Re: A question about passwords and login/authentication

On Tue, 2005-03-15 at 14:53 +0100, Pavol Luptak wrote:
> Try blowfish instead MD5

I feel a bit uneasy about using symmetric ciphers (like DES or blowfish)
for password encryption. I'm not a crypto guy, but doesn't this bring
about the whole bloody key management can of worms?

In order to check a supplied plain text password you'd have to have the
encryption key available. This also means that you've got something
important to lose - whoever steals the key can simply decrypt the entire
password store (rather than brute-forcing it).

With hashes (crypt(), MD*, SHA*) all you have to have in order to verify
a plain text password is the algorithm itself.

Wouldn't it be wiser to use asymmetric ciphers, destroy the private key
and just use the public key to encrypt new passwords. The public key
could then be published for anyone to check supplied plain text for
validity, yet no-one could decrypt the cipher text. Just like with
hashes, only without their limitations (and performance).

Cheers
Steffen.

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