Mission Impossible

This seems to be one of the toughest challenges ever…as the name says though…

To anyone who solved the last part: How long did it take to decrypt the message? Oh man, it’s so slow…

EDIT: Finally got it. 19077 queries. ■■■. I loved this challenge.

I could really use a push on the first part of this challenge. The usual methods don’t seem to work.

i have literally no idea of how to start the challenge, can smb DM me on how to start. I’ll rly appreciate it

Type your comment> @Ugi said:

I could really use a push on the first part of this challenge. The usual methods don’t seem to work.

I used a very basic, usual method for the first part. Consider all possible ways of analyzing the ciphertext.

I can’t decode the message file. Can someone give any clue?

Really liked this challenge. Techniques for both parts were new for me and I learned lots, although I lost my weekend :slight_smile:

This is a nice straightforward challenge. I probably made around 1.5 million queries before I stopped and verified my code and found a silly mistake ( I base64 decoded an initial hex encoded data ¯_(ツ)_/¯ ) After fixing the mistake it took about 19000 queries to find the flag.

I am curious how the challenge was constructed. The paper suggests that it should take around 1 million queries, but this challenge requires 19000 only. It is highly unlikely to be a random occurence. Is there a way to construct this kind of challenge with any given complexity, or was it a trial and error approach?

Took almost 3 hours on my slow machine :frowning: Had to code in a way to reconnect to new HTB docker since the instances kept dying on me

Hi all , cannot even start this challenge, outlook element won’t open, could anyone mp an hint plz ? ty

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 :smiley:

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 :slight_smile:

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 :slight_smile:

looooool im getting spoilled here hahha i think i need to switch to my i7 laptop