[OT] ssh security

[Lowell Gilbert]

Angelin Lalev <lalev.angelin at gmail.com> writes:

;2~> On Sun, Mar 7, 2010 at 11:25 PM, Angelin Lalev <lalev.angelin at gmail.com> wrote:
>> Greetings,
>>
>> I'm doing some research into ssh and its underlying cryptographic
>> methods and I have questions. I don't know whom else to ask and humbly
>> ask for forgiveness if I'm way OT.
>>
>> So, SSH uses algorithms like ssh-dss or ssh-rsa to do key exchange.
>> These algorithms can defeat any attempts on eavesdropping, but cannot
>> defeat man-in-the-middle attacks. To defeat them, some pre-shared
>> information is needed - key fingerprint.
>>
>> If hypothetically someone uses instead of the plain text
>> authentication some challenge-response scheme, based on user's
>> password or even a hash of user's password would ssh be able to avoid
>> the need the user to have key fingerprints of the server prior the
>> first connection?
>>
>
> To clarify, we as users anyway do have shared secret with the server
> and that's the authentication password why we could not use that
> instead of or in addition to a key fingerprint?

Because we don't want to give an attacker access to a shared secret if
we can verify host identity with a public key first.

-- 
Lowell Gilbert, embedded/networking software engineer, Boston area
		http://be-well.ilk.org/~lowell/