#91
Unsolved9.1 BTCStill unsolved, and the public key is not known either — so the only approach is generating keys through the interval one at a time and comparing addresses. There are 290 keys in the interval, so sweeping all of it costs that many attempts (on average, half).
0x40000000000000000000000 ~ 0x7ffffffffffffffffffffff
2^90 = 1.2×10^27
9.10000000 BTC · 3 tx
snapshot from 2026-08-23
A transaction moving puzzle funds carries the public key and the signature. The moment it reaches the mempool, bots take the same coins with a higher fee. That is exactly how #66 and #69 were lost. How to prevent it
How to actually run this puzzle
With no public key there is nothing to do but generate addresses one at a time and compare. BitCrack does that on the GPU. On NVIDIA that means the CUDA build, cuBitCrack.
git clone https://github.com/brichard19/BitCrack cd BitCrack make BUILD_CUDA=1 # On Windows, open BitCrack.sln in Visual Studio and build the cuKeyFinder project # to get cuBitCrack.exe. macOS is not supported.
./cuBitCrack -d 0 -b 288 -t 256 -p 1024 -c --keyspace 40000000000000000000000:7ffffffffffffffffffffff --continue progress-91.txt -o found-91.txt 1EzVHtmbN4fs4MiNk3ppEnKKhsmXYJ4s74
- The best values for -b/-t/-p differ per GPU. Run it once at the defaults, look at the rate, then adjust.
- Always include --continue. It keeps your position across restarts.
- To split across machines, turn on “split the work” above. --share divides the range without overlap.
- This shard covers 40000000000000000000000 ~ 7ffffffffffffffffffffff.
CPU only. Handles both addresses and public keys, and is the easiest to install — good for learning and for checking your setup.
This puzzle's public key is not exposed. There is no discrete logarithm to solve.
On a single RTX 4090 this takes 1.6×10^10 years — 1.1× the age of the universe. That is not “eventually”; in most cases it means “no”. Doing it anyway means accumulating GPUs or joining a pool.