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Re: OpenSSL as a general purpose encryption tool
On Fri, 9 Feb 2001, Seth Arnold wrote:
> > You should probably be using something like GNU PG instead
> > (/usr/ports/security/gnupg), since the key is much larger (e.g.
> > 1024 bits), and the key is protected by a password which you can
> > change over time.
>
> Ack! No!
I disagree ;-)
> Comparing key sizes between public key and symmetric cryptography is
> *not* kosher. 1024 bits of RSA key is roughly equivalent to 64 bits of
> symmetric strength, for a good symmetric cipher. Tough to do right now,
> but not to be considered safe for data that must live more than a few
> months. (Paranoids such as myself would say ``a day or so''.)
Yep, I understand that.
> Protecting a large key with a small key is only as strong as the small
> key. If it is only four characters long, then you have bought yourself
> four characters of security. Changing the small key may be good -- but
> it also means there is the overhead of changing the small key regularly,
> and the security problems that can result from the overhead.
Take the case where just the encrypted document is available.
Using a dictionary attack, a poorly chosen passphrase will usually
result in most other encrypted documents being viewable (since a
human doesn't usually have the capacity to remember more than a
couple dozen passwords).
In the case of GNU PG encrypt-to-self, decrypting the document
is significantly harder because finding the private key is a lot
harder than guessing a passphrase.
I'm really just arguing that a typical user might forget to make
the encrypted document private, in which case you're able to bypass
a step and go straight for a passphrase attack.
Chris Foote SE Net
Technical Manager 222 Grote Street
SE Network Access Adelaide SA 5000
e-mail chris@senet.com.au Australia
phone : (08) 8221 5221 PGP Public Key available from
fax: (08) 8221 5220 http://www.senet.com.au/PGP
support: (08) 8221 5792