Example: upload a few minutes long video to a whatsapp contact, depending on your phone connection it can take up to a few minutes. Then forward it to other contacts or group and it is done instantaneously. For the videos and images to be sent and retrieved instantaneously by my contacts when forwarded while I am using a crappy connection it means they are retrieved from some whatsapp servers which means there is at least some kind of man in the middle proxy-cache stuff involved.
I certainly cannot do the same on other apps I have used doing e2e encryption. On deltachat, atox, jami I have to send back again the data. While inconvenient when using a bad connection I am willing to get the tradeoff to have no mitm on any server. Anyone can share if there is a similar forwarding function on Signal?
For example: Alice wants to send Bob and Claire a encrypted video. Alice encrypts it with a random key and uploads that video to FB's servers, at that moment (given the understanding that encryption is still uncrackable without throwing billions of cores at the problem) only Alice can decrypt that video hosted on those servers.
Alice then takes the link and the key and encrypts that message with Bob's public key and again with Claires public key, Alice then sends the messages to Bob and Claire (Ideally Alice and Bob / Alice and Claire would use a key exchange algorithm to create a ephemeral session key which would then be used to encrypt the key for the video). The message containing the key being sent to Bob and Claire is a lot smaller than the video itself, so it can be sent alot quicker/reliably over the crappy connection. It also removes the need to send the large file to each of the receptants (data transmitted = size of video * number of receptants) as you only need upload it once.
Bob and Claire can now each decrypt the message they got from Alice, get the link and the key, download the video, decrypt the video and play it. To whoever it was caching the video data, its just random data.
If throwing processing time at the problem is the attack vector then you can "just" listen in and record the wire as the data is being transmitted even if its a P2P conenction because its very likely that the data you are transmitting is going to get passed along some hops on its way to the receptant no matter which platform you use. If the attack vector is the messaging platform adding their own keys to the encrypted files, then they are in a position where everything is busted wide open anyways so it comes down to trust of that platform.
I'm not saying FB/WhatsApp are trustworty or not. I personally don't like using their services but people I know IRL do use their services which means if I want to take part in those converstations then I have to too.
EDIT: HOWEVER (this thought only popped in my head after hitting post) this does lead to some information leakage, Even though the message platform can not decode the video, they would be in a position to know if Bob or Claire accessed the video if they also control the caching platform used.
Forwarding media works because it’s just a small blob with a url to the encrypted file and the decryption key.
These things are super well understood, hundreds of independent parties have studied how whatsapp works.
see for example: https://github.com/ddz/whatsapp-media-decrypt
See other comments on how forwarding works.
Technically it's possible that: my client encrypts the file with locally generated key A and uploads it to WhatsApp's server. The server returns a URL. My client takes key A, and sends it to Bob along with the URL, and this message is encrypted with Bob's public key.
When I want to send the same file to Charlie, or Bob wants to send it to Dominic, my or Bob's client just needs the URL, and the key A...
On a tangential note, I find it super cringeworthy how quickly people fell for Facebook‘s rebranding and stopped calling it Facebook.
For me it’s Facebook with all it‘s negative connotations, not Meta.
On HN, there is one comment, and it does question if it's true. GOOD!
I am curious if it's real or not. My bet is it's not. It's easy to screw up some downloading logic with overflows, one-off errors etc, but since WA is E2E encrypted, it would need a lot more "accident" in code to make this possible.
https://old.reddit.com/r/NoStupidQuestions/comments/ry0cnr/d...
https://web.archive.org/web/20220107101132/https://old.reddi...
Edit: The thread has now been deleted, so both reddit threads about this issue are deleted.
TL; DR: photos were from a loaner phone that was never wiped that OP backed up, and then restored onto his new phone.
There are operators recycling numbers after less than a year of inactivity/zero balance on pre paid SIMs.
OP followed up with:
>I actually realized what happened and I didn't want to keep it up and misinform other users or cause more damage to Google or Whatsapp.
>So what happened is I actually used a temporary phone given to me by a repair service prior to buying this phone, due to mine being repaired by said service. The service was handing that phone to anyone who needed one while their phone was in service, like I did and thus was used by dozens of people in the past years, and so had thousands of photos on it. When I used it, whatsapp backed all that data into my drive. So... When I bought a new phone, and restored the backup to it, what essentially happened was all that data from the service phone was transfered onto the new one. That's how I ended up with loads of random people's data.
>So in fact the fault was the fact that the service wasn't deleting data on the phone before handing it over to other clients.
Then, it autodownloads all the data, keep chatting with their contacts, and everything you would normally do when you migrate an existing account to a new phone.
I fathom this is responsibility of the telcos that reuse the numbers, but it seems is already an established practice and apparently there is no procedure to disclose to most common services that the number is dead.
I thought something like that was going on, and even more reasons to move on from SMS/phone auth.
I've actually bought a new phone once and it had someone's list of phone numbers. It still looked pretty new, so I guess someone bought it, used it for a week or two and returned it. I was just annoyed at the scummy seller...
The thread was deleted by the OP, not removed by moderators (reddit visibly differentiates between the two)
TL;DR: he's an idiot.
A bit longer: OP went to a shop to get his phone repaired. Shop gave him a loaner phone, which had been used by many many people and apparently never wiped. OP set up Google backup on that phone and those photos got uploaded onto his WhatsApp backup. OP got a new phone, set up WhatsApp, and WhatsApp downloaded the pics from the loaner phone onto his.
