How can two chessboards represent a Bitcoin private key?

A real chess position with the standard army (one king and queen, two rooks, two bishops, two knights and eight pawns per side, pawns on ranks 2–7) carries about 148 bits of placement information. We split the 256-bit private key into two 128-bit halves and encode each half as one such position via combinatorial unranking. Both directions are a deterministic bijection.

Is it safe to use this converter?

All cryptographic operations happen 100% in your browser using audited libraries (@noble/curves, @noble/hashes). Your private key is never transmitted to any server. That said, never use a key generated by a public tool for storing real funds — this tool is for education and art only.

Can I memorise two chess positions more easily than a 52-character WIF string?

Yes. Humans are dramatically better at remembering visual patterns than random text. Chess players can memorise hundreds of positions effortlessly. A chessboard cold wallet is a legitimate (though experimental) storage technique — print the two boards, hide them in a chess book, and your key is stored in plausible deniability.

What is the secp256k1 curve order and does the encoding leak keys?

The secp256k1 group order n is approximately 2^256 − 2^32 − 977. Almost every 256-bit value decodes to a valid key; the tiny minority that map to 0 or values above n are simply rejected. The combinatorial encoding is information-theoretically lossless and adds no security weakness.

Why two boards instead of one?

A single real position only fits ≈148 bits, which is less than the 256 bits a Bitcoin key needs. With two boards we have ≈296 bits of room, of which we use exactly 256. Each board carries half of the key (128 bits) — a clean split made possible by combinatorial mixed-radix unranking.

Can I paste the FEN into Lichess or Chess.com?

Yes. Below each board we show the standard FEN string. Copy it and paste into the analysis board of Lichess, Chess.com, or any UCI engine to see the position in your favourite chess client.

256-bit bijection · Bitcoin × Chess

Your Bitcoin Key as a Chessboard

A real chess position carries about 148 bits of information. Two boards comfortably hold a 256-bit Bitcoin key — encoded as a perfect mathematical bijection over the standard chess army.

Educational tool. Never store real funds with a key generated or shown here. All cryptography runs locally in your browser — your key is never sent anywhere.

Private-Key Positions

1Low 128 bits

2High 128 bits

Each board carries 128 bits via the unique placement of the standard chess army (16 pieces per side, pawns on ranks 2–7, bishops on opposite colours). You can also paste your own FEN — if it matches the schema, the Bitcoin key updates instantly.

How a 256-bit key becomes two positions

1Split the 256-bit key K into two halves: K = K_low + 2¹²⁸·K_high.

2Place pieces in fixed order (kings, queens, rooks, bishops, knights, pawns). At each step, the remaining squares define a radix; the next digits of the half-key pick the placement combinatorially.

3Pawns can only land on ranks 2–7. Bishops are placed one on a light square and one on a dark square. The result is always a piece-set-legal position.

4Decoding reverses each step: read piece positions in the same order, accumulate the digits back into K via Horner's scheme. The mapping is a perfect bijection.

Live derivation

A Bitcoin private key is simply a 256-bit number — identical on mainnet and testnet. Only the visible WIF prefix and address format change between networks. Outputs below are mainnet.

Raw hex (32 bytes)

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WIF (import to any wallet)

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SegWit address (Bech32)

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Legacy address (P2PKH)

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Compressed public key

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Loading cryptography libraries…

Decode an existing key

Famous keys

How the mapping works

1. Split the key into two halves

A Bitcoin private key is 256 bits. We split it into a low 128-bit half (K_low) and a high 128-bit half (K_high). Each half becomes one of the two chessboards.

2. Encode each half as a chess position

Using mixed-radix combinatorial unranking, the 128-bit value picks one specific placement of the standard 32-piece chess army on the 64 squares (pawns on ranks 2–7, bishops on opposite colours). Each position carries ≈148 bits of capacity, of which 128 are used.

3. Derive the public key with ECDSA

Compute P = k·G on the secp256k1 curve. This step is one-way: nobody can recover k from P. We use the audited @noble/secp256k1 library, fully in your browser.

4. Hash → address

HASH160 = RIPEMD-160(SHA-256(public key)) gives the 20-byte payload that becomes the address (Bech32 for SegWit, Base58Check for legacy).

Want the full theory? Read the deep-dive article →