Pair a phone

Before you start

Pairing is done on the computer Metis runs on, from Devices. “Devices are managed on the computer Metis runs on.” Open More, then Devices, and press “Pair a phone”.

A pairing code is eight characters. It ends after ten minutes, or after 5 wrong tries: “someone may be guessing it.” Press Cancel to end it sooner.

On your home Wi-Fi

This way needs no setup, and the phone must be on the same Wi-Fi as the computer. It takes two scans, because the first one installs the computer’s certificate on the phone.

Where the relay carries phones, Pair a phone shows one code to scan instead. Without the relay, Pair a phone offers “Use Metis away from home” first, and these two scans are under “Pair on this Wi-Fi instead”.

1. “Scan the first code with your phone.” The phone opens a page, “Install this computer’s certificate”, with steps for iPhone and for Android. “Your phone will warn you. That is expected.”
2. Open the installed certificate’s details on the phone, and check its SHA-256 fingerprint against the one on the computer, every character. This check is the only thing that proves the certificate is this computer’s.
3. “Never compare with the phone’s page.” That page arrives over an open connection, so whoever swaps the certificate can rewrite its fingerprint too. Compare with the certificate’s own details on the phone.
4. “If any part differs, remove the certificate and stop: someone on this network may be in between.” Remove it from the phone and press Cancel on the computer.
5. When every character matches, scan the second code, “Finish pairing”. Or open the address shown beside it and type the pairing code.
6. Under “Name this phone”, you can give it a name. The computer lists paired phones by this name. Press “Pair this phone”.

The phone then shows “Paired”, and “Open Metis” opens Metis on it. The phone remembers the address it paired with. Away from the Wi-Fi it cannot reach Metis, unless you also set up use from anywhere (below).

To get notices on the phone, add Metis to its Home Screen: on iPhone tap Share (in Safari’s page menu, ≡), then Add to Home Screen; on Android open the browser’s menu, then Add to Home screen.

On a laptop, a tablet or a borrowed computer

The pairing is kept in the browser, in one cookie that lasts about 400 days. Closing the browser and opening it again keeps the pairing. A browser that holds no Metis cookie, which is how a new private window starts, is not paired: Metis refuses it until a new code is typed there. This was measured in a fresh Chromium browser context with the Wi-Fi way above, not in a real private window. How each browser’s private windows share or forget cookies, and so whether a pairing made inside one is forgotten, is its own rule and was not measured.

Away from home

Your phone can reach Metis away from home through a relay. The relay is a small program run by the author. It is for the beta, and “Using Metis away from home needs two-step sign-in first.”

Set up two-step sign-in

1. On Devices, press “Use Metis away from home”. The first time, the key and the backup codes show at once. Opened again before you turn it on, it shows “Show the key” instead.
2. Scan the code with an authenticator app, or type the key into it. Any authenticator app that makes six-digit codes works. The key is shown this once, and anyone who has it can make your codes.
3. Write down the ten backup codes. “Write them down now: they are shown this once.” Each backup code works once, in place of a code, if you lose the phone.
4. Type the six-digit code the app shows and press “Turn on two-step sign-in”.

“Turn off” on Devices removes the key and the backup codes, and signs phones out of From anywhere. It asks for the code the app shows now; a backup code does not turn it off.

Choose a way in

Once the code is typed, the same press goes on to the ways to be reached from away. With two-step sign-in already on, “Use Metis away from home” opens them at once.

• Through a shared connection is the recommended way. “Open the invite you were sent on this computer.” If that does not work, open “Having trouble?” and paste the invite or its code in the field “The code”. “The connection carries what you and Metis say but cannot read it. Nothing on your router changes.” The code comes from whoever runs the relay, which today is the author.
• Your own way is for a VPN you already use: “A VPN you already use puts your phone on this home network.” Metis sets nothing up for it and uses no relay.
• Your own server is an https address of your own that reaches Metis. The relay’s computer tries it from outside first, and “An address Metis cannot reach is not kept.”

Press Continue. Under “Other ways (advanced)” are the last two. Once the relay is connected, Devices says Connected and shows the address phones open. “Phones can open Metis away from home.”

If the relay does not answer, Devices says “No relay answered” and “Metis keeps trying.” “Try now” asks again, and “Turn off” stops using it.

Pair a phone through the relay

With the relay connected, “Pair a phone” shows one code, whether or not two-step sign-in is set up yet. “One scan with the phone’s camera.”

1. Scan the code. The phone opens a page at the relay’s name, whose certificate comes from a public authority that the phone already trusts. Nothing is installed and no fingerprint is compared.
2. The first phone, before any two-step sign-in is set up: “The phone makes a passkey with its face, fingerprint or PIN, then pairs.” Press “Pair this phone” and let the phone check your face, fingerprint or PIN. That passkey turns two-step sign-in on, and the phone pairs by itself.
3. Once two-step sign-in is on: “The phone asks for two-step sign-in first.” Sign in with a passkey the phone already has, or with the code from your authenticator app. “Pair this phone” then opens with the pairing code filled in. Name the phone if you like and press it.

If the code ran out on the way, the phone says so: “This pairing code has ended. On the computer press Pair a phone for a new one.”

Without the camera, open the address the card shows and type the code beside it.

If a code ends because every wrong try at it came through the relay, Devices says the code was spoiled through the relay, and that pairing on this Wi-Fi gets around it. Press “Pair a phone” for a new code: that one card, and only that one, also offers “Pair on this Wi-Fi instead”, the two scans of the section above, which never go through the relay. “Two scans, no relay: the phone then opens Metis on this Wi-Fi alone.”

A phone that paired on the Wi-Fi needs one more step to work away from home. With reach on, its Paired screen offers it: “To open Metis on this phone away from this Wi-Fi too, tap Use from anywhere.” Also, “On the way it may ask for your two-step sign-in code.”

The same scan in Setup

The last steps of Setup offer “Use Metis from your phone”. It draws the same code as Devices, and only where Devices draws it: with the relay connected, whether or not two-step sign-in is set up. Press “Pair a phone” and scan it; the page then says how many phones are paired, and Continue goes on to Ready. A computer set up from an invite joins its relay at that press, and the step says “Joining the relay…” until the code appears. An invite still waiting for a name, for Join, or for another try is finished on Devices: the step says “Not connected to the relay.” and links “Open Devices”. With no relay and no invite the step says “Not connected to the relay.”, and “No relay? Pair on this Wi-Fi” opens Devices, where the two scans above pair a phone on this Wi-Fi alone. “Not now” goes straight on to Ready and nothing is paired. Without the camera, press the ? beside the code.

What the relay sees

The relay sees little, and it cannot read your chats or your pages.

• It reads only the first bytes of the phone’s connection, to learn which name the connection is for. It then passes the rest on without reading it. The relay holds no encryption key for your pages, so “Pages stay encrypted from your phone to this computer.”
• Its log is connection metadata only: the name, the network address the visitor came from, byte counts and times. It never holds what was carried. The log is kept 30 days, then deleted.
• The relay keeps no list of phones and no phone’s name. Your phone remembers which Metis it connected to in its own browser. For up to a day, in memory only, the relay remembers the network addresses your computer has vouched for, to tell them from strangers; a restart forgets them.
• Its public page does not say whether a name exists. For a name that is off or unknown, it says your computer “can't be reached.” and the same for both.
• The link between your computer and the relay is encrypted when the relay offers it. When it is not, Devices says “The link between this computer and the relay is not encrypted yet.”

Remove a phone

On the computer, open Devices. Under Paired devices, press Remove beside the phone. A borrowed laptop or tablet is removed the same way once you are done. Its row carries the name you gave it under “Name this phone”, and under that the system it runs on, such as “Browser on Windows”, “Browser on a Mac” or “Browser on Linux” for a computer, or “iPad” or “Android” for a tablet. Metis keeps a row for every code typed in, private window or not, so remove that one as well. “Remove all phones” ends every pairing: “Every phone will need to be paired again. A pairing code that is showing ends too.” The phone says the same thing: “To stop this phone reaching Metis, remove it on the computer’s Devices page.”

The way in over the Wi-Fi is open only while a pairing code is live or a phone is paired. It shuts by itself when the last phone is removed, or when a code nobody used ends.