NEEDLESPACE
KREN
The 160/#90

#90

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

1L12FHH2FHjvTviyanuiFVfmzCy46RRATU

mempool.space
Key range (hex)

0x20000000000000000000000 ~ 0x3ffffffffffffffffffffff

Interval size

2^89 = 6.2×10^26

Balance

0.00000000 BTC · 7 tx

snapshot from 2026-08-23

Public key (compressed)

035c38bd9ae4b10e8a250857006f3cfd98ab15a6196d9f4dfd25bc7ecc77d788d5

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)

000000000000000000000000000000000000000002ce00bb2136a445c71e85bf

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 ≈ 2.5×10^13 (2^44.5)
Browser (JS, 1 thread)the search tool on this site44 years
CPU · keyhunt, 8 threads36 days
CPU · keyhunt, 16 threads18 days
GTX 10601 days
RTX 30708.6 hours
RTX 30904.6 hours
RTX 40902.8 hours
RTX 50901.7 hours
RTX 4090 × 1017 min
RTX 4090 × 1002 min
RTX 4090 × 1,000the scale of a large pool10 sec
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 2^89 to around 2^44.5.

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 > in90.txt <<'EOF'
20000000000000000000000
3FFFFFFFFFFFFFFFFFFFFFF
035C38BD9AE4B10E8A250857006F3CFD98AB15A6196D9F4DFD25BC7ECC77D788D5
EOF
2. Run
./kangaroo -t 8 -gpu -gpuId 0 -w save90.work -wi 300 -o found-90.txt in90.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 2^44.5 operations where BitCrack runs 2^89.

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 optionsStart from installation
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#89
unsolved · 8.9 BTC · half the difficulty
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#91
unsolved · 9.1 BTC · twice the difficulty