D-kriptik Blog

So, I recently saw Juno for the first time, and was surprised and happy to hear Kimya Dawson permeate the soundtrack. And, I ate at wd~50, which was, well, an experience - highly recommended if you want to try something truly new.

Anyway, yes, still here. Unfortunately, this rare act of posting will be limited to a quickie - a few miscellaneous items accumulated over a couple of months.

-

A few headaches…

1. Wow, just wow.
   

   The result of this is that for the last two years (from Debian’s “Etch” release until now), anyone doing pretty much any crypto on Debian (and hence Ubuntu) has been using easily guessable keys. This includes SSH keys, SSL keys and OpenVPN keys.

   Update immediately. And be sure to do things such as regenerate all persistent keys that used random data taken from the vulnerable Debian OpenSSL during their generation - some of this type of work is handled automatically when updating your packages (e.g., OpenSSH server keys), but only you know what you have done outside this automated window.

2. I booted up a Windows XP box only to find that some resource of the Logitech QuickCam software had become corrupted, and this resulted in a nasty msi installer loop hitting the box as soon as a user logged in. I found this tool extremely useful in cleaning up the mess.
   

   [..]With the Windows Installer CleanUp Utility, you can remove a program’s Windows Installer configuration information. You may want to remove the Windows Installer configuration information for your program if you experience installation (Setup) problems. For example, you may have to remove a program’s Windows Installer configuration information if you have installation problems when you try to add (or remove) a component of your program that was not included when you first installed your program.

3. Much to my very unpleasant surprise, I upgraded a server over here from Ubuntu Gutsy to Hardy and discovered networking for Xen DomU’s in Ubuntu Hardy 8.04 is somewhat broken. I ended up using the 2.6.24-17-xen kernel from the hardy-proposed repository, but you could also just stick with the Gutsy Xen kernel for DomU’s.
4. When I upgraded to Gnome 2.22 on a particular FreeBSD 7.0 system, certain things, like the clock applet, did not work. This was due to the dbus daemon not being started. Then, the hal daemon and Gnome did not want to play nice together. This page provided the information necessary to get them playing nice - in this particular instance, not mounting procfs was the problem.

Side note, I was helping someone install Ubuntu recently, and it brought to my attention yet again how much I take what I consider to be basic skills for granted when using *nix. Small things, like running an executable from within your environment path versus by directly specifying the path (the most confusing to many example of this seems to be trying to run an executable in the current working directory), are just not common knowledge. Even the whole command line itself is often scary and bizarre to people. This makes it extremely difficult to provide useful guidance for people to blindly follow (posts on this blog should never be assumed to provide step-by-step instructions - they are just some basic notes at best, as extremely helpful comments like this make obvious). And, even Ubuntu is not as trivial to use as it would appear to many that work in the *nix world.

-

Three useful Ubuntu and FreeBSD pages…

USN.

These are the Ubuntu security notices that affect the current supported releases of Ubuntu.[...]

FreeBSD VuXML.

Security issues that affect the FreeBSD operating system or applications in the FreeBSD Ports Collection are documented using the Vulnerabilities and Exposures Markup Language (VuXML).[...]

FreeBSD Security Advisories.

This web page contains a list of released FreeBSD Security Advisories.[...]

-

Story-telling is one of the fundamental tools in a teacher’s toolkit. Having done quite a bit of consulting, I have learned how invaluable a good story is to driving home particular points and building relationships. There is something fundamental about how stories effect us, perhaps stemming from our innate ability to empathesize and our massive pattern recognition horse-power.

Anyway, this site has a useful set of stories. [via exi]

Here are some stories, analogies, research findings and other examples that provide wonderful illustrations for learning, and inspiration for self-development.

In fact, the first story mirrors a recent post.

An old lady had a hearing-aid fitted, discreetly, hidden underneath her hair.

A week later she returned to the doctor for her check-up.

“It’s wonderful - I can hear everything now,” she reported very happily to the doctor.

“And is your family pleased too?” asked the doctor.

“Oh I haven’t told them yet,” said the old lady, “And I’ve changed my will twice already..”

This reminds me of a story I often tell about someone I met a while back, a graduate student in psych. She was studying aspects of the initial meeting/courtship routines of people, and would go out to bars and such and interact with potential suitors. Here these suitors were, following their typical pickup routines and sometimes spilling more than their drinks, and here she was, analyzing their interaction and subsequently writing up notes to be turned into research papers, etc.

-

NIST draft SP 800-108 has been released.

SP 800-108

DRAFT Recommendation for Key Derivation Using Pseudorandom Functions

NIST announces the release of draft Special Publication 800-108, Recommendation for Key Derivation Using Pseudorandom Functions. This Recommendation specifies techniques for key derivation from a secret key using pseudorandom functions (PRF). Please submit comments to draft-SP800-108-comment@nist.gov with “Comments on SP800-108″ in the subject line. The comment period closes on June 28, 2008.

Yet more KDFs.

-

They just don’t quit, do they?

1

This is the first article analyzing the security of SHA-256 against fast collision search which considers the recent attacks by Wang et al. We show the limits of applying techniques known so far to SHA-256. Next we introduce a new type of perturbation vector which circumvents the identified limits. This new technique is then applied to the unmodified SHA-256. Exploiting the combination of Boolean functions and modular addition together with the newly developed technique allows us to derive collision-producing characteristics for step-reduced SHA-256, which was not possible before. Although our results do not threaten the security of SHA-256, we show that the low probability of a single local collision may give rise to a false sense of security.

2

We study the security of step-reduced but otherwise unmodified SHA-256. We show the first collision attacks on SHA-256 reduced to 23 and 24 steps with complexities $2^{18}$ and $2^{50}$, respectively. We give an example colliding message pair for 23-step SHA-256. The best previous, recently obtained result was a collision attack for up to 22 steps. Additionally, we show non-random behaviour of SHA-256 in the form of pseudo-near collisions for up to 31 steps, which is 6 more steps than the recently obtained non-random behaviour in the form of a semi-free start near-collision. Even though this represents a step forwards in terms of cryptanalytic techniques, the results do not threaten the security of applications using SHA-256.

3

[...]First we describe message modification techniques and use them to obtain an algorithm to generate message pairs which collide for the actual SHA-256 reduced to 18 steps. Our second contribution is to present differential paths for 19, 20, 21, 22 and 23 steps of SHA-256. We construct parity check equations in a novel way to find these characteristics. Further, the 19-step differential path presented here is constructed by using only 15 local collisions, as against the previously known 19-step near collision differential path which consists of interleaving of 23 local collisions. Our 19-step differential path can also be seen as a single local collision at the message word level. We use a linearized local collision in this work. These results do not cause any threat to the security of the SHA-256 hash function.

4

[...]We build on the work of Nikoli\’{c} and Biryukov and provide a generalized nonlinear local collision which accepts an arbitrary initial message difference. This local collision succeeds with probability 1. Using this local collision we present attacks against 18-step SHA-256 and 18-step SHA-512 with arbitrary initial difference. Both of these attacks succeed with probability 1. We then present special cases of our local collision and show two different differential paths for attacking 20-step SHA-256 and 20-step SHA-512. One of these paths is the same as presented by Nikoli\’{c} and Biryukov while the other one is a new differential path. Messages following both these differential paths can be found with probability 1. This improves on the previous result where the success probability of 20-step attack was 1/3. Finally, we present two differential paths for 21-step collisions for SHA-256 and SHA-512, one of which is a new path. The success probability of these paths for SHA-256 is roughly $2^{-15}$ and $2^{-17}$ which improves on the 21-step attack having probability $2^{-19}$ reported earlier. We show examples of message pairs following all the presented differential paths for up to 21-step collisions in SHA-256. We also show first real examples of colliding message pairs for up to 20-step reduced SHA-512.

Completely academic, but you know what they say - attacks only get better.

-

Interesting stuff.

NSA/CSS periodically releases declassified documents or indexes to these documents to the public. The documents listed on this page were located in response to numerous requests received by NSA on the various subjects stated and for which there appears to be a general public interest. The date after each entry reflects the most current release date of that material. When additional material for a given subject is updated then a new subject index date is posted. To select a subject index, click on the subject title.

In particular, the Cryptologic Spectrum Articles and Cryptologic Quarterly Articles have some fun reads.

-

An easy to cut ‘n paste into a blog post set of old web server log entries depicting an instance of Tor being used to proxy/anonymize automated probes of this web site.

anonymizer.blutmagie.de - - [13/Mar/2008:00:59:00 -0700] “GET /forum/phpbb/index.php HTTP/1.0″ 404 285 “http://forum.d-kriptik.com/phpbb/index.php” “Mozilla/4.0 (compatible; MSIE 6.0; AOL 9.0; Windows NT 5.1)”

tor.anonymous.proxy.quex.org - - [13/Mar/2008:00:59:01 -0700] “GET /forum/phpbb2/index.php HTTP/1.0″ 404 286 “http://forum.d-kriptik.com/phpbb2/index.php” “Mozilla/4.0 (compatible; MSIE 6.0; AOL 9.0; Windows NT 5.1)”

tor.anonymizer.ccc.de - - [13/Mar/2008:00:59:02 -0700] “GET /forum/forums/index.php HTTP/1.0″ 404 286 “http://forum.d-kriptik.com/forums/index.php” “Mozilla/4.0 (compatible; MSIE 6.0; AOL 9.0; Windows NT 5.1)”

tor.anonymizer.ccc.de - - [13/Mar/2008:00:59:08 -0700] “GET /forum/board/index.php HTTP/1.0″ 404 285 “http://forum.d-kriptik.com/board/index.php” “Mozilla/4.0 (compatible; MSIE 6.0; AOL 9.0; Windows NT 5.1)”

-

Like heat and humidity, free music and Central Park mean summer. The 2008 schedule is up at the Summer Stage web site. And, the opening Saturday looks good to me.

Vampire Weekend
Kid Sister
Ecstatic Sunshine

Saturday, June 14, 2008
From 4:00 PM to 7:30 PM
Central Park SummerStage

This entry was posted on Wednesday, May 21st, 2008 at 9:25 pm and is filed under Anonymity & Privacy, Authentication & Identity, BSD, Conferences, Crypto, Debian & Ubuntu, Off-topic, Security. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.