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title: BRC-121: Simple 402 Payments order: Client Wallet, Client, Server, Server Wallet _: **Initial Request** Client -> Server: GET /somepage Server -> Client: **402 Payment Required** note: Headers returned * **x-bsv-sats** `<amount>` * **x-bsv-server** `<pubkey>` _: **Payment Construction** Client -> Client: BRC-29 BKDS note:* **nonce** `<base64>` (random) * **time** `<unix timestamp>` (now) ``` getPublicKey({ protocolID: BRC29, keyID: nonce + ' ' + time, counterparty: serverPubKey. ) ``` returns publicKey which is hashed and used in an P2PKH output for payment. Client -> Client Wallet: createAction Client Wallet --> Client: tx _: **Paid Request** Client -> Server: GET /articles/some-slug note: * **x-bsv-beef** `<base64 BEEF>` * **x-bsv-sender** `<identityKey>` * **x-bsv-nonce** `<base64>` * **x-bsv-time** `<unix timestamp>` * **x-bsv-vout** `0` _: **Payment Validation** Server -> Server: Verify note: * all headers present * correctly formatted * time is within last 30s * transaction vout satoshis meet needs Server -> Server Wallet: internalizeAction() if: Valid payment Server Wallet -> Server: Success (tx good & KDF works) Server -> Client: **200 OK** *(protected content)* else: Invalid payment Server Wallet -x Server: Error (tx bad or seen already) Server -> Client: **402 Payment Required** end