Substitute Teacher

Discussion of challenges you have already solved
Andr3w
Posts: 40
Joined: Tue Nov 04, 2008 4:36 pm
Location: Germany

Substitute Teacher

Post by Andr3w »

how did you solve the challenge ?

I don't think that its solvable manually like I tried first time ...

did you wrote own scripts ?

if yes in which language ? and could you post it eventually ? i would be really interested in how to solve such a program
MerickOWA
Posts: 182
Joined: Mon Apr 07, 2008 5:54 pm
Location: HkRkoz al KuwaiT 2019 HaCkEr 101

Post by MerickOWA »

I use to do cryptoquotes in newspapers all the time. I just spent some time guessing out the letters starting with guessing that 3 letter words were "the" and going from there and so on.

I did write a little program to make the substitution easy so I didn't make any mistakes but mostly just guess work.
rmplpmpl
Posts: 113
Joined: Sun Oct 26, 2008 10:38 am
Location: Germany

Post by rmplpmpl »

Yes, this was pretty easy to solve, I used a subsitution website to assist me, but you don't really need things like that.
As MerickOWA pointed out, scanning the text for probable "the's" - which has two of the most common letters in English and the first word with the duplicate "L" was all you had to do, before many other words where easily solvable.
Google helped me with the last missing letter ('m') - since "adumbrate" doesn't belong to my vocabulary.
gfoot
Posts: 269
Joined: Wed Sep 05, 2007 11:34 pm
Location: Brighton, UK

Post by gfoot »

I think it's a bit unfair when there's a letter that's only used in the solution word, and the solution word isn't a real word. Edit: I see, this is a real word, my bad. /usr/share/dict/words is a good source of greppage, if you're looking for real words matching a particular pattern.

Generally for substitution ciphers I use external Unix tools, executed on portions of a text file using vim - e.g. "tr", "sort", "uniq" - combined with sed-style manipulations which are built-in with vim.

Although it's crude, I like the way it's rather ad-hoc - it makes it easier to adapt to different techniques (e.g. analysing pair frequencies, analysing transposition ciphers).

For more advanced things I write Python programs, which I can again run as external filters over the text. But on one occasion I made an interactive Python program to analyse a cipher, because it was useful for the program to maintain state.
Allosentient
Posts: 273
Joined: Thu Apr 10, 2008 9:47 pm

Post by Allosentient »

I did this manually without any programs. Searched for common words, letter patterns, etc.
the_impaler
Posts: 61
Joined: Wed Apr 30, 2008 3:31 am

Post by the_impaler »

Yeah, I did it manually too. There are some good online substitute decoders - I would try a letter and see what words would make sense. Kind of like playing 'hangman'. Then there were 2 letters left and only one made a word recognized by google.
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ape
Posts: 6
Joined: Sat Nov 08, 2008 5:28 pm

Post by ape »

i made it with cryptool, great tool :D
sigi
Posts: 37
Joined: Sun Oct 26, 2008 4:58 pm

Post by sigi »

I've used this website for help (and also Simon Singh's helper, which is kind of similar but with more features; it's also quite buggy, at least under Opera).

Going to have a look at cryptool.
Uncle Pat
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Joined: Fri Nov 21, 2008 5:37 am
Location: Germany
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Post by Uncle Pat »

I counted the letters and then compared them to letter frequencies.
theStack
Posts: 72
Joined: Sun Nov 02, 2008 12:46 am

Post by theStack »

ape wrote:i made it with cryptool, great tool :D
Hehe, me too :)
At the time I attempted the challenge I was sitting at a windoze machine, CrypTool was installed, so I thought why not give it a try? It seems to be a nice tool where you can learn a lot about cryptography.
I hope it will be released for linux soon.
gfoot
Posts: 269
Joined: Wed Sep 05, 2007 11:34 pm
Location: Brighton, UK

Post by gfoot »

Reading the page, it looks like there's a Java version.
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Enrico Palazzo
Posts: 2
Joined: Thu Jan 22, 2009 10:10 pm
Location: 127.0.0.1

Post by Enrico Palazzo »

I did it also manually. Counted the letters, then found zvm, hv and hdy twice. hdy together with the frequency was very likely "the".

and so on... :D
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yes-man
Posts: 32
Joined: Fri Jan 30, 2009 5:14 pm

Post by yes-man »

Simply used gedit and search + replace.
Most challenges contain the words 'answer' or 'solution' in their ... well ... solution.
This one had both.
zac
Posts: 1
Joined: Thu Mar 05, 2009 9:50 pm

Post by zac »

I took the time and searched for "answer" (quite easy to find it because there is only one 6 letter word) and did all the guessing in 2 text fields... all by hand^^
Isun
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Joined: Thu Aug 13, 2009 7:11 am
Location: China
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Post by Isun »

The substitution rule is rather wierd....

S?WHPXMTA?DFUGICB?LNVORKEY
^^^^^^^^^^^^^^^^^^^^^^^^^^
ABCDEFGHIJKLMNOPQRSTUVWXYZ

wtf on earth is this ???
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