iCTF 2011 9x9 Choose Your Battles



In this challenge we are tasked to solve a simple sudoku like puzzle and derive the key from the given information By noticing a few key squares such as the 16, 3’s and 5, we can put together a solution to the puzzle rather quickly

.

r1=6
r2=7
r3=7
r4=6
r5=6
r6=6
r7=6
r8=6
r9=5

The second part of the puzzle is determining the key. If we look closely at the format of

“rX + some binary number” we can see that the sums with our r numbers will all fall into ascii range

1001111=79
1011001=89
1100100=100
1100100=100
1110010=114
1101011=107
1100010=98
1011110=94
1101110=110

Now we can put together our characters

6+79=85=U
7+89=96=a
7+100=107=k
6+100=106=j
6+114=120= x
6+107=113=q
6+98=104=h
6+94=100=d
5+110=115= s

Following the instructions the string “Uakjxqhds” is formed. After finding that this in fact is not the key we take a quick look at the puzzle again and find that a few sectors of it can be easily rearranged without affecting the completeness of the solution.

r1=7
r2=8
r3=8
r4=7
r5=7
r6=7
r7=7
r8=7
r9=5
7+79=86= V
8+89=96= a
8+100=108=l
7+100=107=k
7+114=121=y
7+107=114=r
7+98=105= i
7+94=101= e
5+110=115=s

After a few arrangements we come to a winner this time spelling out “Valkyries”

On my orignal attempt at this challenge I did not go through the steps of rearranging the puzzle. Instead I found that by noticing that a few characters could fluctuate going up or down and keep the puzzle intact I was able to pull Valkyries out of the gibberish of “Uajxqhds”

6+79=85=U V
7+89=96=a a
7+100=107=kl
6+100=106=jk
6+114=121= y
6+107=113=qr
6+98=104=h i
6+94=100=d e
5+110=115= s