Wednesday, July 06, 2011

Securing your passw^H^H^H^Hgp private key


I saw this article today by @DSchwartzberg at Sophos about Google indexing PGP private keys, easily found if you know what to search for. It reminded me that I had to finish this old blog post which has been waiting in line for some months now. Lets get straight to the point: How do you protect your GPG/PGP private key?

I use GPG/PGP myself, both at work as well as at home, even though Bruce Schneier says in his book "Secrets & Lies": "Digital certificates provide no actual security for electronic commerce; it's a complete sham." Made me smile when I read it. Of course there are many ways to interpret that statement by itself, with perhaps an interesting view being that a digital certificate identifies an electronic identity, and not necessarily a physical person. DNA testing does that these days. Even more; identifying somebody really doesn't tell you much if they are Alice, Bob or Eve. Well, unless they already have a record, or become subjects of Ethnic Profiling of course.


We have a law here in Norway that says that I am legally bound by anything signed by my #BankID, and similar solutions. BankID is a bank-issued digital certificate, where a single commercial company - owned by various banks - keeps my private keys in their possession, and will NOT give it to me electronically!


Anyway, lets not wake up Auguste Kerckhoff from the dead.


What I am curious about - of course this blog post is about passwords - is how people go about protecting their GPG/PGP secret keys? Do people use strong passphrases? Do they ever change them? What about the password/phrase for shared secret keys, such as those belonging to various CERTs, IRTs, CSIRTs and so on? What if somebody leaves such a team - do they create a brand new key, do they just change the password (Now that's a risk!), or what?


Allow me to quote from the gnupg manual:
"Protecting your private key is the most important job you have to use GnuPG correctly. If someone obtains your private key, then all data encrypted to the private key can be decrypted and signatures can be made in your name. If you lose your private key, then you will no longer be able to decrypt documents encrypted to you in the future or in the past, and you will not be able to make signatures. Losing sole possession of your private key is catastrophic."
If you use PGP Microsoft Windows in a corporate environment, the default configuration will store your keyring, including your private key, under "My Documents". That folder will again probably be stored centrally on a server, making your keyring more easily available 24x7 to lots of other people. Oops - replace "other people" with "unauthorized people" in that last sentence there. It's your secret key, it should be kept in safe storage by you, nobody else (at least not Google's search engine :-))
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(I'm sorry #BankID, but I want my private key!)

I'd like to hear your opinion, ideas, challenges or risk analysis on this subject. Shoot!