42 lines
1.3 KiB
Python
42 lines
1.3 KiB
Python
from time import time
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from hashlib import shake_128
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from secrets import randbits
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class DandelionPhase:
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def __init__(self, seed: bytes, epoch_interval_secs: int):
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self.seed = seed # Seed intended to be from good random source like urandom
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assert len(self.seed) == 32
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self.epoch = int(time())
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self.epoch_interval = epoch_interval_secs
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self._is_stem = bool(randbits(1))
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self.phase_id = b''
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def _update_stem_phase(self, cur_time):
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self.epoch = cur_time
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# Hash the seed with the time stamp to produce 8 pseudorandom bytes
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# Produce an len(8) byte string for time as well for year 2038 problem
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self.phase_id = shake_128(
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self.seed +
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int.to_bytes(cur_time, 8, 'big')).digest(8)
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# Use first byte of phase id as random source for stem phase picking
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if self.phase_id[0] % 2:
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self._is_stem = True
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else:
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self._is_stem = False
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def remaining_time(self) -> int:
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current_time = int(time())
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return max(0, self.epoch_interval - (current_time - self.epoch))
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def is_stem_phase(self) -> bool:
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current_time = int(time())
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if current_time - self.epoch >= self.epoch_interval:
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self._update_stem_phase(current_time)
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return self._is_stem
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