import { IYubico } from '../interfaces';
import { YubicoResponse } from './YubicoResponse';
/**
 * Yubico client
 */
export declare class Yubico {
    /**
     * clientId is retrieved from https://upgrade.yubico.com/getapikey
     */
    private clientId;
    /**
     * secretKey is retrieved from https://upgrade.yubico.com/getapikey
     */
    private secretKey;
    /**
     * A value 0 to 100 indicating percentage of syncing required by client,
     * or strings "fast" or "secure" to use server-configured values;
     * if absent, let the server decide
     */
    private sl?;
    /**
     * Number of seconds to wait for sync responses; if absent, let the server decide.
     */
    private timeout?;
    /**
     * API servers used for verification, leave blank to use Yubico verification servers.
     */
    private apiServers;
    constructor(options: IYubico);
    /**
     * Verify key against Yubico servers
     * More info on OTPs https://developers.yubico.com/OTP/OTPs_Explained.html
     * @param otp {string} The OTP from the YubiKey.
     * @returns {Promise<YubicoResponse>}
     */
    verifyOtp(otp: string): Promise<YubicoResponse>;
}