[Discuss] KeePassX

[richard.pieri at gmail.com (Richard Pieri)]

Daniel Barrett wrote:
> In the absence of the 4096-bit private half of my key, how hard is it
> to decrypt the session key by brute force and thereby decrypt file
> Foo? Do the time arguments from this KeePass discussion apply?

That depends on the symmetric cipher used. CAST-128 (aka CAST5) 
currently has no publicly known weakness so any attacks on the message 
body would require an exhaustive search (brute force) on the session 
key. This is a 128-bit key which is prohibitively expensive operation 
for almost anyone (maybe not the NSA, we don't know for sure). RSA and 
DSA likewise have no publicly known weaknesses so again it would require 
an exhaustive search to recover the "master" key. As Ned pointed out, 
RSA-4096 has an effective key space of 128 bits making it equally 
expensive to perform an exhaustive search. DSA should be no worse than 
RSA for this purpose.

So, barring weaknesses in either the symmetric or asymmetric ciphers 
used, an attacker is stuck with an exhaustive search on a 128-bit key 
space. That's probably good for a few years against anything less than 
the NSA.

-- 
Rich P.