Encrypted vs. Secure
Many apps say they use encryption. That sounds safe. But encryption only protects the content of your message. It does not hide who you talk to, when, or how often. That information is called metadata.
Nobody knows you sent a message at all.
They cannot read the message, but they know you sent one.
Think of encryption like a locked box. The box hides what is inside. But everyone can still see you carrying a box, where you take it, and how heavy it is.
Nobody can see who your contacts are.
Your contact list is stored on a server.
Most encrypted apps still upload your phone contacts to their servers. They know your social network even if they cannot read your messages.
Nobody can see patterns in your communication.
Patterns reveal your habits and relationships.
If you message someone every night at 10pm, that pattern tells a story. Encryption hides the words, but not the pattern.
No phone number needed to use the app.
Your phone number links all your accounts.
Your phone number is tied to your real identity. Even encrypted apps that require a phone number can be linked back to you.
The bottom line: Encryption is necessary but not sufficient. True privacy also hides who you talk to and when.