/**
 * Encrypts a payload using ECDH keys and the Web Push encryption standard
 *
 * @param userPublicKey - The public key of the subscription
 * @param userAuth - The auth secret of the subscription
 * @param payload - The payload to encrypt
 * @param contentEncoding - The content encoding to use
 * @returns Object containing the necessary encryption data
 */
export declare function encrypt(userPublicKey: string, userAuth: string, payload: string | Buffer, contentEncoding: 'aesgcm' | 'aes128gcm' | undefined): {
    localPublicKey: Buffer;
    salt: string;
    cipherText: Buffer;
};