Is it necessary to encrypt chat messages before storing it into firebase?

Question

As far as I know, Firebase sends data over an HTTPS connection, so that the data is already being encrypted. Although Firebase provides security rules to protect my data structure, I can still be able to see the string messages in the database.

I'm just curious whether it is a good idea to encrypt messages before pushing the data to Firebase or not. Should I just move on from this topic to something else?

Thank you.

Solution 1

You seem to have a good grasp of how Firebase Database works: the data is encrypted in transit, and it is stored on encrypted disks on the servers. If you enable local persistence on the device, the on device data is not encrypted.

But administrators of the app can see the data in the Firebase console. If it is a requirement of your app that administrators can't read this data, then you'll need to encrypt it on the client before sending it to Firebase. A while ago a developer explained their end-to-end encrypted chat on the firebase-talk mailing list.

Solution 2

Hey Jeff: you're right that when you write some data into Firebase/Firestore, the data:

1. Is protected over the wire using HTTPS.
2. Then, when it lands on the Firebase REST frontend server, HTTPS terminates and the server has access to the full payload
3. Then the REST server routes the data to the backend/database, which also has access to the data.
4. When the data is written into disk, it's encrypted at-rest, but the at-rest encryption keys are also available to Google and your administrators will also see the Firestore contents

Encrypting data client side (End-to-End Encryption) prohibits all these participants/roles seeing your data.

Encrypting data on client side is fairly simple (compatibility across mobile platforms and browsers is tricky). The other tricky part is the key management to enable one user access to the decryption key without the other user sending the key over in an unsecure channel.

The way you can implement this is:

1. Create private & public keys for your users when you sign them up
2. Encrypt data on user1's device with user2's public key
3. Write the encrypted data into Firestore
4. When user2 reads up the encrypted data, her private key will be able to decrypt it.

Check out this Firebase E2EE chat sample on GitHub for iOS: https://github.com/VirgilSecurity/demo-firebase-ios and Android: https://github.com/VirgilSecurity/demo-firebase-android

HTH, David