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#1 2014-11-24 03:58:00

crosswhit99
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Help please !

Hi Everyone

I am attempting to solve what I believe is a substitution cipher, comprising 345 symbols (30 different types) with no spaces. Included amongst these are just two different digits. I have no programming skills and am struggling to make much headway as I've no idea of word lengths or how many letters of the alphabet are involved. This will clearly affect any attempt to perform a frequency analysis of individual letters, digraphs, trigraphs, etc. I'd be most grateful for any suggestions !  For ease of reproduction I have left the 2 digits unchanged, changed 26 of the symbols to letters and the remaining 2 symbols to * and ?

ABCDEFCGFBGHIJKLMNOEQEEFNKRENHSENODPNTHABONMSOJKEUVWMXJUCYNT*QE*JKPDMRJUCUIRFMNYHJPIXRJNTCFPKFNXEANMWZNM*JKOGMKZZNM*QZNECBQLNTCFHUCCJUMHJDIJTI8QRDPNTIHNPMKDS*JKEGVGCKEXAGRQL*MDERXHCNMQGRKLNEFLCTU*NZXEFHJKRXCVUMZNCCNORQIQRJXFFKEWDR*NZR*GECKBMNGFYGMHNZABMKTCGMLBLCKMNTIU*NONMSENIUHNRWCZZQEDCLNFWKELMBY*UFPBGSMQKRADMXEKA3ADLJQEWTRQE?ABXEX*XGCR


Mark

#2 2014-11-24 04:00:48

Agnishom
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From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,567
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Re: Help please !

Is it the cipher of an english text?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#3 2014-11-24 04:05:05

bobbym
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From: Bumpkinland
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Posts: 107,689

Re: Help please !

Where is it from? A geocache?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#4 2014-11-24 04:50:25

crosswhit99
Member
Registered: 2014-11-24
Posts: 4

Re: Help please !

Yes, the text is in English. It isn't a geocache as such, but it does relate to where an imaginary stash of silver ingots might be buried near Bletchley Park.

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#5 2014-11-24 05:01:53

bobbym
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From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

Alan Turing's stash?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#6 2014-11-24 05:05:45

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,567
Website

Re: Help please !

Why not use a frequency analysis attack on it immediately?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#7 2014-11-24 05:07:39

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

It is kind of short for that.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#8 2014-11-24 05:08:23

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,567
Website

Re: Help please !

What is the frequency of the letter that occurs the most?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#9 2014-11-24 05:09:40

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

E of course but it is like any other sample, that only holds for large numbers.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#10 2014-11-24 05:13:14

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,567
Website

Re: Help please !

You can find out the letter with highest frequency here and say it is actually e.

How large?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#11 2014-11-24 05:16:23

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

The larger the better. In a small sample it might be a something else.

More X's in the ciphertext than anything else suggests that X corresponds to e in the plaintext, but this is not certain; t and a are also very common in English, so X might be either of them also.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#12 2014-11-24 05:21:01

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,567
Website

Re: Help please !

But that is the way you start attacking. You need a dictionary to know if the attck was successful


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#13 2014-11-24 05:22:08

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

There are many texts that do not follow the same frequency for instance some texts are written without any e's.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#14 2014-11-24 05:29:18

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,567
Website

Re: Help please !

Yes, but it is the best way to try.


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#15 2014-11-24 05:30:47

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

The answer to post #5 is waiting.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#16 2014-11-24 05:32:12

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,567
Website

Re: Help please !

What does that mean?


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

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#17 2014-11-24 05:33:30

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

Have you read the Andrew Hodges book about Alan Turing?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#18 2014-11-24 05:35:03

Agnishom
Real Member
From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,567
Website

Re: Help please !

Nah


'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.

Offline

#19 2014-11-24 05:35:51

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

It is rumored that he buried some silver bars, possibly in that area.


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#20 2014-11-24 06:12:20

crosswhit99
Member
Registered: 2014-11-24
Posts: 4

Re: Help please !

Yes, it's the second part of a 3 part challenge to locate the stash on a fictional map. The first code was very straightforward to solve, but this one is foxing me. The most frequent symbol is actually N in the above ciphertext (31 occurences), so it's tempting to assign this to E, but as there are 30 different symbols perhaps a handful of them are 'padding' of some sort ?

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#21 2014-11-27 21:05:46

crosswhit99
Member
Registered: 2014-11-24
Posts: 4

Re: Help please !

A quick update:

As I suspected, the 2 digits were not coded, so that left 28 symbols. There was no occurence of J, Q, X nor Z in the plaintext, so only 22 letters were enciphered by these symbols. As you might expect, E and T each had 3 symbols, and A had 2 symbols. G also had 2 symbols, which I thought was a bit odd for a letter that has a frequency of only 2% ? So it did turn out to be a homophonic cipher in the end - very tricky !!

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#22 2014-11-27 21:19:05

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,689

Re: Help please !

A homophonic cipher? What is that?


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

#23 2014-11-28 02:07:31

crosswhit99
Member
Registered: 2014-11-24
Posts: 4

Re: Help please !

My apologies, it was I that also had 2 symbols, not G, so that fits perfectly with English letter frequencies. Here is a link to a helpful site explaining homophonic ciphers:

http://www.simonsingh.net/The_Black_Chamber/homophonic_cipher.html

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