# XOR Riddle

Discussion in 'Homework Help' started by jegues, Jul 22, 2011.

1. ### jegues Thread Starter Well-Known Member

Sep 13, 2010
735
43
We're given the following image,

and we are given the caption "I feel pretty", and we are questioned, "What's next?"

Does anyone have a guess at what the answer might be?

Looking at how the xors are connected, the output of the leftmost xor will output a 0.

I tried to take the resulting binary string, (i.e. 0101111101110111) and convert it to text via ASCII.

The text it returns is "_w" which is incorrect.

Any ideas?

EDIT: You are required to input the next consequtive shifts.

• ###### d98eded8bb773d7295b683b65efc776b.jpg
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Last edited: Jul 22, 2011
2. ### MrChips Moderator

Oct 2, 2009
12,636
3,454
Keep going... shift one bit right at a time and record the results after every shift.

3. ### ErnieM AAC Fanatic!

Apr 24, 2011
7,439
1,627
I didn't work it out, but I bet the answer is "OH so pretty."

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
I tried but didn't get much sense.

I simulated two steps as shown in pdf's

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5. ### TBayBoy Member

May 25, 2011
148
19
isn't 1011 1110 1110 1111 BEEF in hex?

Last edited: Jul 24, 2011
6. ### narasimhan Member

Dec 3, 2009
72
6
Yes and the next step is 0101 1111 0111 0111 which is 5F77 in hex. But it doesn't make any sense.
Only if we know the relationship between 1011111011101111 and "I feel pretty", we can decode the next step.

7. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
At least I can now make "pretty pictures" even if it is all meaningless.

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8. ### narasimhan Member

Dec 3, 2009
72
6
Is that picture of yours some random step since it doesn't match with either of the 2 values(current and next)
Anyway nice picture

9. ### magnet18 Senior Member

Dec 22, 2010
1,232
125
hmmm...
1011 1110 1110 1111 in decimal gives
11___ 14___ 14___ 15 which when converted to the corresponding number of the alphabet makes
k ____ n ____ n ___ o

then
0101 1111 0111 0111
5 15 7 7
EOOG

I don't think this is going anywhere...

10. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
I thought the values were OK.

I've attached the screens I get after the first and second right shifts.

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11. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Perhaps it's a trick. Looks like an XOR encrypter of sorts.

Who was "pretty"? - The Mona Lisa.

It's the Da Vinci Code!

Where's Jegues? Has he stolen the encoder?

Insanity slowly overtakes me! I'm becoming paranoid.

Loosewire might be able to help.

12. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
It's an LFSR; Linear Feedback Shift Register.

13. ### blah2222 Well-Known Member

May 3, 2010
565
33
Code ( (Unknown Language)):
1.
2. 1 0 1 1 1 1 1 0 1 1 1 0 1 1 1 1
3. 0 1 0 1 1 1 1 1 0 1 1 1 0 1 1 1
4. 1 0 1 0 1 1 1 1 1 0 1 1 1 0 1 1
5. 1 1 0 1 0 1 1 1 1 1 0 1 1 1 0 1
6. 1 1 1 0 1 0 1 1 1 1 1 0 1 1 1 0
7. 1 1 1 1 0 1 0 1 1 1 1 1 0 1 1 1
8. 1 1 1 1 1 0 1 0 1 1 1 1 1 0 1 1
9. 0 1 1 1 1 1 0 1 0 1 1 1 1 1 0 1
10. 1 0 1 1 1 1 1 0 1 0 1 1 1 1 1 0
11. 1 1 0 1 1 1 1 1 0 1 0 1 1 1 1 1
12. 0 1 1 0 1 1 1 1 1 0 1 0 1 1 1 1
13. 0 0 1 1 0 1 1 1 1 1 0 1 0 1 1 1
14. 1 0 0 1 1 0 1 1 1 1 1 0 1 0 1 1
15. 1 1 0 0 1 1 0 1 1 1 1 1 0 1 0 1
16. 0 1 1 0 0 1 1 0 1 1 1 1 1 0 1 0
17. 0 0 1 1 0 0 1 1 0 1 1 1 1 1 0 1
18. 1 0 0 1 1 0 0 1 1 0 1 1 1 1 1 0
19. 1 1 0 0 1 1 0 0 1 1 0 1 1 1 1 1
20. 0 1 1 0 0 1 1 0 0 1 1 0 1 1 1 1
21. 1 0 1 1 0 0 1 1 0 0 1 1 0 1 1 1
22. 0 1 0 1 1 0 0 1 1 0 0 1 1 0 1 1
23. 1 0 1 0 1 1 0 0 1 1 0 0 1 1 0 1
24. 0 1 0 1 0 1 1 0 0 1 1 0 0 1 1 0
25. 0 0 1 0 1 0 1 1 0 0 1 1 0 0 1 1
26. 0 0 0 1 0 1 0 1 1 0 0 1 1 0 0 1
27. 0 0 0 0 1 0 1 0 1 1 0 0 1 1 0 0
28. 0 0 0 0 0 1 0 1 0 1 1 0 0 1 1 0
29. 0 0 0 0 0 0 1 0 1 0 1 1 0 0 1 1
30. 0 0 0 0 0 0 0 1 0 1 0 1 1 0 0 1
31. 1 0 0 0 0 0 0 0 1 0 1 0 1 1 0 0
32. 1 1 0 0 0 0 0 0 0 1 0 1 0 1 1 0
33. 1 1 1 0 0 0 0 0 0 0 1 0 1 0 1 1
34. 0 1 1 1 0 0 0 0 0 0 0 1 0 1 0 1
35. 1 0 1 1 1 0 0 0 0 0 0 0 1 0 1 0
36. 0 1 0 1 1 1 0 0 0 0 0 0 0 1 0 1
37. 0 0 1 0 1 1 1 0 0 0 0 0 0 0 1 0
38. 1 0 0 1 0 1 1 1 0 0 0 0 0 0 0 1
39. 0 1 0 0 1 0 1 1 1 0 0 0 0 0 0 0
40. 0 0 1 0 0 1 0 1 1 1 0 0 0 0 0 0
41. 1 0 0 1 0 0 1 0 1 1 1 0 0 0 0 0
42. 1 1 0 0 1 0 0 1 0 1 1 1 0 0 0 0
43. 0 1 1 0 0 1 0 0 1 0 1 1 1 0 0 0
44. 0 0 1 1 0 0 1 0 0 1 0 1 1 1 0 0
45. 1 0 0 1 1 0 0 1 0 0 1 0 1 1 1 0
46. 0 1 0 0 1 1 0 0 1 0 0 1 0 1 1 1
47. 0 0 1 0 0 1 1 0 0 1 0 0 1 0 1 1
48. 1 0 0 1 0 0 1 1 0 0 1 0 0 1 0 1
49. 0 1 0 0 1 0 0 1 1 0 0 1 0 0 1 0
50. 0 0 1 0 0 1 0 0 1 1 0 0 1 0 0 1
51. 0 0 0 1 0 0 1 0 0 1 1 0 0 1 0 0
52. 1 0 0 0 1 0 0 1 0 0 1 1 0 0 1 0
53. ...
54.

14. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
As SgtWookie correctly notes this is an example of an LFSR.

This configuration corresponds to a so-called Fibonacci LFSR. According to Wikipedia, this case has the property of being able to cycle through all of the possible (65535) 16-bit states other than the all zeros condition - without repetition. So as long as the starting value is non-zero it should work.

Have no idea concerning the relevance of the caption "I feel pretty".

Last edited: Jul 26, 2011
15. ### magnet18 Senior Member

Dec 22, 2010
1,232
125
perhaps the golden ratio plays in somewhere?

16. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
I figure that the answer would be, how many iterations does the LFSR have to go through in order to get to the start of the next verse of the West Side Story song, which would be "Oh", or 4F68 in hex, or 0100 1111 0110 1000 in binary.

It would take you a very long time to determine that answer by hand, as it will take you more than 33,000 iterations to arrive at the correct answer (very big hint).

There are three other possibilities with mixing of upper and lower case "O"s and "H"'s.

Last edited: Jul 26, 2011
t_n_k likes this.

Sep 13, 2010
735
43
18. ### narasimhan Member

Dec 3, 2009
72
6
So this two page discussion regarding that "I feel pretty" is a waste huh? I'm a bit disappointed.

19. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Since you are probably not winning any popularity contests around here at the moment I'd give the caption challenge idea a rest for a while.

20. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Ah, well - here's what I came up with...
Code ( (Unknown Language)):
1. "oh" was at iteration 14,975
2. "OH" "   "  "         33,689
3. "Oh" "   "  "         46,001
4. "oH" "   "  "         63,614
Believe it or not, I used an Excel spreadsheet.