Callas Responds to Green's Criticisms

Is PGP ‘broken’? Jon Callas Responds

A few days ago, Matthew Green, the widely respected cryptographer and research professor at Johns Hopkins University launched a broadside (http://blog.cryptographyengineering.com/2014/08/whats-matter-with-pgp.html) against PGP. In summary, Green said, “The problem with this is that, for all the good PGP has done in the past, it's a model of email encryption that's fundamentally broken.” Further Green said “PGP keys suck,” “PGP key management sucks” and that that there is “no forward secrecy.” His blog post adds more criticisms and also attempts to find some solutions.

In the interests of a balanced view of the issues, CSO asked Jon Callas, one-time Chief Scientist at PGP for his thoughts on Green’s criticisms.

We first observed to Callas that Green’s criticisms were rather forthright.

Callas: Matt's a very smart man. However, he's not an implementer and I think he's essentially arguing for the other side.

I agree with some of what he's saying -- email security is a mess. The problem isn't PGP, though. It's email. Actually, it's SMTP and a few surrounding technologies like MIME and the main email formatting. All of the criticisms he makes are just as true for S/MIME, and just about anything else someone would do at present.

CSO: So, what is the actual problem Green has identified if it isn’t PGP?

Callas: Every email you send leaks your IP address and information about your computer. However, a number of webmail systems like the gmail you're using [the author regularly communicates with Callas via Gmail] do a decent job of hiding as much as they can. It also leaks your social graph, etc.

What we've found out from the SIGINT services [SIGnals INTelligence – NSA and their ilk] is that they decided that they don't need to read the content if they can get your social graph -- your address book and who you talk to, when, etc. They decided if they get the metadata, they don't need the content. The standards that cover SMTP and content security in formatting the raw message encrypt the content and leave the metadata in the clear. This is the problem.

This is why I've been helping out with Darkmail/DIME and coming up with new ways to do that. Matt mentions this in passing, and I agree totally.

CSO: So, is there a solution?

Callas: People are upset and they want to do something. Some companies, like Yahoo and Google have decided they are going to take a stand and start encrypting emails with PGP. They're doing it because people want it, and because that's the right decision for today.

Matt is effectively saying that if you light a candle in the darkness, it's going to drip wax. He's right. We need something better. I know he doesn't mean to be saying that we should just sit in the dark, but that's what he's saying.

CSO: Are you suggesting then that Green is part of the problem, or part of the solution?

Callas: For all the flaws that the present architecture has, it's what we have. I'm incredibly excited that Yahoo and Google are doing something rather than nothing. The biggest problem we have in security and privacy is the experts who go into the better being the enemy of the good and thus essentially arguing that nothing is better than something.

This article is brought to you by Enex TestLab, content directors for CSO Australia.

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Tags Matthew Green criticismsDIMESecurity and PrivacyCSOSMTPinformationcryptographerwebmail systemsJon CallasprivacyMatthew GreenGoogle

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