Glossary

Address batch. A contiguous range of receive addresses assigned to one counter, signed by the owner and Key app device identities. These are separate from their Bitcoin spending keys.

Approval session. The owner reviews queued items with key 2 available. The owner phone presents them; the Key app checks and signs the approved items. Money movements and loosening changes require a session.

Approver. A Key app holding an identity key but no wallet key, used when key 2 is a hardware wallet.

BC-UR. A format used by Sparrow and hardware wallets to transfer data through animated QR codes.

BIP321. The standard for a bitcoin: payment request.

Bitcoin (BTC). The currency accepted by OpenBMT. One bitcoin is 100,000,000 satoshis.

Blockchain. The shared transaction record, extended in groups called blocks. A payment included in a block has its first confirmation.

Box. The shop’s optional server for relaying device messages and reading POS orders. It holds no wallet key.

Cash-out. Sending bitcoin to an exchange the owner chooses, followed by conversion and withdrawal under that exchange’s terms. OpenBMT does not perform the sale or bank withdrawal.

Change. Money returned to the shop’s wallet by its own spending transaction.

Compact block filter. A small summary used by a light client to find blocks that might contain a relevant transaction.

Confirmation. Inclusion of a payment in a block. The shop’s confirmation depth starts at 1 block and its refund depth at 6. A refund can be paid at the latter. Both show “Paid”, with text distinguishing the depth.

Counter. The phone or tablet displaying the sale and payment code. It holds no wallet signing key.

Descriptor (wallet description). Text describing how to derive the wallet’s addresses from its three public keys.

Exchange rate. The quoted relationship between bitcoin and dollars. A checkout quote calculates what to send; it does not convert the receipt.

Exposure. Instant sales still waiting for their first block.

Full node. A computer that checks every block itself. Running one is optional for the shop.

Heartbeat. A signed message from the owner phone telling the counter that the owner’s watcher is running.

Identity key. A device key signing OpenBMT messages and approvals. It is separate from the wallet keys that authorize Bitcoin spends.

Instant. Acceptance before the first block, within the shop’s limit.

Key app. The separate app holding key 2 and providing the second approval.

Light check. A check through Bitcoin peers and compact block filters without running a full node.

Lightning invoice. A request payable over Lightning, supplied by the shop’s own Lightning node in OpenBMT.

Loosening / tightening. A settings change that permits more risk, or one that reduces it.

Multisig, two of three. A wallet requiring any two of its three keys to spend.

On-chain. A payment recorded through the Bitcoin blockchain, as distinct from an individual payment made through Lightning channels.

Orbot. A separate Android app providing Tor connections to other apps.

Private key. Secret information used to authorize spending. OpenBMT’s wallet needs two of its three wallet keys to spend.

PSBT. A standard transaction file passed between signers.

Recovery kit. A printed page of wallet recovery information, without secret keys or seed words.

Recovery words (seed words). A secret word sequence that can recreate a key. It is not a payment address or the public wallet description.

Release key. A key signing an app for distribution, separate from the wallet’s keys.

Reorganization (reorg). Replacement of blocks by a different set of blocks.

Root. An owner-phone or Key-app identity key pinned by a counter at pairing.

Satoshi (sat). One hundred-millionth of a bitcoin.

Tor. A network that hides where a connection originates.

Unconfirmed. Seen as a transaction but not yet included in a block. It can still be replaced and is subject to the shop’s instant-acceptance limits.

Watch-only. A wallet view using public information to display payments without holding keys that can spend them.

xpub. A public key used to derive addresses without being able to spend.