export declare class CryptoHelper {
    /**
     * Decrypt a base64-encoded `iv::cipherText` string using AES-256-CBC.
     */
    static decrypt(encrypted: string, key: string): string;
    /**
     * Encrypt a plaintext string into base64(iv::cipherText) format.
     */
    static encrypt(plaintext: string, key: string): string;
}