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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.com
*/
#include "tomcrypt.h"
/**
@file rng_make_prng.c
portable way to get secure random bits to feed a PRNG (Tom St Denis)
*/
/**
Create a PRNG from a RNG
@param bits Number of bits of entropy desired (64 ... 1024)
@param wprng Index of which PRNG to setup
@param prng [out] PRNG state to initialize
@param callback A pointer to a void function for when the RNG is slow, this can be NULL
@return CRYPT_OK if successful
*/
int rng_make_prng(int bits, int wprng, prng_state *prng,
void (*callback)(void))
{
unsigned char buf[256];
int err;
LTC_ARGCHK(prng != NULL);
/* check parameter */
if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
return err;
}
if (bits < 64 || bits > 1024) {
return CRYPT_INVALID_PRNGSIZE;
}
if ((err = prng_descriptor[wprng].start(prng)) != CRYPT_OK) {
return err;
}
bits = ((bits/8)+((bits&7)!=0?1:0)) * 2;
if (rng_get_bytes(buf, (unsigned long)bits, callback) != (unsigned long)bits) {
return CRYPT_ERROR_READPRNG;
}
if ((err = prng_descriptor[wprng].add_entropy(buf, (unsigned long)bits, prng)) != CRYPT_OK) {
return err;
}
if ((err = prng_descriptor[wprng].ready(prng)) != CRYPT_OK) {
return err;
}
#ifdef LTC_CLEAN_STACK
zeromem(buf, sizeof(buf));
#endif
return CRYPT_OK;
}
/* $Source: /cvs/libtom/libtomcrypt/src/prngs/rng_make_prng.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/03/31 14:15:35 $ */
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