[prmoustache]

I am still waiting for someone to explain me why you can forward medias (image or videos) in whatsapp to new recipients without uploading it again completely if those images and videos are encrypted with the public keys of your recipients.

Since the forward is instantaneous and not involve a reupload, it looks to me the files are cached on the servers. If the recipient can see thee files and they are encrypted, it means that the server itself encrypted it using their public cryptographic key. If the server can do that, it means it either: - can decrypt your own files - cache them unencrypted

Correct me if I am wrong.

It is easy to test by sending a large video recording over a crappy connection, then forwarding it to another recipient. First upload can literally take a minute or more, the second action is immediate.

[bryan_w]

Consider the following:

You encrypt and upload the media to the storage server.

You share the download URL and key with person #1

Now how long would it take to forward that same message with the url and key to person #2...n?

[prmoustache]

Are you saying they would be using symmetric encryption?

[bryan_w]

Not necessarily, sender generates a private key for the piece of media, and shares the public key for that media item along with the download location to person 1&2 over their encrypted chat channels.