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/*************************************************
* SHA1PRNG Source File *
* (C) 2007 FlexSecure GmbH / Manuel Hartl *
* (C) 2008 Jack Lloyd *
*************************************************/
#include <botan/sha1prng.h>
#include <botan/lookup.h>
#include <botan/bit_ops.h>
#include <algorithm>
namespace Botan {
/*************************************************
* Generate a buffer of random bytes *
*************************************************/
void SHA1PRNG::randomize(byte result[], u32bit length) throw(PRNG_Unseeded)
{
if(!is_seeded())
throw PRNG_Unseeded(name());
const u32bit SHA1_BYTES = hash->OUTPUT_LENGTH;
u32bit resultIndex=0;
/**
* use ramining bytes from buffer for result
*/
if(buf_pos>0)
{
u32bit remainderCountIndex=buf_pos;
unsigned int j = length >= (unsigned)(SHA1_BYTES - buf_pos) ? SHA1_BYTES - buf_pos : length;
for(;resultIndex < j;resultIndex++)
{
result[resultIndex] = buffer[remainderCountIndex];
buffer[remainderCountIndex++] = 0;
}
buf_pos += j;
}
/**
* fill result with fresh random bytes
*/
while(resultIndex < length)
{
hash->update(state.begin(),SHA1_BYTES);
hash->final(buffer.begin());
update_state(buffer.begin());
int k=length-1 <= SHA1_BYTES ? length : SHA1_BYTES;
for(int j = 0;j < k; j++)
{
result[resultIndex++] = buffer[j];
buffer[j] = 0;
}
buf_pos+=k;
}
buf_pos %=SHA1_BYTES;
}
/*************************************************
* Refill the internal state *
*************************************************/
void SHA1PRNG::update_state(byte update[])
{
signed int i = 1;
bool flag2 = false;
for(u32bit k = 0; k < state.size(); k++)
{
int b1 = state[k]%256;
if(b1>128)
{
b1-=256;
}
int b2 = update[k]%256;
if(b2>128)
{
b2-=256;
}
int j = b1+b2+i;
if(j>256)
{
j-=256;
}
flag2 |= state.begin()[k] != (byte)j;
state.begin()[k] = (byte)j;
i = j >> 8;
}
if(!flag2)
{
state[0]++;
}
}
/*************************************************
* Add entropy to internal state *
*************************************************/
void SHA1PRNG::add_randomness(const byte data[], u32bit length)
{
prng->add_entropy(data, length);
MemoryVector<byte> for_rand;
for_rand.set(data, length);
if(prng->is_seeded())
{
prng->randomize(for_rand, length);
hash->clear();
hash->update(for_rand,length);
hash->final(state.begin());
}
}
/*************************************************
* Check if the RNG is seeded *
*************************************************/
bool SHA1PRNG::is_seeded() const
{
return prng->is_seeded();
}
/*************************************************
* Clear memory of sensitive data *
*************************************************/
void SHA1PRNG::clear() throw()
{
hash->clear();
prng->clear();
}
/*************************************************
* Return the name of this type *
*************************************************/
std::string SHA1PRNG::name() const
{
return "SHA1PRNG";
}
/*************************************************
* SHA1PRNG Constructor *
*************************************************/
SHA1PRNG::SHA1PRNG(RandomNumberGenerator* prng_ptr)
{
if(!prng_ptr)
throw Invalid_Argument("SHA1PRNG constructor: NULL prng");
hash = get_hash("SHA-1");
prng = prng_ptr;
buf_pos = 0;
state.grow_to(hash->OUTPUT_LENGTH);
buffer.grow_to(hash->OUTPUT_LENGTH);
}
/*************************************************
* SHA1PRNG Destructor *
*************************************************/
SHA1PRNG::~SHA1PRNG()
{
delete hash;
delete prng;
}
}
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