Crpytography Challenge: I answers

Posted by: paradox

Crpytography Challenge: I answers - 10/27/03 10:47 AM

Cryptography- the science of hiding messages. how does cryptography work?
The words, characters or letters of the original intelligible message constitute the Plain Text (PT).
The words, characters or letters of the secret form of the message are called Cipher Text (CT) and
together they constitute a Cryptogram.

Cryptograms are roughly divided into Ciphers and Codes.

Well with that brief explanation out of the way i will begin guiding you through how to break the
encryption i gave you.

What type of cipher did i use, the most popular cipher of course the substitution cipher...
even little kids use this, they make there to character sets
e.g.
the alphabet{abcdefghijklmnopqrstuvwxyz} and then make a substitution character set
substitution{zyxwvutsrqponmlkjihgfedcba} or cryptobet as i call it
of course this is reverse but this is just an example
Well my challenge had a different character set and i didn't add as many probable words as i should have
but thats the whole point of a challenge

Four basic operations in cryptanalysis
William F. Friedman presents the fundamental operations for the solution of practically every cryptogram:
(1) The determination of the language employed in the plain text version.
(2) The determination of the general system of cryptography employed.
(3) The reconstruction of the specific key in the case of a cipher system, or the reconstruction of,
partial or complete, of the code book, in the case of a code system or both in the case of an enciphered code system.
(4) The reconstruction or establishment of the plain text.

Just read the cryptogram i gave you it is
Sfq ohrl yqjjlyymqccu klmlhzlk zopy johcclenl, zoheb ufq mfx ufqx ghxzpjpghzpfe
. Zol yljxlz sfxk py efs jxugzfnxhd

well at first glance it looks like gibberish but you know its english what i do when tackling substitution ciphers is
count the letters in each word, its all about probability here

we can see a huge word 13 letters long and as you know there ainít many big words like that
then we have 5 three letter words, we will start with the small letters and build up

The most frequent English trigraphs per 200 letters are:
THE--89 TIO--33 EDT--27
AND--54 FOR--33 TIS--25
THA--47 NDE--31 OFT--23
ENT--39 HAS--28 STH--21
ION--36 NCE--27 MEN--20

you normally look for a flow as english language does tend to flow,
but this is tricky..a hard one to start off with huh?

The ???? ?e??????e??? ???????? ???? ????????, ????? ?he ?h? ?he? ???????????h? (stoped here)
. ??? ?????? ?h?? ?? ?h? ? (stoped because don't know any 13 letter words that end with h?)

ok lets try another word seeing as how this is a challenge

You ???? ?u??????u??? ???????? ???? ????????, ????? ?ou ?o? ?ou? ???????????o?(could be ion most likely probablity says so)
. ??? ?????? ?o?? ?? ?o? ?????o????

this looks promising the best way is to start out with a template of ? marks, like i did above then u just substitue values
in until you find a good match..
ok continuing on with the explanation we will stick with this because it seems probable with the ?o? ending on the big word

Sfq ohrl yqjjlyymqccu klmlhzlk zopy johcclenl, zoheb ufq mfx ufqx ghxzpjpghzpfe
. Zol yljxlz sfxk py efs jxugzfnxhd
You ???? ?u??????u??? ???????? ???? ????????, ????? ?ou ?o? ?ou? ???????????o?
. ??? ?????? ?o?? ?? ?o? ?????o????
the bold words are ones we could defintly see as you and your so we now have r fill in the blanks
You ???? ?u??????u??? ???????? ???? ????????, ????? you ?or your ??r????????o?
. ??? ???r?? ?or? ?? ?o? ?????o?r??
and then again we find two more probable words its like a chain reaction
its for and word now we have f d and w this is starting to look promising and im sure u can work out the rest
so i'll leave it upto you
Hope i taught you something