Didactic Scrambled Egg Cipher

MerickOWA · Post by **MerickOWA** » Tue Oct 21, 2008 4:22 pm

The challenge text is incomplete, unless the problem is to unscramble the pseudocode

MerickOWA · Post by **MerickOWA** » Tue Oct 21, 2008 6:20 pm

heh ok, I see the problem now, actually, if you leave it the way it is, it might be more 'interesting' (depending on your browser ofcourse)

the flip array isn't defined, and unless its a bug they key variable is never used.

MerickOWA · Post by **MerickOWA** » Tue Oct 21, 2008 6:26 pm

maybe it would be better if you posted the encryption algorithm in a language like java or something so that you can be assured that questions about exact byte order or custom arrays are easily answered.

As these problems get more complicated, I can see it getting harder to explain the algorithm without just giving all the details of each function or line of code.

tails · Post by **tails** » Tue Oct 21, 2008 8:44 pm

key is a 16-byte value and flip has 16 elements, so flip are 8-bit independent values ...?

If so, this challenge should be very tough!

MerickOWA · Post by **MerickOWA** » Tue Oct 21, 2008 10:17 pm

tails wrote:key is a 16-byte value and flip has 16 elements, so flip are 8-bit independent values ...?

If so, this challenge should be very tough!

O that seems very likely. Yea, this will be an extremely difficult challenge. 128 bits of possibilities ><. Maybe at least could we hope that flip is some permutation of the 0-15 (meaning no repeats or duplications of numbers)

Post by **adum** » Tue Oct 21, 2008 11:14 pm

sorry about the mess... added that one late last night while tired, and didn't check it thru carefully.

should be better now. flip was meant to read 'key'.

good luck!

adum

MerickOWA · Post by **MerickOWA** » Wed Oct 22, 2008 4:15 pm

adum wrote:sorry about the mess... added that one late last night while tired, and didn't check it thru carefully.

should be better now. flip was meant to read 'key'.

good luck!

adum

Is it safe to assume that "print eggs;" prints out a hex encoded number with the most significant byte (of the three) first?

Or to put it another way, is the first encoded "eggs" 0x0043ed82 or 0x0082ed43?

Also just to be clear on "for (int eggs = {each 3-byte tuple in plaintext})"

If the plain text bytes were (in order from least significant to most significant) {0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, ... }

would eggs start off being 0x00ccddaa the first time around and 0xffeedd the second time around?
OR
would eggs start off being 0x00ccddaa the first time around and 0xddccbb the second time around?

Post by **adum** » Wed Oct 22, 2008 7:44 pm

Is it safe to assume that "print eggs;" prints out a hex encoded number with the most significant byte (of the three) first?

yes.

Also just to be clear on "for (int eggs = {each 3-byte tuple in plaintext})"

If the plain text bytes were (in order from least significant to most significant) {0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, ... }

would eggs start off being 0x00ccddaa the first time around and 0xffeedd the second time around?
OR
would eggs start off being 0x00ccddaa the first time around and 0xddccbb the second time around?

eggs would first be 0x00aabbcc, then 0x00ddeeff. and there is no feedback between the first tuple and the second.

MerickOWA · Post by **MerickOWA** » Wed Oct 22, 2008 9:27 pm

I really don't see much hope of this problem being solved ><

I'm not even sure I could solve the problem if i knew the first half of the sentence!

Possibly if LOOP wasn't so high, and there wasn't several bytes of key overlapping each bit of the "egg" variable, it might be possible.

This is one evil problem!

Post by **adum** » Wed Oct 22, 2008 9:57 pm

in the original cipher, the LOOP was 1000 =)

i played around with it. at lower than 10, it barely looked scrambled. i guess i can put on a simpler version just for people to get their feet wet...

falcon2424 · Post by **falcon2424** » Wed Oct 22, 2008 10:23 pm

I don't know if figuring this out is part of the challenge, but how are you defining the << and >> operators?

I'm assuming that they're just left and right shifts, where zeros are inserted when new bits are required, but I want to double check. (Wiki says that '>>' is implementation defined)

Post by **adum** » Wed Oct 22, 2008 11:05 pm

I don't know if figuring this out is part of the challenge, but how are you defining the << and >> operators?

I'm assuming that they're just left and right shifts, where zeros are inserted when new bits are required, but I want to double check. (Wiki says that '>>' is implementation defined)

just so: like in C.

therethinker · Post by **therethinker** » Sat Oct 25, 2008 1:48 am

I'm with MerickOWA on this one, its looking pretty tough. I can't believe this is the "warmup"!

The only solace I can find is that you're given every 1 in 3 key "code nibbles", and a single bit of another.

Overall, I'm loving these didactic challenges (especially since crypto is a bit of a weak spot for me) Although, you might want to start moving somewhere else

There's all those castles/forts down at the bottom that might be worth invading

MerickOWA · Post by **MerickOWA** » Sat Oct 25, 2008 5:20 pm

therethinker wrote:I'm with MerickOWA on this one, its looking pretty tough. I can't believe this is the "warmup"!

The only solace I can find is that you're given every 1 in 3 key "code nibbles", and a single bit of another.

Overall, I'm loving these didactic challenges (especially since crypto is a bit of a weak spot for me) Although, you might want to start moving somewhere else There's all those castles/forts down at the bottom that might be worth invading

Yea, and I'm having a hard time even knowing that to figure out the key. I think i've got about 14 out of the 128 bits, and anytime I try to guess at the others, it never makes any sense.

therethinker · Post by **therethinker** » Sat Oct 25, 2008 7:48 pm

You can also make confident guesses for several more.

This challenge is looking to be more paper & pencil, or at least a significant portion of it.