blindPayload function

Uint8List blindPayload({ required Uint8List payload, required Uint8List mask, })

XOR-blinds (or unblinds) a payment code payload.

Bytes 3..34 (pubkey x-coordinate) are XORed with mask0..31. Bytes 35..66 (chain code) are XORed with mask32..63.

Implementation

Uint8List blindPayload({
  required Uint8List payload,
  required Uint8List mask,
}) {
  if (payload.length != 80) {
    throw ArgumentError('Payload must be 80 bytes');
  }
  if (mask.length != 64) {
    throw ArgumentError('Mask must be 64 bytes');
  }

  final result = Uint8List.fromList(payload);

  for (var i = 0; i < 32; i++) {
    result[3 + i] ^= mask[i];
  }

  for (var i = 0; i < 32; i++) {
    result[35 + i] ^= mask[32 + i];
  }

  return result;
}