Vanishingly small utility ...

["Rob, grandpa of Ryan, Trevor, Devon & Hannah" <rMslade () shaw ca>]

This system has had some discussion in the forensics world over the past few days:

"Computers have made it virtually impossible to leave the past behind. College 
Facebook posts or pictures can resurface during a job interview. A lost cell phone 
can expose personal photos or text messages. A legal investigation can subpoena 
the entire contents of a home or work computer. The University of Washington 
has developed a way to make such information expire. After a set time period, 
electronic communications such as e-mail, Facebook posts and chat messages 
would automatically self-destruct, becoming irretrievable from all Web sites, 
inboxes, outboxes, backup sites and home computers. Not even the sender could 
retrieve them.  

"The team of UW computer scientists developed a prototype system called 
Vanish that can place a time limit on text uploaded to any Web service through a 
Web browser.  

[Perhaps a bit narrower focus than the original promise, but it is a prototype - rms]

"After a set time text written using Vanish will, in essence, self-destruct.  The 
Vanish prototype washes away data using the natural turnover, called “churn,” on 
large file-sharing systems known as peer-to-peer networks. For each message that 
it sends, Vanish creates a secret key, which it never reveals to the user, and then 
encrypts the message with that key. It then divides the key into dozens of pieces 
and sprinkles those pieces on random computers that belong to worldwide file-
sharing networks. The file-sharing system constantly changes as computers join or 
leave the network, meaning that over time parts of the key become permanently 
inaccessible. Once enough key parts are lost, the original message can no longer be 
deciphered."

http://www.sciencedaily.com/releases/2009/07/090721113309.htm  

http://vanish.cs.washington.edu/

http://vanish.cs.washington.edu/pubs/usenixsec09-geambasu.pdf

However, given the promise to clean up social networking sites, and as I started to 
read the paper, an immediate problem occurred to me.  And, lo and hehold, the 
authors admit it:

"We therefore focus our threat model and subsequent analyses on attackers who 
wish to compromise data privacy. Two key properties of our threat model are:  
1. Trusted data owners. Users with legitimate access to the same VDOs trust each 
other.
2. Retroactive attacks on privacy. Attackers do not know which VDOs they wish 
to access until after the VDOs expire.
The former aspect of the threat model is straightforward, and in fact is a shared 
assumption with traditional encryption schemes: it would be impossible for our 
system to protect against a user who chooses to leak or permanently preserve the 
cleartext contents of a VDO-encapsulated file through out-of-band means. For 
example, if Ann sends Carla a VDO-encapsulated email, Ann must trust Carla not 
to print and store a hard-copy of the email in cleartext."

So, this system works perfectly.  If you only communicate with people you trust 
(both in terms of intent, and competence), and who only use the system properly, 
and never use any of the information in any program that is not part of the 
system, it's completely secure.

How often have we heard that said?

The default to privacy aspect is interesting, and the automatic transparency for 
the user as well, but this simply moves the problem one step back, as it were.  In 
terms of utility to social networking, the social networks would have to be 
completely rewritten to adher to the system, and even then it would be pretty 
much impossible to ensure that nobody would have the ability to scrape data and 
keep or publish it elsewhere.

(Plus, the data is still there, and so is Moore's Law ...)

======================  (quote inserted randomly by Pegasus Mailer)
rslade () vcn bc ca     slade () victoria tc ca     rslade () computercrime org
My opinions may have changed, but not the fact that I am right.
                                                - Ashleigh Brilliant
http://victoria.tc.ca/techrev/rms.htm 
http://blog.isc2.org/isc2_blog/slade/index.html http://twitter.com/rslade
http://blogs.securiteam.com/index.php/archives/author/p1/
http://twitter.com/NoticeBored

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