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Wachter Space 🚀

This site is somewhere between a personal notebook and a way of not repeating myself.

Currently I write about:

Exam Anti-Patterns

There is no such thing as the perfect university exam, but if we agree that its purpose is to give an objective score about an individual’s comprehension of the covered topics, then there is clearly a way to be less wrong when creating exams. This post lists a few DONT’S that can be easily avoided. If you think there is an anti-pattern in this post, you can write me an email and I will add it here.

Operation System Security Lecture Summary

Lecture summary of the lecture operation systems security, organized with self test toggles. The lecture is concerned with binary exploitation from an offensive as well as a defensive point of view. I can really recommend the lecture, if you are interested in modern security mechanisms implemented by operating systems and hardware. Basic DefinitionsWhat is a vulnerability?What is the definition of an exploit? Set-uid-bitAllows an executable, that is owned by the user, to use root privileges during execution

b01lers CTF resnet Model Inversion

With KITCTF we participated in the bo01lers CTF and finished 6th. There were some quite fun challenges. Including the resnet challenge, which is a machine learning challenge. I hope to see more machine learning challenges in the future. Challenge description: A naive AI startup released a new visual password system based on State-of-the-Art Neural Network technology. Wanting to save on costs they reuse the popular Resnet model to create embeddings which input password images are checked against hoping to leverage the feature extraction capabilities of Resnet.

Self Test Questions Data Science I

Answers to self test questions for the lecture “Data Science I” at KIT. If you spot any errors, write me an e-mail or Discord message. Lecture 1: IntroductionGive examples of applications of clustering.Customer groups clustered based on bought productsUnsupervised malware family identificationOutlier DetectionDescribe a scenario from natural sciences, in which classification is useful: What are the attributes/class? How would you try to solve it?Flower family classification: Attributes (features)Color of different partsShape of different partsSize of different partsSolve it by training a multi-class NN with enough high quality training dataExplain the principle of the One Rule classifier.

Self Test Questions Machine Learning

Self test questions for the lecture “Machine Learning - Foundations and Algorithms” at KIT. Lecture 3: Model SelectionWhy is it a bad idea to evaluate your algorithm on the training set?Evaluating on the training set, rewards overfitting. Overfitting means learning training points by heart, instead of approximating the distribution the training points were drawn from. A trivial algorithm that just stores and queries all training points, has 100 % accuracy on the training set.

Insomnihack Teaser 2022: Herald

Read more writeups at kitctf.de Challenge description: Our lab administrator has just passed out from a strange virus. Please help us find the password to his messaging app so we can identify what he was working on and save his life. We are given an apk (Android Package) starting it, it asks for username and password to enter. It does not require any network connection, so it is a classical CrackMe.

hxp CTF: shitty blog

Read more writeups at kitctf.de Challenge description: Please use my shitty blog 🤎! We are given a docker container running php. The only notable things about it, is that there is a readflag binary on the server and that the webroot is /var/www/html. Other than that only index.php is interesting: <?php // TODO: fully implement multi-user / guest feature :( $secret = 'SECRET_PLACEHOLDER'; $salt = '$6$'.substr(hash_hmac('md5', $_SERVER['REMOTE_ADDR'], $secret), 16).'$'; if(! isset($_COOKIE['session'])){ $id = random_int(1, PHP_INT_MAX); $mac = substr(crypt(hash_hmac('md5', $id, $secret, true), $salt), 20); } else { $session = explode('|', $_COOKIE['session']); if( !

Self Test Questions Entrepreneurship

Self test questions for the lecture entrepreneurship at KIT. Session 1: IntroductionWhat is the activity of an entrepreneur according to Jean Baptiste Say?The entrepreneur shifts economic resources out of an area of lower and into an area of higher productivity. 🐎How does Joseph Schumpeter define “entrepreneurship”?Entrepreneurship is about new factor combinations leading to new products, production methods or new markets. It is about creative destruction. 🤯What are the career reasons of nascent entrepreneurs?

hack.lu CTF 2021 Writeups

Tenbagger # Challenge description: I think I took it too far and made some trades and lost everything. My only chance to fix my account balance is a tenbagger. We are given a pcap and open in Wireshark. It contains a lot of what looks like normal web browsing. But somewhere in there are a few FIX messages. FIX is the Financial Information eXchange protocol. First, I thought that we need to get the credentials from the FIX login, but there are no such packages.

ASIS CTF 2021 Writeups

These are writeups for the first CTF I participated in during a weekend. Before that I only solved some picoctf and Google Beginners quest challenges after the events. I played with KITCTF the CTF team of the Karlsruhe Institute of Technology. Factory # Challenge description In the simplest terms, factory misco-graphy is the ratio of output to input! The challenge file is only one pdf. Opening the only shows the text “Real-World Misco-graphy”.