byte
randPoolGetByte(void)
{
if (randPoolGetPos == sizeof(randPool))
randPoolStir();
return ((byte *)randPool)[randPoolGetPos++];
}
/*
* Withdraw some bits from the pool. Regardless of the distribution of the
* input bits, the bits returned are uniformly distributed, although they
* cannot, of course, contain more Shannon entropy than the input bits.
*/
void
randPoolGetBytes(byte *buf, unsigned len)
{
unsigned t;
while (len > (t = sizeof(randPool) - randPoolGetPos)) {
memcpy(buf, (byte *)randPool+randPoolGetPos, t);
buf += t;
len -= t;
randPoolStir();
}
if (len) {
memcpy(buf, (byte *)randPool+randPoolGetPos, len);
randPoolGetPos += len;
}
}
/*
* Make a deposit of information (entropy) into the pool. The bits
* deposited need not have any particular distribution; the stirring
* operation transformes them to uniformly-distributed bits.
*/
void
randPoolAddBytes(byte const *buf, unsigned len)
{
unsigned t;
while (len > (t = sizeof(randPool) - randPoolAddPos)) {
xorbytes((byte *)randPool+randPoolAddPos, buf, t);
buf += t;
len -= t;
randPoolStir();
}
if (len) {
xorbytes((byte *)randPool+randPoolAddPos, buf, len);
randPoolAddPos += len;
randPoolGetPos = sizeof(randPool); /* Force stir on get */
}
}
/*
* Make a deposit of information (entropy) into the pool. This is done by
* XORing them into the key which is used to encrypt the pool. Before any
* bytes are retrieved from the pool, the altered key will be used to encrypt
* the whole pool, causing all bits in the pool to depend on the new
* information.
*
* The bits deposited need not have any particular distribution; the stirring
* operation transforms them to uniformly-distributed bits.
*/
void
randPoolAddBytes(byte const *buf, unsigned len)
{
byte *p = (byte *)randKey + randKeyAddPos;
unsigned t = sizeof(randKey) - randKeyAddPos;
while (len > t) {
len -= t;
while (t--)
*p++ ^= *buf++;
randPoolStir(); /* sets randKeyAddPos to 0 */
p = (byte *)randKey;
t = sizeof(randKey);
}
if (len) {
randKeyAddPos += len;
do
*p++ ^= *buf++;
while (--len);
randPoolGetPos = sizeof(randPool); /* Force stir on get */
}
}
