/**
 * Retrieves the master key from the Keychain, or generates a new one if it doesn't exist.
 * @returns The master key as a Buffer
 */
export declare function getMasterKey(): Promise<Buffer>;
/**
 * Encrypts data using AES-256-GCM with the provided key.
 * @param key - The encryption key
 * @param data - The string data to encrypt
 * @returns A JSON string containing IV, Auth Tag, and encrypted content
 */
export declare const encryptData: (key: Buffer, data: string) => string;
/**
 * Decrypts data using AES-256-GCM with the provided key and payload.
 * @param key - The decryption key
 * @param payloadStr - The JSON string containing IV, Auth Tag, and content
 * @returns The decrypted string
 */
export declare const decryptData: (key: Buffer, payloadStr: string) => string;
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