Symmetric encryption

Atom 'Smasher' atom at suspicious.org
Tue Oct 26 07:58:48 CEST 2004


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On Mon, 25 Oct 2004, Per Tunedal Casual wrote:

> I thought once more about this :-) It's hard enough to put up a 
> passphrase that matches an 128 bit-key. The hash, if any, doesn't 
> matter, because it can hardly decrease the strength of the passphrase,.
>
> Thus any cipher with a key longer than 128-bits is overkill when you 
> encrypt symmetrically. Right?
===================

i have several passphrases that are 20+ characters. 22 characters of 
uppercase, lowercase, numbers and spaces is *stronger* than 128 bit.

that's not counting the full range of characters that can be used... 
assuming that 95 characters are generally suitable (read: safe) for use in 
passphrases, it only takes a theoretical 19.5 characters to equal 128 bits 
and 39 characters to hit 256 bits. such passphrases may not be suitable 
for all applications, but they're not entirely ridiculous. IMHO it's 
posible to come up with passwords that are that long, easy to remember and 
strong.

AFAIK, the session key used for symmetric encryption is derived from the 
user supplied passphrase, then salted and iterated (this may have changed 
recently). if symmetric and asymmetric encryption is used then the session 
key is derived in the usual random way.


- -- 
         ...atom

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