The Puzzle is a volunteer computing project working on the Bitcoin puzzle. In 2015 someone sent bitcoin to a series of addresses whose private keys were picked from deliberately small ranges: the key for puzzle #1 is 1 bit long, #2 is 2 bits, and so on up to 160. The small ones were found long ago. Puzzle #71 is the lowest one still unsolved. Its key is somewhere between 2⁷⁰ and 2⁷¹, and the address holds about 7.1 BTC.

There is no shortcut for this one, just checking keys one after another, and there are a lot of them (2⁷⁰ is about 1.2 sextillion). We split the range into blocks of 2³⁴ keys, roughly 17 billion each, and hand them out through BOINC. Your computer checks a block and sends back an encrypted result, which is verified before any credit is given.

Prize sharing. If the key turns up, the coins are split like this: 20% is set aside for taxes, 40% goes to the project operator and 40% goes to the volunteers. The volunteer part is divided between everyone who returned valid work, in proportion to their credit. One verified block is 1 credit. It does not matter whose computer actually finds the key.

About the odds: the range is huge, and nobody can say how long it will take or whether we will get there first.

The app runs on 64-bit Windows and Linux, CPU only for now. A GPU version is planned.

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