Mobile appMessaging & callsOriginal by Signal Foundation
Signal is a messaging app that makes privacy the product itself rather than a feature. Beyond message content, even metadata such as who talks to whom is collected as little as possible. Open source code and an encryption protocol open to independent audits are the basis of trust, which is why journalists, lawyers and privacy-minded users prefer it.
Building something similar means putting encryption at the very start of the architecture: key exchange, forward secrecy, metadata-hiding techniques such as sealed sender, and private contact discovery. Mobile and desktop clients, servers that hold as little data as possible, an encrypted calling infrastructure, disappearing messages and a registration lock PIN are the core of the product. Publishing the source code and running regular security audits are part of the trust plan.
How Signal works: the core user flow
How many apps and dashboards do you need?
Mobile app
The main app for encrypted one-to-one and group messaging, calls and disappearing message settings.
Desktop client
The computer app that links securely to the phone and holds its own encryption keys.
Minimal-data server
A back end that keeps only the information needed for delivery and cannot see content or the social graph.
Critical features of a product like Signal
Proven encryption protocol
The double ratchet algorithm encrypts every message with a different key and provides forward secrecy.
Sealed sender
The server delivers a message without knowing who it came from, which keeps metadata leakage to a minimum.
Private contact discovery
Registered contacts in the address book are matched in a secure hardware enclave without exposing numbers to the server.
Disappearing messages
When the time set for a chat runs out, messages are deleted automatically from all devices.
Registration lock
A PIN-protected registration lock stops an account from being opened on another device even if the number is hijacked.
Encrypted group calls
Group voice and video calls are also end-to-end encrypted.
What goes into the first version, what comes later
First version (MVP)
- End-to-end encrypted one-to-one and group chat
- Disappearing messages
- Registration lock PIN
- Encrypted media and voice notes
- Safety number verification
Later releases
- Encrypted voice and video group calls
- Desktop client
- Usernames for communication without a phone number
- Encrypted backup and device transfer
Modules and how the budget is calculated
The budget is calculated with 360 SOFT’s pricing model from the modules below, about 26 screens and the project’s complexity: roughly 174 person-days for the full scope and 122 person-days for the first version. Every module you drop lowers the budget directly.
| Module | Phase |
|---|---|
| Sign-up, login, social login | First version |
| User profile and settings | First version |
| Real-time messaging | First version |
| Push notifications | First version |
| File, photo, video upload | First version |
| Video / voice calls | First version |
| GDPR and security hardening | First version |
| Offline mode and sync | First version |
| Email / SMS notifications | First version |
| Multi-language | First version |
| Admin dashboard | First version |
Hosting, SMS, map APIs, app store accounts and payment-provider fees are separate items. Maintenance and improvements (optional): €600 / month. We send a fixed written price within 24 hours after a free discovery call.
The hard parts
Cryptography expertise
A small implementation mistake wrecks all security, so proven libraries and an independent audit are mandatory.
Operating on minimal data
Fighting spam and debugging without collecting user data is much harder than with traditional methods.
Sustainable funding
Without ads or data sales, you need to set up from the start a model that covers infrastructure costs.
Business model
Advertising and data sales do not fit a privacy-focused product. A donation and foundation model, a paid admin console and on-premise licence for organisations, and a secure communication subscription for regulated sectors are more consistent options. Optional paid services such as extra storage and backup can be offered too.
Get a free quote for your project
Let us scope it together and send a fixed written quote within 24 hours. NDA on request; you own the source code.
Choosing a company to build an app like Signal
Most people searching “build an app like signal” are really looking for a reliable app development company. When comparing quotes, check four things:
- Can you try similar products they have shipped, in the stores or live?
- Are the source code, design files, servers and store accounts transferred to you by contract?
- Do they show a working demo every two weeks, with written scope and acceptance criteria?
- Are maintenance, scaling and GDPR/security costs written into the quote?
Copyright and trademarks
A business model and features are generally not protected on their own, but the Signal name, logo, interface design, content and source code are. That is why we build a product with similar functionality but your own brand, design and code. This is not legal advice; we recommend a trademark search before launch.
Frequently asked questions
How long does it take to build an app like Signal?
A first version with encrypted messaging, disappearing messages and registration lock can be ready in a few months. A security audit and encrypted group calls need extra time.
Should we write the encryption ourselves?
No. Open source, audited protocol libraries should be used within their licence terms. Inventing your own cryptography is the most common and most expensive mistake.
Will there be copyright or trademark issues?
The encrypted messaging business model is generally free to use, but the name, logo, design and code cannot be copied, and open source licence terms must be followed. This is not legal advice.
What should I look for when choosing a company to build a secure messaging app?
Ask about security engineering experience, their threat modelling approach and an independent penetration testing plan, and request a GDPR-compliant minimal data policy.
