> ## Documentation Index
> Fetch the complete documentation index at: https://docs.zerokeyusb.com/llms.txt
> Use this file to discover all available pages before exploring further.
# 2FA Codes (TOTP)
> How to enter date/time the first time, view the 6-digit code with countdown and have it typed automatically to your computer.
ZeroKeyUSB can generate **TOTP codes (RFC 6238)** fully offline — the same ones you'd see in Google Authenticator, without a phone. This guide covers the usage flow. To add a TOTP secret to a credential, see [Importing credentials](/getting-started/importing-credentials).
**Before you start:** the credential must have a TOTP secret loaded (in the `2FA` field). If you see `2FA --` on screen, it doesn't have one. Load the secret from the web manager or over USB-CDC first.
***
## Step 1 — Navigate to the 2FA field
From the credential's main screen, press **Down** until you reach the 2FA field. The icon switches from padlock (Pass) to key (2FA). If the credential has a secret loaded, you'll see `2FA (OK)`. Otherwise, `2FA --`.
*With the 2FA field selected (inverted key icon), press **Center** (short) to start calculating the code.*
***
## Step 2 — Enter the date (first time per session)
The ATECC608A has no RTC. It needs date and time **just once** per session (between power cycles). The device asks for the date first in `DD/MM/YY` format.
| Button | Action |
| -------------- | ------------------------------------------------- |
| **Up/Down** | Increase/decrease the current digit (0–9) |
| **Left/Right** | Move the cursor between digits (skipping the `/`) |
| **Center** | Confirm the date and move to the time |
*Set today's date and press **Center**.*
***
## Step 3 — Enter the time
Same flow, now in `HH:MM` (24h local time) format.
*Same buttons as the date. When done, press **Center** to compute the code.*
The time can be your exact local time — the device does not apply a timezone. If the service expects UTC and you live elsewhere, adjust manually.
***
## Step 4 — View the TOTP code
After entering date and time, the ATECC608A computes HMAC-SHA1 of secret + epoch/30 and shows the resulting 6 digits. The bottom bar empties as the 30-second window approaches its end.
*With your cursor on the 2FA input field of your app, short-press **Center**. The device types the 6 code digits to the host as if from a normal keyboard.*
If the countdown reaches 0 before you confirm, the code regenerates automatically — you don't have to re-enter the time.
***
## Step 5 — Subsequent codes in the same session
While the device stays plugged in, you won't have to re-enter date and time. The next time you enter a 2FA field (in any credential), you jump straight to step 4 with a code computed using the current time.
*Short-press **Center** to type the code to the host, or **Left** to return to the credential's main view without typing anything.*
***
## Quick reference
| Screen | Useful buttons |
| ---------------- | ----------------------------------------------------------------- |
| `2FA (OK)` field | **Center** → enter TOTP flow |
| `2FA --` field | (no secret loaded, nothing to do) |
| Enter date | **Up/Down**: digit · **Left/Right**: cursor · **Center**: confirm |
| Enter time | Same as date |
| View code | **Center**: type to host · **Left**: exit |
***
## Next steps
How to load the Base32 secret from your service into a credential.
If you don't have credentials with TOTP yet, start by creating one.