import { ByteArray } from '../../types.js';
import { Cipher } from '../types.js';
/**
 * Creates an RC4 cipher for PDF encryption.
 * RC4 is a symmetric stream cipher where encryption and decryption
 * use the same operation (XOR with the key stream).
 *
 * @param key - The encryption key (variable length).
 * @returns A Cipher object with encrypt and decrypt methods.
 *
 * @example
 * ```typescript
 * const cipher = rc4(key)
 * const encrypted = await cipher.encrypt(plaintext)
 * const decrypted = await cipher.decrypt(encrypted)
 * ```
 */
export declare function rc4(key: ByteArray): Cipher;