[Security] About the Firefox 3 Security Dialog & others

Dirk Meyer dmeyer at tzi.de
Sat Aug 23 08:08:10 CDT 2008


Pedro Melo wrote:
> Hi,
>
> On Aug 23, 2008, at 1:18 PM, Jonathan Schleifer wrote:
>
>> Am 23.08.2008 um 11:04 schrieb Dirk Meyer:
>>
>>> SAS does not work for me when I use bots. It also reduces it to one
>>> way removing the option of X.509 certificates which is something I
>>> need.
>>
>> I never said SAS should be the only way, we need multiple ways. I
>> suggest those:
>>
>> * SAS with mnemonics
>> * Fingerprint verification
>> * CA, but no CA added in the client by default (so the user has to
>> trust the CA manually, for example useful in a company so you don't
>> have to verify every co-worker)
>
> Exactly. For bots, I personally would create my own CA and tell those
> pesky little devils just to trust certificates signed by that.

Half off-topic: is there an easy way to create a CA and sign keys with
that? The only howtos I found are very complicated, require a password
and stuff like that. I want to have a script 'create-ca' with some
parameter and 'sign' getting a key.

>> BTW: It was argued a lot that ESessions misses a cryptanalysis, but
>> if we are going to do extensions to TLS, we might need a
>> cryptanalysis for this stuff too. TLS is useless if we add a
>> verification method that is insecure.
>
> Well, SAS and SRP are IETF (draft?) extensions. SRP has more than 10
> years of field tests and debate (up to current SRP-6, I believe).

TLS-SRP is a RFC, SAS over TLS is a draft not sumitted to the IETF as
it seems. So SAS is more or less not an option right now. But if we
use TLS it could be an option in the future.

> Mnemonic or base32 encoding of the 32bit challenge, that's just
> cosmetics applied.

SAS has one big advantage over SRP: I can verify the key later. For
SRP we could generate a random password (short) the users should uee,
but they need to talk on the phone _before_ using it. But since SAS
without verification is useless it is ok for me to only allow SRP
after the users talked.


Dirk

-- 
The Web isn't better than sex, but sliced bread is in serious trouble.


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