Is Signal Safe? Encryption Behind Messaging Apps

Quick Verdict: Is Signal Safe?

Yes — for personal use, Signal is the most secure mainstream messaging app available. Its end-to-end encryption, open-source codebase, and minimal data collection make it the gold standard among privacy-focused tools. However, “safe” is not unconditional: Signal’s security depends heavily on device integrity, user behavior, and your specific threat model.

Understanding What Signal is Exactly?

Product: Signal

Signal is a free, open-source messaging application that lets users exchange texts, voice notes, images, files, and make audio/video calls — all protected by default end-to-end encryption. It was co-founded by cryptographer Moxie Marlinspike and WhatsApp co-founder Brian Acton, who has loaned the Signal Foundation over $100 million toward its long-term development.

Signal’s Core Security Features — Summary Table

Now, let’s stop and discuss Signal’s security system in more detail.

End-to-end Encryption

As previously mentioned, Signal utilizes end-to-end encryption, provided by a proprietary protocol, as one of its main methods of protection. With this type of information processing, encryption and decryption occur on the devices of users. It is important to note that the data remains encrypted until it reaches its destination.

After encryption, the information looks like a set of unrelated characters. That is why, even if attackers intercept your message, they will not be able to gain anything from it. Images, videos, and other files that you want to share with your interlocutor are also encrypted.

Signal was ahead of many applications by creating its own protocol that implements end-to-end encryption. Large companies such as Microsoft, Google, and Facebook now use it to ensure the security of their solutions.

Signal Security Numbers

As another protective measure, Signal utilizes a security number. Each chat has a unique number, so you can confirm it with your interlocutor to ensure its authenticity.

It is especially important to be confident in another user when discussing confidential information.

If the interlocutor changes devices or reinstalls the application during the conversation, you will be immediately notified. This feature is specifically designed to protect against «Man-in-the-Middle» (MITM) attacks, in which a hacker disguises themselves as another user to obtain sensitive data.

In the event of a mismatch of security numbers or a notification of an unexpected device change, you should contact Signal Support to ensure your protection and prevent potential leaks.

Open-source

Signal has a decentralized model and open-source code, allowing any developer to modify the technology and share it. The main goal, as stated by the creators of the app, is to disseminate knowledge.

What Personal Data Does Signal Collect?

Signal stores the absolute minimum data required for the service to function. Unlike most messaging platforms, it has no advertising model and no commercial incentive to collect behavioral data.

According to Signal’s privacy policy, the only personal information stored server-side is:

• Your phone number (required for account registration)

• Your account creation date

• The date you last connected to Signal

All message content, media, contacts, call history, group memberships, and profile information are either end-to-end encrypted (meaning Signal cannot read them) or stored only on your device. When you send a message, it is temporarily stored on Signal’s servers only until delivery — and in encrypted form that Signal’s own team cannot read.

Known Limitations and Real-World Risks

Signal’s encryption is cryptographically sound — but the app is not risk-free in every scenario. Understanding where the protection ends is essential to using it safely.

The “Signalgate” Incident: What It Actually Means for Security

In early 2025, a high-profile incident involving US national security officials drew global attention to Signal. Senior advisors, including National Security Advisor Mike Waltz, accidentally added Jeffrey Goldberg — editor-in-chief of The Atlantic — to a Signal group chat discussing sensitive military operations.

The crucial point: Signal’s encryption was not breached. The incident was entirely a user error — a wrong contact was added to a group chat. The CIA Director later testified that the CIA actively uses Signal for day-to-day internal communication. The episode illustrates a universal security principle: no cryptographic protocol can protect against trusting the wrong person. Signal is “secure by default,” but it cannot make access control decisions on behalf of its users.

Disadvantages Of Using Signal App

Despite its strong security posture, Signal has practical limitations that make it unsuitable for some use cases.

• Smaller user base than mainstream apps. With approximately 70 million active users, Signal is dwarfed by WhatsApp (~2 billion) and Telegram (~900 million). If your contacts don’t use Signal, the benefit of its encryption disappears for those conversations.

• No multi-device synchronization by default. Signal ties your account to a primary smartphone. While desktop and tablet clients exist, they function as extensions of the mobile app — your phone must remain connected for the desktop version to work correctly. Users who regularly switch between devices find this friction significant.

• No message history backup to cloud. Because Signal stores everything on-device by default and doesn’t sync to a cloud server, switching phones without a manual backup means losing all message history. This is a feature for privacy, but a practical inconvenience for most users.

• Limited business and enterprise functionality. Signal does not support admin-managed multi-user channels, third-party integrations, compliance logging, or the kind of audit trail that regulated industries require. It is not positioned as a business communication platform.

• The 2022 Twilio data breach. In 2022, a cyberattack on Signal’s SMS verification provider Twilio exposed the phone numbers of approximately 1,900 users. Attackers used this data to re-register accounts and attempt fraud impersonation. The breach did not compromise any message content — the encryption remained intact — but it highlighted the vulnerability of the phone-number-based identity model.

Signal vs. Main Competitors

Messaging App Security Comparison

TrueConf

Thanks to its multi-level protection system, TrueConf is already being used by government and law enforcement agencies in many countries. TrueConf solution utilizes methods such as working on a single port, access control, and data storage on-premises, making potential data leaks almost impossible.

TrueConf not only enables safety messaging, but also audio and video conferencing with the ability to use collaboration tools, such as presentation showing, content sharing, remote desktop management, and much more.

Of particular interest to many are the advanced features based on Artificial Intelligence, which allow one to use TrueConf even in the most adverse conditions. This feature is provided by both smart noise reduction and background blurring, guaranteeing absolute privacy for communication.

WhatsApp

The main reasons for WhatsApp’s popularity among businessmen are its ability to create working channels and its large user base. At the same time, you can make audio and video calls, and share various types of files, from images to documents.

WhatsApp employs end-to-end encryption for security, just like Signal. However, many potential users are confused by the amount of personal information that Meta collects without the ability to make a ban.

Telegram

Another application that is gaining increasing popularity among business representatives is Telegram. The application’s extensive capabilities, including not only audio and video communication but also channels with an unlimited number of subscribers, have already attracted a large number of regular users.

However, not everything is good with Telegram’s privacy, despite the apparent security of the solution. The application uses encryption at the transport layer, but it is not end-to-end. This means that Telegram IT specialists can read your messages at any time, regardless of the type of сhat. What’s even more worrying is the fact that the solution stores all user data on its servers, ultimately making privacy a mirage.

How to Maximize Your Security on Signal

The following settings should be configured by any user who relies on Signal for sensitive communications.

• Enable Registration Lock (Settings → Account → Registration Lock). Requires your Signal PIN to register your phone number on a new device. Prevents SIM-swap account takeovers.

• Enable Screen Security (Settings → Privacy → Screen Security). Hides message content in the app switcher and prevents screenshots inside the app.

• Set disappearing messages as default for new conversations (Settings → Privacy → Default Timer). Messages are deleted from both devices after your chosen interval.

• Disable read receipts (Settings → Privacy → Read Receipts). Reduces metadata leakage from delivery receipt timing analysis.

• Use a strong, alphanumeric Signal PIN. Signal uses secure enclaves to limit brute-force attempts, but a strong PIN adds a critical layer of protection for your registration lock and encrypted backup.

• Verify Safety Numbers with any contact you share sensitive information with. Do this in person or via a secondary trusted communication channel.

• Keep Signal and your device OS updated. Protocol-level security is sound, but device-layer vulnerabilities are the primary real-world attack vector.

• Use a non-personal phone number if anonymity is required (VoIP number or Google Voice). Signal itself does not offer anonymous registration.

Who Should (and Shouldn’t) Use Signal

Signal is the right choice if you are:

• An individual who wants private messaging without technical complexity

• A journalist, activist, or researcher communicating with sources

• Someone concerned about data collection by platforms like Meta or Google

• A small team that needs secure, ad-free communication

• A government official conducting non-classified internal communications

Signal is not the right choice if you need:

• Legal compliance or message archiving (FOIA, financial recordkeeping, eDiscovery)

• Discussion of classified or sensitive government/military information

• Enterprise features: admin controls, integrations, SSO, compliance dashboards

• A platform your entire user base already uses (Signal’s adoption is much lower than WhatsApp or iMessage)

• On-premises deployment for data sovereignty in regulated industries

The Bottom Line. Is Signal right for you?

Signal stands out from other communication applications due to its wide range of features and reliable user data protection system. The main goal of the solution is to create a safe space for people to discuss any topic and share necessary files.

Thus, Signal will appeal to those users who want to communicate freely while feeling completely secure from any invasions of their personal data.

However, this solution is not suitable for businesses due to security-related restrictions. If you are looking for a solution for corporate interaction, then it is much better to turn to TrueConf.