Re: ssh gives "Permission denied, please try again"

On Fri, 25 Jul 2008 20:27:16 +0100, Nix wrote:

On 25 Jul 2008, Jonathan Buzzard spake thusly:
On Tue, 22 Jul 2008 08:39:45 +0100, Nix wrote:
No random password that's short enough for you to remember it can
possibly have enough entropy to be secure. Keys have as much entropy as
you like (depending on how long you make them), with no human memory
burden, and the shortest has far more entropy than the longest password.

Really, as secure as those Debian generated keys...

Well, duh, if your cryptosystem's PRNG is broken you're sort of screwed.
If you always pick passwords whose first four letters are 'A' you're
screwed too.


The point being that keys are not some panacia and those that think they
are, are silly.


The point is that nobody is doing brute force ssh attacks. In nearly a

Excellent. That's an even better reason to use a key rather than a
password: lots of people attack passwords, nobody attacks keys.


Wrong, people are currently attacking keys as well...


decade of having dozens of public internet facing machines on well
connected networks (that in todays terms means in excess of 1Gbps upstream
internet connected bandwidth) have I ever seen such an attack.

I've seen a lot of dictionary attacks, but that's all remotely. I've
seen brute-force attacks from hostile insiders over a local net (yes,
it was obvious, but principally because he didn't clean the logs so the
disk filled up with error messages: he did it at night while rolling
compiles were running so the CPU usage wouldn't have been very
noticeable. We did notice that the compiles were taking longer...)


You where allowing more than one login attempt per second...


The reality is that it is simply not a feasible proposition. If you just
stick to an eight character password with a mixture of upper and lower
letters plus the digits, that is 218 trillion possible passwords. How do

And you have to *remember* them. Nobody does. Everyone either writes
them down or carries them around on a USB stick. If they do that they
can carry around a key instead.


Funny I seem to remember random passwords quite easily. In fact 99.99% of
people I know seem to be able to remember random sequences of numbers and
digits without problem. They are called telephone numbers and postcodes.


you propose brute forcing that, especially if I rate limit login attempts
to one per second. It would take you the best part of 7000 millennium.

Most passwords have *dramatically* less entropy than you suggest for the
simple reason that nobody can remember gibberish passwords. This is so
well known it's made the national news (along with the news that people
will give away their passwords --- or at least what they *say* is their
passwords --- for paltry rewards.)

Do they, none of mine do, and any system admin who cannot pick a random
password and


So the added aggravation of carrying a key around buys you zilch additional
security in reality.

Passwords are definitely crackable: I've seen it done, over and over again.
Keys are not, without insane resources.

Only if you pick bunk passwords, just like if you generate bunk keys.


You really need a passworded keyphrase: that way at least you have two
parts of the security mantra: something you have and something you know.
Passwords alone only allow for one of those.

No I don't.

OK, so you don't care about security. Great.


I do, which is why I have *never* had a compromised system that I have
been responsible for.


What hassle? It's not as if tracking a key is any harder than tracking
a gibberish password that you can't remember (in fact it's easier because
you don't need the key to be human-readable, and it's more secure not least
because you can passphrase it against someone nicking your key: if someone
nicks your written-down gibberish password you are dead meat.)

Except my gibberish password is not written down anywhere, and I have no
issue remembering it. For anyone who can remember a sequence of eight
random characters, which I maintain is not hard to do, a key buys no
additional worthwhile security and a whole bunch of hassle.

JAB.

--
Jonathan A. Buzzard Email: jonathan (at) buzzard.me.uk
St. Andrews, United Kingdom.
.

Relevant Pages

  • Re: ssh gives "Permission denied, please try again"
    ... as secure as those Debian generated keys... ... If you always pick passwords whose first four letters are 'A' you're ... The point being that keys are not some panacia and those that think they ... lots of people attack passwords, nobody attacks keys. ...
    (uk.comp.os.linux)
  • Re: Any Way to Defeat Cracker Login Attempts? (OS X)
    ... Ssh keys are more secure than passwords. ... By ssh keys I assume you mean PKA keys, unless I am misreading you yet ...
    (comp.sys.mac.system)
  • Re: SSH as root
    ... and the passwords are sent securely. ... unix passwords is when the same passwordcan be used to compromise ... > you are in the same boat if you choose passwords, or keys with passphrases. ... Yes, indeed, if the client system is compromised then all bets are off, ...
    (SSH)
  • Re: SSH as root
    ... > on a system if someone compromises it. ... Passwords are inferior to keys in at least 3 regards: ... itself as well as somehow obtain/bruteforce the passphrase, ...
    (SSH)
  • Re: See what a weak password will get ya?
    ... >>Just wanted to share the need for strong passwords. ... are that even the relatively mnemonic lists are of very high quality. ... I find that these keys are usually pretty ... and typical keys run 10-15 characters. ...
    (Debian-User)