import type { TotpOptions } from './types/totp-options';
/**
 * Clear the CryptoKey cache
 *
 * @remarks
 * Useful for testing or when secrets should be purged from memory.
 */
export declare const clearKeyCache: () => void;
/**
 * HMAC-based One-Time Password (HOTP) implementation per RFC 4226
 *
 * @remarks
 * Security: Validates minimum secret length (128 bits per RFC 4226).
 * Performance: Caches CryptoKey objects for repeated calls.
 *
 * @param secret - Secret key as bytes (minimum 16 bytes)
 * @param counter - Counter value
 * @param opts - HOTP options
 *
 * @throws ({@link InternalError}) - if secret is too short
 *
 * @returns Promise resolving to the HOTP code
 */
export declare const hotp: (secret: Uint8Array, counter: number | bigint, { algorithm, digits }?: TotpOptions) => Promise<string>;