Communication changed once and for all when people started using gadgets and applications to make calls and exchange text messages. At first glance, everything is great. We can communicate with other people from anywhere in the world and spend less money on international calls. All of the above factors drive the popularity of messengers.

However, there are certain drawbacks that undermine our trust in said messengers - privacy and data security. This is why secure messaging apps are becoming more and more popular. The Signal messenger app, a popular solution for encrypted messaging, is a great example of how to make communication secure.

If you have ever wondered how to create an application like Signal private messenger, this article is exactly what you should read to understand. We will show you all the ins and outs of how to develop the next Signal messaging app, what features it should include, and how much it would cost you.

Magic Behind Signal Messenger App

Signal Messenger App
Signal Messenger App

So, what makes Signal private messenger unique, how does Signal work, and why is it considered a precursor to the most secure free messaging apps on the market? Let’s review the Signal messenger app in detail to answer these questions.

What is Signal App and How Does it Work

So, how does Signal work? The Signal messenger app was built on the basis of the existing RedPhone and TextSecure applications and was launched in March 2015 by Open Whisper Systems. The application is free for users and receives revenue only from donations and grants.

What also distinguishes the Signal messenger app from other chat apps is the fact that Signal source code is available on GitHub for anyone who wants to examine it or check for security flaws. In fact, in 2016 Signal was independently audited. The audit resulted in the Signal encryption app and has been officially deemed secure.

Aside from that, their repository is set up with BitHub so that highly-experienced developers can easily configure and deploy Signal and make money from it if their pull request is accepted.

Signal allows for encrypted calls to be made from anywhere in the world; the same goes for Signal text messages. Unlike SMS, Signal encrypted messaging is protected by end-to-end encryption. Read on to learn more on the matter.

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Is Signal App Really Secure?

Messaging apps have billions of users all over the world. According to research by Messenger People, the user base of WhatsApp and Facebook Messenger accounts for 1.5 billion users worldwide. This means the data of millions of users is in danger of being compromised.

Many of data breaches happen each year. Business Insider states that in 2018 the personal information of millions of people around the world was compromised.

Signal app security is the primary concern for developers who stand behind the app. This is why the app uses end-to-end encryption, as it means that all messages are encrypted before they are sent and can only be decrypted on the device of the intended recipient. The only way to read the message is on the sender’s or recipient’s device.

The Signal private messenger app relies on the following cryptographic protocols:

  • Extended Triple Diffie-Hellman (X3DH)
  • Double Ratchet algorithm, Curve25519
  • AES-256
  • HMAC-SHA256

The applied protocols ensure protection against the MITM (man-in-the-middle).

After one particular Signal update, all voice and video calls were protected with the same Signal Protocol that used to secure only text messages. This protocol was developed in 2013 by Open Whisper Systems and was first implemented in the TextSecure× apps, on which Signal messenger app was later developed.

Signal encryption also provides users with additional security features such as the protection of messages and notifications with a passphrase. The keyboard works in incognito mode and does not collect data on what text is typed. As well, Signal disappearing messages are quite useful, just like those that Snapchat utilizes.

The Signal messenger app also provides a mechanism to verify the identities of your contacts with a unique safety number (fingerprint).

What exactly does it mean to be secure? According to the Electronic Frontier Foundation (EFF), there are seven criteria to assess how secure a chat app is. They are:

  • communication encrypted in transit
  • no provider has access to the key the communication is encrypted with
  • independent verification of a correspondent's identity
  • secure past communications if the keys are stolen
  • code open to independent review
  • well-documented cryptographic design
  • an independent security audit

Unlike other apps, Signal messenger app conforms to all the standards. Additionally, below you can see the security assessment of the Signal encrypted messaging app in comparison to other chat apps:

Facebook Messenger iMessage Telegram WhatsApp Wire Signal
Provides transparency reports X
Doesn’t collect user data X X X X
Encryption by default X X
(secret chats only)
Open source (code and server) X X X X
Metadata is encrypted X X X X X
Doesn’t store timestamps and IP addresses X X X X X
Has refused to provide intelligence agencies with user data X X

So, is Signal messenger secure? According to these criteria, the Signal messenger app provides unprecedented security compared with its main competitors. The app can be expected to maintain this level of security so long as encrypted messaging is being used.

Signal Messaging App: Features to Include

Features of Signal Private Messenger
Features of Signal Private Messenger

Along with the idea of developing your own peer-to-peer chat application, you should also consider all the risks and opportunities this may bring. The core feature of the Signal private messenger is encrypted messaging, but it certainly has more functions that are worth mentioning. In fact, the application can tick all the boxes for even the pickiest users.

  • Registration with a phone number

Convenience is king, and when it comes to registration, things become even easier when you don't need to remember passwords or login information. This is why the Signal messaging app uses a phone number and confirmation code to verify user registration and login.

  • Disappearing messages

A user can set up a timer ranging from 5 seconds to 1 week for all the seen messages to disappear. It is impossible to even take a screenshot of a chat because the app simply doesn't allow it. However, push notifications with Signal disappearing messages (whether or not it is disappearing) can be captured via screenshot since the security of the Signal messenger app, running in the background, can't block standard device functions.

  • Voice and video calls

The Signal messaging app provides its users with the ability to make crystal-clear and secure voice and video calls that make the application suitable for business communication.

  • Group chats

By using one-to-one secure chats, users can have private, encrypted conversations with their friends. As well, the Signal messaging app server has no access to any group metadata including icons, titles, and membership lists.

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  • Content sharing and entertainment

As it is quite popular, the Signal messenger app never stops developing and introducing new features. So far, the safe chat app allows users to share not only texts, but also gifs, photos, videos, locations, any document or file, and even voice messages (which are very convenient for a quick exchange of information).

  • Platform-specific features

On Android, users can set Signal private messenger as their default application for SMS/MMS, which allows SMS messages to be sent to, and received from, either non-Signal users or in the event that there is no internet connection. The only caveat is that these messages are then not encrypted.

  • Security and encryption

Application Security
Application Security

Implementing security protocols is not an easy task, rather, it requires a huge amount of effort. There are, however, some comparatively easier options. One of them, for example, is using Telegram API (another secure chat app). The advantage is that you do not need to develop back-end and a database, which will save you time and money. This solution has its drawbacks as well; you do not have access to, or control over, the database, therefore, making it impossible to change the flow or be 100% sure that user data is safe.

Relying strongly on third- party security is a questionable decision. Your provider can change something in their terms of use and you won’t be able to do anything with it or influence it. And it can happen so fast that you will have no time to switch to anything else or create your own implementation of storing and transferring messages on back end.


Also, no matter how secure a protocol is, technologies are evolving very fast and hackers are also honing their skills. The things that were secure before can be compromised in a few years. Just like it happened with RSA cryptographic algorithm. So, someday even the best encrypted messaging app might be corrupted and user sensitive data may come to the wrong hands.



Igor Vlasenko, Team Leader, Senior Back-end Developer

Not having end-to-end encryption doesn't mean that all of your chat history will be corrupted and used with bad intentions. Actually, unlike the Signal messaging app, many well-known messengers gained their popularity and user base without having super security protocols implemented. Let's take, for example, giants like Facebook Messenger and WhatsApp, which became encrypted only recently using Signal protocol (developed by Open Whisper Systems).

Most of us do not often share highly confidential data in our messages. Still, however, end-to-end encryption serves as an extra safety measure when you are sending any private information like payment details, Social Security numbers, usernames, passwords, etc. Signal end-to-end encryption and disappearing messages can give you peace of mind and confidence in data security.

Signal Messenger App Development: Minimum Budget Required

Cost to Develop a Solution Like Signal Messenger App
Cost to Develop a Solution Like Signal Messenger App

So how much does it cost to develop a solution like the Signal messenger app? The price and timeline will greatly depend on the features your messenger will ultimately have, their complexity, the application design (based on native or custom controls), and the vendor you hire. These factors make it hard to provide an accurate estimate without knowing the details.

There are hundreds of different messaging apps, but only a dozen or two of them have gained widespread popularity and success. Just cloning the existing Signal messaging app is not a very good idea on its own. To successfully penetrate the market, you should think of some innovative and unique features or develop a niche application. In other words, make it different from what already exists – make it stand out from the crowd. Take the best practices from Signal private messenger and add your own touch.

At MLSDev, the whole process of software development is divided between the discovery and development stages. The image below describes this in more detail:

Software Development Process at MLSDev
Software Development Process at MLSDev

Let’s use the most basic features that every chat app should have to calculate a minimum required budget for a solution like the Signal messenger app. They include the following:

Registration

  • Login with a phone number
  • Phone number confirmation

Contacts

  • Access to all contacts
  • Segmentation of contacts into those that have and do not have the messenger installed

Invitations and sharing

  • Ability to invite friends or spread the word using the native sharing function

Chat

  • One-to-one instant message exchange
  • Message statuses (read, unread)
  • Edit or delete messages
  • Send pictures from the gallery or camera
  • Push notifications

Additional Features

  • Voice messages
  • Stickers

If we add up all the services that are included in our process and the time required for the development of the above features, the first version of your product will cost you not less than $50,000 - $80,000 (discovery and development stages combined). However, when you move to the next versions of your application, features will add up and increase the overall app development cost.

Please note that our estimations are very rough and that the final cost of app development may be extremely different. The cost depends on many factors including, but not limited to, the price of mobile app development services, features you want to include in your app, and the app development company you hire to build the next Signal messenger app.

Do you want to get more insight into how app development cost is calculated?

Is Building the Next Signal Messenger App Worthwhile?

When developing a brand new secure chat service, you should take into account that Signal private messenger is not one-of-a-kind in the world. There are some strong competitors like Telegram, WhatsApp, Google Allo, and Facebook Messenger, just to name a few.

Despite possessing the same core functionality, each of these apps has its own tweaks and unique features that make them lighthouses in the endless ocean of applications.

If you feel that your app idea can bring value to users and meet their needs, it is definitely worth giving it a try.

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Frequently Asked Questions:

🔐 Which cryptographic protocols are used in a Signal messenger?
The Signal app provides end-to-end encryption of the messages before they are sent and can only be decrypted on the device of the intended recipient. For this purpose, Signal uses cryptographic protocols like Extended Triple Diffie-Hellman (X3DH), Double Ratchet algorithm, Curve25519, AES-256, HMAC-SHA256.
🔒 Why Signal is so secure?
In contrast with other messaging apps, based on the completed security assessment, Signal provides transparency reports, doesn’t collect user data or store timestamps and IP addresses, and encrypts data by default. Aside from these aspects, the messenger is open-source and has refused to provide intelligence agencies with user data.
⏳ How much time does it take to develop a secure messenger like Signal?
It takes around 1200 - 2500 hours to create the first version of the Signal-like app, if you work with a development team from Ukraine. In general, many other factors may influence the Signal app development timeline. Among those are the number of features and their complexity, design complexity, third-party integration, development vendor you choose, vendor’s rates and location.
🌟 What benefits will I get when outsourcing the encrypted chat app development to Ukraine?
Ukraine offers the best price-quality ratio for developing apps of any complexity and functionality. Eastern Europe, and Ukraine in particular, is widely known as the primary destination for those who search for experienced technology outsourcing providers. Ukraine attracts with favorable rates of ~$30-50 an hour, meaning you could save anywhere from 20% to 60% of your budget and receive a great quality of software development services.