import { ByteArray } from '../../types.js';
import { Cipher } from '../types.js';
/**
 * Creates an AES-128-CBC cipher for PDF encryption.
 * The cipher prepends a random IV to encrypted data during encryption
 * and extracts the IV from the first 16 bytes during decryption.
 *
 * @param key - The 16-byte encryption key.
 * @returns A Cipher object with encrypt and decrypt methods.
 * @throws Error if the key is not exactly 16 bytes.
 *
 * @example
 * ```typescript
 * const cipher = aes128(key)
 * const encrypted = await cipher.encrypt(plaintext)
 * const decrypted = await cipher.decrypt(encrypted)
 * ```
 */
export declare function aes128(key: ByteArray): Cipher;