KelvinY
asked on
Crypto challenge 7: DCQIZ YIZZE ZWEZR NTFBR QIPVC WBAQA QI
QBIBL OQOFQ QOIED QRFQH BUEIL OIVDQ TMEUB ATMAH
RBNUE KHENQ WCBAY THDHI QOIAQ HBUEI LONQK ERXBV
IHDEN ROGQI ABHDB FBLMP YTRLQ HEAAK MTILC VIEIG
FTYIK CQGIQ QOFQV CTMIF LVQBF ZKTCB UZGOF QCKHB
XBQDH LQDBF AEILQ BQWBA ZXWCL OYKPI CXCQR YMTYT
RZZLB QICBU ENLQT KWEAB CBOFI ABQQD TWABQ LBFBL
HGLTT KKPBQ XBTPG TBLKT ABSPH NBTWP NQQHQ NEATW
EISYQ NWCQB IFTWQ PBAEC KBIFZ LCBLO QONAG NNGIC
LOQZL OQCSX YTRLC DMCCV PBHYB HXNLK TQKEB YTOPV
CQPFT PGTDQ QOBQI AQHBU EILOB QQSGH QIXBR BICBU
ZUTKW EABZH QIFQI QYHZL HBTOK CQGIQ QNYSY TCEFD
QCKRB LMPYT QPGHN QQOLQ KNFYT PKERX BVIHN TVGHE
NQGTM TSYQO BQWPE FHBTO TFNHO YQARY MFBRF KEAQI
STTOD CIZLZ XPTPG TDQXP VZNPQ AFERX IQGXT PNIIL
FKABZ XRBLO QOBQD HBQAK BHAHT PQAPV BQRNT FTPGT
FTQNQ OFQQO IQAHQ IRYGT MTRBN BEBRN BQQAQ IILMB
RBNUE KHENQ WCBAY THDHI QOIAQ HBUEI LONQK ERXBV
IHDEN ROGQI ABHDB FBLMP YTRLQ HEAAK MTILC VIEIG
FTYIK CQGIQ QOFQV CTMIF LVQBF ZKTCB UZGOF QCKHB
XBQDH LQDBF AEILQ BQWBA ZXWCL OYKPI CXCQR YMTYT
RZZLB QICBU ENLQT KWEAB CBOFI ABQQD TWABQ LBFBL
HGLTT KKPBQ XBTPG TBLKT ABSPH NBTWP NQQHQ NEATW
EISYQ NWCQB IFTWQ PBAEC KBIFZ LCBLO QONAG NNGIC
LOQZL OQCSX YTRLC DMCCV PBHYB HXNLK TQKEB YTOPV
CQPFT PGTDQ QOBQI AQHBU EILOB QQSGH QIXBR BICBU
ZUTKW EABZH QIFQI QYHZL HBTOK CQGIQ QNYSY TCEFD
QCKRB LMPYT QPGHN QQOLQ KNFYT PKERX BVIHN TVGHE
NQGTM TSYQO BQWPE FHBTO TFNHO YQARY MFBRF KEAQI
STTOD CIZLZ XPTPG TDQXP VZNPQ AFERX IQGXT PNIIL
FKABZ XRBLO QOBQD HBQAK BHAHT PQAPV BQRNT FTPGT
FTQNQ OFQQO IQAHQ IRYGT MTRBN BEBRN BQQAQ IILMB
A difficult one, KelvinY ....any clues for the key?
ASKER
maramom,
No clues for the key just yet, but maybe one for the type of cipher. It would have been more natural if this puzzle had be presented as
DC QI ZY IZ ZE ZW EZ RN TF BR QI PV CW BA QA QI
Another clue soon if this doesn't give it away.
No clues for the key just yet, but maybe one for the type of cipher. It would have been more natural if this puzzle had be presented as
DC QI ZY IZ ZE ZW EZ RN TF BR QI PV CW BA QA QI
Another clue soon if this doesn't give it away.
Thanks, KelvinY.
The type of puzzle is clear (I won't give it away -- unless you're looking for a response to the type of cipher). Cracking it has been extremely difficult! I've tried every imaginable key without success. I've resorted to pencil (not pen) and paper (lots of it). I'm sure many others are doing the same. You weren't kidding when you said you'd toughen it up! Good work!
The type of puzzle is clear (I won't give it away -- unless you're looking for a response to the type of cipher). Cracking it has been extremely difficult! I've tried every imaginable key without success. I've resorted to pencil (not pen) and paper (lots of it). I'm sure many others are doing the same. You weren't kidding when you said you'd toughen it up! Good work!
I made a few stabs at figuring it out, but have to wait till I have a bit more time...
ASKER
Another clue then. If this doesn't yield results then I'll give a partial decipherment and turn it into a known-plaintext attack in a couple of days.
As you have probably guessed this is a playfair cipher. The keyword fairly short (< 10 chars), but not an English word i.e. it's a proper noun.
A good tutorial on reconstructing the key for a Playfair cipher can be found in chapter 7, "Solution to Polygraphic Substitution Systems," of Field Manual 34-40-2, produced by the United States Army. http://www.umich.edu/~umich/fm-34-40-2/ch7.pdf [PDF - sorry].
As you have probably guessed this is a playfair cipher. The keyword fairly short (< 10 chars), but not an English word i.e. it's a proper noun.
A good tutorial on reconstructing the key for a Playfair cipher can be found in chapter 7, "Solution to Polygraphic Substitution Systems," of Field Manual 34-40-2, produced by the United States Army. http://www.umich.edu/~umich/fm-34-40-2/ch7.pdf [PDF - sorry].
Looks cool and interesting, I'll print it and read it in the train later.
ASKER CERTIFIED SOLUTION
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ASKER
It looks like it's time for another clue.
A frequency count of the digraphs (pairs) in the message yields the following:
QO 11
BQ 10
LO 9
TP 7
AB 6
GT 6
QI 6
YT 6
BU 5
FQ 5
IQ 5
NQ 5
QH 5
Based on previous challenges you would expect the message to finish with the word 'end' and contains several occurrences of the word 'stop'. So we know that MB = ND, which is not too helpful as it's the only occurrence. There are also several occurrences of TP GT, which look like a good fit for ST OP. The most common digraph is QO, which you can assume is a common pair like TH (which it is in this case. Trust me - I know). A number of the QO(=TH)s are followed by the pair BQ, which turns out to be ES. Also given the nature of the Playfair cipher it's highly likely that QB=SE.
If this does not lead to a breakthrough soon I will post a full decrypt of the question title next.
A frequency count of the digraphs (pairs) in the message yields the following:
QO 11
BQ 10
LO 9
TP 7
AB 6
GT 6
QI 6
YT 6
BU 5
FQ 5
IQ 5
NQ 5
QH 5
Based on previous challenges you would expect the message to finish with the word 'end' and contains several occurrences of the word 'stop'. So we know that MB = ND, which is not too helpful as it's the only occurrence. There are also several occurrences of TP GT, which look like a good fit for ST OP. The most common digraph is QO, which you can assume is a common pair like TH (which it is in this case. Trust me - I know). A number of the QO(=TH)s are followed by the pair BQ, which turns out to be ES. Also given the nature of the Playfair cipher it's highly likely that QB=SE.
If this does not lead to a breakthrough soon I will post a full decrypt of the question title next.
ASKER
Well done, RobinD. You got in just before I posted the next clue. The points are yours and I will assign them after leaving the question open for a short while longer. Please post a brief description of how you cracked the code, if you have the time.
I have a rather clever program that will fit a phrase where it can and build some of the grid from it. You can switch back to the ct/pt display and guess at more digram associations as you build up words. These can be added to the grid until most of the text is readable.
You could start with the most commonly occurring digrams, but I found it easier to guess at a phrase that might be included :7)
You could start with the most commonly occurring digrams, but I found it easier to guess at a phrase that might be included :7)
ASKER
The answers to this week's challenge were Leibniz (EIBNLBDU), which was the key to the cipher, or, RobinD's winning answer, Newton (LIYRTF). This week the cipher was a Playfair and the full key to the cipher was
LEIBN
ZACDF
GHKMO
PQRST
UVWXY
The full message was
SEEING THAT THE LAST CHALLENGE WAS SOLVED SO EASILY I HAVE TRIED TO MAKE THE CHALLENGE THIS WEEK A BIT MORE DEMANDING STOP I HAVE CHOSEN A WELL KNOWN CIPHER THAT WAS ONCE USED FOR DIPLOMATIC MESSAGES AND EVEN SERVED DURING WORLD WAR TWO STOP CLUES WILL BE PROVIDED IF NECESSARY DEPENDING ON PROGRESS STOP IN ORDER TO ENSURE THAT EVERY LETTER IS ENCRYPTED I AM INCLUDING THE FOLLOWING PANGRAM STOP JACKDAWS LOVE MY BIG SPHINX OF QUARTZ STOP AS THESE CHALLENGES PROGRESS I WILL PROVIDE A GREATER VOLUME OF CIPHERTEXT TO AID CRACKING STOP TO GET THE POINTS THIS WEEK YOU HAVE TO POST THE SURNAME OF ONE OF THE TWO DISCOVERERS OF CALCULUS STOP AS USUAL THE ANSWER MUST BE ENCODED USING THE SAME SCHEME AS THE QUESTION STOP NOTE THAT THERE ARE TWO POSSIBILITIES HERE END
There are a number of on-line implementations of this cipher. For example, http://ourworld.compuserve.com/homepages/christopher_webster/Crypto/Playfair/PlayTexApplet.html or http://il2fb-bellum.com.ar/pf_cipher.html.
The Playfair cipher can be broken using digraph frequency analysis. Some tools are available for automating the process. This is obviously the lazy/smart way to do it. A good implementation of a playfair cracker is Jan Stumpel's program, playn, available with source code at http://www.cs.miami.edu/~burt/learning/Csc609.051/programs/playn/.
LEIBN
ZACDF
GHKMO
PQRST
UVWXY
The full message was
SEEING THAT THE LAST CHALLENGE WAS SOLVED SO EASILY I HAVE TRIED TO MAKE THE CHALLENGE THIS WEEK A BIT MORE DEMANDING STOP I HAVE CHOSEN A WELL KNOWN CIPHER THAT WAS ONCE USED FOR DIPLOMATIC MESSAGES AND EVEN SERVED DURING WORLD WAR TWO STOP CLUES WILL BE PROVIDED IF NECESSARY DEPENDING ON PROGRESS STOP IN ORDER TO ENSURE THAT EVERY LETTER IS ENCRYPTED I AM INCLUDING THE FOLLOWING PANGRAM STOP JACKDAWS LOVE MY BIG SPHINX OF QUARTZ STOP AS THESE CHALLENGES PROGRESS I WILL PROVIDE A GREATER VOLUME OF CIPHERTEXT TO AID CRACKING STOP TO GET THE POINTS THIS WEEK YOU HAVE TO POST THE SURNAME OF ONE OF THE TWO DISCOVERERS OF CALCULUS STOP AS USUAL THE ANSWER MUST BE ENCODED USING THE SAME SCHEME AS THE QUESTION STOP NOTE THAT THERE ARE TWO POSSIBILITIES HERE END
There are a number of on-line implementations of this cipher. For example, http://ourworld.compuserve.com/homepages/christopher_webster/Crypto/Playfair/PlayTexApplet.html or http://il2fb-bellum.com.ar/pf_cipher.html.
The Playfair cipher can be broken using digraph frequency analysis. Some tools are available for automating the process. This is obviously the lazy/smart way to do it. A good implementation of a playfair cracker is Jan Stumpel's program, playn, available with source code at http://www.cs.miami.edu/~burt/learning/Csc609.051/programs/playn/.
Jan Stumpel's program is the one I used - I've found that he's improved it since the version I was using.
It was just called playfair.exe where I found it.
Thanks for the puzzle.
It was just called playfair.exe where I found it.
Thanks for the puzzle.
I've read it in the train but found it a bit over my head for trying it myself. Too many other things also need attention.
I'll need to read up a bit more on some things to really understand.
Still I'll keep following your challanges.
Cheers, Nico
I'll need to read up a bit more on some things to really understand.
Still I'll keep following your challanges.
Cheers, Nico
If E=MC^2 then it says...
"Your shoelace is untied." ????