/**
 * Generates HMAC-SHA256 signature for eSewa request
 * @param requestId Unique request identifier
 * @param amount Payment amount
 * @param clientSecret Base64 encoded client secret
 */
export declare function generateEsewaSignature(requestId: string, amount: number, clientSecret: string): string;
/**
 * Validates eSewa signature
 * @param signature Signature to validate
 * @param requestId Unique request identifier
 * @param amount Payment amount
 * @param clientSecret Base64 encoded client secret
 */
export declare function validateEsewaSignature(signature: string, requestId: string, amount: number, clientSecret: string): boolean;