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Didactic XOR Cipher 3
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tails



Joined: 10 Jun 2008
Posts: 191
Location: Tokyo

Post Reply with quote
In fact I also tried the 255 modulus on the first broken version, but this time I didn't try it. How regrettable!

gfoot wrote:
No doubt there'll be another variant of the challenge up soon, where you also need to figure out the modulus.

Great foresight!
Fri Oct 10, 2008 5:08 pm View user's profile Send private message
canine



Joined: 14 Sep 2008
Posts: 189

Post Reply with quote
gfoot wrote:
canine wrote:
If I am missing something, or someone has a hint for me, it would be greatly appreciated.

It's not a large search space, and it's easy to scan the results for things that might be correct. I think most of us tripped up on the fact that none of the results actually look correct to begin with!

That said, I used a state-of-the-art pattern-recognition device coupled to optical sensors to scan the search space more efficiently, reducing it to O(n log n) rather than O(n^2).

Unfortunately the pattern-recognition device is slower than brute-forcing it, and relatively expensive to run, but (much like Mortal Coil) it's more fun that way. Smile


I am not sure how that would work. There aren't pattern recognition devices that can recognize human language.

Could you elaborate?
Sat Oct 11, 2008 6:37 am View user's profile Send private message
xtracool



Joined: 27 Oct 2008
Posts: 1

Post Reply with quote
canine wrote:
gfoot wrote:
canine wrote:
If I am missing something, or someone has a hint for me, it would be greatly appreciated.

It's not a large search space, and it's easy to scan the results for things that might be correct. I think most of us tripped up on the fact that none of the results actually look correct to begin with!

That said, I used a state-of-the-art pattern-recognition device coupled to optical sensors to scan the search space more efficiently, reducing it to O(n log n) rather than O(n^2).

Unfortunately the pattern-recognition device is slower than brute-forcing it, and relatively expensive to run, but (much like Mortal Coil) it's more fun that way. :)


I am not sure how that would work. There aren't pattern recognition devices that can recognize human language.

Could you elaborate?


just an idea

for human text recognition there are devices already in use like camera/scanner and OCR software.. or voice/text to language parser for human voice recognition. one could even apply this to frame buffer/memory for "screen recognition".
Mon Oct 27, 2008 2:29 pm View user's profile Send private message
m!nus



Joined: 28 Jul 2007
Posts: 202
Location: Germany

Post Reply with quote
since i don't know much about cryptography i've been bruteforcing on the didactic cipher challenges which went good so far (solved xor cipher 1-3 + long + broken 3, xor feedback + long
Mon Oct 27, 2008 5:14 pm View user's profile Send private message
gfoot



Joined: 05 Sep 2007
Posts: 269
Location: Brighton, UK

Post Reply with quote
Haha, sorry for being obscure - I was really referring to the human brain and eyes. Best patternmatching equipment known to man!
Mon Oct 27, 2008 5:57 pm View user's profile Send private message
m!nus



Joined: 28 Jul 2007
Posts: 202
Location: Germany

Post Reply with quote
thought so Very Happy
but ctrl + f helps a lot too
Mon Oct 27, 2008 10:14 pm View user's profile Send private message
AlterHacker



Joined: 06 Mar 2009
Posts: 1

Post Reply with quote
This was a nice one^^


It take a few minutes building the program, and then I finished^^

"Smart" Brute-force attack^^
Fri Mar 06, 2009 3:10 pm View user's profile Send private message
nighthalk



Joined: 31 Jul 2009
Posts: 41

Post still stuck Reply with quote
edit: sily me did the loop in the wrong order weeee.


Last edited by nighthalk on Wed Aug 05, 2009 2:35 am; edited 1 time in total
Mon Aug 03, 2009 10:42 pm View user's profile Send private message
fido2509



Joined: 16 Jul 2009
Posts: 10

Post Reply with quote
Hi nighthalk,

I couldn't find junk bytes, so your answer is no.

Cool idea to solve the challenge in ASM, but maybe you should rethink algorithm.
So far I can tell there's a small bug in your code.
And there's still potential to increase performance.

Fido
Tue Aug 04, 2009 9:41 am View user's profile Send private message
ftfish



Joined: 20 Aug 2009
Posts: 12

Post Reply with quote
sorry for being spoiler Sad


Last edited by ftfish on Sat Sep 05, 2009 9:09 am; edited 1 time in total
Fri Sep 04, 2009 2:58 am View user's profile Send private message
Yharaskrik



Joined: 05 Nov 2008
Posts: 31
Location: Germany

Post Reply with quote
Hi ftfish,
could you please post solutions to the "Challenges Solved" forum so you wouldn't take others the fun of finding there own solution.
Thanks
Fri Sep 04, 2009 6:26 am View user's profile Send private message
Masti6



Joined: 15 May 2010
Posts: 55
Location: Finland, Nurmes

Post About Didactic XOR Cipher 2 Reply with quote
I know this thread is for DXORC 3, but I couldn't find a thread for the second one, and I'm too lazy to post one myself, so I'll ask here.

I've been trying to get the key for the Second XOR Cipher challenge for a couple of days now (of course not nonstop working) but after fully, manually XOR'ing all of the code, multiple times, I finally gave up and decided to ask for some extra advice or hints about the "key" to this case.

Thanks in advance.
Sat May 15, 2010 7:46 pm View user's profile Send private message MSN Messenger
watary



Joined: 05 Jul 2010
Posts: 1

Post Reply with quote
hi hackers,this CHALLENGE make me crazy
i try 256 value for x*256 value for b=65,536 value
but all results don't have any clue to solve this CHALLENGE.
can sum one give me a hint to the answer or pm me pls.

Code:
#include <iostream>
#include <fstream>
using namespace std;
ifstream Cin("Cin.in");
ofstream Cout("Cout.out");
int main()
{
   int hexa[]={0x31,0xcf,0x55,0xaa,0x0c,0x91,0xfb,0x6f,0xcb,0x33,0xf3,0x47,0x93,0xfe,0x00,0xc7,0x2e,0xbc,0x4c,0x88,0xfd,0x57,0xdc,0x6b,0xa7,0x1e,0x71,0xb7,0x59,0xd8,0x35,0x88};
   int a;char c;
   while(Cin)
   {

      Cin>>hex>>a;
      int b=a;
      for(int x=0;x<256;x++)
      {
         a=b;
         for(int i=0;i<46;i++)
         {
            c=char(a^hexa[i]);
            if( ( (c >= 65) && (c <= 90) ) || ( (c >= 65) && (c <= 90) ) ||(c == 44) || (c == 46) )
            Cout<<c;
            a = (a + x) % 256;
         }
         Cout<<endl;
      }
   }
   return 0;
}



Code:

Cin.in::
0
1
2
3
4
5
6
7
8
9
a
b
c
d
e
f
10
11
12
13
14
15
16
17
18
19
1a
1b
1c
1d
1e
1f
20
21
22
23
24
25
26
27
28
29
2a
2b
2c
2d
2e
2f
30
31
32
33
34
35
36
37
38
39
3a
3b
3c
3d
3e
3f
40
41
42
43
44
45
46
47
48
49
4a
4b
4c
4d
4e
4f
50
51
52
53
54
55
56
57
58
59
5a
5b
5c
5d
5e
5f
60
61
62
63
64
65
66
67
68
69
6a
6b
6c
6d
6e
6f
70
71
72
73
74
75
76
77
78
79
7a
7b
7c
7d
7e
7f
80
81
82
83
84
85
86
87
88
89
8a
8b
8c
8d
8e
8f
90
91
92
93
94
95
96
97
98
99
9a
9b
9c
9d
9e
9f
a0
a1
a2
a3
a4
a5
a6
a7
a8
a9
aa
ab
ac
ad
ae
af
b0
b1
b2
b3
b4
b5
b6
b7
b8
b9
ba
bb
bc
bd
be
bf
c0
c1
c2
c3
c4
c5
c6
c7
c8
c9
ca
cb
cc
cd
ce
cf
d0
d1
d2
d3
d4
d5
d6
d7
d8
d9
da
db
dc
dd
de
df
e0
e1
e2
e3
e4
e5
e6
e7
e8
e9
ea
eb
ec
ed
ee
ef
f0
f1
f2
f3
f4
f5
f6
f7
f8
f9
fa
fb
fc
fd
fe
ff

thx.
Sun Aug 01, 2010 2:12 pm View user's profile Send private message Yahoo Messenger MSN Messenger
compudemon



Joined: 13 Aug 2011
Posts: 33

Post brute force solved it Reply with quote
all i did was code a simple thing in python that cycled through all possible b x pairs
256x256 in total then simply culled out the strings that contained a char outside the 32 - 126 printable range of normal ASCII text. this had no spam 'only one line printed out!' despite this lax requirement
i expected 100 lines of garbage but it didn't happen. the delay to find the answer was less then 1 second even with the brute force method and no early termination.
Mon Aug 15, 2011 7:45 am View user's profile Send private message
fragman



Joined: 05 Mar 2009
Posts: 15

Post Reply with quote
ok, here's the deal... this challenge really gets me.
I'm pretty sure my solver isn't that bad, but I just can't get any positive result.

Would someone who already solved it (and ideally has some python knowledge) please send me a private message? I'd like to have someone telling me if my approach is correct without giving up too much information...

//EDIT:
nevermind. my code was ok, apart from the fact that sometimes I'm a fucking moron. one night's sleep and the error was so obvious.
Fri Jun 22, 2012 9:35 pm View user's profile Send private message
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