###dm248.github.io

[Tarock] [Rubik]

I tend to think back fondly of the good old times when I was a student but I must have had it easy. Here is an assignment someone else got recently: Find the worst-case swap count for (13,4,1) shellsort on 25 elements. The official solution offered was simple, just shy of 1 billion core years to run (trying all 25! permutations). So that got me curious, is the problem doable? Well, it turns out that it is, just not quite that way...

TBA

I tried a couple problems at UIUCTF last weekend, crypto and pwn mostly. It had an interesting mixture of simple and hard problems with not much in between. Overall, it was fun and educational...

NahamCon CTF was a fun event last weekend. I only had about 10 hours for it, so I did what tends to suit me best: crypto plus some misc challenges. Overall I scored close to 1500, which is OK but there is always room to do more. Here are some of my thoughts about the problems..

Two weeks ago, the USAF and DDS put up a Hack-A-Sat space hacking challenge. I only had time to check out a handful of the problems, one of which was Where's the Sat that asked people to identify a satellite by location and time and then predict where it would be at another time. It turns out that with the right tools, such as Skyfield, the problem is straightforward (check, e.g., here). But the solution is not very satisfying unless one understands what goes on inside the black box... so if you are curious, read on...

I decided to give GitHub Pages a try so that I do not have to bother with hosting these posts elsewhere. Take-off was quite smooth but not without a few hiccups...