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Signing · Bitcoin Core

Signing a message in Bitcoin Core: step by step

In Bitcoin Core, signing is a one-minute task, entirely inside the program and with no connection to anyone. The only catch is that it only works with a certain address type, and it is worth knowing before you start.

September 29, 2026 · 4-minute read

The steps

  1. Open Bitcoin Core with your wallet loaded.
  2. In the file menu, find the sign-message option. It sits next to verify message.
  3. In the first field, put the address you want to sign with.
  4. In the text field, type the message you want to sign.
  5. Click sign. If the wallet is encrypted, it will ask for the password.
  6. Copy the signature that appears below.

The limitation to know about

Bitcoin Core’s message signing works with classic-format addresses, the ones starting with 1. With addresses starting with 3 or bc1 the option may reject them or error out — and that doesn’t mean your wallet is faulty: it means you need to sign with a different address.

If all your addresses are modern, check the wallet’s address list for a classic-format one with history. If there isn’t one, other ways of proving ownership exist, and they are in what counts as proof when you can’t get in.

What text to sign

Something specific and dated: «I am the holder of this wallet. For KeyStone, 20 September 2026.» That stops the signature being reused elsewhere or presented as something else.

What you hand over is three things and none is secret: the address, the exact text and the signature. Whoever receives them can check them from Bitcoin Core’s own verify-message option, with no website or external tool needed.

If you don’t remember the wallet password

Then you can’t sign, but you can prove quite a lot: Bitcoin Core lets you see your addresses and balance even when the wallet is encrypted, because the password only protects the spending part. That alone can establish ownership without signing. And your case is an ordinary password recovery: wallet.dat with a forgotten password.

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