Hi, I’m also stuck on this challenge for a while now, tried some basic analysis on the ciphertext but got nowhere. If anyone that did can pm an hint… I can share all what I have tried. thanks
I liked this challenge, much more creative than the guessing games that many of the other challenges become. The first part is non-trivial, look at classical cryptanalysis and try to adapt one of the methods. I actually found part 2 easier since I’d recently been studying the attack.
If you do a bit of research on the IP they use, you can take out a VPS very physically close to their server - perhaps in the same datacentre ;), which speeds up the attack a lot. I’d also reccomend Sagemath since it makes the mathsy bits a bit easier than raw Python.
got it special thanks @electrifeye and @0xlimE, fill free to PM me
I was hoping to use this challenge as a learning exercise but all I’ve learnt so far is I know f*ck all about crypto analysis. I’ve tried a few python scripts to XOR and shift the bytes in the file but I’m getting nothing useful back and it feels like I’m wildly guessing without any strategy.
Can anyone suggest some good resources that would be helpful on this and the other crypto challenges.
Any hints on this one would be welcome.
this was surprisingly easy! after the first step it tells you what to do, from there i just got a script off the web, adjusted it a bit and waited :3
anyone in 2020 
Oh man, part 2 is taking so long on my old quad 5i laptop 1.7ghz. Can any solvers tell me how many hours did it take them on various speed machines? After about 7 hours my test s is around 10^140, at 3500 queries, it’s going to take days to get there…
Update: after 36 hrs I have 5900 queries, s is 10^259, and using ice packs on my laptop but I can read half the flag so far 
Update: 60 hours later, 6773 queries, got the flag! I’m Puzzled as to why my routine used so few queries compared to other reports though.
Feel free to PM for help.
Fun challenge! First part was most challenging for me, but @electrifeye’s hint about classic cryptanalysis is great!
Second step was easy as @0x41 mentioned and making the 19077 requests took me only 15 minutes, don’t know why it is so fast for me…
If anyone does need a small nudge, feel free to send me a pm
looooool im getting spoilled here hahha i think i need to switch to my i7 laptop