/**
 * Generate HMAC-SHA512 hash for ABA PayWay API requests
 *
 * @param data - Concatenated string of parameters in specific order
 * @param apiKey - API key provided by ABA Bank
 * @returns Base64 encoded HMAC-SHA512 hash
 *
 * @example
 * ```typescript
 * const data = req_time + merchant_id + tran_id + amount + ...;
 * const hash = generateHash(data, apiKey);
 * ```
 */
export declare function generateHash(data: string, apiKey: string): string;
/**
 * Verify webhook signature from ABA PayWay
 *
 * @param payload - Raw webhook payload string
 * @param signature - Signature from webhook header
 * @param apiKey - API key provided by ABA Bank
 * @returns true if signature is valid, false otherwise
 *
 * @example
 * ```typescript
 * // In Next.js API route
 * const signature = request.headers.get('x-payway-signature');
 * const payload = await request.text();
 * const isValid = verifyWebhookSignature(payload, signature, apiKey);
 * ```
 */
export declare function verifyWebhookSignature(payload: string, signature: string, apiKey: string): boolean;
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