Signal Private Messenger

What is Signal?

Signal is an end-to-end encrypted messaging app developed by the non-profit Signal Foundation. Created by cryptographer Moxie Marlinspike and WhatsApp co-founder Brian Acton, it's become the standard for secure communications among journalists, activists, and privacy-conscious users worldwide.

Key Features

Core Security

• End-to-end encryption - All messages, calls, and files
• Signal Protocol - The gold standard, used by WhatsApp
• Disappearing messages - Auto-delete after set time
• Screen security - Blocks screenshots in app
• No ads or tracking - Non-profit model

Communication Features

• Text messaging
• Voice calls
• Video calls
• Group chats (up to 1000 members)
• File sharing (100MB limit)
• Voice notes
• Reactions and stickers
• Story feature

Privacy Architecture

What Signal Knows

✅ Phone number (required for registration)

✅ Last connection date (not time)

✅ Total messages sent (not content)

What Signal DOESN'T Know

❌ Your contacts

❌ Who you message

❌ Message content

❌ Group memberships

❌ Profile information

❌ Location data

Setup Guide

Getting Started

1. Download Signal from official sources only
2. Register with phone number (required)
3. Set up PIN for account recovery
4. Verify safety numbers with contacts
5. Enable disappearing messages by default

Recommended Settings

• Enable registration lock - Prevents SIM swap attacks
• Turn on screen lock - Requires biometric/PIN
• Disable link previews - Prevents metadata leaks
• Hide keyboard personalization - Stops learning
• Enable relay calls - Hides IP address

Security Features Explained

Sealed Sender

Hides who's messaging whom from Signal servers. Even Signal can't see the sender's identity.

Safety Numbers

Cryptographic fingerprints that verify you're talking to the right person. Always verify for sensitive conversations.

Disappearing Messages

Messages auto-delete after:

• 30 seconds to 4 weeks
• Custom timer per conversation
• Applies to all message types

Screen Security

• Blocks screenshots within app (Android)
• Blurs app in recent apps
• Face blur for video calls
• Incognito keyboard mode

Limitations & Concerns

Phone Number Requirement

The biggest weakness: You must register with a phone number, which can be subpoenaed or SIM-swapped. Mitigation strategies:

• Use burner phone for registration
• Enable registration lock
• Use Signal PIN
• Consider Session or Briar for anonymous messaging

Metadata Collection

While minimal, Signal does collect:

• Registration date
• Last connection date (not time)
• No message metadata

US Jurisdiction

• Based in United States
• Subject to US laws
• Can be compelled to provide data (though they have little)

Signal vs. Alternatives

Signal vs. WhatsApp

• Signal: Non-profit, minimal data, open source
• WhatsApp: Meta-owned, metadata collection, closed source

Signal vs. Telegram

• Signal: Default E2EE, proven crypto, non-profit
• Telegram: No default E2EE, questionable crypto, for-profit

Signal vs. Element/Matrix

• Signal: Easier setup, phone number required
• Element: Decentralized, anonymous possible, complex

Signal vs. Session

• Signal: Requires phone number, more features
• Session: No phone number, based on Signal protocol

Real-World Usage

Perfect For:

• Journalists protecting sources
• Activists organizing safely
• Lawyers with privileged communications
• Whistleblowers sharing information
• Anyone wanting private conversations

Not Ideal For:

• Anonymous communication (phone number required)
• Large file sharing (100MB limit)
• Users in countries where Signal is blocked
• Those avoiding all US-based services

Articles Referencing Signal

• Protesting Without Surveillance
• Surveillance-Resistant Digital Life
• Your Phone vs. ICE
• Privacy Score Calculator

Advanced Usage

Using Signal with Tor

1. Enable Orbot on Android
2. Set Signal to use Tor proxy
3. Enables censorship circumvention
4. Hides IP from Signal servers

Burner Phone Setup

1. Buy prepaid phone with cash
2. Activate away from home
3. Register Signal account
4. Never use with personal phone on
5. Keep powered off when not needed

Group Security

• Verify all members' safety numbers
• Use disappearing messages
• Limit group size
• Avoid sensitive group names
• Regularly review members

Government Requests

What Signal Has Provided

In response to subpoenas, Signal can only provide:

• Unix timestamp of account creation
• Unix timestamp of last connection

Example: In 2021, Signal provided these two data points to FBI. That's all they had.

Grand Jury Subpoenas

Signal has been transparent about government requests, publishing them when legally allowed.

Common Issues

Message Delivery

• Requires internet connection
• Both parties must have Signal
• Notifications can be delayed
• Battery optimization can interfere

Verification Problems

• Phone number changes require re-registration
• Safety numbers change with reinstalls
• Group members need individual verification

Tips for Maximum Security

Operational Security

1. Verify safety numbers in person
2. Use disappearing messages always
3. Avoid SMS fallback (removed in 2023)
4. Regular safety number checks
5. Don't backup to cloud

Physical Security

• Enable app lock
• Use complex PIN
• Hide notifications content
• Enable registration lock
• Regular app updates

Development & Transparency

Open Source

• Client code on GitHub
• Server code on GitHub
• Reproducible builds
• Regular security audits
• Active development

Funding Model

• Non-profit Signal Foundation
• Initial $50M from Brian Acton
• Donations from users
• No ads or data sales
• Sustainable operations

Getting Signal

Official Downloads

• Signal.org
• Apple App Store
• Google Play Store
• Direct APK download
• Desktop apps (Windows, Mac, Linux)

Verify Authenticity

Always verify downloads:

• Check website certificate
• Verify app signatures
• Use official sources only
• Check SHA256 hashes

Frequently Asked Questions

Is Signal really secure?

Yes. Signal uses the most advanced end-to-end encryption protocol available, has been audited multiple times, and is recommended by security experts worldwide.

Can government agencies read Signal messages?

No. Due to end-to-end encryption, not even Signal can read your messages. Government agencies would need physical access to your unlocked device.

Why does Signal need my phone number?

Phone numbers prevent spam and enable contact discovery. It's Signal's biggest privacy trade-off for usability.

Is Signal blocked in my country?

Signal is blocked in China, Iran, Egypt, UAE, and others. Use Signal's censorship circumvention (domain fronting) or Tor.

Can I use Signal anonymously?

Not truly anonymous due to phone number requirement. For anonymous messaging, consider Session or Briar.

The Bottom Line

Signal remains the best option for secure messaging for most users. While the phone number requirement is a limitation, the security benefits far outweigh this for non-anonymous use cases.

Use Signal when:

• You need proven, audited encryption
• Communicating sensitive information
• Ease of use matters
• You trust US-based services

Consider alternatives when:

• Anonymous communication is required
• Avoiding US jurisdiction
• Decentralization is priority
• Phone number registration is dealbreaker

Additional Resources

• Signal.org
• Signal Support
• Signal GitHub
• Signal Protocol Documentation
• EFF on Signal