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Date:      Wed, 17 Sep 2014 13:18:46 +0700
From:      Olivier Nicole <>
To:        Daniel Staal <>
Cc:        John Case <>, "" <>
Subject:   Re: comparing SSH key and passphrase auth vs. an SSH key *with* a passphrase ...
Message-ID:  <>
In-Reply-To: <E79B9D9533E6F405B49EA064@>
References:  <> <> <> <E79B9D9533E6F405B49EA064@>

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On Wed, Sep 17, 2014 at 11:00 AM, Daniel Staal <> wrote:
> --As of September 15, 2014 7:09:46 PM +0000, John Case is alleged to have
> said:
>>> Key based auth is definitely the better choice out of those two.
>> Ok, agreed.
>> However, just out of curiousity - let's pretend that sshd *did* allow you
>> to use both an SSH key and a UNIX password at the same time ... would
>> that be more or less secure than using an SSH key with a built-in
>> passphrase ?
> --As for the rest, it is mine.
> Lots of variables there: How does sshd store the password?  (Does it use the
> system's user password?  How are you storing that?)  Can you *require* using
> a password with a SSH key?  How does the SSH key store the password? etc.
> On a basic level, at that point you need both something you have (the SSH
> key) and something you know (the password).  The two pieces are the same in
> both cases, so the security comes down to implementations - and since one
> isn't implemented, we can't compare implementations.  ;)  Chuck mentioned
> that the storage for passwords with private keys isn't super great, so if it
> used the system's user password that should be better - because there's been
> a lot of work on storing those securely.

Is the password for the private key actually stored in the key? That
sounds odd to me. I'd better see the password being used to
encode/decode the private key, so no need for storage of the password,
if you provide the wrong password, you decode the private key into
something that is not working, done.

Best regards,


> BTW: Since a couple of people have pointed to Google's two-factor system, I
> thought I'd point to my current favorite: Yubikey[1].  There's a PAM module,
> so it can be set up moderately easily.  (I'll admit I haven't tried: I
> mostly rely on physical security for my main network...)
> Daniel T. Staal
> [1]: <>;
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