> For the complete documentation index, see [llms.txt](https://doc.lockerprotocol.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.lockerprotocol.com/reference/qr-formats.md).

# QR formats (BC-UR / Keystone)

For developers: the codes the Vault and the extension exchange.

Everything that crosses the air gap is a **BC-UR** payload (`ur:<type>/…`), single-frame or animated (fountain-coded) when it does not fit in one QR. The formats come from the Keystone family, so the signing requests are the ones hardware wallets already speak.

## Sync (Vault → extension)

| UR type                 | Content                                                                                                                                                                                          |
| ----------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `crypto-multi-accounts` | All chain families of one account (Ethereum, Bitcoin payment + ordinals, Solana, Tron, Sui, Stellar) with their derivation paths. **The only payload the Vault emits**, from **Extension Sync**. |
| `crypto-account`        | EVM-only account descriptor. The extension still *reads* it (paste path, older syncs), but the Vault no longer produces one: the EVM-only mode was removed.                                      |

## Requests (extension → Vault)

| UR type                            | Chain                                                                                                            |
| ---------------------------------- | ---------------------------------------------------------------------------------------------------------------- |
| `eth-sign-request`                 | Ethereum & EVM: transactions (legacy, EIP-2930, EIP-1559), `personal_sign`, EIP-712 typed data, EIP-5792 batches |
| `crypto-psbt` / `btc-sign-request` | Bitcoin PSBT / message                                                                                           |
| `sol-sign-request`                 | Solana transaction or off-chain message                                                                          |
| `sui-sign-request`                 | Sui transaction or message                                                                                       |
| `stellar-sign-request`             | Stellar transaction or sign-in                                                                                   |
| Tron                               | Tron transaction or message (Locker envelope)                                                                    |

## Responses (Vault → extension)

`eth-signature`, `btc-signature` / signed `crypto-psbt`, `sol-signature`, `sui-signature`, `stellar-signature`, and the Tron response. Each response carries the request's id, so a stale signature is rejected (*That QR does not answer this request*).

## Backups

The **encrypted QR backup** is a Locker-specific payload: AES-encrypted account data under a dedicated password. It is not a Keystone format and only a Locker Vault can restore it.

{% hint style="info" %}
Reference implementations: the extension's `core/background/keystone/` and `core/background/multichain/`, and the Vault's `keystone-sync.service.ts`, `ur.service.ts` and the per-chain signer services.
{% endhint %}


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