[tahoe-dev] cleversafe says: 3 Reasons Why Encryption is Overrated

[james hughes]

On Aug 6, 2009, at 1:52 AM, Ben Laurie wrote:

> Zooko Wilcox-O'Hearn wrote:
>> I don't think there is any basis to the claims that Cleversafe makes
>> that their erasure-coding ("Information Dispersal")-based system is
>> fundamentally safer, e.g. these claims from [3]: "a malicious party
>> cannot recreate data from a slice, or two, or three, no matter what  
>> the
>> advances in processing power." ... "Maybe encryption alone is 'good
>> enough' in some cases now  - but Dispersal is 'good always' and
>> represents the future."
>
> Surely this is fundamental to threshold secret sharing - until you  
> reach
> the threshold, you have not reduced the cost of an attack?

Until you reach the threshold, you do not have the information to  
attack. It becomes information theoretic secure.

They are correct, if you lose a "slice, or two, or three" that's fine,  
but once you have the threshold number, then you have it all. This  
means that you must still defend the site from attackers, protect your  
media from loss, ensure your admins are trusted. As such, you have  
accomplished nothing to make the management of the data easier.

Assume your threshold is 5. You lost 5 disks... Whose information was  
lost? Anyone? Do you know? What if the 5 drives were lost over 5  
years, what then? CleverSafe can not provide any security guarantees  
unless these questions can be answered. Without answers, CleverSafe is  
neither Clever nor Safe.

Jim