Encrypted Chat

Learn how Mixin Messenger uses Signal Protocol to protect your communication privacy.

Signal Protocol

What is Signal Protocol

Signal Protocol is the industry-leading end-to-end encryption protocol, widely recognized as one of the most secure communication encryption schemes.

Apps Using Signal Protocol:

• Signal
• WhatsApp
• Mixin Messenger
• Google Messages (partial)

Core Features

1. End-to-End Encryption

• Messages encrypted on sender's device
• Only decrypted on receiver's device
• Server cannot read content
• Network transmission completely encrypted

2. Perfect Forward Secrecy

• Each message uses independent key
• Even if current key compromised
• Historical messages still secure
• Automatic key rotation

3. Future Secrecy

• Keys regularly updated
• Even if past keys compromised
• Future messages still secure

Using Encrypted Chat

One-on-One Chat

All one-on-one chats automatically encrypted:

1. Start Chat

   • Select contact
   • Send message
   • Automatically end-to-end encrypted

2. Verify Encryption Status

   • View top of chat interface
   • Shows encryption icon
   • Indicates connection is encrypted

Group Chat

Group chats are also encrypted:

1. Create Encrypted Group

   • Click "New Group"
   • Add members
   • Encryption automatically enabled

2. Group Encryption Features

   • All members end-to-end encrypted
   • Server cannot read
   • Supports up to 256 people

Message Types

Supported Message Types

All message types are encrypted:

Text Messages

• Plain text
• Emojis
• Link previews

Multimedia

• Images
• Videos
• Audio files
• Documents

Special Messages

• Location sharing
• Contact cards
• Cryptocurrency transfers
• Voice calls

Message Status

• ✓ Sent
• ✓✓ Delivered
• Blue ✓✓ Read

Privacy Protection Features

Disappearing Messages

Set messages to auto-destroy:

1. Enable Feature

   • Open chat settings
   • Enable "Disappearing Messages"
   • Set destruction time

2. Time Options

   • 10 seconds
   • 30 seconds
   • 1 minute
   • 5 minutes
   • 1 hour
   • 1 day
   • 1 week

3. How It Works

   • Timer starts after message sent
   • Automatically deleted from both devices when expired
   • Cannot be recovered

Screenshot Notification

• Notified when other party takes screenshot
• Disappearing messages screenshot will notify
• Protects sensitive information

Hide Chat

1. Hide Conversation

   • Long press conversation
   • Select "Hide"
   • Requires PIN verification to view

2. Hide Features

   • Not shown in chat list
   • No notification preview
   • Requires password access

Group Features

Create Group

1. New Group

   • Click "+" in top right
   • Select "New Group"
   • Add members

2. Group Settings

   • Group name
   • Group avatar
   • Group announcement

Group Management

Admin Functions

• Add/remove members
• Set admins
• Modify group info
• Manage group permissions

Member Permissions

• Mute settings
• Invite permissions
• View member list
• Group links

Group Types

Normal Group

• Up to 256 people
• Any member can invite
• Public member list

Private Group

• Only admins can invite
• Stricter privacy settings
• Can prohibit members from adding each other

Voice Messages

Send Voice

1. Record

   • Long press microphone icon
   • Speak
   • Release to send

2. Cancel Send

   • Swipe up to cancel
   • Delete recording

3. Preview

   • Can preview before releasing
   • Send after confirmation

Voice Features

• End-to-end encrypted
• Auto transcribe to text (optional)
• Playback speed adjustment
• Progress dragging

File Transfer

Send Files

1. Select File

   • Click "+" button
   • Select file type
   • Choose file to send

2. File Types

   • Images/photos
   • Videos
   • Documents
   • Audio
   • Contacts

3. File Limits

   • Single file max: Usually 100MB
   • Supports multiple file sending
   • Auto compress images (optional)

Receive Files

1. Auto Download

   • Can set auto download conditions
   • Auto download on Wi-Fi
   • Save data

2. Manual Download

   • Click file to download
   • View download progress
   • Auto notify when complete

Security Verification

Verify Contact Identity

Prevent man-in-the-middle attacks:

1. View Security Code

   • Open contact info
   • View "Security Code"
   • Shows string of numbers

2. Verification Methods

   Method 1: In-Person Verification

   • Both parties compare security code
   • Numbers completely same means secure
   • Different may indicate attack

   Method 2: QR Code Verification

   • Scan other party's QR code
   • Automatically verify match
   • Show verification result

3. Mark as Verified

   • Can mark after verification
   • Subsequent sessions auto-verify
   • Warned if changed

Best Practices

Protect Privacy

1. Important Conversations

   • Use disappearing messages
   • Regularly clear chat history
   • Verify contact identity

2. Group Chat

   • Carefully add members
   • Regularly review members
   • Use one-on-one for important info

3. File Sharing

   • Extra encrypt sensitive files
   • Use password protection
   • Delete promptly after sending

Device Security

1. Enable Lock Screen

   • Set PIN code
   • Use biometrics
   • Auto lock time

2. Local Encryption

   • Enable app lock
   • Encrypt local database
   • Regular backups

3. Public Places

   • Pay attention to screen privacy
   • Lock screen when leaving
   • Don't send sensitive info on public Wi-Fi

Comparison with Other Apps

Feature	Mixin	WhatsApp	Telegram	Signal
End-to-End Encryption	✅ All	✅ All	🔸 Optional	✅ All
Open-Source	✅	🔸 Partial	🔸 Client	✅
Anonymous Registration	✅	❌	✅	❌
Disappearing Messages	✅	✅	✅	✅
Group Size	256 people	1024 people	200k people	1000 people
Cryptocurrency	✅	❌	❌	Partial

Common Questions

Can Mixin see my messages?

No. Because:

• End-to-end encryption
• Keys only on your device
• Server only forwards encrypted data
• Completely unable to decrypt

Where are chat records stored?

• Only stored on your device
• Server does not save
• Won't sync when changing devices
• Protects your privacy

How to ensure truly encrypted?

1. Check encryption icon
2. Verify security code
3. View open-source code
4. Independent security audits

Can I forward encrypted messages?

Yes, but note:

• Forwarded to new conversation re-encrypted
• Original conversation encryption protection does not continue
• Pay attention to privacy when forwarding

Can deleted messages be recovered?

Local delete:

• Deleted from your device
• Other party's device still has
• Cannot remotely delete

Both delete:

• Both parties delete
• Cannot recover
• No backup

Technical Details

Encryption Process

Sender
  ↓
Compose message
  ↓
Local encryption (Signal Protocol)
  ↓
Upload to server (encrypted data)
  ↓
Server forwards (does not decrypt)
  ↓
Receiver downloads
  ↓
Local decryption
  ↓
Display message

Key Exchange

• Exchange public keys on first chat
• Use X3DH key agreement
• Double Ratchet algorithm
• Automatic key rotation

Related Resources

• Privacy Protection - Comprehensive privacy guide
• Voice Calls - Encrypted voice calls
• Group Features - Group management details
• Security Best Practices - Improve account security