def add_event(self, s=''):
"""add_event(s:string)
Add an event to the random pool. The current time is stored
between calls and used to estimate the entropy. The optional
's' parameter is a string that will also be XORed into the pool.
Returns the estimated number of additional bits of entropy gain.
"""
event = time.time()*1000
delta = self._noise()
s = (s + long_to_bytes(event) +
4*chr(0xaa) + long_to_bytes(delta) )
self._addBytes(s)
if event==self._event1 and event==self._event2:
# If events are coming too closely together, assume there's
# no effective entropy being added.
bits=0
else:
# Count the number of bits in delta, and assume that's the entropy.
bits=0
while delta:
delta, bits = delta>>1, bits+1
if bits>8: bits=8
self._event1, self._event2 = event, self._event1
self._updateEntropyEstimate(bits)
return bits
def _noise(self):
# Adds a bit of noise to the random pool, by adding in the
# current time and CPU usage of this process.
# The difference from the previous call to _noise() is taken
# in an effort to estimate the entropy.
t=time.time()
delta = (t - self._lastcounter)/self._ticksize*1e6
self._lastcounter = t
self._addBytes(long_to_bytes(long(1000*time.time())))
self._addBytes(long_to_bytes(long(1000*time.clock())))
self._addBytes(long_to_bytes(long(1000*time.time())))
self._addBytes(long_to_bytes(long(delta)))
# Reduce delta to a maximum of 8 bits so we don't add too much
# entropy as a result of this call.
delta=delta % 0xff
return int(delta)