privacy-toolkit/tools/simplex/README.md

SimpleX Chat - Private Messaging Without Identifiers

The most private messaging app - no phone number, email, or username required

🎯 Threat Model

What Problem Does This Solve?

Most "encrypted" messaging apps still leak critical metadata:

• Phone/Email Linking: Signal, WhatsApp, Telegram require phone numbers
• Username Tracking: Session, Threema use permanent usernames
• Contact Graph: Servers know who talks to whom
• Central Compromise: Single point of failure if servers are seized

How SimpleX is Different

No User Identifiers

• No phone number
• No email address
• No username
• No blockchain address
• Nothing that identifies you across connections

Each Contact is Isolated

• Every contact uses different message routing
• Server can't build a social graph
• Compromise of one contact doesn't expose others

Decentralized Infrastructure

• Run your own server or use defaults
• Messages routed through different servers
• Ephemeral message queues (deleted after delivery)

🔐 Privacy Features

• ✅ End-to-end encryption (Signal Double Ratchet + post-quantum)
• ✅ Perfect forward secrecy
• ✅ No metadata leakage to servers
• ✅ Disappearing messages
• ✅ Incognito mode (temporary identities)
• ✅ Voice/video calls (also E2E encrypted)
• ✅ Group chats (fully decentralized)
• ✅ File sharing (encrypted)

🚀 Installation

Debian Trixie (glibc 2.40+)

cd ~/github/privacy-toolkit
./tools/simplex/install.sh

The script automatically selects:

• Ubuntu 24.04 package for Debian Trixie
• Ubuntu 22.04 package for older systems

Manual Installation

Check your glibc version:

ldd --version | head -1

• If glibc ≥ 2.39: Download ubuntu-24-04 package
• If glibc < 2.39: Download ubuntu-22-04 package

Download from: https://github.com/simplex-chat/simplex-chat/releases/latest

📖 Usage

First Launch

1. Open SimpleX from application menu
2. Choose "Create new profile"
3. Set display name (not sent to servers!)
4. Optionally set profile image

Adding Contacts

1. Click "+" → "Add contact"
2. Share your connection link OR
3. Scan contact's QR code

Important: Each contact gets a unique connection link. You can't be tracked across contacts.

Restoring from Backup

If you have a backup (from /tmp/restore-simplex.sh):

1. Launch SimpleX
2. It will automatically detect restored data
3. Verify your contacts appear
4. Database files are at ~/.local/share/simplex/

🔒 Security Best Practices

Message Retention

• Enable disappearing messages for sensitive conversations
• Default: Messages stored locally forever
• Recommendation: 1 week retention for most chats

Connection Security

• Delete old connection links after contact accepts
• Use incognito mode for temporary conversations
• Verify contact fingerprints for high-security conversations

Server Trust

• Default servers are run by SimpleX team (good reputation)
• For maximum privacy: Run your own SimpleX server
• Or use community servers you trust

Backup Your Data

SimpleX stores everything locally:

~/.local/share/simplex/         # Databases
~/.config/simplex/              # Settings

Backup regularly! If you lose this data, you lose all messages.

🆚 Comparison with Other Apps

Feature	SimpleX	Signal	Session	Matrix
No phone/email	✅	❌	✅	✅
No username	✅	❌	❌	❌
No user ID at all	✅	❌	❌	❌
Decentralized routing	✅	❌	✅	✅
Contact graph hidden	✅	❌	❌	Partial
Post-quantum crypto	✅	Partial	❌	❌
Metadata resistance	Excellent	Good	Good	Moderate

🛠️ Advanced: Run Your Own Server

For maximum privacy, run your own SimpleX SMP server:

# Docker method
docker run -d \
  --name simplex-smp \
  -p 5223:5223 \
  simplexchat/smp-server

# Configure SimpleX app to use your server

Instructions: https://github.com/simplex-chat/simplexmq#smp-server

🔗 Resources

• Official Website: https://simplex.chat/
• Documentation: https://simplex.chat/docs/
• GitHub: https://github.com/simplex-chat/simplex-chat
• Security Audit: https://simplex.chat/blog/simplex-chat-v5.8-private-message-routing-chat-themes/
• Whitepaper: https://github.com/simplex-chat/simplexmq/blob/stable/protocol/overview-tjr.md

⚠️ Limitations

• No cloud sync: Messages are device-local only
• Manual backups: You must backup yourself
• Contact management: Need to share new links for each contact
• Group limitations: Decentralized groups have size limits

Trade-off: Maximum privacy requires some inconvenience. SimpleX chooses privacy over convenience.

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Maintained by: SimpleX Chat team License: AGPL-3.0 Last Updated: 2025-11-12