research/casper_sm/test.py

181 lines
6.4 KiB
Python

# The purpose of this script is to test selfish-mining-like strategies
# in the randao-based single-chain Casper.
import random
# Reward for mining a block with nonzero skips
NON_PRIMARY_REWARD = 0.5
# Penalty for mining a dunkle
DUNKLE_PENALTY = 0.75
# Penalty to a main-chain block which has a dunkle as a sister
DUNKLE_SISTER_PENALTY = 0.375
# Attacker stake power (out of 100). Try setting this value to any
# amount, even values above 50!
attacker_share = 60
# A simulated Casper randao
def randao_successor(parent, index):
return (((parent ^ 53) + index) ** 3) % (10**20 - 11)
# We categorize "scenarios" by seeing how far ahead we get a chain
# of 0-skips from each "path"; if the path itself isn't clear then
# return zero
heads_of_interest = ['', '1']
# Only scan down this far
scandepth = 4
# eg. (0, 2) means "going straight from the current randao, you
# can descend zero, but if you make a one-skip block, from there
# you get two 0-skips in a row"
scenarios = [None, (0, 1), (0, 2), (0, 3), (0, 4)]
# For each scenario, this is the corresponding "path" to go down
paths = ['', '10', '100', '100', '1000']
# Determine the scenario ID (zero is catch-all) from a chain
def extract_scenario(chain):
chain = chain.copy()
o = []
for h in heads_of_interest:
# Make sure that we can descend down "the path"
succeed = True
for step in h:
if not chain.can_i_extend(int(step)):
succeed = False
break
chain.extend_me(int(step))
if not succeed:
o.append(0)
else:
# See how far down we can go
i = 0
while chain.can_i_extend(0) and i < scandepth:
i += 1
chain.extend_me(0)
o.append(i)
if tuple(o) in scenarios:
return scenarios.index(tuple(o))
else:
return 0
# Class to represent simulated chains
class Chain():
def __init__(self, randao=0, time=0, length=0, me=0, them=0):
self.randao = randao
self.time = time
self.length = length
self.me = me
self.them = them
def copy(self):
return Chain(self.randao, self.time, self.length, self.me, self.them)
def can_i_extend(self, skips):
return randao_successor(self.randao, skips) % 100 < attacker_share
def can_they_extend(self, skips):
return randao_successor(self.randao, skips) % 100 >= attacker_share
def extend_me(self, skips):
new_randao = randao_successor(self.randao, skips)
assert new_randao % 100 < attacker_share
self.randao = new_randao
self.time += skips
self.length += 1
self.me += NON_PRIMARY_REWARD if skips else 1
def extend_them(self, skips):
new_randao = randao_successor(self.randao, skips)
assert new_randao % 100 >= attacker_share
self.randao = new_randao
self.time += skips
self.length += 1
self.them += NON_PRIMARY_REWARD if skips else 1
def add_my_dunkles(self, n):
self.me -= n * DUNKLE_PENALTY
self.them -= n * DUNKLE_SISTER_PENALTY
def add_their_dunkles(self, n):
self.them -= n * DUNKLE_PENALTY
self.me -= n * DUNKLE_SISTER_PENALTY
my_total_loss = 0
their_total_loss = 0
for strat_id in range(2**len(scenarios)):
# Strategy map: scenario to 0 = publish, 1 = selfish-validate
strategy = [0] + [((strat_id // 2**i) % 2) for i in range(1, len(scenarios))]
# 1 = once we go through the selfish-validating "path", reveal it instantly
# 0 = don't reveal until the "main chain" looks like it's close to catching up
insta_reveal = strat_id % 2
print 'Testing strategy: %r, insta_reveal: %d' % (strategy, insta_reveal)
pubchain = Chain(randao=random.randrange(10**20))
time = 0
while time < 100000:
# You honestly get a block
if pubchain.can_i_extend(0):
pubchain.extend_me(0)
time += 1
continue
e = extract_scenario(pubchain)
if strategy[e] == 0:
# You honestly let them get a block
pubchain.extend_them(0)
time += 1
continue
# Build up the secret chain based on the detected path
# print 'Selfish mining along path %r' % paths[e]
old_me = pubchain.me
old_them = pubchain.them
old_time = time
secchain = pubchain.copy()
sectime = time
for skipz in paths[e]:
skips = int(skipz)
secchain.extend_me(skips)
sectime += skips + 1
# Public chain builds itself up in the meantime
pubwait = 0
while time < sectime:
if pubchain.can_they_extend(pubwait):
pubchain.extend_them(pubwait)
pubwait = 0
else:
pubwait += 1
time += 1
secwait = 0
# If the two chains have equal length, or if the secret chain is more than 1 longer, they duel
while (secchain.length > pubchain.length + 1 or secchain.length == pubchain.length) and time < 100000 and not insta_reveal:
if pubchain.can_they_extend(pubwait):
pubchain.extend_them(pubwait)
pubwait = 0
else:
pubwait += 1
if secchain.can_i_extend(secwait):
secchain.extend_me(secwait)
secwait = 0
else:
secwait += 1
time += 1
# Secret chain is longer, takes over public chain, public chain goes in as dunkles
if secchain.length > pubchain.length:
pubchain_blocks = pubchain.them - old_them
assert pubchain.me == old_me
pubchain = secchain
pubchain.add_their_dunkles(pubchain_blocks)
# Public chain is longer, miner deletes secret chain so no dunkling
else:
pass
# print 'Score deltas: me %.2f them %.2f, time delta %d' % (pubchain.me - old_me, pubchain.them - old_them, time - old_time)
my_loss = 100000 * attacker_share / 100 - pubchain.me
their_loss = 100000 * (100 - attacker_share) / 100 - pubchain.them
my_total_loss += my_loss
their_total_loss += their_loss
gf = their_loss / my_loss if my_loss > 0 else 999.99
print 'My revenue: %d, their revenue: %d, griefing factor %.2f' % (pubchain.me, pubchain.them, gf)
print 'Total griefing factor: %.2f' % (their_total_loss / my_total_loss)