The ~1000 BTC Bitcoin Challenge

What if I actually find a key on this site?

The chances are astronomically small, but mathematically it can happen. If the random search on this page lands on the right key, here is what you should do:

1. Save the key immediately. Copy the WIF key displayed on screen and store it securely offline.
2. Import into Electrum. Open Electrum Wallet, go to File → New/Restore → Import Bitcoin addresses or private keys, and paste the WIF key.
3. Do NOT broadcast a regular transaction. This is critical, especially for puzzles #71 and possibly #72, where the key range is narrow enough for a fast attack. When you broadcast a transaction, your public key is revealed in the mempool before the block is confirmed. Attackers running Pollard's kangaroo algorithm (a mathematical method that exploits the public key) can use the public key to drastically narrow the search space and find your private key in minutes, far less than the ~10 minutes needed to confirm a block. They will replace your transaction with their own and steal the funds.
   
   This is not theoretical. On April 30, 2025, puzzle #69 was solved by bc1qlp0z45...awxctah. The finder broadcast a regular transaction instead of using MARA Slipstream. Within minutes, bots extracted the public key from the mempool, computed the private key via the kangaroo method, and started replacing the transaction. Multiple bots outbid each other, and ultimately the prize of 6.888 BTC was stolen by 15g7XHM6...GPHXZ. Don't let this happen to you.
4. Use MARA Slipstream. Create and sign the transaction in Electrum, but instead of broadcasting it, copy the raw signed transaction and submit it directly to a miner via MARA Slipstream. This bypasses the public mempool, so your public key is never exposed before confirmation.

Why are puzzles #1–70 solved but #71+ not yet?

The difficulty doubles with every puzzle number, meaning each next puzzle takes twice as long to brute force. Puzzle #70 has a key space of 2⁷⁰ (~1.2 sextillion keys). Modern GPUs can search billions of keys per second, making puzzles up to ~70 bits feasible within weeks or months on clusters consuming several megawatts of power. But puzzle #71 has twice the range, #72 has four times, and so on. By puzzle #80, the brute force time already exceeds thousands of years even on the fastest hardware. That said, hardware keeps improving, so puzzles #71–74 may eventually fall to brute force on conventional GPU farms.

Then how were puzzles #75, #80, #85, ... #130 solved?

These puzzles (every 5th starting from #75) were solved not by brute force, but using Pollard's kangaroo algorithm, a mathematical method that exploits the public key to find the private key much faster than brute force.

When someone spends Bitcoin from an address, the public key is revealed on the blockchain. For these puzzles, the creator intentionally moved small amounts to expose the public keys, effectively challenging the community to test the limits of the kangaroo algorithm. Once the public key is known, the kangaroo algorithm reduces the search from O(2ⁿ) to O(2^n/2), the square root of the range. For puzzle #130, this means searching ~2⁶⁵ instead of 2¹³⁰. According to the author of the popular Kangaroo solver, puzzle #130 was estimated to take several years on 256 Tesla V100 GPUs. It was eventually solved in September 2024, likely by a modified approach or a large distributed effort. For higher puzzles like #135 (2^67.5 operations), the compute time and GPU coordination requirements grow even further.

You can see which unsolved puzzles have known public keys in the table (#135, #140, #145, #150, #155, #160), these are the next targets for kangaroo solvers or quantum computers.

Are modern Bitcoin address formats safe from quantum attacks?

No. This is a common misconception. All current Bitcoin address formats are vulnerable to quantum attacks once the public key is exposed:

• Legacy (P2PKH): public key revealed when you send a transaction
• SegWit (P2WPKH): same, public key revealed in witness data when spending
• Taproot (P2TR): the public key is embedded directly in the address, exposed from the moment you receive funds. This is actually the most vulnerable format

For non-Taproot addresses, the only way to keep your public key hidden and your Bitcoin safe from quantum threats is to never spend from the address. If you do need to send a transaction, make sure to move all remaining funds to a fresh, unused address in the same transaction, so no Bitcoin is left on an address with an exposed public key. For Taproot, there is no protection at all: you should not even receive Bitcoin to a Taproot address if you are concerned about quantum threats, because the public key is exposed the moment the address appears on the blockchain.

Post-quantum cryptography has not yet been integrated into Bitcoin. Until it is, no address format offers true quantum resistance.

Can I speed up the search?

The browser-based search on this page is intentionally simple: it uses JavaScript and is limited to your CPU. Specialized tools like BitCrack, Kangaroo, or KeyHunt can leverage powerful GPUs (NVIDIA CUDA / AMD OpenCL) to search roughly ~1,000× faster than what you see in the browser benchmark.

For example, a single RTX 4090 can test ~1.5 billion keys per second for brute force. Even so, puzzle #71 would take ~25,000 years on a single card. A farm of 1,000 GPUs could bring that down to ~25 years, and even larger clusters could potentially solve it in months. But puzzles above ~75 bits remain out of reach for brute force even with massive farms: the math simply doesn't allow it. The kangaroo algorithm with known public keys is the only realistic approach for higher puzzles.

There is also an economic problem: starting from puzzle #71, the GPU rental cost required for brute force at current hardware generation would likely exceed the reward in Bitcoin at current prices. The puzzle reward would need to be worth significantly more (or hardware would need to be significantly faster) for brute force to become profitable.

What is a "canary in the coal mine"?

In the 19th and 20th centuries, coal miners brought canaries into the tunnels as an early warning system. The birds were far more sensitive to toxic gases like carbon monoxide than humans. If the canary stopped singing or died, miners knew to evacuate immediately, even before they could detect any danger themselves.

The Bitcoin Puzzle serves the same purpose for quantum computing threats. With Shor's algorithm, the puzzles are no harder to crack than any other Bitcoin address with a known public key. But unlike personal wallets, the puzzle coins are unclaimed bounties, the most obvious and ethical first target for anyone with a quantum computer. If puzzles #135, #140, #145 and beyond are all solved within days, weeks, or months of each other, that would be the canary's silence, a clear signal that a quantum computer powerful enough to threaten all of Bitcoin's cryptography has arrived.

Can quantum computers break this?

Yes, and possibly sooner than expected. In March 2026, Google Quantum AI published a whitepaper showing that breaking elliptic curve cryptography (which protects Bitcoin) could require fewer than 500,000 physical qubits, a ~20× reduction from prior estimates of millions. The Bitcoin Puzzle is vulnerable to quantum attack in two distinct ways:

For Shor's attack, the number of qubits and computation time depend on the elliptic curve (secp256k1 = 256 bits), not the key range. Puzzles need the same ~500,000 physical qubits and the same time as cracking any regular Bitcoin address. The key range simply does not matter for Shor's algorithm.

For Grover's attack, the puzzles actually need fewer qubits since the search register scales with the key range, not the curve size. Most of the qubits still go to the oracle circuit (computing the address from a key), but a less powerful quantum machine that can't yet run full Shor's on 256-bit keys might still be able to brute-force smaller puzzles via Grover.

All it takes is one researcher with access to a sufficiently capable quantum computer to notice this puzzle. If all remaining puzzles are suddenly solved in a short period, you can be certain: a quantum computer did it. Given Google's latest findings, this will likely happen within just a few years.

Another sign to watch for: sudden movement of very old coins from long-dormant wallets within a short timeframe. Thousands of early Bitcoin addresses (2009–2012 era) used the P2PK format with public keys permanently exposed. If many of these ancient wallets start moving funds simultaneously, it likely means someone is using Shor's algorithm to sweep them at scale.