Your devices

Conversations in Tacq are encrypted so that only the devices you have added to your account can read them. Not the account in general — the devices: your phone, a second phone, a browser on your computer. That is why entering your Master ID and password on a new device is not enough: the device has to be linked.

Main device and linked devices

The main device is the one you created the account on. It decides who else belongs to your circle: it links new devices and unlinks old ones.

A linked device is one the main device has admitted. It reads and writes just like the main one, but it adds nobody itself.

There is always exactly one main device. If you bring your access back with the recovery phrase on another device, that device becomes the main one.

How to add a second device

The usual way is simply to sign in.

1. On the new device, enter your Master ID and password.
2. The app will say the device is not connected yet and offer to ask your main device. Tap it — the request goes out.
3. Pick up your main device and open Tacq. A question will be waiting: “New device. Is this you?” — with the kind of device and the time.
4. Tap “Yes, connect it”. Within a few seconds messages start arriving on the new device.

If that question appears and you did not connect anything, tap “No, it is not me” and change your password right away: only someone who knows it can send the request.

If your main device is not at hand

There is a second way — linking by code, when both devices are side by side:

1. On the new device: Settings → Link a device → “This is a new device”. It will show a code.
2. On the main device: Settings → Link a device → “This is my main device”, and scan the code. If there is no camera, the code can be typed in by hand.
3. The same six digits appear on both screens. Compare them with your own eyes. If the digits differ, stop: someone else is on the other end.
4. Done. If you choose so, the most recent part of your conversations moves to the new device as well — directly, bypassing the Tacq server.

If you no longer have your main device at all, the recovery phrase is what helps: see If you lose your phone.

Signing in on new devices with the password alone

Settings has a switch, “Sign in on new devices with the password alone”. It is off by default, and that is deliberate.

While it is off, a guessed or overheard password opens the way into the server to a stranger, but not your conversations: the server has no keys to them, and the stranger sees only ciphertext. To read your messages, they would also need your confirmation on your main device.

If you turn it on, signing in on a new device no longer needs a confirmation — but then the password becomes the only lock: whoever learns it will read everything you write from then on, on any device. Turn it on only if confirming sign-ins is inconvenient for you, and keep the password truly strong.

“This device is not connected”

This is the app saying that you have signed in, but the device has not been added to the account yet. Until then the app cannot be used: instead of the list of conversations you will see a screen with two buttons — ask for confirmation on your main device, or bring your access back with the recovery phrase.

Such a device used to show the normal app and even let you send messages, although not a single incoming message reached it. That was confusing and unsafe, so now, for Tacq, an unconnected device simply does not exist.

What happens when you sign out

Signing out is not “stepping away for a minute”. It takes everything off the device:

• the conversations stored here are erased;
• the keys are erased too, and the device stops being linked.

After you sign in again, this device has to be linked anew. This is deliberate: if somebody else sits down at that computer and signs into their own account, your conversations must not come along.

Clearing the site data in a browser does exactly the same. For the app it is indistinguishable from signing out: you will see the sign-in screen again, and after signing in — “this device is not linked”.

Unlinking a device

Settings → My devices lists all your devices. Only the main device can unlink.

Unlinking is the same as signing out on that device — only remotely. It stops receiving new messages at once, and as soon as it is online it erases everything on itself: the saved conversations, the keys and the settings, and shows the sign-in screen. If it is switched off or offline, the command waits: it erases on the first connection.

What unlinking does not do, and this matters:

• it does not replace changing your password. If a stranger has learned your password, they can sign in again — and ask to connect a new device. The confirmation will come to you, but it is safer to change the password in your profile straight away;
• it cannot take data off a device that never comes online again.

A device you signed out from may stay in the list — it reads nothing, but it takes up a line. Such an entry can be unlinked by hand.

If you have several devices

• Messages arrive on every linked device.
• The mark showing unread messages in a session is separate on each device. It goes out when you open that session on that device.
• The recovery phrase is created on the main device only.