On Tue, Aug 30, 2005 at 09:36:58PM -0700, Sebastian Smith wrote: > > On Tue, 30 Aug 2005, Ben Johnson wrote: > > >On Tue, Aug 30, 2005 at 08:12:47PM -0700, Sebastian Smith wrote: > >... > >>Why not have a passphrase-less ssh key? Well... it breaks the public key > >>crytography. If you don't require a passphrase there is no way to > >>validate that the connecting user is who they say they are (I'm sure you > > > >I don't agree, but maybe I just don't understand. > > > >When an ssh key public/private key pair is created I can choose to add a > >layer of protection to the private half in the form of a passphrase > >which, if I'm not mistaken, is used to encrypt the private key. this > >makes it so I have to enter the passphrase in order to "unlock" the > >private key so that I can use it. everything else is the same. right? > >this would only break public key crypto if I always left my private key > >in a place where someone else could reach it. > > > >I only create passphrase-less keys using the root account on well > >protected systems I admin, so it think they can be trusted pretty well. > > > > > In the strictest sense you are not breaking PKC by using a blank > passphrase. But, if you box is compromised the attacker can gain access > to remote machines without requiring proof of identity -- thus defeating > PKC (they would probably have your private key anyway, but there are ways > of defending it). > > PKC security is derived from user interaction -- I can be confident that, > because your key requires a secret passphrase (and that you, and only you > will be able to enter it), signed objects have come from you, and objects > encrypted with your public key can be decrypted by you. Of course, the > key word is "confident" as anyone who knows your passphrase can masquerade > as you. Removing the passphrase from the equation virtually elimates this > "confidence", as anyone could pass as you. You eluded to this in your > statement above when you said that you think your keys can be trusted > pretty well due to the security of your systems. It's clear, in this > case, that you're not relying on PKC for security, but, rather, as a means > of thwarting the man-in-the-middle from stealing data from you. > > Not sure if that makes any sense... so give me feedback.
yeah. that makes sense. I contend that my private key is password protected though because my account is password protected. One thing a good book, Practical Cryptography, really got across to me is security is only as good as the weakest link. an example they used: office doors may have locks but the walls they're set into often don't extend above the lift-able ceiling tile. Adding a pass phrase to my private key would raise my bar a little, but I doubt very much. my confidence in other peoples' usage of PKC is not raised a whole lot by knowing they have a good passphrase on their private key. For instance, maybe people use long strings of dictionary words that may be surprisingly crack-able, or... that private key may be located on a public server, where I can't be sure who's got root, who is able to look at the memory image of the user's ssh-agent process. My confidence goes up when I'm sure people know how to keep their systems secure. I'm always a little floored when I'm dealing with some company who wants to generate a key pair for me and send *both* of them to me in clear text email. it's incredible how much clueless weirdness goes on out there. - Ben _______________________________________________ RLUG mailing list RLUG@rlug.org http://lists.rlug.org/mailman/listinfo/rlug
