#140
UnsolvedKey exposed14 BTCStill unsolved. But its public key is exposed, so it yields to Pollard's Kangaroo rather than brute force. The work required falls from 2139 to its square root, around 269.5.
0x80000000000000000000000000000000000 ~ 0xfffffffffffffffffffffffffffffffffff
2^139 = 7.0×10^41
14.00001600 BTC · 7 tx
snapshot from 2026-08-23
031f6a332d3c5c4f2de2378c012f429cd109ba07d69690c6c701b6bb87860d6640
Exposed on 31 May 2019, when the creator withdrew 1,000 satoshis from this address. This is the value BSGS and Kangaroo take as input.
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
The public key is known, so the discrete logarithm is solved directly. The work drops from 2^139 to around 2^69.5.
git clone https://github.com/JeanLucPons/Kangaroo cd Kangaroo make gpu=1 ccap=86 # ccap is your GPU's compute capability (4090=89, 3090=86, 1060=61) # On Windows open VC_CUDA102/Kangaroo.sln in Visual Studio. macOS and AMD are not supported.
cat > in140.txt <<'EOF' 80000000000000000000000000000000000 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF 031F6A332D3C5C4F2DE2378C012F429CD109BA07D69690C6C701B6BB87860D6640 EOF
./kangaroo -t 8 -gpu -gpuId 0 -w save140.work -wi 300 -o found-140.txt in140.txt
- Order matters in the input file — range start, range end, public key. Get it wrong and it finds nothing.
- -d is the distinguished-point bit count. Leave it out and it picks one; only touch it when distributing.
- -w and -wi save progress every five minutes. On a job that runs for days this is not optional.
- To combine machines use -s (server) / -c (client) mode. It is more efficient than splitting the range.
CPU only. Handles both addresses and public keys, and is the easiest to install — good for learning and for checking your setup.
Address brute force. The de facto standard for puzzles with no public key, and the only one that runs on AMD.
The public key is known, so brute-forcing addresses is a waste. Kangaroo needs 2^69.5 operations where BitCrack runs 2^139.
On a single RTX 4090 this takes 10,581 years. That is not “eventually”; in most cases it means “no”. Doing it anyway means accumulating GPUs or joining a pool.