Unix, C/C++, Pixel, Algorithmen, Katzen
"Life is really simple, but we insist on making it complicated." -- Confucius via ChatGPT Exercise Setup OpenBSD 7.5 on a physical machine with Hetzner (~35 EUR per month) with RAID1 on 2 SSD drives and encrypted partition. We neither have access to OpenBSD installation images directly nor can we use an OpenBSD rescue system. Hetzner actually offers access to web based KVM interface to your…
Not the board game A couple of years ago, when I first heard about Game of Life, all I could think of was the board game . When I ran the program for the first time - probably an ASCII version under FreeBSD, somewhere around 2003 - , I did not understand at all what all these moving, blinking and vanishing pixels meant. In an interview with the original author , Conway states that he is pretty…
Overview With all the calculations and lookup tables from the previous articles, we are now able to specify the actual enciphering and deciphering functions, including some tests taken from the original paper to make sure the implementation works in a sane manner. Configuration By using the macro definition AES_CALCULATE_LOOKUP_TABLES in config.h , we decide if the library has to create the lookup…
Proof of concept The actual motivation behind the previous article is that I did not want to just copy & paste the AES lookup tables from the book or other implementations, I wanted them to calculate them by myself. It might make sense for a tiny implementation, with limited ram and rom, to calculate the result of the byte substitution from scratch every time. However, this was not my intention.…
Progression can only be achieved by something you have never done before. Unlike DES, which is a Feistel cipher, AES is using substitution-permutation networks. These substitution permutations happen within Finite Fields, so called Galois Fields, in honour of the French mathematician Évariste Galois. Before we start going deeper into the algorithm, I want to explain the basic concepts behind…
Overview : Advanced Encryption Standard (AES, 2001) AES (1/3): An Introduction to Galois Fields AES (2/3): A Description of AES Lookup Tables AES (3/3): Encryption and Decryption We choose to go to the Moon As a self-imposed programming challenge I started to have a closer look into the topic of Cryptography. I wanted to know much more about the (probably) most important cipher in the world: The…
Background One of the caveats regarding block ciphers I mentioned in my DES article was “Encrypting identical input blocks” . The actual problem here is that redundant input blocks will always result in the same output block when encrypted. Encrypting data, holding recurring structure or metadata, with a so called Electronic Codebook Block Cipher ( ECB ) could make the resulting ciphertext…
Background Base64 encoding can be found in many modern applications like browsers or e-mail Clients. Stating RFC 4648 , base64 “is used in many situations to store or transfer data in environments that, perhaps for legacy reasons, are restricted to US-ASCII” . However, it is also very handy in case you want to edit binary data with your text editor, i.e. adding your Public SSH Key to the…
Hmm? It must have been around 1996 when I first heard about X-COM : TERROR FROM THE DEEP. It is the sequel to the round-based strategy game classic UFO : ENEMY UNKOWN, where you have to defeat an alien invasion with your pixel soldier squad. This time the mean alien bastards came back (actually, they never left) and continue with their plan to get in control of planet earth while doing nasty…