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Here come the encryption apps

blog.cryptographyengineering.com

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Re: Here come the encryption apps

#41

Post by moxie »

loeg wrote: post #24
moxie wrote: post #5

I work on two of the apps Matthew reviews here (RedPhone and TextSecure). What I didn't expect when I started working on these types of projects is that the cryptography is the easy part. I'm really honored to hear that my code has the ability to make Matthew Green drool, but that ZRTP stack was a two or three day project three years ago, and hasn't changed much since. The bulk of the work over the intervening period…

moxie, I'm curious how the "short authentication string" prevents MITM attacks — can you shed some light on this or point me to existing documentation? Thanks!

The SAS section of the ZRTP RFC has all the details: https://tools.ietf.org/html/rfc6189#section-7

But the short answer is that part of the negotiated key material for the call is used to derive two words from the PGP word list, which are displayed to the user.

If the users then have a conversation about those words and they are the same, then chances are that they have the same key material. In the case of a MITM, they would have different key material, and thus different short authentication strings.

Re: Here come the encryption apps

#42

Post by frisco »

What is the realistic risk of a hardware backdoor in mainstream smartphones? I assume that there's nothing apps like these could do against those. Is that a risk even worth worrying about at this point? If it is, is there anything that can be done about it? It is safe to trust, say, Google or HTC and their manufacturing chain?

Further, if the handset is attacked and silently owned, all bets are off, too, right?

Re: Here come the encryption apps

#43

Post by loeg »

MichaelGG wrote: post #38
loeg wrote: post #28

Earlier quoted context omitted.

Does this assume that the voice channel can't be doctored? But couldn't a MITM attacker do just that — compute the "correct" fingerprint and speak it to the recipient?

Yes, it assumes an attacker cannot imitate the other person's voice without detection. If you introduce enough latency or have a system fast enough to do on-the-fly voice changing you'd be set. It's such a great, simple idea, I felt stupid for not having thought of it. To be sure, the voice channel establishes before the verbal authentication. I see your fingerprint is "banana", you see "kitchen". We can chat and I c…

Okay, cool. It sounds like this sort of attack is very difficult for now — but I would rather be aware of it than not.

It sounds like RedPhone doesn't actually save the keys yet — it's a work-in-progress. But that makes lots of sense.

Re: Here come the encryption apps

#44

Post by jsnell »

daxelrod wrote: post #31

A minor point of curiosity: one of the captions says "Using SilentCircle on a Huawei complete negates the point of using SilentCircle." I appreciate that it may be somewhat tongue in cheek, but is that a riff on the US accusing Huawei of being a national security threat[0], or do Huawei phones have a track record of known security vulnerabilities? [0] http://www.nytimes.com/2012/10/09/us/us-panel-calls-huawei-a...

Well, it's not just that one US incident, the level of paranoia regarding Huawei is much wider than that. For example IIRC the UK blocked a Huawei bid to provide cell phone service during the olympics. I'm not sure why exactly they have such a shitty reputation compared to other Chinese companies. For example, has anyone every said that running ssh on a ThinkPad completely negates the point? But the reputation is there, which is what makes it a decent joke.

(And yes, I chuckled at the image before reading the caption.)

Re: Here come the encryption apps

#45

Post by pknight »

SoftwareMaven wrote: post #35
moxie wrote: post #5

I work on two of the apps Matthew reviews here (RedPhone and TextSecure). What I didn't expect when I started working on these types of projects is that the cryptography is the easy part. I'm really honored to hear that my code has the ability to make Matthew Green drool, but that ZRTP stack was a two or three day project three years ago, and hasn't changed much since. The bulk of the work over the intervening period…

Having tried to build a secure messaging platform, I can't agree more that, for the average user, security is so far below the bottom of the list of important things as to not exist. Unfortunately, for those of us who do care, the removes the network effects that make secure software usable. It doesn't make how many calls or emails I encrypt if nobody I talk to can receive them. It is encouraging to hear people 1) un…

I don't think the average user feels it is at the bottom of the list, rather the average user trusts webservices for various reasons without realizing how much insecurity and lack of privacy results from using common webservices. I think that is slowly changing though.

Re: Here come the encryption apps

#46

Post by jacques_chester »

btipling wrote: post #29

> While Cryptocat is written in Javascript (aaggh!) Is there something inherently insecure about using JavaScript or is this not meant to actually be relevant?

If it's served from a webpage, then it's insecure.

Either the publishing server can replace it with a malicious version, or another server might inject javascript that modifies or replaces it with a malicious version.

This particular point hilariously broke a crypto protocol project of mine, so I guess I'm touchy about it.

Shipping as a browser module is more secure.

Re: Here come the encryption apps

#47

Post by matthewdgreen »

tptacek wrote: post #33
loeg wrote: post #27

Earlier quoted context omitted.

""" Overall code quality: Who knows Should I use this to fight my oppressive regime? Yes -- if your fight consists of sending dirty self-portraits to your fellow comrades-at-arms. Otherwise, probably not. """ Am I missing something?

His answer to "should I use this to fight my impressive regime" was the same for all the tools, just with different wording.

My answer to that question was the same everywhere, because I think you'd be crazy to use these tools to fight an oppressive regime. Just different levels of crazy.

Re: Here come the encryption apps

#48

Post by rapind »

pknight wrote: post #45
SoftwareMaven wrote: post #35

Earlier quoted context omitted.

Having tried to build a secure messaging platform, I can't agree more that, for the average user, security is so far below the bottom of the list of important things as to not exist. Unfortunately, for those of us who do care, the removes the network effects that make secure software usable. It doesn't make how many calls or emails I encrypt if nobody I talk to can receive them. It is encouraging to hear people 1) un…

I don't think the average user feels it is at the bottom of the list, rather the average user trusts webservices for various reasons without realizing how much insecurity and lack of privacy results from using common webservices. I think that is slowly changing though.

The problem I've experienced is that whenever I talk about software security with non technical people I get a lot of "I thought this dude was normal until he put on the tinfoil hat" looks and overall lack of interest.

The only time people become more aware of security is once they've suffered the consequences of a lack of security. To be fair, the only reason it concerns me is because I've been exposed to so many stories and somewhat have to deal with it in my field.

So it follows naturally that as incidents of security crimes and overreaching governments and corporations increase, then so will the awareness surrounding information security. It has to be actually happening to most for humans on a crowd scale to pay attention.

Re: Here come the encryption apps

#50

Post by scott_s »

tptacek wrote: post #18
miloshadzic wrote: post #15

Earlier quoted context omitted.

I think he maybe meant that the competition is the incumbent apps that don't have encryption as their selling point.

Yes, I'm clear on that. But maybe it shouldn't be. At least those unencrypted apps send a clear signal to their users about the level of assurance they provide.

He's just making an observation about people's behavior, not saying whether or not people should behave like that.
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