Level 21

Not sure if it's the sequence...

You've actually seen the pattern before somewhere... B-)

The fact that the data's uncompressible must mean that it's already compressed, or it's encrypted (Interestingly enough; I ran a chi-square on the ZIP file and it's even lower than the .pack file, just 295!). Seeing as how this is supposed to be a programming challenge, I was expecting something that I could actually decipher with a program, but so far I'm coming up empty. Even the last few comments, which have some specific information in them, are meaningless to me.

What the hell is with this level? I really don't get any of the hints (I tried reversing all the bits in the file, but that didn't get me anywhere, and as the designated outcast, I didn't play with anybody else as a kid, so I have no idea what game he's talking about.)

btw, i think it's obvious what game he played as a kid.

So did you figure that out before or after you discerned the as-yet-invisible-to-me sequence you've been mentioning?

-tah

btw, i think it's obvious what game he played as a kid.

So did you figure that out before or after you discerned the as-yet-invisible-to-me sequence you've been mentioning?

Before. It's how I got the sequence that reminded me of a game I used to play at birthday parties.

[mjpieters]

It's how I got the sequence that reminded me of a game I used to play at birthday parties.

Any hints towards what game this might be; games differ from culture to culture, and the games I can come up with from my youth don't offer me any clues..

Any hints towards what game this might be; games differ from culture to culture, and the games I can come up with from my youth don't offer me any clues..

I only remembered the kids' game after I'd completed it. It's a 2nd-law-of-thermodynamics problem; and one that gets proposed from time to time by the same people who think they've made a perpetual motion machine. (The tricky bit is working out where the header went; and what to use that doesn't require headers. I had to write my first Python program to solve this---about 15 lines! I'm very impressed now with Python's power and string handling.)

It's how I got the sequence that reminded me of a game I used to play at birthday parties.

Any hints towards what game this might be; games differ from culture to culture, and the games I can come up with from my youth don't offer me any clues..

Well, I only made the connection *once* I'd solved it. I don't think it helps you solve it.

The biggest hint I can give for someone who is still stuck with package.pack is to encourage you to think about WHY IT DOESN'T COMPRESS.

The hint about looking backwards is useful later on.

The tricky bit is working out where the header went; and what to use that doesn't require headers.

Right. This is the key insight that unblocked me. I was thinking it can't be a such-and-such file because it doesn't have the right header. Well, there is a format that doesn't need such a header and it took a Python library rather than a Unix command for me to discover that.

Well, I only made the connection *once* I'd solved it. I don't think it helps you solve it.

Ah, good, at least that gives us no disadvantage.

The biggest hint I can give for someone who is still stuck with package.pack is to encourage you to think about WHY IT DOESN'T COMPRESS.

Yes, I've been thinking about that almost immediately after I saw the data. I see 3 possibilities:
- it's (mostly) random data, but that seems rather unlikely
- it's compressed
- it's encrypted

The second option seems most likely, I guess.

[mjpieters]

It's a 2nd-law-of-thermodynamics problem; and one that gets proposed from time to time by the same people who think they've made a perpetual motion machine.

Yup, got that far too; lot's of entropy here, how do I make something less chaotic from it. Just was hoping on a clue as to what game is referred too.

(The tricky bit is working out where the header went; and what to use that doesn't require headers. I had to write my first Python program to solve this---about 15 lines!

Doesn't sound too bad a problem then, if it can be solved in a handful of lines of Python.

Doesn't sound too bad a problem then, if it can be solved in a handful of lines of Python. :)

OTOH a handful of lines of Perl would be a puzzle al by itself :)

Oh, and the recurring 7-byte pattern in the first 35 bytes makes a lot more sense once you start down the path of cracking open the file.

Again, it doesn't really help you solve it but it is obvious once you've started to solve it.

[mjpieters]

Oh, and the recurring 7-byte pattern in the first 35 bytes makes a lot more sense once you start down the path of cracking open the file.

Well, that pattern appears to be excluding a module I was testing to see if it applied; that module expects 4-byte chunks. Next module!

Yup, got that far too; lot's of entropy here, how do I make something less chaotic from it.

Right, there's only about 400 bits of real entropy there. (Not counting the font information, or properties of the English language.) It's reversible.

[mjpieters]

Not there yet, but I know the game now; I only know it because my wife (who's a Scot) introduced me to it at my childrens' birthdays.

I do get the same feeling as at my birthday though; what might be inside!