Password auth. vs. Key auth. for SSH
 

Hi!
I have a server running Ubuntu Server 12.04.03 LTS, and it currently has keyfile-only authentication. However, I was thinking about setting it back to a password login, mainly for convenience. I am the only user of the server. Also, it does not listen of port 22.

Is password login a big no-no, or is it safe if there is a long enough password? What should a good password look like?

Thanks for your time!

security
 

security is a difficult thing to give advice on...

it really comes down to comforts and preferences

you say you want to go back to passwords for convenience sake but for some the keyfile may be more convenient,
you are free from keeping track and memorising many different passwords for many different services, also good passwords should be difficult to memorise

which leads to your second question of what a good password looks like,
well a good password, again is about your interests

if you are the only one on this server and your work is pretty anonymous then a password for you may just be about detering superficial shenanigans and so a good password would be one you can easily remember

if you are talking about high security password then you would want to go with something that looks like the output of a hash function: c0e81794384491...

numbers and letters seemingly randomised
if you use common words the attacker can use a dictionary attack but if an attacker wants to guess your password and you have a password like this then the attacker would have to guess every possible combination of letters, 26 a-z, and numbers, 10 0-9
at 36 possible characters for each character of the password string you can calculate the number of guesses by taking 36**(PASS_LEN)

36**4 = 1679616
36**5 = 60466176
36**6 = 2176782336 possible combinations

that escalates quickly.. obviously more guesses required the more secure the pass phrase will be, so i'd suggest a minimum of 6 characters

Hi,
Good, that's how I set up all my machines. I also have have "PermitRootLogin no" and make use of "AllowUsers".
That doesn't hurt and may reduce the number of entries in your logs, but do a search on "security through obscurity" and read what pops up.
A password being long is not enough to make is strong.
See this recent article by Bruce Schneier http://boingboing.net/2014/02/25/cho...-password.html

I suggest you stick with what key based authentication. Protect your keys with a strong passphrases and if you need to, carry them with you on a usb stick.

Evo2.

Thanks!
I'll take your advice and keep the password authentication.

Sorry if this was a overly "newbie" question. Regardless of what it says to the left of this post, I'm still pretty new to this.

solved?
 

great, it's a fine question to ask for clarification between different security measures

if you're decided could you mark the thread as solved?

Marked as solved. Thanks!

I disagree: the port the service listens on doesn't enter the equation and you being the only user doesn't matter either. Many things get sacrificed under the misnomer of "convenience" and in this case (unless you care to explain otherwise) completely unnecessary as you would just use ssh-agent to load your keys for the duration of your session. Also see screen, autossh and sshfs.

The strength of a key, versus a password, is that it is unique and non-forgeable. Therefore, you can issue access to individual people and revoke it to individual people. The (private) key, itself, should of course be encrypted. But, even if the equipment upon which the key was stolen and the owner forced to divulge the password (ouch!), you can still individually deny access by that key.