/**
* PEAC Protocol — Cryptographic Receipt Layer
*
* On successful x402 payment, generates a signed PEAC-Receipt header.
* Agents can verify receipts offline without calling BTCFi again.
*
* Receipt format: base64url-encoded JSON Web Signature (JWS)
* Signing: HMAC-SHA256 (upgradeable to Ed25519 when keypair is configured)
*/
import { createHmac } from 'crypto';
const PEAC_SECRET = process.env.PEAC_SIGNING_KEY || 'btcfi-peac-default-key';
if (!process.env.PEAC_SIGNING_KEY) {
console.warn('[PEAC] WARNING: Using default signing key. Set PEAC_SIGNING_KEY in production.');
}
const PEAC_VERSION = '0.9.15';
export interface PEACReceiptPayload {
/** PEAC protocol version */
v: string;
/** ISO timestamp */
ts: string;
/** Resource path */
res: string;
/** Amount paid (USDC base units) */
amt: string;
/** Currency */
cur: string;
/** Payment rail (base or solana) */
rail: string;
/** SHA-256 hash of response body (first 16 chars) */
rh: string;
/** Provider */
iss: string;
}
function base64url(data: string): string {
return Buffer.from(data).toString('base64url');
}
function sha256short(data: string): string {
return createHmac('sha256', 'hash').update(data).digest('hex').slice(0, 16);
}
/**
* Generate a PEAC receipt for a successful payment.
*/
export function generatePEACReceipt(
resource: string,
amount: string,
network: string,
responseBody: string
): string {
const payload: PEACReceiptPayload = {
v: PEAC_VERSION,
ts: new Date().toISOString(),
res: resource,
amt: amount,
cur: 'USDC',
rail: network,
rh: sha256short(responseBody),
iss: 'btcfi.aiindigo.com',
};
const header = base64url(JSON.stringify({ alg: 'HS256', typ: 'PEAC' }));
const body = base64url(JSON.stringify(payload));
const signature = createHmac('sha256', PEAC_SECRET)
.update(`${header}.${body}`)
.digest('base64url');
return `${header}.${body}.${signature}`;
}
/**
* Verify a PEAC receipt locally.
*/
export function verifyPEACReceipt(receipt: string): { valid: boolean; payload?: PEACReceiptPayload; error?: string } {
try {
const parts = receipt.split('.');
if (parts.length !== 3) return { valid: false, error: 'invalid_format' };
const [header, body, signature] = parts;
const expectedSig = createHmac('sha256', PEAC_SECRET)
.update(`${header}.${body}`)
.digest('base64url');
if (signature !== expectedSig) return { valid: false, error: 'invalid_signature' };
const payload = JSON.parse(Buffer.from(body, 'base64url').toString()) as PEACReceiptPayload;
return { valid: true, payload };
} catch {
return { valid: false, error: 'parse_error' };
}
}
