Hard disk hacking (08 Aug 2013)

Jereon also held a presentation on this topic at OHM 2013. I wasn't there, so I cannot wait to see the video recording to show up on the OHM2013 web site. If, like me, you are a reverse engineer deep down in your heart, this article is a must-read for you. It shows how with a little bit of hardware tweaking, but mostly systematic and logical thinking and debugging, hard disks can be hacked so that they will present fake contents to users - which is a very troublesome thought to anyone concerned about security.

In one of those startling coincidences, just before I found Jereon's article, I had dug up old 8085 programming manuals at home. 8085 CPUs were used in the controller hardware used for Atari's SH20x and Megafile hard disks (I specialized into Atari hardware in the 80s and early 80s). My plan back then was to learn enough about 8085 assembler and architecture so that I'd be able to disassemble and reverse-engineer the controller's firmware. That project never got too far, unfortunately, and so I am really happy to see that a new generation of coders is fascinated by the same idea and, unlike me, follows through. Bravo!

HTTPS (30 Jul 2013)

Hartley Brody's "How HTTPS Secures Connections: What Every Web Dev Should Know" happened to float by on Hacker News (IIRC) the other day. For me, it was a great start to start exploring this wide field.

Key learnings:

• Certificates are required to authenticate communication partners. In other words, make sure you are really talking to your bank and not to someone who enjoys spending spare time on building web sites which look surprisingly like your bank's
• Following authentication, a "common secret" is established which is henceforth used to encrypt communication contents. The magic sauce is the Diffie-Hellman-Merkle algorithm. Algorithms like this make it possible to exchange enough information in the open to establish this common secret.
• For performance reasons, subsequent encrypted communication is symmetric.

Which pushes the following items on my reading/viewing list:

• Diffie-Hellman key exchange (video)
• Other key exchange algorithms: PSK (pre-shared key), elliptic-curve Diffie-Hellman, RSA, SRP
• What is Diffie-Hellman? (RSA Labs)
• Discrete Logarithm Problem (video)
• Simon Singh: Geheime Botschaften
• https://www.boxcryptor.com
• The First Few Milliseconds of an HTTPS Connection
• https://konklone.com/post/switch-to-https-now-for-free

A subset of Python (30 Jun 2013)

import random
import array
import sys

numbers = array.array('i')
flags = array.array('c')
solutions = 0

def find_solutions(k, target_sum):
    global solutions

    if target_sum == 0:
        print "  Solution:",
        for i in range(0, len(numbers)):
            if flags[i] != 0:
                print numbers[i],
        print
        solutions = solutions + 1
    else:
        if k < len(numbers):
            if (numbers[k] * (len(numbers)-k+1)) >= target_sum:
                if target_sum >= numbers[k]:
                    flags[k] = 1
                    find_solutions(k+1, target_sum - numbers[k])
                    flags[k] = 0
                find_solutions(k+1, target_sum)

def find_subset_sum(target_sum):
    global solutions
    global flags
    print "Subsets which sum up to %s:" % target_sum
    flags = [0] * len(numbers)
    find_solutions(0, target_sum)
    print "Found", solutions, "different solutions"

def subset_sum_test(size):
    global numbers
    total = 0

    print "Random values:\n  ",
    for i in range(0, size):
        numbers.append(random.randint(0, 1000))
        total = total + numbers[i]
        print numbers[i],
    print

    numbers = sorted(numbers, reverse = True)
    target_sum = total/2
    find_subset_sum(target_sum)

subset_sum_test(15 if len(sys.argv) < 2 else int(sys.argv[1]))

Catching up with web frameworks (07 May 2013)

In both cases, I liked what I saw, but of course I need to learn a lot more about those frameworks to see when and for which kind of projects I would choose either Vaadin or Play over Spring MVC, which I have been using professionally for a while now.

It's obvious, however, that Spring MVC and Play share a similar, web-oriented notion of the MVC pattern, while I am not sure whether MVC plays much of a role in Vaadin at all, with its focus on RIA and one-page web applications. (In Vaadin, I guess MVC would be applied in a way similar to desktop apps.)

Würdiges Angebot (06 May 2013)

Betreff: Würdiges Angebot von haltbarer Holdinggesellschaft!

Sie haben ausgezeichnete verwaltungsmäßige Kenntnisse, ausreichende Fertigkeit im MS-Office. Sie sind aufmerksam, organisiert, repräsentativ, zuverlässig und pünktlich, bewandert im Gebrauch von sozialen Netzwerkseiten wie Twitter und Facebook. Außerdem können Sie gleich in der Belegschaft und unabhängig arbeiten, verstehen und durchführen Sie Erfolgsorientierte Instruktionen, dann suchen wir Sie.

Haben Sie Interesse für diesen Job, bitte, senden Sie uns Ihre Kontakt-Information:

Voller Name:
Land:
Stadt:
E-Mail:

Bitte bewerben Sie uns per Email für weitere Beschreibung:xxx@yyy.com

Hier will jemand auf recht naïve Art Emailadressen sammeln, um sie für Zwecke zu verkaufen, die vom Abseitigen zum Verabscheuungswerten reichen. Nicht weiter der Rede wert eigentlich - abgesehen davon, daß das Deutsch mal wieder so entlarvend spaßig ist, daß man sich fragen muß, wer auf solche Email wohl antworten mag.

Die Phishing-Kampagne verwendet als Lockvogel die Begriffe "Würde" und "Haltbarkeit" (Nachhaltigkeit), um den vermeintlichen Arbeitgeber attraktiv zu machen. In diesen unseren Zeiten des Raubritterkapitalismus fast schon ein erfolgversprechendes Rezept, denn genau wegen dieser Begriffe blieb ich an der Nachricht hängen. Liegt aber sicher nur an mir...

JavaScript: The Good Parts (04 May 2013)

All in all, a great book! However, it left me even more confused about how JavaScript sets "this" than I was before. Fortunately, I found the discussion at http://stackoverflow.com/questions/3127429/javascript-this-keyword and the article at http://www.digital-web.com/articles/scope_in_javascript/ which both clarified open questions for me. But I am pretty sure I will forget JavaScript's context subtleties fairly quickly, and then I will have to look them up again. Oh well.

Crockford's approach is to focus on a subset of JavaScript which he considers sane, Of course there is much debate on what belongs into the subset and what doesn't. For example, Crockford bans the ++ and -- operators because they remind him too much of obfuscated C++ code. I did not find this particular advice too convincing, and it seems I am not alone.

To experiment with code from the book and test some code of my own, I used the jsc command-line JS interpreter on the Mac, and also toyed with http://jsfiddle.net/. (On Ubuntu, I guess I could have used rhino.)

Older topics...

• 2012

Add a new blog entry.

to top