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 January 30, 2015 and the prize was claimed.
1L5sU9qvJeuwQUdt4y1eiLmquFxKjtHr3EThe private key of this address is a number between 240 and 241, which is 1,099,511,627,776 possible keys. In hex, the range looks like this:
100000000001ffffffffffSince 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.
153869acc5bThis 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 41 sits at the 41 bit mark, so its key is one of 1,099,511,627,776 candidates.
This range was small enough for conventional brute force. GPU search tools walked through the keyspace until one of them produced the matching address, and the key was confirmed on January 30, 2015. Every solved puzzle like this one calibrates the difficulty curve: it marks how far real hardware has actually reached, which makes the still standing puzzles above it all the more meaningful.
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.