Bitcoin

This section summarizes PSBT data handling for offline signing with animated UR codes.

Data types

• Request/response UR type: crypto-psbt

• See also: Basic API (UR primitives and structures)

Flow

1. Build an unsigned PSBT with your wallet backend.

2. Encode PSBT → UR (crypto-psbt) and display as animated QR.

3. Device scans → returns signed PSBT as crypto-psbt.

4. Finalize and broadcast.

Tip: Keep PSBT size within practical QR limits; split across frames as needed.

Examples

Decode animated QR → signed PSBT

import { URDecoder } from '@ngraveio/bc-ur';
import { CryptoPSBT } from '@keystonehq/bc-ur-registry-btc';

const dec = new URDecoder();
// For each scanned frame string from camera:
// dec.receivePart(frameString)

if (dec.isComplete()) {
  const ur = dec.resultUR();              // ur.type should be 'crypto-psbt'
  const psbt = CryptoPSBT.fromCBOR(ur.cbor);
  const signedPsbt = psbt.getPSBT();      // Buffer of PSBT (signed or partially signed)
  // finalize & broadcast using your backend
}

Encode unsigned PSBT → animated QR

import { CryptoPSBT } from '@keystonehq/bc-ur-registry-btc';
import { airGapUrUtils } from '@keystonehq/keystone-sdk';

const psbtBytes = Buffer.from(unsignedPsbtBase64, 'base64');
const req = CryptoPSBT.fromPSBT(psbtBytes); // or new CryptoPSBT(psbtBytes)
const ur = req.toUR();
const frames = airGapUrUtils.urToQrcode(ur); // render frames in your UI