ssh : password against keys

ssh : password against keys

Post by Gabrie » Mon, 27 Dec 2004 07:40:36


I'm asking myself if I'm going to user keys instead of passwords to
access to my linux box through ssh.
If I have understood things correctly, I just drop the private key on my
client, the public key on the server and, voila, I can log to my server
without typing any password.

The problem is the following : my client is a windows Box, a laptop in
fact. If someone manages to get in my windows Box, he is able to grab
the key and log to my server from his own machine ?

now, on the other hand, If I do not use keys, he has to install some
keyLogger in order to capture my password when I type it (I did not
store the password in putty).

Seems to me that even if the password flies "through the wire", it is
more secure.

This is no Troll, I'm juste wondering whether it actually worths the
hassle to install rsa keys on my server :)

Oh and by the way, Merry Christmas people ;)

ssh : password against keys

Post by unru » Mon, 27 Dec 2004 09:32:06

Gabriel < XXXX@XXXXX.COM > writes:


In general yes. It is possible to protect the private key file with a
password (well , at least under Linux it is and I would assume that under
one of the Windows implimentations it is as well) so that each time you log
on you have to type in the local password to decrypt the local private part
of the public key. Many find this inconvenient -- ie equivalent to just
using password logon with the remote machine. Some implimentations of ssh
keep a copy of the password protecting the private key file in memory so
you need enter it only once at the beginning of the sessions. That has its
own advantages and disadvantages.

Once he has such access to your machine than he can install a keylogger you
are dead in the water anyway. He can then read your private key file and
record the password you use to protect it anyway.
ssh is NOT secure against your own machine being comprimised.

No. It is neither more or less secure against your machine itself being

I do not, some do.


ssh : password against keys

Post by Juha Laih » Mon, 27 Dec 2004 16:35:31

XXXX@XXXXX.COM (Bill Unruh) said:

Using keys provides flexibility not available with regular
password-based schemes:
- it is possible to have several copies of the same private key
with different protection passwords, so if one of the passwords
is compromised, other copies of the keys won't work with the
same password (but then, in this case the whole key must be
considered compromised, because the attacker now has "unlimited
copies" of the key; this may still slow down the attacker in
some cases)
- for a single target account it is possible to have multiple
simultaneously active keys (so, you could have key for connecting
from untrusted machines, and a key for connecting from trusted
- keys can be restricted to be valid only for connections from
some given IP addresses (giving more fine-grained control for
the above multiple keys)

Of course, one disadvantage with the multiple-valid-keys-per-account
is that upon key compromise, the attacker may install a backdoor in
the form of an additional key. So, you may change your regular keys,
but if you fail to notice the one additional key in your configs,
the attacker still has access to your machine.
Wolf a.k.a. Juha Laiho Espoo, Finland
(GC 3.0) GIT d- s+: a C++ ULSH++++$ P++@ L+++ E- W+$@ N++ !K w !O !M V
PS(+) PE Y+ PGP(+) t- 5 !X R !tv b+ !DI D G e+ h---- r+++ y++++
"...cancel my subscription to the resurrection!" (Jim Morrison)

ssh : password against keys

Post by Mark Schre » Mon, 27 Dec 2004 17:11:07

Hash: SHA1

PuTTY (and, of course, cygwin's openssh) will do this.

- --
Best of luck,
Mark Schreiber
Version: GnuPG v1.2.6 (GNU/Linux)


ssh : password against keys

Post by Rolf Arne » Mon, 27 Dec 2004 21:08:45

Using keys instead of passwords is a security-thing, not a convenience
thing. Using passphrase-free keys is, IMHO, compromising security and
even less secure than password auth. But usage of keys with passphrase
may also be easier if you use a ssh-agent, that caches the passphrase
during the session, so that you type the passphrase only on the first

I have the keys on my usb keyring, so that I won't get in trouble if
someone gets their hands on my computer.

Rolf Arne Schulze
Trans-atlantic weightloss challenge:
Personal weblog:

ssh : password against keys

Post by Rolf Arne » Mon, 27 Dec 2004 21:09:37's ssh client also.

Rolf Arne Schulze
Trans-atlantic weightloss challenge:
Personal weblog:

ssh : password against keys

Post by Lawrence D » Tue, 11 Jan 2005 19:28:07

In article < XXXX@XXXXX.COM >,

If your computer gets compromised, they can steal your keys the next
time you plug in the keyring.

ssh : password against keys

Post by Rolf Arne » Wed, 12 Jan 2005 02:36:58

My computer does not get compromised ;). The only way to be completely
safe is to remove all network connections on your computer. That is
not an option. :)

Rolf Arne Schulze
Trans-atlantic weightloss challenge:
Personal weblog: