[tahoe-dev] So how do *you* manage your keys, then? Re: cleversafe says: 3 Reasons Why Encryption isOverrated

Zooko Wilcox-O'Hearn zooko at zooko.com
Tue Aug 18 15:11:49 UTC 2009


Jason:

Thank you for your thoughtful message.

I made a mistake yesterday by describing only the lowest layer of the  
Tahoe-LAFS architecture and, when my bus arrived at work, sending the  
mail without first making clear that this was only the lowest layer.   
Tahoe-LAFS includes a "secure distributed directories" layer on top  
of the "secure distributed immutable files" that I already described,  
and then it also has a RESTful API, a command-line interface, and a  
web user interface.  Then on top of *that* there are many different  
things built on top of Tahoe-LAFS, including a Windows client that  
integrates into the Windows filesystem, a plugin for the "duplicity"  
backup tool, Shawn Willden's nascent new backup tool, and more [1].

These layers solve some of the problem that you point out, and I'm  
sorry I gave you an inaccurate target in my previous mail.

Despite this handicap, many of your criticisms are still valid,  
because the fundamental availability-vs.-confidentiality trade-off  
that you describe is one of those "abstraction-piercing" problems, so  
none of the added layers of Tahoe-LAFS are able to completely solve  
it.  For what it is worth, I don't think Cleversafe's approach  
completely solves it either, as I think Shawn Willden and Brian  
Warner have pointed out -- the abstraction-piercing problem keeps  
going on up through authentication, user interface, corporate policy,  
etc. etc!

As a thought experiment, consider that one *could* write a new layer  
on top of Tahoe-LAFS that used secret-sharing to split a cap into  
secret shares.  Then the composition of the Tahoe-LAFS "secure  
distributed storage" layer along with the secret-sharing of the cap  
would have similar properties to Cleversafe.  I've often wanted to do  
that so that users of allmydata.com's backup services would have a  
third option instead of just "allmydata.com keeps my key safe for me"  
and "I keep my own key and take my chances".  The reason I never did  
it yet is that I don't see how to integrate it smoothly enough into  
UI/customer experience/etc.  How would a customer who wants to backup  
their files to allmydata.com deliver the various shares of their  
secret to various locations -- email them to friends?  It sounds like  
too much confusion and too much work for the average backup customer,  
who after all is really trying to buy simplicity and peace-of-mind,  
not to invest a lot of time learning a new tool!

Okay, now I gotta go to work again.  :-)

Regards,

Zooko

[1] http://allmydata.org/trac/tahoe/wiki/RelatedProjects



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