#120

SolvedKey exposed

The private key to this puzzle is public and the balance has been swept. Everything below was re-derived with secp256k1 and confirmed to match the address — never take a copied value on trust.

Address

17s2b9ksz5y7abUm92cHwG8jEPCzK3dLnT

mempool.space

Key range (hex)

0x800000000000000000000000000000 ~ 0xffffffffffffffffffffffffffffff

Interval size

2^119 = 6.6×10^35

Balance

0.00000000 BTC · 5 tx

snapshot from 2026-08-23

Public key (compressed)

02ceb6cbbcdbdf5ef7150682150f4ce2c6f4807b349827dcdbdd1f2efa885a2630

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.

Private key (already public)

0000000000000000000000000000000000b10f22572c497a836ea187f2e1fc23

The balance is zero. This value is useful for verification and learning only — import it into a wallet and you will find nothing there.

Method of attack

Pollard's Kangaroo

work ≈ 8.2×10^17 (2^59.5)

Browser (JS, 1 thread)the search tool on this site1,435,186 years

CPU · keyhunt, 8 threads3,229 years

CPU · keyhunt, 16 threads1,615 years

GTX 1060129 years

RTX 307032 years

RTX 309017 years

RTX 409010 years

RTX 50906.5 years

RTX 4090 × 101.0 years

RTX 4090 × 10038 days

RTX 4090 × 1,000the scale of a large pool4 days

All approximate. Implementation, clocks and target count move these by multiples, so read the order of magnitude and nothing finer. The calculator lets you put your own rate in.

Doing it

How to actually run this puzzle

Recommended: Kangaroo (GPU)

The public key is known, so the discrete logarithm is solved directly. The work drops from 2^119 to around 2^59.5.

0. Build (Linux · CUDA)

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.

1. Input file — three lines: range start, range end, public key

cat > in120.txt <<'EOF'
800000000000000000000000000000
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
02CEB6CBBCDBDF5EF7150682150F4CE2C6F4807B349827DCDBDD1F2EFA885A2630
EOF

2. Run

./kangaroo -t 8 -gpu -gpuId 0 -w save120.work -wi 300 -o found-120.txt in120.txt

Watch out for

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.

Other options

keyhuntCPU

CPU only. Handles both addresses and public keys, and is the easiest to install — good for learning and for checking your setup.

BitCrackGPU

Address brute force. The de facto standard for puzzles with no public key, and the only one that runs on AMD.

BitCracknot usable

The public key is known, so brute-forcing addresses is a waste. Kangaroo needs 2^59.5 operations where BitCrack runs 2^119.

A reality check

This one is already solved. The commands above are for learning — knowing the answer makes it a good way to confirm your tool actually works.

Build it with your own options Start from installation

#119

unsolved · 11.9 BTC · half the difficulty

#121

unsolved · 12.1 BTC · twice the difficulty