1 from __future__ import division
8 from twisted.python import log
11 from p2pool import skiplists, namecoin, ixcoin, i0coin
12 from p2pool.bitcoin import data as bitcoin_data, script
13 from p2pool.util import memoize, expiring_dict, math
16 merkle_branch_type = bitcoin_data.ListType(bitcoin_data.ComposedType([
17 ('side', bitcoin_data.StructType('<B')), # enum?
18 ('hash', bitcoin_data.HashType()),
22 share_data_type = bitcoin_data.ComposedType([
23 ('previous_share_hash', bitcoin_data.PossiblyNoneType(0, bitcoin_data.HashType())),
24 ('target', bitcoin_data.FloatingIntegerType()),
25 ('nonce', bitcoin_data.VarStrType()),
29 coinbase_type = bitcoin_data.ComposedType([
30 ('identifier', bitcoin_data.FixedStrType(8)),
31 ('share_data', share_data_type),
34 share_info_type = bitcoin_data.ComposedType([
35 ('share_data', share_data_type),
36 ('new_script', bitcoin_data.VarStrType()),
37 ('subsidy', bitcoin_data.StructType('<Q')),
41 share1a_type = bitcoin_data.ComposedType([
42 ('header', bitcoin_data.block_header_type),
43 ('share_info', share_info_type),
44 ('merkle_branch', merkle_branch_type),
47 share1b_type = bitcoin_data.ComposedType([
48 ('header', bitcoin_data.block_header_type),
49 ('share_info', share_info_type),
50 ('other_txs', bitcoin_data.ListType(bitcoin_data.tx_type)),
53 def calculate_merkle_branch(txs, index):
54 hash_list = [(bitcoin_data.tx_type.hash256(tx), i == index, []) for i, tx in enumerate(txs)]
56 while len(hash_list) > 1:
59 bitcoin_data.merkle_record_type.hash256(dict(left=left, right=right)),
61 (left_l if left_f else right_l) + [dict(side=1, hash=right) if left_f else dict(side=0, hash=left)],
63 for (left, left_f, left_l), (right, right_f, right_l) in
64 zip(hash_list[::2], hash_list[1::2] + [hash_list[::2][-1]])
67 assert hash_list[0][1]
68 assert check_merkle_branch(txs[index], hash_list[0][2]) == hash_list[0][0]
70 return hash_list[0][2]
72 def check_merkle_branch(tx, branch):
73 hash_ = bitcoin_data.tx_type.hash256(tx)
76 hash_ = bitcoin_data.merkle_record_type.hash256(dict(left=step['hash'], right=hash_))
78 hash_ = bitcoin_data.merkle_record_type.hash256(dict(left=hash_, right=step['hash']))
81 def gentx_to_share_info(gentx):
83 share_data=coinbase_type.unpack(gentx['tx_ins'][0]['script'])['share_data'],
84 subsidy=sum(tx_out['value'] for tx_out in gentx['tx_outs']),
85 new_script=gentx['tx_outs'][-1]['script'],
88 def share_info_to_gentx(share_info, block_target, tracker, net):
89 return generate_transaction(
91 previous_share_hash=share_info['share_data']['previous_share_hash'],
92 new_script=share_info['new_script'],
93 subsidy=share_info['subsidy'],
94 nonce=share_info['share_data']['nonce'],
95 block_target=block_target,
101 def from_block(cls, block):
102 return cls(block['header'], gentx_to_share_info(block['txs'][0]), other_txs=block['txs'][1:])
105 def from_share1a(cls, share1a):
106 return cls(**share1a)
109 def from_share1b(cls, share1b):
110 return cls(**share1b)
112 __slots__ = 'header previous_block share_info merkle_branch other_txs timestamp share_data new_script subsidy previous_hash previous_share_hash target nonce bitcoin_hash hash time_seen shared stored peer'.split(' ')
114 def __init__(self, header, share_info, merkle_branch=None, other_txs=None):
115 if merkle_branch is None and other_txs is None:
116 raise ValueError('need either merkle_branch or other_txs')
117 if other_txs is not None:
118 new_merkle_branch = calculate_merkle_branch([dict(version=0, tx_ins=[], tx_outs=[], lock_time=0)] + other_txs, 0)
119 if merkle_branch is not None:
120 if merke_branch != new_merkle_branch:
121 raise ValueError('invalid merkle_branch and other_txs')
122 merkle_branch = new_merkle_branch
124 if len(merkle_branch) > 16:
125 raise ValueError('merkle_branch too long!')
128 self.previous_block = header['previous_block']
129 self.share_info = share_info
130 self.merkle_branch = merkle_branch
131 self.other_txs = other_txs
133 self.timestamp = self.header['timestamp']
135 self.share_data = self.share_info['share_data']
136 self.new_script = self.share_info['new_script']
137 self.subsidy = self.share_info['subsidy']
139 if len(self.new_script) > 100:
140 raise ValueError('new_script too long!')
142 self.previous_hash = self.previous_share_hash = self.share_data['previous_share_hash']
143 self.target = self.share_data['target']
144 self.nonce = self.share_data['nonce']
146 if len(self.nonce) > 100:
147 raise ValueError('nonce too long!')
149 self.bitcoin_hash = bitcoin_data.block_header_type.hash256(header)
150 self.hash = share1a_type.hash256(self.as_share1a())
152 if self.bitcoin_hash > self.target:
153 print 'hash', hex(self.bitcoin_hash)
154 print 'targ', hex(self.target)
155 raise ValueError('not enough work!')
157 if script.get_sigop_count(self.new_script) > 1:
158 raise ValueError('too many sigops!')
161 self.time_seen = time.time()
166 def as_block(self, tracker, net):
167 if self.other_txs is None:
168 raise ValueError('share does not contain all txs')
170 gentx = share_info_to_gentx(self.share_info, self.header['target'], tracker, net)
172 return dict(header=self.header, txs=[gentx] + self.other_txs)
174 def as_share1a(self):
175 return dict(header=self.header, share_info=self.share_info, merkle_branch=self.merkle_branch)
177 def as_share1b(self):
178 return dict(header=self.header, share_info=self.share_info, other_txs=self.other_txs)
180 def check(self, tracker, now, net):
182 if self.previous_share_hash is not None:
183 if self.header['timestamp'] <= math.median((s.timestamp for s in itertools.islice(tracker.get_chain_to_root(self.previous_share_hash), 11)), use_float=False):
184 raise ValueError('share from too far in the past!')
186 if self.header['timestamp'] > now + 2*60*60:
187 raise ValueError('share from too far in the future!')
189 gentx = share_info_to_gentx(self.share_info, self.header['target'], tracker, net)
191 if len(gentx['tx_ins'][0]['script']) > 100:
192 raise ValueError('''coinbase too large!''')
194 if check_merkle_branch(gentx, self.merkle_branch) != self.header['merkle_root']:
195 raise ValueError('''gentx doesn't match header via merkle_branch''')
197 if self.other_txs is not None:
198 if bitcoin_data.merkle_hash([gentx] + self.other_txs) != self.header['merkle_root']:
199 raise ValueError('''gentx doesn't match header via other_txs''')
201 if len(bitcoin_data.block_type.pack(dict(header=self.header, txs=[gentx] + self.other_txs))) > 1000000 - 1000:
202 raise ValueError('''block size too large''')
204 def flag_shared(self):
208 return '<Share %s>' % (' '.join('%s=%r' % (k, getattr(self, k)) for k in self.__slots__),)
210 def get_pool_attempts_per_second(tracker, previous_share_hash, net, dist=None):
212 dist = net.TARGET_LOOKBEHIND
213 near = tracker.shares[previous_share_hash]
214 far = tracker.shares[tracker.get_nth_parent_hash(previous_share_hash, dist - 1)]
215 attempts = tracker.get_work(near.hash) - tracker.get_work(far.hash)
216 time = near.timestamp - far.timestamp
219 return attempts//time
221 def generate_transaction(tracker, previous_share_hash, new_script, subsidy, nonce, block_target, net):
222 height, last = tracker.get_height_and_last(previous_share_hash)
223 assert height >= net.CHAIN_LENGTH or last is None
224 if height < net.TARGET_LOOKBEHIND:
225 target = bitcoin_data.FloatingInteger.from_target_upper_bound(net.MAX_TARGET)
227 attempts_per_second = get_pool_attempts_per_second(tracker, previous_share_hash, net)
228 pre_target = 2**256//(net.SHARE_PERIOD*attempts_per_second) - 1
229 previous_share = tracker.shares[previous_share_hash] if previous_share_hash is not None else None
230 pre_target2 = math.clip(pre_target, (previous_share.target*9//10, previous_share.target*11//10))
231 pre_target3 = math.clip(pre_target2, (0, net.MAX_TARGET))
232 target = bitcoin_data.FloatingInteger.from_target_upper_bound(pre_target3)
234 attempts_to_block = bitcoin_data.target_to_average_attempts(block_target)
235 max_weight = net.SPREAD * attempts_to_block
237 this_weight = min(bitcoin_data.target_to_average_attempts(target), max_weight)
238 other_weights, other_weights_total = tracker.get_cumulative_weights(previous_share_hash, min(height, net.CHAIN_LENGTH), max(0, max_weight - this_weight))
239 dest_weights, total_weight = math.add_dicts([{new_script: this_weight}, other_weights]), this_weight + other_weights_total
240 assert total_weight == sum(dest_weights.itervalues())
242 amounts = dict((script, subsidy*(396*weight)//(400*total_weight)) for (script, weight) in dest_weights.iteritems())
243 amounts[new_script] = amounts.get(new_script, 0) + subsidy*2//400
244 amounts[net.SCRIPT] = amounts.get(net.SCRIPT, 0) + subsidy*2//400
245 amounts[net.SCRIPT] = amounts.get(net.SCRIPT, 0) + subsidy - sum(amounts.itervalues()) # collect any extra
246 if sum(amounts.itervalues()) != subsidy:
248 if any(x < 0 for x in amounts.itervalues()):
251 pre_dests = sorted(amounts.iterkeys(), key=lambda script: (amounts[script], script))
252 pre_dests = pre_dests[-4000:] # block length limit, unlikely to ever be hit
254 dests = sorted(pre_dests, key=lambda script: (script == new_script, script))
255 assert dests[-1] == new_script
260 previous_output=None,
262 script=coinbase_type.pack(dict(
263 identifier=net.IDENTIFIER,
265 previous_share_hash=previous_share_hash,
271 tx_outs=[dict(value=amounts[script], script=script) for script in dests if amounts[script]],
277 class OkayTracker(bitcoin_data.Tracker):
278 def __init__(self, net):
279 bitcoin_data.Tracker.__init__(self)
281 self.verified = bitcoin_data.Tracker()
282 self.verified.get_nth_parent_hash = self.get_nth_parent_hash # self is a superset of self.verified
284 self.get_cumulative_weights = skiplists.WeightsSkipList(self)
286 def add(self, share, known_verified=False):
287 bitcoin_data.Tracker.add(self, share)
289 self.verified.add(share)
291 def attempt_verify(self, share, now):
292 if share.hash in self.verified.shares:
294 height, last = self.get_height_and_last(share.hash)
295 if height < self.net.CHAIN_LENGTH + 1 and last is not None:
296 raise AssertionError()
298 share.check(self, now, self.net)
300 log.err(None, 'Share check failed:')
303 self.verified.add(share)
306 def think(self, ht, previous_block, now):
310 # make 'unverified heads' set?
311 # for each overall head, attempt verification
312 # if it fails, attempt on parent, and repeat
313 # if no successful verification because of lack of parents, request parent
315 for head in set(self.heads) - set(self.verified.heads):
316 head_height, last = self.get_height_and_last(head)
318 for share in itertools.islice(self.get_chain_known(head), None if last is None else min(5, max(0, head_height - self.net.CHAIN_LENGTH))):
319 if self.attempt_verify(share, now):
321 if share.hash in self.heads:
325 desired.add((self.shares[random.choice(list(self.reverse_shares[last]))].peer, last))
327 assert bad not in self.verified.shares
328 assert bad in self.heads
333 # try to get at least CHAIN_LENGTH height for each verified head, requesting parents if needed
334 for head in list(self.verified.heads):
335 head_height, last_hash = self.verified.get_height_and_last(head)
336 last_height, last_last_hash = self.get_height_and_last(last_hash)
337 # XXX review boundary conditions
338 want = max(self.net.CHAIN_LENGTH - head_height, 0)
339 can = max(last_height - 1 - self.net.CHAIN_LENGTH, 0) if last_last_hash is not None else last_height
341 #print 'Z', head_height, last_hash is None, last_height, last_last_hash is None, want, can, get
342 for share in itertools.islice(self.get_chain_known(last_hash), get):
343 if not self.attempt_verify(share, now):
345 if head_height < self.net.CHAIN_LENGTH and last_last_hash is not None:
346 desired.add((self.verified.shares[random.choice(list(self.verified.reverse_shares[last_hash]))].peer, last_last_hash))
349 best_tail = max(self.verified.tails, key=lambda h: self.score(max(self.verified.tails[h], key=self.verified.get_height), ht)) if self.verified.tails else None
350 # decide best verified head
351 scores = sorted(self.verified.tails.get(best_tail, []), key=lambda h: (
352 self.verified.get_work(self.verified.get_nth_parent_hash(h, min(5, self.verified.get_height(h)))),
353 ht.get_min_height(self.verified.shares[h].previous_block),
354 #self.verified.shares[h].peer is None,
355 -self.verified.shares[h].time_seen
360 print len(self.verified.tails.get(best_tail, [])), '\\/\\/\\/\\/\\/'
363 for h in scores[-10:]:
364 print ' ', format_hash(h), format_hash(self.verified.shares[h].previous_hash), (
365 self.verified.get_work(self.verified.get_nth_parent_hash(h, min(5, self.verified.get_height(h)))),
366 ht.get_min_height(self.verified.shares[h].previous_block),
367 self.verified.shares[h].peer is None,
368 -self.verified.shares[h].time_seen
375 for share_hash, tail in self.heads.iteritems():
376 if share_hash in scores[-5:]:
379 if self.shares[share_hash].time_seen > time.time() - 300:
382 if share_hash not in self.verified.shares and max(self.shares[after_tail_hash].time_seen for after_tail_hash in self.reverse_shares.get(tail)) > time.time() - 120: # XXX stupid
385 to_remove.add(share_hash)
388 for share_hash in to_remove:
389 self.remove(share_hash)
390 if share_hash in self.verified.shares:
391 self.verified.remove(share_hash)
392 #print "_________", to_remove
397 for tail, heads in self.tails.iteritems():
398 if min(self.get_height(head) for head in heads) < 2*self.net.CHAIN_LENGTH + 10:
400 for aftertail in self.reverse_shares.get(tail, set()):
401 if len(self.reverse_shares[self.shares[aftertail].previous_hash]) > 1: # XXX
404 to_remove.add(aftertail)
407 # if removed from this, it must be removed from verified
409 for aftertail in to_remove:
410 if self.shares[aftertail].previous_hash not in self.tails:
411 print "erk", aftertail, self.shares[aftertail].previous_hash
413 self.remove(aftertail)
414 if aftertail in self.verified.shares:
415 self.verified.remove(aftertail)
417 #print "removed! %i %f" % (len(to_remove), (end - start)/len(to_remove))
419 best = scores[-1] if scores else None
422 best_share = self.verified.shares[best]
423 if ht.get_min_height(best_share.header['previous_block']) < ht.get_min_height(previous_block) and best_share.bitcoin_hash != previous_block: # and best_share.peer is not None:
425 print 'Stale detected! %x < %x' % (best_share.header['previous_block'], previous_block)
426 best = best_share.previous_hash
430 @memoize.memoize_with_backing(expiring_dict.ExpiringDict(5, get_touches=False))
431 def score(self, share_hash, ht):
432 head_height, last = self.verified.get_height_and_last(share_hash)
436 share2_hash = self.verified.get_nth_parent_hash(share_hash, min(self.net.CHAIN_LENGTH//2, head_height//2)) if last is not None else share_hash
437 for share in reversed(list(itertools.islice(self.verified.get_chain_known(share2_hash), self.net.CHAIN_LENGTH))):
438 max_height = max(max_height, ht.get_min_height(share.header['previous_block']))
439 attempts += bitcoin_data.target_to_average_attempts(share.target)
440 this_score = attempts//(ht.get_highest_height() - max_height + 1)
441 if this_score > score2:
443 return min(head_height, self.net.CHAIN_LENGTH), score2
448 return '%08x' % (x % 2**32)
450 class ShareStore(object):
451 def __init__(self, prefix, net):
452 self.filename = prefix
454 self.known = None # will be filename -> set of share hashes, set of verified hashes
456 def get_shares(self):
457 if self.known is not None:
458 raise AssertionError()
460 filenames, next = self.get_filenames_and_next()
461 for filename in filenames:
462 share_hashes, verified_hashes = known.setdefault(filename, (set(), set()))
463 with open(filename, 'rb') as f:
466 type_id_str, data_hex = line.strip().split(' ')
467 type_id = int(type_id_str)
469 share = Share.from_share1a(share1a_type.unpack(data_hex.decode('hex')))
471 share_hashes.add(share.hash)
473 share = Share.from_share1b(share1b_type.unpack(data_hex.decode('hex')))
475 share_hashes.add(share.hash)
477 verified_hash = int(data_hex, 16)
478 yield 'verified_hash', verified_hash
479 verified_hashes.add(verified_hash)
481 raise NotImplementedError("share type %i" % (type_id,))
483 log.err(None, "Error while reading saved shares, continuing where left off:")
486 def _add_line(self, line):
487 filenames, next = self.get_filenames_and_next()
488 if filenames and os.path.getsize(filenames[-1]) < 10e6:
489 filename = filenames[-1]
493 with open(filename, 'ab') as f:
498 def add_share(self, share):
499 if share.bitcoin_hash <= share.header['target']:
500 type_id, data = 1, share1b_type.pack(share.as_share1b())
502 type_id, data = 0, share1a_type.pack(share.as_share1a())
503 filename = self._add_line("%i %s" % (type_id, data.encode('hex')))
504 share_hashes, verified_hashes = self.known.setdefault(filename, (set(), set()))
505 share_hashes.add(share.hash)
507 def add_verified_hash(self, share_hash):
508 filename = self._add_line("%i %x" % (2, share_hash))
509 share_hashes, verified_hashes = self.known.setdefault(filename, (set(), set()))
510 verified_hashes.add(share_hash)
512 def get_filenames_and_next(self):
513 suffixes = sorted(int(x[len(self.filename):]) for x in os.listdir('.') if x.startswith(self.filename) and x[len(self.filename):].isdigit())
514 return [self.filename + str(suffix) for suffix in suffixes], self.filename + str(suffixes[-1] + 1) if suffixes else self.filename + str(0)
516 def forget_share(self, share_hash):
518 for filename, (share_hashes, verified_hashes) in self.known.iteritems():
519 if share_hash in share_hashes:
520 share_hashes.remove(share_hash)
521 if not share_hashes and not verified_hashes:
522 to_remove.add(filename)
523 for filename in to_remove:
524 self.known.pop(filename)
526 print "REMOVED", filename
528 def forget_verified_share(self, share_hash):
530 for filename, (share_hashes, verified_hashes) in self.known.iteritems():
531 if share_hash in verified_hashes:
532 verified_hashes.remove(share_hash)
533 if not share_hashes and not verified_hashes:
534 to_remove.add(filename)
535 for filename in to_remove:
536 self.known.pop(filename)
538 print "REMOVED", filename
540 class Mainnet(bitcoin_data.Mainnet):
541 SHARE_PERIOD = 5 # seconds
542 CHAIN_LENGTH = 24*60*60//5 # shares
543 TARGET_LOOKBEHIND = 200 # shares
545 SCRIPT = '4104ffd03de44a6e11b9917f3a29f9443283d9871c9d743ef30d5eddcd37094b64d1b3d8090496b53256786bf5c82932ec23c3b74d9f05a6f95a8b5529352656664bac'.decode('hex')
546 IDENTIFIER = 'fc70035c7a81bc6f'.decode('hex')
547 PREFIX = '2472ef181efcd37b'.decode('hex')
550 MAX_TARGET = 2**256//2**32 - 1
554 class Testnet(bitcoin_data.Testnet):
555 SHARE_PERIOD = 1 # seconds
556 CHAIN_LENGTH = 24*60*60//5 # shares
557 TARGET_LOOKBEHIND = 200 # shares
559 SCRIPT = '410403ad3dee8ab3d8a9ce5dd2abfbe7364ccd9413df1d279bf1a207849310465b0956e5904b1155ecd17574778f9949589ebfd4fb33ce837c241474a225cf08d85dac'.decode('hex')
560 IDENTIFIER = '5fc2be2d4f0d6bfb'.decode('hex')
561 PREFIX = '3f6057a15036f441'.decode('hex')
562 NAME = 'bitcoin_testnet'
564 MAX_TARGET = 2**256//2**20 - 1
568 class NamecoinMainnet(namecoin.NamecoinMainnet):
569 SHARE_PERIOD = 10 # seconds
570 CHAIN_LENGTH = 24*60*60//10 # shares
571 TARGET_LOOKBEHIND = 3600//10 # shares
573 SCRIPT = '41043da5beb73f8f18cede1a41b0ed953123f1342b8e0216ab5bf71ed3e024201b4017f472bddb6041f17978d89ed8f8ed84f9e726b0bca80cacf96347c7153e8df0ac'.decode('hex')
574 IDENTIFIER = 'd5b1192062c4c454'.decode('hex')
575 PREFIX = 'b56f3d0fb24fc982'.decode('hex')
578 MAX_TARGET = 2**256//2**32 - 1
582 class NamecoinTestnet(namecoin.NamecoinTestnet):
583 SHARE_PERIOD = 1 # seconds
584 CHAIN_LENGTH = 24*60*60//5 # shares
585 TARGET_LOOKBEHIND = 200 # shares
587 SCRIPT = '410403ad3dee8ab3d8a9ce5dd2abfbe7364ccd9413df1d279bf1a207849310465b0956e5904b1155ecd17574778f9949589ebfd4fb33ce837c241474a225cf08d85dac'.decode('hex')
588 IDENTIFIER = '8dd303d014a01a60'.decode('hex')
589 PREFIX = '4d6581d24f51acbf'.decode('hex')
590 NAME = 'namecoin_testnet'
592 MAX_TARGET = 2**256//2**20 - 1
596 class IxcoinMainnet(ixcoin.IxcoinMainnet):
597 SHARE_PERIOD = 10 # seconds
598 CHAIN_LENGTH = 24*60*60//10 # shares
599 TARGET_LOOKBEHIND = 3600//10 # shares
601 SCRIPT = '41043da5beb73f8f18cede1a41b0ed953123f1342b8e0216ab5bf71ed3e024201b4017f472bddb6041f17978d89ed8f8ed84f9e726b0bca80cacf96347c7153e8df0ac'.decode('hex')
602 IDENTIFIER = '27b564116e2a2666'.decode('hex')
603 PREFIX = '9dd6c4a619401f2f'.decode('hex')
606 MAX_TARGET = 2**256//2**32 - 1
610 class IxcoinTestnet(ixcoin.IxcoinTestnet):
611 SHARE_PERIOD = 1 # seconds
612 CHAIN_LENGTH = 24*60*60//5 # shares
613 TARGET_LOOKBEHIND = 200 # shares
615 SCRIPT = '410403ad3dee8ab3d8a9ce5dd2abfbe7364ccd9413df1d279bf1a207849310465b0956e5904b1155ecd17574778f9949589ebfd4fb33ce837c241474a225cf08d85dac'.decode('hex')
616 IDENTIFIER = '7430cbeb01249e44'.decode('hex')
617 PREFIX = '7cfffda946709c1f'.decode('hex')
618 NAME = 'ixcoin_testnet'
620 MAX_TARGET = 2**256//2**20 - 1
624 class I0coinMainnet(i0coin.I0coinMainnet):
625 SHARE_PERIOD = 10 # seconds
626 CHAIN_LENGTH = 24*60*60//10 # shares
627 TARGET_LOOKBEHIND = 3600//10 # shares
629 SCRIPT = '410403ad3dee8ab3d8a9ce5dd2abfbe7364ccd9413df1d279bf1a207849310465b0956e5904b1155ecd17574778f9949589ebfd4fb33ce837c241474a225cf08d85dac'.decode('hex')
630 IDENTIFIER = 'b32e3f10c2ff221b'.decode('hex')
631 PREFIX = '6155537ed977a3b5'.decode('hex')
634 MAX_TARGET = 2**256//2**32 - 1
638 class I0coinTestnet(i0coin.I0coinTestnet):
639 SHARE_PERIOD = 1 # seconds
640 CHAIN_LENGTH = 24*60*60//5 # shares
641 TARGET_LOOKBEHIND = 200 # shares
643 SCRIPT = '410403ad3dee8ab3d8a9ce5dd2abfbe7364ccd9413df1d279bf1a207849310465b0956e5904b1155ecd17574778f9949589ebfd4fb33ce837c241474a225cf08d85dac'.decode('hex')
644 IDENTIFIER = '7712c1a8181b5f2e'.decode('hex')
645 PREFIX = '792d2e7d770fbe68'.decode('hex')
646 NAME = 'i0coin_testnet'
648 MAX_TARGET = 2**256//2**20 - 1