Why Crypto Backdoors Wouldn't Work

An anonymous reader writes: Your devices should come with a government backdoor. That's according to the heads of the FBI, NSA, and DHS. There are many objections, especially that backdoors add massive security risks.

Would backdoors even be effective, though? In a new writeup, a prominent Stanford security researcher argues that crypto backdoors "will not work." Walking step-by-step through a hypothetical backdoored Android, he argues that "in order to make secure apps just slightly more difficult for criminals to obtain, and just slightly less worthwhile for developers, the government would have to go to extraordinary lengths. In an arms race between cryptographic backdoors and secure apps, the United States would inevitably lose."

Comments

It's about more than that

[monkeyzoo]

Reading the article, it's very intersting. His argument is that you CAN'T backdoor a platform. Summarizing:
1) Say Android rolls over and backdoors the encrypted filesystem.
2) 3rd party apps can use the cryptography library, so Google would also have to backdoor that.
3) Then apps could use a 3rd party crypto library, so gov't would have to compel google to monitor for at least respond to takedown requests for strong crypto 3rd party apps.
4) But apps can easily download and incorporate new code, so Google would have to audit running apps with static and dynamic analysis.
5) Even then, people could use other app stores or sideloads, so Google would have to have an app kill switch option. This would be HUGE INTRUSION and delete apps from people's phones (even innocent people).
6) But how to identify apps? Sideloaded apps could generate a new appID with each download, so Google would have to scan for app characteristics (think antivirus software here).
7) Even if the above worked, browser-based apps could be built that use secure data stores or end-to-end messaging. This would mean the gov't would have to block these web apps, i.e., Internet censorship.

It's just not technically feasible if there is any respect for liberty, not to mention the significant technical challenges involved.

Re:It's about more than that

[johanw]

" a privacy-respecting nation such as Netherlands"

Ouch... You don't live in The Netherlands, do you? We have, like most western countries, our share of privacy attacks from the government. Mostly to satisfy the tax service, like storing all license plates of cars who drive on the highways or park in a private parking garage (to catch drivers of a leasecar who claim they use it only for business and don't pay the extra income tax). And there is discussion about forcing people to give up their encryption keys if the police wants them, ignoring laws that you have the right to remain silent (except when...).

Re:The author forgot one other option.

[pushing-robot]

They could do that, but it wouldn't be a backdoor.

Re:The author forgot one other option.

[Nonesuch]

I just read the entire article and the author forgot one other solution: the British solution Instead of putting the burden on app developers to include backdoors, or on Google to block apps that don't, put the burden on end users to turn over their keys to police when asked. I'm not saying I like this solution, but it is a solution the author of the article didn't consider. If you make the sentence for non-cooperation long enough, it doesn't really matter if the police find what they're looking for: they can just lock you up for not handing over the keys.

In the USA, this would likely require a constitutional amendment, it is widely held that the Fifth Amendment "Right Against Self-Incrimination" protects the right not to divulge an encryption key.

Re:The author forgot one other option.

[dcollins117]

In the USA, this would likely require a constitutional amendment...

... and a government that recognizes constitutional authority and the limits it places on government actions. First things, first.

Re:The author forgot one other option.

[BitterOak]

In the USA, this would likely require a constitutional amendment, it is widely held that the Fifth Amendment "Right Against Self-Incrimination" protects the right not to divulge an encryption key.

If you had read the article you link to (and I just did) you'd see that it does not conclude the same thing you do. Instead the article points out that it is far from a settled question on whether or not a defendant or suspect can be compelled to decrypt files. The Supreme Court has yet to deal with that issue directly, and the Circuit Courts of Appeal that have considered the issue have adopted a standard in which the government must first show they know the location and existence of encrypted data. If they've seized a suspect's phone, they certainly can know these two things, so the Fifth Amendment, under that analysis, would offer no real protection.