/**
 * Nonce length in bytes for all flavours of XChaCha20.
 *
 * @see https://libsodium.gitbook.io/doc/advanced/stream_ciphers/xchacha20#notes
 */
export declare const xchacha20NonceLength = 24;
export declare class Xchacha20poly1305Ietf {
    static encrypt(message: Uint8Array, key: Uint8Array, nonce: Uint8Array): Promise<Uint8Array>;
    static decrypt(ciphertext: Uint8Array, key: Uint8Array, nonce: Uint8Array): Promise<Uint8Array>;
}