Contact Exchange

Adding a contact in Vauchi looks almost too simple — you hold up a code, they scan it, done. The simplicity is the achievement. Underneath that moment sits the thing every messaging app quietly struggles with: how do you know the person you just connected with is really them, and that nobody slipped into the middle? Vauchi's answer is wonderfully low-tech — you were both there.

How it works

The default exchange is a deliberate, two-way act between people in the same place:

 ┌─────┐               ┌─────────┐   
 │ You │               │ Contact │   
 └──┬──┘               └────┬────┘   
    │                       │        
    │     Show QR code      │        
    │───────────────────────▶        
    │                       │        
    │     Scan QR code      │        
    ◀───────────────────────│        
    │                       │        
    │┌────────────────────┐ │        
    ││ Proximity verified │ │        
    │└────────────────────┘ │        
    │                       │        
    │  Scan their QR code   │        
    │───────────────────────▶        
    │                       │        
    │┌────────────────────┐ │        
    ││ Exchange complete! │ │        
    │└────────────────────┘ │        
    │                       │        
┌──────────────────────────────┐     
│ Both have each other's cards │     
└──────────────────────────────┘     
    │                       │        
 ┌──┴──┐               ┌────┴────┐   
 │ You │               │ Contact │   
 └─────┘               └─────────┘   

Why in person?

Presence is a security feature you've trusted your whole life without calling it one. Standing in front of someone does, for free, what elaborate protocols strain to do:

A connection you made in the room is one you meant to make. That intention is exactly what spam, bots, and impostors can't reproduce.

Ways to exchange

QR code — the one to start with

Works on every device, every time:

1. Open the Exchange tab
2. Show your QR code
3. Have them scan it
4. Scan theirs
5. Connected

For security, a QR code expires after 5 minutes — long enough to introduce yourselves, short enough that a stale screenshot is worthless.

And, when you need them, others

QR is the dependable default, but it isn't the only door. Depending on your devices you may also exchange by tapping phones together, bumping them, or — when you simply can't be in the same room — by sharing a one-off Link (vauchi://exchange?…) that completes remotely through the relay over the next few days. The in-person methods give the strongest guarantee; Link mode trades a little of that for reach. The full menu lives in the Exchange Contacts guide.

Proximity verification

On iOS, Vauchi confirms you're actually together using sound your ears can't hear:

• Both phones emit and listen for an ultrasonic handshake (18–20 kHz)
• Range: roughly 3 metres
• If it can't hear the other phone, it falls back to manual confirmation
• This is what stops someone exchanging with a photo of your code instead of you

(Android proximity verification is planned; on desktop and CLI/TUI you simply confirm manually.)

If proximity won't verify (iOS)

1. Check both phones have working speakers and microphones
2. Move closer — within 2–3 metres
3. Quieten the surroundings
4. Disable anything that hijacks audio
5. Try again, or just confirm manually when prompted

After the exchange

The moment it completes:

• The new contact appears in your Contacts list
• You see the fields they chose to share
• They see the fields you chose to share
• From here on, both cards keep themselves up to date

Security properties

Related

• How to Exchange Contacts — step by step
• Privacy Controls — deciding what they see
• Encryption — how the exchange is protected