# Paymail BEEF Transaction

Deggen (<deggen@kschw.com>)

## Abstract

We specify a paymail capability extension which supports the passing of BEEF Transactions between hosts. The procedure for service discovery and requesting outputs is not detailed, rather this proposal contains only a recommendation to replace [BRC-12 RawTx](/transactions/0012.md) hex data with [BRC-62 BEEF](/transactions/0062.md) hex data.

## Motivation

We propose that [p2p destination and receive raw transaction](/payments/0028.md) functionality between hosts to include the data required for the counterparty to run SPV on the transaction.

## BRFCID

A random ID was generated in order to avoid label collisions in the capability document of a paymail server.

```yaml
brfcid: 5c55a7fdb7bb
title: Background Evaluation Extended Format Transaction
author: Darren Kellenschwiler
version: 1.0.0
```

## Specification

### Status Note

BRC-70 is a Paymail capability extension and is external to the current `bsv-blockchain/ts-sdk` / `bsv-blockchain/wallet-toolbox` BRC-100 wallet implementation. It remains useful for Paymail-specific interoperability, but current SDK/toolbox payment flows should not be expected to expose this capability unless a Paymail integration is added explicitly.

We specify that an endpoint for delivery of transaction data ought to be added to the capabilities object in the .well-known response of a paymail service with the label: `5c55a7fdb7bb`.

```json
<!-- capabilities document of the host -->
{
    "capabilities": {
        "5c55a7fdb7bb": "https://paymail.domain.tld/api/v1/beef/{alias}@{domain.tld}",
        <!-- ...others -->
    }
}
```

#### Client Request

The sender must replace the `{alias}` and `{domain.tld}` placeholders in the URI template provided by `capabilities.5c55a7fdb7bb` with a valid Paymail handle. The client must then perform a POST HTTP request with the following body:

```json
{
  "beef": "<beef_transaction_hex>", <!-- note the label is different >
  "metadata": {
    "sender": "<sender_paymail>",
    "pubkey": "<sender_public_key>",
    "signature": "<signature_of_txid>",
    "note": "<optional_human_readable_note>"
  },
  "reference": "<payment_reference>"
}
```

BEEF transaction hex is a string encoding of the binary format detailed in [BRC-62](/transactions/0062.md).

#### Server Response

The server must validate the transaction and respond with the accepted transaction ID and an optional human-readable note.

```json
{
  "txid": "<accepted_txid>",
  "note": "<optional_human_readable_note>"
}
```

### Swimlanes

A swimlanes diagram is included here for further clarification: <https://swimlanes.io/u/6J2q8QCEb>

![swimlanes](https://static.swimlanes.io/fd5ffc82e217ec5d5aeb9a8d0b5ec5e9.png)


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