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Comment by gfodor | Hacker News Reader

This is common and necessary for WebRTC SFUs, which perhaps is why Discord does it to support the least common denominator of their web browser based clients.

Edit: Yep, I thought I remembered reading this. Their voice servers are WebRTC SFUs. So this is basically state-of-the-art when it comes to voice over WebRTC. End to end encryption in WebRTC is not possible if you are using a SFU. https://blog.discordapp.com/how-discord-handles-two-and-half...

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End to end encryption in WebRTC is indeed possible even if you are using an SFU, this is achieved via Privacy Enhanced RTP Conferencing (PERC).

[1]. https://www.callstats.io/blog/2018/06/01/examining-srtp-doub...

No, it’s not, because PERC is a proposal and is not implemented in any browsers.

That does not mean it isn't possible; the implementation simply has not occurred.

> That does not mean it isn't possible; the implementation simply has not occurred.

You can say that about almost anything.

The question is: is it possible today where it has an impact today in actual browsers today.

Future technology does not matter when there is no implementation

That’s a pretty unique definition of “possible!”

You can just admit you googled it and didn’t realize it was not something you can do today in browsers, it’s ok :)

You must be new here ;)

Didn't know what an SFU was. https://webrtcglossary.com/sfu/

For convenience:

> SFU stands for Selective Forwarding Unit.

> At times, the term is used to describe a type of video routing device, while at other times it will be used to indicate the support of routing technology and not a specific device.

> An SFU is capable of receiving multiple media streams and then decide which of these media streams should be sent to which participants.

This transport mode is also publicly documented here: https://discordapp.com/developers/docs/topics/voice-connecti...

Why don't SFUs support end-to-end encryption? Is it just a missing feature in the WebRTC protocol or am I missing some fundamental reason?

Yes its simply missing in the WebRTC spec. webRTC defines end-to-end encryption between two peers. But if you want to transmit data to many peers you need a server which is doing the fanout so the encryption is client1<->server and server<->client2.

This is true for all WebRTC implementations/services. They all state having end-to-end encryption but dont tell you that it means something different in WebRTC contexts.

PERC will solve this one day, but its sadly just a draft: https://webrtcglossary.com/perc/

As I understand, Discord server doesn't need to do audio processing, all mixing is done on the clients. So it would benefit from the "one-to-many" encryption, because currently it has to decrypt from one p2p connection and to encrypt to several p2p connections when someone talks (which breaks the end-to-end).

Yes, that is what SFU is except there is apparently not support for one-to-many end-to-end encryption yet in the WebRTC protocol.

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