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December 07, 2005
last chance for 7B
Here are the first two row fo the decryption matrix for Challenge 7B
2 21 17
10 4 9
You should be able to do the rest by looking at what this gives you.
[By the way, if you are doing the decryption as vM, where M is the matrix and v is a row vector then these are the first two columns instead.]
Posted by Harry at December 7, 2005 03:32 PM
Comments
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woo woo
Posted by: cynthia balee-neijbo at December 8, 2005 06:53 PM
To be honest I don't own a computer. Writing comment @ school. Hee hee. Old fruit. Cynnie
Posted by: cynthia balee-neijbo at December 8, 2005 04:43 PM
i think its awfully silly to try and do it with pencil and paper. buy a new computer. do consider the investment. i used mine to do the last one ever so quickly. good luck chumms. the old fruit. cynnie
[Crikey, can you just buy me a new computer? Harry]
Posted by: cynthia at December 8, 2005 12:47 PM
Is anyone planning to do this with pencil and paper? Originally, I wasn't planning to, but the more I think about it, the more of a challenge it seems. After all, isn't the cipher challenge about learning more about everything? I look forward to it :)
I've tried it with a 10-rotor Fialka, and I figure I can test one wiring every 15 minutes, working fast. So it's goodbye to all my homework then!
Fantastic. It's probably farewellt o jsut about everything at that speed! Just as well we don't have ten rotors! Harry]
Posted by: naomi at December 8, 2005 12:32 PM
even 18 hours 15 minutes?
Posted by: at December 8, 2005 10:40 AM
Harry,
Please don't reveal too many settings to begin with. We think we know
an algorithm to crack it quickly even if we don't know too many
settings.
A similar approach could have cracked last year's Solitaire cipher
even when you had only revealed the first 28 cards.
Thank you.
Posted by: Sean at December 7, 2005 11:21 PM
I like to think I do :( One hour is the word on the street. Which is reasonable, provided 8A is done fast enough and I'm a quick enough programmer :P
Posted by: Ian at December 7, 2005 10:26 PM
How long IS the first timing interval Harry?
[Probably (though I may change my mind) 4 hours again as before. Personally I don't think the cipher can be cracked that fast with the information we will provide at the beginning, but I am still considering how much to reveal at the start. Harry]
Posted by: Jess at December 7, 2005 10:19 PM
plz plz plz tel me y the 1st line of 7a i trnslated from vigenere with lauras keyword (thanx) was correct but the rest was ...WOAH
plz plz pzl
[How can the rest be wrong? Harry]
Posted by: izzy at December 7, 2005 10:11 PM
Well, logically 8B must be possible to do within the first timing interval if you have prepared a program REALLY well, because otherwise it's pointless :P So I guess I should be reasonably okay, I think I'm ready for just about anything. Got it working Enigma-Fialka, and a few other tricks up my sleeve as well ;)
[You don't know how long the first timing interval is yet! Harry]
Posted by: Ian at December 7, 2005 10:10 PM
3 hours difference. lol, he/she must be too excited to even count ;)
i want to win. u open to bribes harry? :P
chidders
Posted by: chidders at December 7, 2005 10:00 PM
its the evening before the day after...
16 hours, 15 minutes reamining.
chidders seems prepared. eek. bring on the next challenge.
[Err isn't that 19 hours fifteen minutes? Harry]
Posted by: excited at December 7, 2005 09:46 PM
and if harry didnt let my last message through, for those of you doing 7a, you should know this:
Hard work And Responsibility Results in Your success
Posted by: laura at December 7, 2005 09:44 PM
for those of you stuck on the keyword of 7a:
what was the keyword again? harry? Harry? HARRY???
i hope that wasnt too obvious. good luck.
Posted by: laura at December 7, 2005 09:42 PM
That was hard, i just put in E's for all the letters i couldn't get as i couldn't work out the rest of the matrix. I hope i get atleast some marks. Oh well, not bad for a first attempt.
Posted by: Hugh Bird at December 7, 2005 09:41 PM
hmmm, top 15 will do the trick for me :P
my program is now working ok for 8b, but i need certain info. also, my program is for the enigma not the fialka so i now need to work out how to switch it to a fialka. hopefully wont be too difficult
chidders
Posted by: chidders at December 7, 2005 09:27 PM
Please can you give us one last hint for the bottom row. I will be truely grateful.
Thanks, Hugh
[Like the entries? You don't need it really, you can more or less guess the missing letters (the top two rows give you the first, second, fourth, fifth, seventh, eighth, tenth, eleventh letters and so on. Harry]
Posted by: hugh bird at December 7, 2005 09:17 PM
please please please give us a clu 4 7a i avnt ad tym 2 do it sooo plzzzzzz giv us a clu
[It's a Vigenere cipher with keylength 5. Want to know the keyword? Harry]
Posted by: izzy at December 7, 2005 09:13 PM
can anyone tell me a good website for information about the rotary cipher? i can't find one and i'd quite like to get 8B done asap. please help!! thanks
Posted by: chloe at December 7, 2005 09:01 PM
...rather like an essay I was writing today... "The writer gradually reveals the story to add to the mystery and keep the reader guessing." ==> "The cipher master releases hints in such a way to involve many different people who would otherwise not take part."
Good thing I said this before Challenge 8... I don't expect to feel so positive after it is published... =D
Posted by: cecil at December 7, 2005 08:02 PM
yay i dun it!!!!!!!!!!
unusual techinque...
brute force usng spinners in excel for every number...
001
002
003...
tuk a while but i finished yay
now i just gota read it !
[Well done! Harry]
Posted by: Insane (FHS) at December 7, 2005 07:52 PM
Congratulations to Harry for the way in which he chooses the ciphers, includes cribs and releases hints. The challenges could so easily be way beyond pupils' abilities but they are made amenable to solution using applets from the web, pencil and paper and Word/Excel. Well done and thank you.
Posted by: cecil's dad at December 7, 2005 07:44 PM
Excellent, I hope we'll get enough to feasibly run (and modify!) programs successfully. I'm aiming for a top 10 finish this year.
Posted by: Ian at December 7, 2005 06:16 PM
I don't think I can help much more with 7B, except give the answer. You just need to understand what's going on. You need to make the first 9 letters of the ciphertext (SSODTUQOE) into the crib (COMRADESW). Because of how the cipher works the letters of the whole ciphertext can be broken into 3 individual groups, corresponding to the 3 rows of the matrix. Distributing the letters between 3 groups gives you the following things to make happen:
First row makes SDQ into CRE
Second row makes STO into OAS
Third row makes OUE into MDW (The W was not available earlier in the challenge, making it necessary to guess this letter)
The first row and second row are already complete, so that only leaves you with the third row to do. You should be able to make 3 equations and then solve them to find the row.
Posted by: Jason at December 7, 2005 06:02 PM
Can you really guess the rotor wirings? for each one there is 26! possibilities, and there is going to be more than one rotor. Brute force will not work unless you have the wirings, which I believe we are given.
[Up to a point. Harry]
Posted by: Stephen Harris at December 7, 2005 04:49 PM
Heh, last chance for 7B, and first major panic about 8B... I've got my program rearranging the wirings (in the simplest rotors!) around 6000 times a second, which sucks :P My calculator claims it will take me slightly over 2 quadrillion years to brute-force the challenge at that rate. And that's if there is one rotor, which would make the challenge stupid anyway :P Just a 26-part Vigenere with silly keyword.
Still, at least if I guess the first rotors wirings and there's only 2 rotors, I suppose most of the rest fall into place with the help of the crib :P Please make it easy!
Posted by: Ian at December 7, 2005 04:33 PM
good luck everyone. now you have the first 2 rows, you can decrypt 2/3 of the message. and if you are not sure, just guess. theworst thing that can happen is it's wrong. good luck, fellow strugglers =)
Posted by: laura at December 7, 2005 04:30 PM