import { Header } from './header';
import { type Label } from './map';
import { Key, type Encryptor } from './key';
/**
 * Encrypt0Message represents a COSE_Encrypt0 object.
 *
 * Use this structure when the recipient already knows the content encryption
 * key. The protected header bytes and optional externalData are authenticated
 * as AEAD additional data.
 *
 * @example
 * ```ts
 * const key = AesGcmKey.generate(iana.AlgorithmA128GCM)
 * const aad = utf8ToBytes('profile:v1')
 * const cose = await new Encrypt0Message(plaintext).toBytes(key, aad)
 * const decrypted = await Encrypt0Message.fromBytes(key, cose, aad)
 * ```
 *
 * Reference https://datatracker.ietf.org/doc/html/rfc9052#name-single-recipient-encrypted.
 */
export declare class Encrypt0Message {
    payload: Uint8Array;
    protected: Header | null;
    unprotected: Header | null;
    private static encBytes;
    static fromBytes(key: Key & Encryptor, coseData: Uint8Array, externalData?: Uint8Array, understoodCriticalLabels?: Iterable<Label>): Promise<Encrypt0Message>;
    static withTag(coseData: Uint8Array): Uint8Array;
    /**
     * @param payload - The plaintext bytes to encrypt.
     * @param protectedHeader - Optional protected (authenticated) header. When
     *   omitted, `toBytes` creates one and sets `alg` from the content key.
     * @param unprotected - Optional unprotected header. `toBytes` puts the
     *   generated IV here unless one is already set.
     */
    constructor(payload: Uint8Array, protectedHeader?: Header, unprotected?: Header);
    toBytes(key: Key & Encryptor, externalData?: Uint8Array): Promise<Uint8Array>;
}