An ongoing tracker and knowledge base for the Bitcoin Puzzle Transaction, also known as the 1000 BTC Challenge — one of the most fascinating cryptographic puzzles in Bitcoin history.
In January 2015, an anonymous user created a single transaction sending Bitcoin to 256 addresses, each locked by a private key with an incrementally increasing bit length. The amounts matched the key size: puzzle #1 received 0.001 BTC, puzzle #2 received 0.002 BTC, and so on up to puzzle #256 at 0.256 BTC — totaling ~32.9 BTC.
The private keys are random values within constrained ranges. Puzzle #N has a key between 2^(N-1) and 2^N, meaning each puzzle is exactly twice as hard as the previous one.
The creator later described it on BitcoinTalk:
"There is no pattern. It is just consecutive keys from a deterministic wallet (masked with leading 000...0001 to set difficulty). It is simply a crude measuring instrument, of the cracking strength of the community."
2015-01-15 — Original transaction created in block #339085. 256 addresses funded with ~32.9 BTC total. Puzzles #1 through ~50 solved almost immediately.
2017-07-11 — The creator moved funds from addresses #161–256 (unsolvable in practice) to the lower-range addresses #53–160, effectively increasing the prize pool by 10x.
2019-05-31 — Creator sends 1,000-satoshi transactions from addresses #65, #70, #75, #80… #160 (every 5th key). This exposes the public keys for those addresses, enabling the use of the Pollard's kangaroo algorithm — reducing the search space from O(2^N) to O(2^(N/2)).
2023-04-16 — Creator increases unsolved puzzle prizes by another 10x, bringing the total pool to approximately ~1,000 BTC. Puzzle #66 is now worth 6.6 BTC, #67 is 6.7 BTC, all the way up to #160 at 16 BTC.
2024-09-12 — Puzzle #66 solved (6.6 BTC, ~$400K). The solver broadcast the transaction publicly, and it was front-run in the mempool — the original transaction was replaced, and most of the prize was taken by a different address.
2025-02-21 — Puzzle #67 solved (6.7 BTC). Lessons learned from #66: the solver bypassed the public mempool entirely to avoid interception.
2025-04-07 — Puzzle #68 solved (6.8 BTC). Also mined bypassing the public mempool.
2025-04-30 — Puzzle #69 solved (6.9 BTC). The key was found near the very beginning of the search range (0.72%). The solver broadcast publicly, and it was stolen again — bots extracted the public key from the mempool, computed the private key, and replaced the transaction multiple times.
82 puzzles solved out of 160. All keys from #1–#70, plus every 5th key up to #130 (#75, #80, #85, #90, #95, #100, #105, #110, #115, #120, #125, #130) have been cracked.
Next targets:
- Puzzle #71 — 71-bit key space, brute-force only. The easiest remaining puzzle. Reward: 7.1 BTC. Estimated: ~33.55 million search ranges. A single RTX 4090 at ~1.5 billion keys/second would take roughly 25,000 years — but distributed GPU pools are actively working on it.
- Puzzle #135 — Public key is exposed, making it solvable with the Pollard's kangaroo algorithm. Reward: 13.5 BTC.
Remaining prize pool: ~900+ BTC across unsolved puzzles #71–#160 (excluding every 5th key already cracked up to #130).
Brute-force (puzzles without exposed public keys): Iterate through all possible private keys in the range 2^(N-1) to 2^N. For each key, derive the Bitcoin address and check if it matches the target. Difficulty doubles with every puzzle.
Pollard's kangaroo algorithm (every 5th puzzle with exposed public keys): The creator's 1,000-satoshi transactions exposed public keys for #65, #70, #75… etc. This allows solving the Elliptic Curve Discrete Logarithm Problem (ECDLP) directly, reducing complexity from O(2^N) to O(2^(N/2)) — a massive speedup.
The mempool problem: When a solver broadcasts a spending transaction, the private key becomes visible in the mempool. Bots can extract it and submit a competing transaction with a higher fee. This has led to prize theft on puzzles #66 and #69. Solvers now use private mining services (like MARA Slipstream) to bypass the public mempool.
| Tool | Type | Description |
|---|---|---|
| BitCrack | GPU brute-force | CUDA/OpenCL key space search |
| Kangaroo | GPU ECDLP | Pollard's kangaroo for puzzles with exposed public keys |
| Keyhunt | CPU | BSGS and brute-force modes |
| RCKangaroo | GPU ECDLP | SOTA Kangaroo with symmetry (K=1.15). ~8 GKeys/s on RTX 4090. Used to solve puzzles #125, #130, and others |
| Keyhunt-CUDA | GPU | CUDA-accelerated version of Keyhunt |
- BitcoinTalk — Original thread — The primary community discussion, running since 2015. Thousands of posts covering tools, strategies, solved keys, and analysis.
- BitcoinTalk — Challenge thread (updated) — The "~1000 BTC total bounty" thread with current status updates.
- privatekeys.pw/puzzles/bitcoin-puzzle-tx — Comprehensive tracker with all addresses, solved keys, and transaction links.
- btcpuzzle.info — Puzzle list, progress calculator, and pool-based searching.
- Hacker News discussion (Puzzle #66) — Technical discussion around the September 2024 solve.
- OEIS A369920 — The solved private keys are registered as a sequence in the Online Encyclopedia of Integer Sequences.
The Bitcoin Puzzle is more than a treasure hunt. It serves as:
- A real-time benchmark of the community's key-cracking capability against elliptic curve cryptography
- A canary for quantum computing threats — when higher puzzles start falling faster than expected, it signals advancing threats to Bitcoin's cryptographic assumptions
- A practical lesson in operational security — the mempool front-running incidents on puzzles #66 and #69 demonstrate real risks in transaction broadcasting
BTC-Solved-Unsolved.txt— Current state of all 160 puzzles (solved/unsolved, key values where known)
If you have corrections, additional historical events, or links to resources, feel free to open an issue or PR.
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