Why might your private messages not be private enough? Understand end-to-end encryption (E2EE)

Introduction: Who has seen your message?

Every time you send a message using your phone, you might think this is a private conversation between you and your friends. But the reality is that messages are stored and forwarded through central servers. The operators of these servers can see everything about you – your content, the time, your contacts. This is why end-to-end encryption (E2EE) is becoming an essential tool for privacy protection.

The Truth About Unencrypted Messages: The Server is the Middleman

Imagine how traditional messaging applications work. You open the app, create an account, write a message, and hit send. The message first flies to the server, which then forwards it to your friend. Throughout this process, the server sees everything clearly.

Although the message is encrypted during the process from your mobile phone to the server (using technologies such as TLS), once it reaches the server, the administrator can read it directly. It's like a letter that, although sealed during the mailing process, can still be opened and viewed by postal workers.

Massive data breach incidents have repeatedly proven the reality of this risk – compromised servers mean the exposure of information for hundreds of millions of users.

What is E2EE? Only the sender and receiver can see the messages.

End-to-end encryption changes the game. It ensures that messages are encrypted from the moment they are sent, and only the recipient can decrypt them with their own key. Even if the server is hacked, all the hacker sees is indecipherable gibberish.

Applications like WhatsApp, Signal, and Google Duo all use E2EE. When you chat with your friends, encryption and decryption happen entirely on your respective devices. Without the keys, no one – including app developers, governments, or hackers – can eavesdrop.

How Does It Work? The Secret of Key Exchange

The core of E2EE lies in a technique called key exchange, with the Diffie-Hellman algorithm being the most critical. This cryptographic technique allows two parties to establish a shared key that only they know in an insecure environment.

Understanding key exchange through paint

Cryptographers came up with a nice analogy. Suppose Alice and Bob are in rooms at opposite ends of a corridor, with many spies in between.

First, they openly discussed using yellow paint. Each took half back to their room.

Next, they each secretly added their own secret colors - Alice added blue, and Bob added red. The spies could not see this step.

Then they exchanged their mixtures (blue-yellow and red-yellow) in the corridor. Even if the spy saw it, he could not deduce the secret color.

In the end, Alice took Bob's mixture and added her own blue, while Bob took Alice's mixture and added his own red. Amazingly, the final colors they both obtained were exactly the same – and the spy could never replicate this color.

Real mathematical operations are much more complex than pigments, but the principles are the same. This is how end-to-end encryption establishes secret connections over public channels.

The True Value of E2EE: It's Not Just About Hiding

Many people mistakenly believe that E2EE is only useful for criminals and whistleblowers. In fact, ordinary people need it even more.

Personal Privacy Protection: Even technology giants like Apple and Google have been hacked. If the applications you rely on use E2EE, the data stolen by hackers is just gibberish, completely useless.

Prevent Data Abuse: Without E2EE, app providers can analyze your message content, search your habits, and extract your location information for advertising. E2EE completely cuts off this route.

Prevent Targeted Surveillance: Political dissidents, journalists, and lawyers benefit from E2EE due to their need for privacy.

The Flaws of E2EE: Even Perfect Armor Has Cracks

Although E2EE is powerful, it is not万能.

Endpoints still pose a risk: Messages will be displayed in plaintext on your device before and after encryption. If your phone is stolen or infected with malware, messages will still be exposed.

Man-in-the-Middle Attack: If you cannot confirm the identity of the other party during key exchange, an attacker may impersonate a friend and establish a connection with you, allowing them to eavesdrop on all messages. Many applications have therefore added a security code feature – you can verify a string of numbers through offline channels (such as face-to-face) to ensure that no one is tampering with it.

Political Dilemma: Some politicians oppose E2EE, believing it hinders law enforcement. However, once backdoors are opened for the government, criminals will also exploit this vulnerability. This is a dilemma that cannot be perfectly balanced.

Summary: E2EE is your privacy shield

In addition to the aforementioned applications, an increasing number of free E2EE tools have emerged. iMessage, Google Duo, Telegram, and Signal all provide this protection.

End-to-end encryption is not a magic solution against all online threats. However, when combined with tools like VPNs and Tor, it can significantly reduce your risk of online exposure with almost no effort. In the arsenal of digital privacy, E2EE has become an indispensable part.