#135

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

16RGFo6hjq9ym6Pj7N5H7L1NR1rVPJyw2v

mempool.space

Key range (hex)

0x4000000000000000000000000000000000 ~ 0x7fffffffffffffffffffffffffffffffff

Interval size

2^134 = 2.2×10^40

Balance

0.00000000 BTC · 10 tx

snapshot from 2026-08-23

Public key (compressed)

02145d2611c823a396ef6712ce0f712f09b9b4f3135e3e0aa3230fb9b6d08d1e16

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)

0000000000000000000000000000006d9392a16883f90903d5f78da57af07eb2

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 ≈ 1.5×10^20 (2^67)

Browser (JS, 1 thread)the search tool on this site2.6×10^8 years

CPU · keyhunt, 8 threads584,542 years

CPU · keyhunt, 16 threads292,271 years

GTX 106023,382 years

RTX 30705,845 years

RTX 30903,118 years

RTX 40901,871 years

RTX 50901,169 years

RTX 4090 × 10187 years

RTX 4090 × 10019 years

RTX 4090 × 1,000the scale of a large pool1.9 years

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 2^134 to around 2^67.

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 > in135.txt <<'EOF'
4000000000000000000000000000000000
7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
02145D2611C823A396EF6712CE0F712F09B9B4F3135E3E0AA3230FB9B6D08D1E16
EOF

2. Run

./kangaroo -t 8 -gpu -gpuId 0 -w save135.work -wi 300 -o found-135.txt in135.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 2^67 operations where BitCrack runs 2^134.

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

#134

unsolved · 13.4 BTC · half the difficulty

#136

unsolved · 13.6 BTC · twice the difficulty