What is end-to-end encryption?

1. The short answer

2. How end-to-end encryption works

End-to-end encryption is built on public-key cryptography. Every device creates a pair of mathematically linked keys:

• A public key, which can be shared with anyone. Think of it as an open padlock you hand out freely.
• A private key, which never leaves the device. It is the only key that opens that padlock.

Sending a message then goes like this:

1. When your friend signs up, their app creates a key pair and uploads only the public half to a key directory on the server.
2. When you message them, your app fetches their public key and uses it to agree a shared secret with their device. Nobody watching can work that secret out.
3. Your phone encrypts the message with a key derived from that secret and sends it. The server only ever sees ciphertext, which looks like random bytes.
4. Your friend's phone uses its private key to derive the same secret and decrypt the message. No other device holds a key that can.

The server's job shrinks to two things: publishing public keys, and passing along sealed envelopes it can't open.

3. End-to-end vs. "encrypted in transit"

"Encrypted" in an app's marketing can mean two very different things. Encryption in transit (TLS, the padlock in your browser) protects data on its way to a company's servers, and the company decrypts it on arrival. End-to-end encryption means the company never can.

The question worth asking of any app: could the company read my messages if it wanted to, or was ordered to? With end-to-end encryption, the answer is no.

4. The Signal protocol, briefly

The Signal protocol is the most widely used end-to-end encryption design for messaging. It was created for the Signal app, WhatsApp uses it too, and it is what YumeBee uses. It combines two pieces:

• X3DH (Extended Triple Diffie-Hellman) lets you start an encrypted conversation with someone even while their phone is offline. Their device publishes an identity key, a signed prekey and a batch of one-time prekeys in advance, and your device combines them with its own keys to derive a shared secret.
• The Double Ratchet keeps the keys changing after the first message. Every message is encrypted with a fresh key, and old keys are deleted. That gives two guarantees:
  • Forward secrecy: a key stolen today can't decrypt messages from the past.
  • Post-compromise security: once the ratchet turns, a stolen key stops working for future messages too.

5. How YumeBee uses end-to-end encryption

YumeBee is a private chat app for iPhone and Android. Its server acts as a public-key directory and a delivery service: it stores public keys, hands out one-time prekeys so friends can start sessions with you, and relays encrypted envelopes. It never receives your private keys and has no way to decrypt your messages.

Photos and videos

Before a photo or video is uploaded, your phone generates a fresh random key just for that file, encrypts the file with AES-GCM and uploads only the ciphertext. The key travels inside the end-to-end encrypted message, so only the recipient can open the file. The encrypted file is deleted from storage after 24 hours.

Group chats

YumeBee encrypts group messages pairwise: your phone encrypts a separate copy for each member, using your one-to-one session with that person. The server relays the copies but never gets a key that opens any of them. Groups hold 2 to 20 people.

One phone per account

Your private keys exist on exactly one phone. Signing in on a new phone creates a brand-new set of keys and revokes the old device's keys and connection, and your friends' apps are told to set up fresh sessions with you. There is no key backup, so messages sent before the switch can't be decrypted on the new phone. That's deliberate.

Every detail, including what notifications reveal, is in the usage guide and the privacy policy.

6. What end-to-end encryption doesn't protect

E2EE is the strongest protection a messaging app can offer, but it isn't magic. Its limits:

• Metadata. It hides what you say, not that you're talking. A server has to know where to deliver a message, so YumeBee's servers, like any messaging service's, can see who is chatting with whom and roughly when.
• The devices at either end. Once a message is decrypted, it can be read on the phone that decrypted it. An unlocked phone in someone else's hands, or spyware, gets past any encryption. Use a screen lock and keep your software updated.
• The person you're talking to. Encryption can't stop a recipient from showing their screen to someone else or photographing it with another phone.
• Trust in the key directory. The server hands out public keys, so a malicious server could in theory hand out a fake one. That's why E2EE apps watch for a contact's identity key changing, and why comparing keys in person (often called safety numbers) is the strongest check.
• Backups. On many apps, a cloud backup of your chats sits outside end-to-end encryption unless you turn on encrypted backup. YumeBee has no chat backup at all, so there is nothing there to leak.

7. Why disappearing messages matter too

Encryption protects a message on its way and on the server. It doesn't protect years of chat history sitting on a phone. Disappearing messages close that gap: the less history exists, the less there is to lose if a phone is lost, stolen, seized or hacked.

On YumeBee, every message, photo, video and voice message disappears 24 hours after it's sent, read or not. It isn't a setting you have to remember to turn on. Forward secrecy means the keys that could have decrypted those messages are gone as well.

8. How to tell if a chat app is really end-to-end encrypted

• Is it on by default? Some apps only use end-to-end encryption in a special mode, such as Telegram's Secret Chats. Defaults matter because most people never change settings.
• Does it cover group chats? Some apps encrypt one-to-one chats end to end but not groups. Telegram's groups, for example, are not end-to-end encrypted.
• Which protocol does it use? Look for a published, well-studied design such as the Signal protocol.
• What happens to backups? Find out whether chat backups are end-to-end encrypted, optional, or don't exist.
• Does it say what isn't encrypted? An honest app lists the gaps: metadata, notifications, anything the server can read.
• Where do the private keys live? They should be created on your device and never leave it.

For how YumeBee, WhatsApp, Signal, Telegram and Snapchat compare on these points, see the side-by-side comparison.

9. FAQ

What is end-to-end encryption?

End-to-end encryption (E2EE) is a way of sending messages so that only the sender and the intended recipient can read them. The message is encrypted on the sender's device and can only be decrypted on the recipient's device, so networks, internet providers and the messaging company's own servers only ever handle scrambled data they have no key for.

Can the app company read end-to-end encrypted messages?

No. The private keys that decrypt messages are created and kept on users' phones, so the company's servers only ever hold ciphertext. The company can still see metadata, such as who is messaging whom and when. YumeBee, for example, cannot read your messages, photos or videos.

Is WhatsApp end-to-end encrypted?

Yes. Personal messages and calls on WhatsApp are end-to-end encrypted by default using the Signal protocol. Chat backups to Google Drive or iCloud are only end-to-end encrypted if you turn on WhatsApp's end-to-end encrypted backup.

Is Telegram end-to-end encrypted?

Only in Secret Chats, which are one-to-one and have to be started deliberately. Telegram's default cloud chats and all of its group chats are encrypted between your device and Telegram's servers, not end-to-end.

Can end-to-end encryption be hacked?

Well-designed protocols such as the Signal protocol have no known practical break. Real-world attacks go after the ends instead: phishing, spyware, or someone with access to an unlocked phone. A screen lock and up-to-date software matter as much as the encryption.

Does end-to-end encryption hide who I'm talking to?

No. It hides what you say, not that you're talking. A messaging server still needs to know where to deliver each message, so it can see who is chatting with whom and roughly when.

Is YumeBee end-to-end encrypted?

Yes. YumeBee uses the Signal protocol to end-to-end encrypt messages, photos, videos, voice messages, custom stickers and emoji reactions, in one-to-one and group chats. Typing indicators, read receipts, online status and watch cards are not end-to-end encrypted. Every message also disappears 24 hours after it's sent.

Can I get my YumeBee messages back on a new phone?

No. YumeBee has no chat history or backup, and a new phone gets brand-new encryption keys, so messages sent before you switched can't be decrypted on it. A new phone only sees messages sent after it's set up.