/**
 * Convert a counter value to an 8-byte big-endian buffer
 *
 * @remarks
 * Always uses BigInt internally to support full 64-bit counter values.
 * This fixes potential integer overflow issues when counter exceeds 2^32-1.
 *
 * For TOTP, time steps are calculated as Math.floor(Date.now() / 1000 / period).
 * Current time steps are ~57 million, well within 32-bit range, but this
 * ensures correctness for far-future dates and high-precision use cases.
 *
 * @param counter - Counter value as number or bigint
 *
 * @returns ArrayBuffer containing the counter in big-endian format (8 bytes)
 */
export declare const createCounterBuffer: (counter: number | bigint) => ArrayBuffer;