What is End-to-End Encryption (E2EE) and why does it matter?

What is End-to-End Encryption (E2EE)? End-to-End Encryption (E2EE) is a technology that allows a conversation to stay private. E2EE ensures only the sender and the recipient can read a message (or data transfer). This ensures robust data privacy and creates data security by design.

Encryption hides information so outsiders cannot read it. Symmetric Encryption uses the same secret on both ends. Asymmetric Encryption pairs a public key with a private key for added ease of use and relies on hard math to provide strong, long-term security. We’ll explain these technologies in more detail, including how key exchange and digital signatures prove that keys are valid and untampered.

Messaging apps and RCS Chats sometimes support E2EE to prevent data interception by hackers or government snoops (depends on the app). TLS (Transport Layer Security) offers encryption for data in transit between a client and a server; however, it is not the same as full E2EE, which provides peer-to-peer encryption between two clients. This guide explains the differences and how E2EE defends against Man-in-the-Middle (MITM) attacks and helps reduce metadata surveillance.

E2EE helps protect against server compromise and improves resistance to data breaches. However, you must combine it with encryption at rest, E2EE for backups, and solid endpoint security (or robust device-level security) to ensure complete protection against cyberattacks.

Keep reading to learn how E2EE works, what it stops, and how to pick services that actually protect your data.

What is End-to-End Encryption (E2EE)?

End-to-End Encryption (E2EE) is a security method for transferring data that locks a message (or file) on your device, so only the intended recipient can open it. In other words, the message (or data) is scrambled before it leaves your phone or computer, and remains undecipherable until it arrives on the recipient’s device and is unlocked with a private key that nobody else has.

This allows E2EE to protect your data privacy using a method that security experts call data security by design. The important thing to remember is that E2EE is not some kind of magic, and it is not a silver bullet that suddenly makes everything safe and private.

Instead, E2EE is just one part of the digital security jigsaw puzzle. It must be paired with other OpSec practices such as encryption at rest, secure backups, and solid Endpoint Security to be effective. Beware services that accept Backdoors in Encryption. Pick audited E2EE in trusted Messaging Apps or RCS Chats, verify keys, and you’ll have the strongest practical defence for private conversations.

How End-to-End Encryption works

The mathematics involved in reliable encryption (cryptography) is extremely technical and advanced. Understanding and implementing this type of cryptography (as well as assessing whether E2EE has been implemented properly) requires specialist expertise, which is why security auditors are sparse and highly paid.

Thankfully, anybody can understand the basics of what is happening when they use E2EE. Under the hood, E2EE uses one of two approaches to provide tamper-proof security:

1. Symmetric Encryption uses one shared secret for speed. In modern systems, that secret is usually negotiated securely at the start of a session. Sharing a secret in person avoids the risk of interception, because if the secret is stolen, it would destroy the security of E2EE by giving a third party the ability to unlock messages.
2. Asymmetric Encryption uses a Public Key and a Private Key pair for key management and ease of use. This system enables people to secure messages with E2EE without the need to share a secret, making it more practical for online environments where two parties cannot easily meet to exchange a secret.

With either of these methods, key exchange security and digital signatures allow both sides to identify each other and spot any tampering. The math behind these exchange and authentication methods is extremely difficult to crack (either old-school prime-number systems or newer elliptic-curve techniques such as elliptic-curve Diffie–Hellman (ECDH) key exchange).

Important note: These techniques are not necessarily impossible to crack, but are considered “future-proof” because they would take an extremely long time (possibly hundreds, if not thousands of years) to crack open using current technologies. (Though this could change due to emerging tech such as quantum computing.)

What are the four steps of E2EE?

Now that you know the basics of how E2EE works, we break E2EE down into four simple stages below. Understanding each stage will give you a deeper appreciation of how this technology works to protect your messages or file transfers. Each step is an indispensable playbook that keeps your communications private from A to B.

1. Encryption: Lock it on your device

E2EE scrambles the message before it leaves your device. Usually, that means a fast symmetric cipher for the message itself, and an asymmetric step to manage keys. The result? The payload (message, file, or folder) is unreadable by anyone who intercepts it.

2. Transmission: Send the locked message or file

The scrambled message travels across the network. TLS can protect the connection hop-by-hop, but the important bit is that the payload remains encrypted end-to-end. Even if a server or router sees the packet, it can’t open your locked message. Header data, such as the destination IP address, is left unencrypted to allow your message to be routed to the intended recipient. This is why we always recommend using a VPN to add an extra layer of privacy.

A VPN hides the destination IP from your ISP and local eavesdroppers. The VPN provider will still be able to see the destination, so use a trusted provider with a strict no-logs policy.

3. Authentication: Prove who you’re talking to

This is the system’s identity safety check. Key exchange (ECDH or similar) and digital signatures are used to verify the sender’s and recipient’s identities, which enables the system to proceed to the next step (decryption).

Modern protocols use authenticated encryption (AEAD), so integrity checks run during decryption, and the message is rejected if authentication fails, which is how E2EE prevents MITM attacks and tampering.

4. Decryption: only the recipient opens it

Only the recipient’s private key (or a session key derived via a secure key exchange such as ECDH) can unlock the message. If keys are handled correctly, no intermediary, not even the messaging service provider, will be able to read message contents.

Why are backdoors for E2EE dangerous?

Because E2EE works so well, police and intelligence agencies often argue they need an encryption backdoor for national security. Their claim is pretty straightforward: if they can’t read every message, they can’t stop criminals. The good news? It proves the tech is working, as police can’t read messages even when they want to.

To get that power, you’d need a skeleton key – a master key or key-escrow system that lets an authorised middleman unlock any encrypted message. It might sound feasible on paper, but it breaks the entire point of E2EE because the channel is no longer secure only between the sender and recipient.

That skeleton key (backdoor) can be stolen, leaked, or shared, which means that hackers, foreign governments, or rogue insiders (like crooked officials) might get hold of the backdoor to access everyone’s messages and files. The extra key becomes a single point of failure that breaks E2EE.

Client-side scanning or “targeted” access may sound safer, but it widens the attack surface, and attackers can abuse or misapply it. In other words, they aren’t secure.

Ultimately, there’s no way to have your cake and eat it. You either secure data properly, or you build backdoors that trade “legitimate” access for long-term insecurity. If we accept backdoors, we also accept that messages, passwords, files, or biometrics will eventually be stolen or misused.

That’s why Signal, WhatsApp, and other secure messaging services have pushed back against backdoors. They know attackers will eventually steal a skeleton key, and that theft would trigger a massive hacking incident that compromises everyone’s data and creates chaos.

What is the difference between TLS and E2EE?

TLS (Transport Layer Security) protects data in transit by encrypting it between a client and a server. TLS is the type of encryption used to secure the data that travels from your device to a website: HTTPS.

You can tell TLS is active from the padlock in your browser’s address bar. It prevents most on-network observers from reading what you send to a website or service, though some connection metadata (like the site name/SNI and IP address) remains visible.

However, TLS stops protecting your data at the server, which means the website or service operator can still see the decrypted data. That’s no good if you want your data to stay private until it reaches your intended recipient.

E2EE is different. It encrypts on the sender’s device and only decrypts on the recipient’s device; the server never holds any vulnerable plaintext data. That’s why E2EE is the gold standard for communication privacy and security! It blocks Man-in-the-Middle attacks, reduces metadata vulnerability, and limits what an attacker can access, even if they breach a server.

How to choose an E2EE service

E2EE is not a standalone product you buy once and use everywhere. It’s a feature built into a service or app. Messaging apps, email providers, file-sharing tools and cloud backup systems each implement E2EE (or not) in their own way. So when we say “choose an E2EE service,” we mean choose a service or app that implements genuine, usable end-to-end encryption.

How do you pick a reliable provider? Start with services that advertise E2EE as a core feature. Also, stick to services that have completed a full, recent security audit so you can be confident their E2EE claims are genuine and implemented securely. Errors can create a false feeling of security.

What to look for when choosing a service provider:

1. E2EE by default: We look for services that enable E2EE automatically. If users must opt in, most won’t, which means that they don’t actually get the protection they need.
2. Third-party audits and transparency:  Look for recent, public security audits and transparency reports. Open-source clients are a big plus because researchers can inspect the code.
3. Key handling and easy verification: Good services let you verify public-key fingerprints and warn about changed keys. Clear key management reduces MITM risk.
4. Backup policy: E2EE is only effective if it also applies to backups and stored data. Avoid services that decrypt on the server for backups. Prefer client-side, zero-knowledge backups or password-protected exports.
5. Group chats and multi-device behavior: Check how group encryption and cross-device sync work. Some providers trade security for convenience here; read the docs.
6. Metadata, logging, and minimisation: E2EE won’t hide metadata. Check what metadata the provider collects and whether they keep logs. Less is better.
7. Jurisdiction and legal exposure: Where the company is incorporated affects legal risk. Prefer companies with strong legal protections and a record of pushing back on broad data requests.
8. Endpoint guidance and recovery options: E2EE depends on your devices. The provider should give clear advice on endpoint security, PINs, and safe recovery options that don’t defeat E2EE. True zero-knowledge setups usually mean the provider can’t offer server-side recovery, so account recovery and content access are the end user’s responsibility.
9. Bug bounties and compliance: We prefer services that offer a public bug bounty program. This encourages individuals to search for vulnerabilities and helps the company keep users secure by spotting zero-day vulnerabilities sooner. A trustworthy service will also be GDPR, HIPAA, and CMMC compliant (as well as compliant with any other emerging privacy and security regulations) with an active security program on hand to keep improving the service as necessary.

How to set up an E2EE service

The setup process will depend on the service you are using and what it is for. For this reason, we generally recommend that you follow a specific setup guide for the encrypted service you intend to use. That said, we have provided a basic outline of the steps you will need below, as a general guide.

1. Install the app and check that you have the latest version. If you have already been using it for some time, ensure it is up-to-date.
2. Check whether E2EE is built-in or optional. Native, permanent E2EE is ideal because you can just install and keep the app updated. If E2EE is optional, enable it in settings before you start sending sensitive data.
3. Be sure to enable E2EE for chats, calls, backups, and anything else that is available for the specific service you use: you want encryption at all stages.
4. Check that your operating system is up to date. Hackers can exploit vulnerabilities in your operating system to infect your device with malware or use other attack vectors to steal data before the app encrypts it. This is why it is essential to keep your device’s operating system fully patched.
5. Verify fingerprints. Compare the chat’s safety number (or scan the QR code) and verify that it matches the person you’re talking to. This ensures that your message truly travels to your intended recipient.
6. Configure backups. If the service stores data on company servers, confirm it encrypts backups client-side, in transit and at rest, using keys you control. If not, disable cloud backups or switch to a provider that offers zero-knowledge backups.
7. Secure endpoints: E2EE can only work if the devices owned by both parties are secure. Make sure both users follow basic security practices: use a strong device passcode, enable screen lock and device encryption, use a robust password and two-factor auth for the app, and run anti-malware where relevant. Enable app-level protections (PIN or biometrics) and disable message previews on the lock screen to improve privacy.
8. Multi-device and group-chat checks: If you use group chat or cross-device sync, check the docs to confirm these features use E2EE. Some providers weaken encryption for convenience: know the trade-offs before you enable sync.
9. Recovery and account options: True zero-knowledge apps usually can’t recover your data for you. Keep the recovery code or passphrase the service gives you offline or in a secure password manager – you control it, and no one else should have access. If you lose it, the provider generally can’t help.
10. Test it: send a test message or file, verify the fingerprint or QR code, and confirm the recipient can decrypt it. Check that backups behave the way you expect.

Do I need a VPN in addition to E2EE?

When a service gives you E2EE, nobody sees the contents of your messages or files – that’s a huge win. However, there is one caveat. When you send messages or files, the network still needs packet header data, such as destination IP addresses. Routers use that header information to deliver your packets to the right place.

This is where a VPN can help. It adds another layer of privacy. A VPN wraps all your internet traffic in an encrypted tunnel and sends it to a VPN server first. As a result, your local network and ISP can only see that your traffic is headed to the VPN. This hides the real destination IP, making it much harder for data snoops and your ISP to know who you’re talking to.

The VPN provider still sees the destination because it has to forward your traffic to the recipient. If you choose a reputable VPN with a strict no-logs policy, the provider will not keep records of where your traffic is routed. VPNs vary, so for the best results, stick to one of our trusted recommendations.

Also note that E2EE and a VPN won’t help if one of the endpoints is compromised. Both you and your recipient must keep your devices patched and malware-free so hackers can’t steal your data directly from your phone or computer.

Does a VPN provide E2EE for data transfers?

No. E2EE means only the sender and the intended recipient can read the payload. A VPN only encrypts the path between you and the VPN server (end-to-VPN, not end-to-recipient). The VPN provider must forward the traffic and can see the destination IP, and may see more if it inspects your packets.

TLS (HTTPS) protects data to the server, whereas E2EE protects data all the way to the recipient. If you want true content confidentiality between people, you need E2EE. That means you should be using a service with E2EE to protect the payload, and a VPN to conceal who you are sending messages or files to – they work together to give you security and privacy.

What E2EE protects against and what it doesn’t

E2EE locks the actual content of your messages and files so only the sender and recipient can read them. It’s hugely effective, but it’s not a magic shield for everything. For complete transparency, here is what E2EE can and can’t do:

What E2EE protects against

• Reading by intermediaries: Networks, ISPs, servers, and email hosts can’t read the body of your messages or files.
• Server breaches: When implemented correctly, a hacked server still won’t offer hackers access to E2EE-encrypted messages.
• Man-in-the-Middle tampering: Proper key verification prevents MITM attacks.
• Provider snooping: If a provider does not hold your keys or recovery data and E2EE is implemented correctly, the provider should not be able to read your messages or files.
• Data theft in transit: Intercepting packets will never reveal plaintext – only packet header data such as the IP address (but you can use a VPN alongside E2EE to block this too).

What E2EE does not protect against

• Compromised endpoints: Malware on your phone or the recipient’s device lets attackers read messages before encryption or after decryption.
• Server-side backups that aren’t client-side encrypted: If the provider holds the backup keys, the provider can read your backups.
• Metadata and traffic analysis: Local networks, ISPs, and other eavesdroppers can still track who you talk to, when, how often, plus message sizes and IPs. Use a VPN to hide that metadata.
• Malicious insiders or coerced developers: Authorities or attackers can force vendors to push vulnerable updates or build backdoors.
• Client-side scanning or feature-based scanning that decrypts data for processing.
• Lost keys or user error: If you lose recovery secrets, you can permanently lose data. In addition, improper key handling can create a threat of unauthorized access.

Which messaging, email, and backup services offer E2EE?

Looking for a reliable E2EE service? We have included examples below for you to pick from.

Messaging apps

Email services

Cloud backups & storage

E2EE FAQs

Related:

• A guide to AES encryption
• A guide to IPsec encryption
• Encryption laws by country