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Comment by gojomo | Hacker News Reader

Unaddressed: that the reliance on Intel SGX for MobileCoin's consensus-system gives Intel a kill-switch for the network.

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Signal's increasing reliance on SGX is the elephant in the room. They keep announcing new features that require sending your cryptographic keys to someone else's "super trustworthy" computer.

What alternative do you suggest?

Not developing features that pretend secure remote computation is a real thing.

You don't think the sealed sender feature is an improvement at all?

Nobody relies on it. But if we can make an attack 10 times more expensive (because we can't prevent it completely), why not do it?

Secure remote computation is better than nothing. I'd start having problem with it when people rely on it when there are better solutions, but that hasn't been the case so far, AFAICT.

I think this point is too technical to be addressed in this blog post, and it's already addressed in technical documents / talks from MobileCoin. In short, and IIUC, no Intel SGX means a bit less privacy but is still ok. In particular, it's not a kill-switch. Happy to be corrected though, I still know little about MobileCoin.

It's true an SGX compromise means most of the MobileCoin privacy goals are still met. But dsome compromises would open up new methods of traffic analysis, and the SGX-dependency still makes the consensus process dependent on Intel's trustworthy key-management.

If I understand correctly, Intel could (if compromised or untrustworthy):

* revoke any node's SGX keys - knocking any number of consensus nodes out at zero cost * create false attestations of what code was run (which would presumably be detectd eventually) * dominate the consensus mechanism with its hand-picked SGX nodes

Among other things, this means Intel could turn off the MobileCoin chain, if commanded to do so.

(I could be somewhat off on some of this – if so, corrections with explanations very welcome.)

So, if your threat model is "Intel Inc is always trustworthy & secure", Signal & MobileCoin are wonderful. If you have doubts about Intel's trustworthiness/security, the designed privacy properties start to degrade.

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