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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
*/
#include "tomcrypt.h"
/**
@file pkcs_1_mgf1.c
The Mask Generation Function (MGF1) for PKCS #1, Tom St Denis
*/
#ifdef PKCS_1
/**
Perform PKCS #1 MGF1 (internal)
@param seed The seed for MGF1
@param seedlen The length of the seed
@param hash_idx The index of the hash desired
@param mask [out] The destination
@param masklen The length of the mask desired
@return CRYPT_OK if successful
*/
int pkcs_1_mgf1(const unsigned char *seed, unsigned long seedlen,
int hash_idx,
unsigned char *mask, unsigned long masklen)
{
unsigned long hLen, x;
ulong32 counter;
int err;
hash_state *md;
unsigned char *buf;
LTC_ARGCHK(seed != NULL);
LTC_ARGCHK(mask != NULL);
/* ensure valid hash */
if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
return err;
}
/* get hash output size */
hLen = hash_descriptor[hash_idx].hashsize;
/* allocate memory */
md = XMALLOC(sizeof(hash_state));
buf = XMALLOC(hLen);
if (md == NULL || buf == NULL) {
if (md != NULL) {
XFREE(md);
}
if (buf != NULL) {
XFREE(buf);
}
return CRYPT_MEM;
}
/* start counter */
counter = 0;
while (masklen > 0) {
/* handle counter */
STORE32H(counter, buf);
++counter;
/* get hash of seed || counter */
if ((err = hash_descriptor[hash_idx].init(md)) != CRYPT_OK) {
goto LBL_ERR;
}
if ((err = hash_descriptor[hash_idx].process(md, seed, seedlen)) != CRYPT_OK) {
goto LBL_ERR;
}
if ((err = hash_descriptor[hash_idx].process(md, buf, 4)) != CRYPT_OK) {
goto LBL_ERR;
}
if ((err = hash_descriptor[hash_idx].done(md, buf)) != CRYPT_OK) {
goto LBL_ERR;
}
/* store it */
for (x = 0; x < hLen && masklen > 0; x++, masklen--) {
*mask++ = buf[x];
}
}
err = CRYPT_OK;
LBL_ERR:
#ifdef LTC_CLEAN_STACK
zeromem(buf, hLen);
zeromem(md, sizeof(hash_state));
#endif
XFREE(buf);
XFREE(md);
return err;
}
#endif /* PKCS_1 */
/* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_mgf1.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2005/05/05 14:35:59 $ */
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