/*---------------------------------------------------------------------------*
  Project:  NitroSDK - CRYPTO - demos
  File:     prng.c

  Copyright 2006-2008 Nintendo. All rights reserved.

  These coded instructions, statements, and computer programs contain
  proprietary information of Nintendo of America Inc. and/or Nintendo
  Company Ltd., and are protected by Federal copyright law. They may
  not be disclosed to third parties or copied or duplicated in any form,
  in whole or in part, without the prior written consent of Nintendo.

  $Date:: 2008-10-20#$
  $Rev: 9005 $
  $Author: okubata_ryoma $
 *---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*
  Pseudorandom Number Generator
 *---------------------------------------------------------------------------*/

#include <nitro.h>
#include <nitro/crypto.h>

#include "prng.h"

/*---------------------------------------------------------------------------*
    Variable Definitions
 *---------------------------------------------------------------------------*/
static u8 RandomPool[MATH_SHA1_DIGEST_SIZE];
static u32 RandomCount = 0;

/*---------------------------------------------------------------------------*
    Function Definitions
 *---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------*
  Name:         AddRandomSeed

  Description:  Adds a random seed to the PRNG.

  Arguments:    random_seed: Pointer to the random seed to be added
                len: Length of the random seed to be added

  Returns:      None.
 *---------------------------------------------------------------------------*/
void AddRandomSeed(u8* random_seed, u32 len)
{
    MATHSHA1Context context;
    MATH_SHA1Init(&context);
    MATH_SHA1Update(&context, RandomPool, sizeof(RandomPool));
    MATH_SHA1Update(&context, random_seed, len);
    MATH_SHA1GetHash(&context, RandomPool);
}

/*---------------------------------------------------------------------------*
  Name:         ChurnRandomPool

  Description:  Adds the current system status as a random seed to the PRNG.

  Arguments:    None.

  Returns:      None.
 *---------------------------------------------------------------------------*/
void ChurnRandomPool(void)
{
    u32 data[OS_LOW_ENTROPY_DATA_SIZE/sizeof(u32)];
    OS_GetLowEntropyData(data);
    AddRandomSeed((u8*)data, sizeof(data));
}

/*---------------------------------------------------------------------------*
  Name:         GetRandomBytes

  Description:  Gets a random number from the PRNG.

  Arguments:    Pointer to the buffer that stores the random number
                len: Length of the random number to be obtained in bytes

  Returns:      None.
 *---------------------------------------------------------------------------*/
void GetRandomBytes(u8* buffer, u32 len)
{
    MATHSHA1Context context;
    u8 tmp[MATH_SHA1_DIGEST_SIZE];
    u32 n;
    
    while (len > 0)
    {
        MATH_SHA1Init(&context);
        MATH_SHA1Update(&context, RandomPool, sizeof(RandomPool));
        MATH_SHA1Update(&context, &RandomCount, sizeof(RandomCount));
        MATH_SHA1GetHash(&context, tmp);
        RandomCount++;
        
        n = (len < MATH_SHA1_DIGEST_SIZE) ? len : MATH_SHA1_DIGEST_SIZE;
        MI_CpuCopy8(tmp, buffer, n);
        buffer += n;
        len -= n;
    }
}

/*---------------------------------------------------------------------------*
  End of file
 *---------------------------------------------------------------------------*/