The 1000 BTC Puzzle
A mysterious creator seeded 256 Bitcoin wallets with private keys of increasing difficulty, challenging the world to crack them. A decade later, the puzzle has become a landmark experiment in cryptographic security — with over 916 BTC still unclaimed and solvers pushing the boundaries of brute-force and probabilistic algorithms.
What if someone offered you a public challenge: crack these Bitcoin wallets if you can? That is precisely what happened in 2015, when a mysterious actor seeded 256 wallets with private keys engineered to be progressively harder to guess — each one roughly twice as difficult as the last. The challenge became known as the Bitcoin Puzzle Transaction, and it has captivated cryptographers and hobbyists ever since.
The Beginning: December 2015
The story started on December 27, 2015, when a user named Bulista posted on a Bitcoin forum about building an address scanner that iterated through private keys sequentially. To everyone's astonishment, Bulista reported cracking 53 wallets with remarkably weak private keys — values like 1, 3, 5, 8, 12, 22, 111, 247. These weren't random finds: the keys had been deliberately made simple.
The community went through stages of disbelief, then fascination. The wallets were real, the funds were real, and someone had clearly placed them there intentionally. The question was: who, and why?
2017: The Creator Speaks
In 2017, a user calling themselves saatoshi_rising (a play on "Satoshi") stepped forward as the puzzle's creator. Their stated goal was to test the cryptographic cracking capabilities of the community. They acknowledged a design flaw in early versions restricting high-entropy wallets above 160 bits, and redistributed funds from wallets 161–256 into the lower-numbered ones, consolidating roughly 100 BTC into the active puzzle space.
2019: Public Keys Revealed
A mysterious transaction in 2019 exposed the public keys for every fifth wallet. This was a significant development: knowing a public key dramatically narrows the search space and enables the use of more efficient algorithms — most notably Pollard's Kangaroo algorithm, a probabilistic method that can solve the elliptic-curve discrete logarithm problem far faster than brute force for mid-range key sizes.
2023: Prizes Multiplied Tenfold
An unknown party increased all rewards approximately tenfold, tying each wallet's value directly to its difficulty level: puzzle #71 now holds 7.1 BTC, puzzle #100 holds 10 BTC, and so on. This injection of capital renewed intense interest and set the total unclaimed prize pool at approximately 916.5 BTC.
Two Schools of Attack
Solvers have split into two broad camps:
- Brute-force / sequential search: Systematically iterating through all possible private keys in the target range. A single CPU core can test around 200,000 keys per second. For lower-numbered puzzles (keys under 70 bits), this is tractable with enough hardware and time. For the full 160-bit keyspace, however, a complete brute-force search would require approximately 1.43 × 10⁶³ years on modern hardware — effectively impossible.
- Pollard's Kangaroo algorithm: A probabilistic "meet-in-the-middle" approach operating on the elliptic curve. For wallets where the public key is known, it dramatically reduces the number of operations required, scaling as roughly √N rather than N. This makes it the method of choice for mid-range puzzles (bits 71–130).
Notable Solvers and Recent Breakthroughs
The solver community has produced some remarkable achievements. A user known as RetiredCoder used a cluster of 400 RX 4090 GPUs running for approximately two months to solve puzzles 120, 125, and 130, achieving roughly 1×√N efficiency improvements in Kangaroo implementations — a milestone in GPU-accelerated elliptic-curve cryptanalysis.
Early 2025 saw a burst of activity on the lower-difficulty wallets:
- February 21, 2025: Puzzle #67 solved (reward: 6.7 BTC)
- April 6, 2025: Puzzle #68 solved (reward: 6.8 BTC)
- April 30, 2025: Puzzle #69 solved (reward: 6.9 BTC)
All wallets numbered 1 through 70 have now been solved. The remaining challenge begins at puzzle #71.
What the Puzzle Teaches Us
Beyond the prize money, the Bitcoin Puzzle Transaction serves as a living laboratory for applied cryptography. It has driven real advances in GPU-accelerated elliptic-curve computation, in optimized implementations of Pollard's Kangaroo, and in collaborative distributed computation. It has also concretely demonstrated the practical security margin of Bitcoin's secp256k1 curve: brute-forcing a randomly generated 256-bit private key remains astronomically infeasible, while keys with artificially constrained entropy (even 67–70 bits) can be cracked with commodity hardware given enough time.
With roughly 916.5 BTC still locked in puzzles #71 through #160, the challenge continues — a monument to the ingenuity of its anonymous creator and a benchmark for the world's cryptographers.
