One of the 160 puzzle addresses created in 2015 to show how hard it is to guess a Bitcoin private key. This one has fallen: the key was found on June 11, 2019 and the prize was claimed.
1BCf6rHUW6m3iH2ptsvnjgLruAiPQQepLeThe private key of this address is a number between 279 and 280, which is 6.0 × 1023 possible keys. In hex, the range looks like this:
80000000000000000000fffffffffffffffffffffSince this puzzle is solved, its private key is public knowledge and the prize was claimed long ago. It is shown here for reference and study: you can verify that this key really does produce the address above.
ea1a5c66dcc11b5ad180This puzzle is already solved, so the demo scans the range from the start and stops when it reaches the known key. It is a replay, not a treasure hunt.
In 2015, an anonymous user created 160 Bitcoin addresses and funded them with about 1000 BTC in total. Each address hides its private key in a range that doubles with every puzzle number: puzzle 1 uses a 1 bit range, puzzle 160 a 160 bit range. Puzzle 80 sits at the 80 bit mark, so its key is one of 6.0 × 1023 candidates.
A range this size is far beyond raw brute force. This puzzle fell because its public key was deliberately exposed, which let solvers use Pollard's kangaroo algorithm to cut the work down to roughly the square root of the range. The key was found on June 11, 2019. It stands as a real world benchmark of how far that technique scales.
The whole series is best understood as a public experiment, not a hacking contest. These coins were placed on purpose to be found, and the solved and unsolved puzzles together map the exact frontier of what today's hardware can do against Bitcoin's cryptography. Guessing the key of a normal wallet remains astronomically out of reach: a real 256 bit key has a keyspace about 1029 times larger than even puzzle 160. Read more about the math and the quantum angle in the FAQ on the main page.