Unsolved
Bitcoin puzzle #81
Bitcoin puzzle #81 is unsolved. It holds 8.10 BTC, and its private key is an unknown number between 280 and 281−1 — a keyspace of 1.20 × 1024 possible keys. You can search that range with the solver below; it runs in your browser and never sends anything to a server.
Solver — #81
IdleJump to a random point in the range, sweep a block of keys, jump again. Best when many people search the same puzzle.
Each thread is one Web Worker on one core. Leaving a core free keeps the page responsive.
Walk the range in order from your start key up to the end of the range, splitting that region evenly across threads. Keys below the start key are not searched. Best when you are coordinating a systematic sweep.
Range covered: 0%
· Current key: 100000000000000000000
Puzzle #81 at a glance
- Reward
- 8.100015 BTC
- Address
- 15qsCm78whspNQFydGJQk5rexzxTQopnHZ
- HASH160
- 351e605fac813965951ba433b7c2956bf8ad95ce
- Range start
- 100000000000000000000
- Range end
- 1ffffffffffffffffffff
- Bit length
- 81-bit
- Keys in range
- 1.20 × 1024 (1208925819614629174706176)
- Transactions
- 4
The arithmetic
The range for puzzle #81 contains 1.20 × 1024 private keys. A modern eight-core laptop running this solver checks on the order of four million keys per second, so an exhaustive sweep would take about 9.58 billion years. Searching randomly instead of in order does not change that expectation — it only changes which unlucky order you fail in.
Puzzle #81 — common questions
How many private keys does Bitcoin puzzle #81 contain?
Puzzle #81 spans the range 2^80 to 2^81−1, which is exactly 1.20 × 10^24 private keys — twice as many as puzzle #80.
How long would it take to solve Bitcoin puzzle #81?
An eight-core machine running this browser solver at four million keys per second would need about 9.58 billion years to sweep the whole range. A pooled GPU cluster reaching one trillion keys per second would need about 38,309 years.
How much is Bitcoin puzzle #81 worth?
The address holds 8.100015 BTC, roughly $633,867 at a reference price of $78,255 per BTC.
Is Bitcoin puzzle #81 solved?
No. #81 is one of the 78 unsolved puzzles. Its public key has never been exposed, so square-root methods like Pollard's Kangaroo do not apply — brute force over the range is the only option.
What is the key range for puzzle #81?
From 100000000000000000000 to 1ffffffffffffffffffff in hexadecimal. The address is 15qsCm78whspNQFydGJQk5rexzxTQopnHZ and its HASH160 is 351e605fac813965951ba433b7c2956bf8ad95ce.