;
/* allocate ram */
buf = XMALLOC(taglen);
eax = XMALLOC(sizeof(*eax));
if (eax == NULL || buf == NULL) {
if (eax != NULL) {
XFREE(eax);
}
if (buf != NULL) {
XFREE(buf);
}
return CRYPT_MEM;
}
if ((err = eax_init(eax, cipher, key, keylen, nonce, noncelen, header, headerlen)) != CRYPT_OK) {
goto LBL_ERR;
}
if ((err = eax_decrypt(eax, ct, pt, ctlen)) != CRYPT_OK) {
goto LBL_ERR;
}
buflen = taglen;
if ((err = eax_done(eax, buf, &buflen)) != CRYPT_OK) {
goto LBL_ERR;
}
/* compare tags */
if (buflen >= taglen && memcmp(buf, tag, taglen) == 0) {
*stat = 1;
}
err = CRYPT_OK;
LBL_ERR:
#ifdef LTC_CLEAN_STACK
zeromem(buf, taglen);
zeromem(eax, sizeof(*eax));
#endif
XFREE(eax);
XFREE(buf);
return err;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/encauth/eax/eax_decrypt_verify_memory.c,v $ */
/* $Revision: 1.3 $ */
/* $Date: 2005/05/05 14:35:58 $ */
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