# Cryptology and codes vigenere code formula

1. Dec 17, 2007

### lordlactose

http://en.wikipedia.org/wiki/Vigenère_cipher

I have comprehended how to make a cod using this method. I understand frequency analysis for the most part. But does anyone know how the formula for decoding a vigenere code work. I have read that part of the wikipedia article many times. The formula is 2 confusing for me to grasp based upon the info I have received so far. Can anyone explain this to me?

Also does anyone have a link to a good cryptology site. I already googled but couldn't find one with puzzles and challenge ect.

I also have a thread in the computer section i need help with plees ehelp

Last edited: Dec 17, 2007
2. Dec 17, 2007

### mgb_phys

It's just like doing a frequency attack on a regular cipher but you have to do a separate frequency count on every 26th letter.
All the equation means is that you split the message into 26 separate messages, starting with the first character then put the second into the second list and so on. It's security comes from the fsact that in short messages you will only have a few characters in each set to do the frequency analysis on.

This book is one of the most acessible intros to crypto http://www.simonsingh.net/The_Code_Book.html [Broken] there is a lot of info on the site.

Last edited by a moderator: May 3, 2017
3. Dec 17, 2007

### lordlactose

wow thanx for the great link you provided... That Indian guy has a great website for cryptology. After reading more about decoding vinegre i decided to decode other codes instead that 1 is way to confusing to decode

Last edited by a moderator: May 3, 2017
4. Dec 17, 2007

### mgb_phys

The vigenere cipher did stand up for 300 years and is still quite good if you keep the message short and don't put the same long greeting at the start and the end.

ps. Simon Singh is British

5. Dec 18, 2007

### dodo

For your amusement, here you have a challenge: a text encoded as described in the Wikipedia page above.
Code (Text):

IDYT HSRUUZG JEYVJ VJD, RLV XKXPF SW VQ FPNII CHMLGMR FVPT UNSE V QZOI RV
FDYFSWZQB PD RLV JWWPRQ, EPW HHGGY CDS NCEIOT IHO TRJZV ZF LFPJJTYEMYJ GLCPS.
YH VWZWCH KDV QILH WJ P WYRUHMLCR BITRYHG WFS WJOS HGQ WCH WILIJ RHGP UVZWOHC
IL GRMWJRUCWV; RISEPW VVLS TFIP RHGP WMUGDVW. UMKKDQ L AIEWPUN, RLV GDCRUYKV
RDH EQXREGLHSEB: D VPXOWIULX ATTFYRQDDC DGECHXW ZF KLDMDCT, AZWC RWAQWZFVO
LRYFZDI XYFJITWDRCD. XYH FDYTCRK RDH AJWF YHRTPFIIHY: DOKI QJWXZNQ FI FDXBGRRWDYT
ALECBNLH, GPCXNWGLTCH ZDWW EVEDSGHH OD MDMLPEIMRJ RLIS SRCLHLIPD VVSZWXEIMR.
OKTDE IODHSAPS QRGZ XE NSJVDEAP DSI V ATBPEILVQ ZF KVQDXH TM ULNFDGEP KKZ
UFNBEDHIWPW JEN JI EHC CLWUPCY. KKDV EHGRBHM DMSCVMHY ISAR ROG ISE FFRFV,
NM DDOWTC FSN YLKPRQI WCHN MGKYW ET, YVV HDSP ST RA ISE WRPZ TWEKIEWN:
EHC JSVFT, RLV KHGTOB, WCH NOKQR, WWP RAVQOB-EWM CHOWTCS SW OKT AJTYDWHI.
FI DGVD AJPVJZG L DETW ZWTCF KUVYTWEPW KVYT CMRWLMPTO: ME OKT VYWK GLQCAPC
WCHGP YVV IR EWM ZGZQITCYP EJRZD. JIRH ISEQI WRR TNASEWMRKPRRMSOZ ECEKMJHN
WP BIUXXHS TFEK OKT LGFIDMB TS XFWVO LNB KKVW TTQ JKZOKPS VVJDVIPR ECO WWP
NSJVDEAP ASDEDQPEIMRJ JI EHC KZZQIJ-MHU JUISOEVRSCLRLL WPPWRAD (E QPPQPR AYLXK,
TFSLJC TITPIDHGB GAQX, DV YOR ZQALCTTC): ZYTCYRLZQB: EHC DLIXIPLW UHODXWEB YLNWDCY
SW OKT FSXLUZ, EHC RUXKPYGCPJ' DJEOZMFJMDESICW, OKT FYMKKAXA CYXROJJJPS SW OKT
LGFIDMB, TFSLVVQSD YRU OKDFSYRUV RU FYPJH FPEAJSXXZV, TFI GZPDYSRVRWDRC OD KKZ
ULLJETB RU TFSJH FPEAJSXXZV, TFI GZPDYSRVRWDRC OD KKZ ULLJETB RU TFI WMXT CYXROJJJP,
XYH JCZSRMT BRHAEJ FI EPDIJMUHN, EHC TRHPTYTYVP JQ EHYX JJVEPL, KKZ RZMKIEWVUN OL
KKZ RZMKIEWVUN OL KKVW ROQTVO, ISE XIXZ HEOPC RA NZUP UHVWW, RLV OUPYSJEKLJQ ZF
IMHMB MOMO LI PWL PRQBXPREQ, WCH TNRIISJOPEIMRJ JI PVCVP WRDV GR DGO MOMOJ.

6. Dec 18, 2007

### lordlactose

is that a vigenere cypher. I am afraid of vigenere cyphers but if it is a substitution cypher then I will try and solve it but I won't do vigenere

7. Dec 18, 2007

### dodo

It's a Vigenere. Here is an extra hint: the code that produced that text.

Hey, somebody please compile, run and give some output roughly of the same size, so I can play too. :)

#### Attached Files:

• ###### vigenere.zip
File size:
1.2 KB
Views:
74
Last edited: Dec 18, 2007
8. Dec 18, 2007

### lordlactose

here i will give u a code when i get done making it. Or I will just use simonsingh.net to make it. You should check it out it has cheat programs to for breaking codes ( I would only use it if I was stumped)

Last edited: Dec 18, 2007
9. Dec 18, 2007

### dodo

Ok, thanks... And BTW, the Vigenere (stage 4 of the challenges) at SimonSingh,
http://www.simonsingh.net/The_Ciphertexts.html [Broken]
is rather easy. (Even if the clear text was in French -- well, I don't know French, but it looks French :) It matched the English frequency distribution, roughly enough.) Spoilers on the attachment.

#### Attached Files:

• ###### stage4.zip
File size:
628 bytes
Views:
63
Last edited by a moderator: May 3, 2017
10. Dec 18, 2007

### lordlactose

EO UBL KVORCL UBL FERBUN JPSLAU UBL CEPO ACLLHA UPOERBU. E BPHL SPO HGVC QLDPFLA HSLAEWLOU. EJ NPV APCXL UBEA EUA HSPQGQCN QLDGVAL NPV VALW WGUG JSLTVLODN GOGCNAEA. E IGOWLS EJ APFLPOL DPVCW APCXL G ABPSU POL IBLO WGUG JSLTVLODN GOGCNAEA EA OPU LJJLDUEXL.

its not necessarily a vigenere cypher. solve this if u wish i made it. I used simonsingh.net code maker. But i typed the code.

Last edited: Dec 18, 2007
11. Dec 18, 2007

### lordlactose

is that the 1 in french that u speak of?

Last edited: Dec 18, 2007
12. Dec 18, 2007

### dodo

No, this is in English. In the post where I mention a message in French, there is a link; on that page, click on "stage 4".

13. Dec 18, 2007

### lordlactose

http://www.simonsingh.net/The_Black_Chamber/cracking_tool.html [Broken]

I don't completely understand how to solve the vinegre square. The article didn't clearly explain.

I copy and pasted this from his site. I don't know how to decipher it because its a vinegre. If we work together I bet I will figure it out. Or if you don't feel like working on this cryptogram it I will just do hidden message cryptograms instead.

QVUEVAIOHJCFMINRCFIYTMPZTFGVKIEKSQAVLOXWVBEK@CEOX@
TEXPKI@QVX@RHTRQISPZYBRSWEHJPOGHJYDXJGEJTWPH@XEX@RIESK
VITHVJDVGXBMAMEBXQWEPIMMHSKVEIAIFFCPTPHIMMPRFVEJTX
QUIZPPNXHMXTKZMSTTKKVFEEUFCCPXJXVPUEOBPV@CEOX@SKILGT
YQWS@TBX@VDJJBWQDQDLXLCICGHJNWKLXBGQTLNLTKCKKBGCYA
SJPVTBIAILGUPXROUFMQWEUBRBKITLETBCHTXETVQKQVBSVAIOP
RFGISTVUTAXCCNBOBCIULSCTMVAIODJVAIJUST@MLBXV@FTCPLITXP
LCKDXJLGIVAIAPCUHJMWSVHKOPTJLQVUMTLXCPREBIPGIITVAXRI
PLXIXJXCTTVGEMHTAGKIRCVGTWLCEDECATVKOIAUVQFXETMTM
SJQWVHRBHXJXWEPTGHJQWINXXQTVUHRJNJCMLBGWITZBBICGSA
SMFXEQWEVAITPWCLURPVGLXLJXFTVHBEPPMQWGWKPVQPCVOE
PMTYVLBXJXGEPVCVXBGEPWXRGRQYXETMPLGOXTVBSKPPUHKBD
VIBEKPAKYILUXJXEYDZGBHOTACVLFAHKLLZDREEYPXSPMLXIQAF
SQWITPEPUVGVOITHCGHPXGMECQDJKOIIXXVEIPISPXPLOIPZIPTEEA
EYDYVTJLDXCGHXWENYPLCKYAMZWAGKIXGVCGKBSMPTRBPXTHA
YTWKWIQWIKKKOPZGTRALITXWXRVGWXLILGFIJDVAHJCXZGEMQIP
GUVLILGKWLUQKGITWSITZBJTVKCFCKVHKBIENBZFCKGQGBTHKGK
INICKPVXRVAEQJRKOIOHENLXOJKIEIFPQKGHBQXGWJLGEDXPFTJKK
IIXKKHYPACGGXBGXCBRBSXJTXQWIAAEAPPNUIBCFQKRLCXJXMOQ
EEDWTXXJ@MLBXV@JTRAHMP@MLBXV@VKSRHITLTLROGMWXCHJTHKTZG
KXXZIPMLBBSWMMKILKLW@QPX@GHJBMMUMIKRIQNVPLEUMLBBETLL
ZDYPMVVSSYGFVILGKMSTVYBXEXRCLXETVKOIOLSWGHQLIPMCJX
PGLSCILGLIXBCHBVPIQ@QLX@SXZKWEKSFTHEAXQRKIPHMQGSCILGBH
BCXKMCLUXJBRDHWGXQPISOXXLWEXXFBTRITMKTHQGEJTQQKEY
AITTAXUXGKRLDRVHAXGHUXZBCMPZEQHYEAEQXQGBJLJRFHYQUST
VIOIEKGXEPXVAMPQPGTOMAEEXSSTVIKSTCAKMLKTXVEIPLEUML
BRLWKGENETWEKSXJTXMWMNBTMXVTBTIPXGHJQWMUIEOXWJTRAP
PUHKBDVIBEKPAKYILUXJXEYDZGPIOTHG@THX@CHDNVF@THC@GHQWE
VTPBMEPWIOQETMLLASOXAXQVCAEJISDBEPPRFKSDTVKGJXCXEAMIS
VGGSCILGTJLGIUTMALITXEIHSFXEAPRFUYOXIFTRAILCMXE@THC@KOC
AEVPMISITGIPHFGRSKSXJXGEJVEACXGHKGXBGWGVXBSAKMLANO
GLEKSQQNRAHEPWKXIIUPMQWWETXQTVGWGXIXNXJBTHKGKLCM
VPEPILGFEOHLGLEKSXJTXQWINHAITEFXRIXRGUIVDRFPEPILGKMST
VCGHQWEV@MLB@SMUMEKIWCOEDTPCBVCGSOPLFRLVAITXRFPEPGY
UAMKVACLXETWGTEKSXJTXQWIUFEIAFWGHITSHLLFKITLKODAKG
KXUVCBHLUMVTPIPRFUIDXRPBRDISEKCTPWRBT

The letter Q appears approximately 47 times
ceox appears 2 times i used @ symbols to make their location stand out
I found other reocurring combox marked with @

Last edited by a moderator: May 3, 2017
14. Dec 19, 2007

### dodo

Key: EXPECT

MYFATHERSFAMILYNAMEBEINGPIRRIPANDMYCHRISTIANNAMEPHILIPMYINFANTTONGUECOULDMAKEOFB
OTHNAMESNOTHINGLONGERORMOREEXPLICITTHANPIPSOICALLEDMYSELFPIPANDCAMETOBECALLEDPIP
IGIVEPIRRIPASMYFATHERSFAMILYNAMEONTHEAUTHORITYOFHISTOMBSTONEANDMYSISTERMRSJOEGAR
GERYWHOMARRIEDTHEBLACKSMITHASINEVERSAWMYFATHERORMYMOTHERANDNEVERSAWANYLIKENESSOF
EITHEROFTHEMFORTHEIRDAYSWERELONGBEFORETHEDAYSOFPHOTOGRAPHSMYFIRSTFANCIESREGARDIN
GWHATTHEYWERELIKEWEREUNREASONABLYDERIVEDFROMTHEIRTOMBSTONESTHESHAPEOFTHELETTERSO
NMYFATHERSGAVEMEANODDIDEATHATHEWASASQUARESTOUTDARKMANWITHCURLYBLACKHAIRFROMTHECH
ARACTERANDTURNOFTHEINSCRIPTIONALSOGEORGIANAWIFEOFTHEABOVEIDREWACHILDISHCONCLUSIO
LONGWHICHWEREARRANGEDINANEATROWBESIDETHEIRGRAVEANDWERESACREDTOTHEMEMORYOFFIVELIT
TLEBROTHERSOFMINEWHOGAVEUPTRYINGTOGETALIVINGEXCEEDINGLYEARLYINTHATUNIVERSALSTRUG
CEOURSWASTHEMARSHCOUNTRYDOWNBYTHERIVERWITHINASTHERIVERWOUNDTWENTYMILESOFTHESEAMY
AMEMORABLERAWAFTERNOONTOWARDSEVENINGATSUCHATIMEIFOUNDOUTFORCERTAINTHATTHISBLEAKP
LACEOVERGROWNWITHNETTLESWASTHECHURCHYARDANDTHATPHILIPPIRRIPLATEOFTHISPARISHANDAL
DERNESSBEYONDTHECHURCHYARDINTERSECTEDWITHDYKESANDMOUNDSANDGATESWITHSCATTEREDCATT
ANTSAVAGELAIRFROMWHICHTHEWINDWASRUSHINGWASTHESEAANDTHATTHESMALLBUNDLEOFSHIVERSGR
OWINGAFRAIDOFITALLANDBEGINNINGTOCRYWASPIP

I wrote the program below, and used its output sorted by the 4th column (using the "sort" command) to help getting the key length. The 1st and 2nd column tell the letter and its position, respectively.

#### Attached Files:

• ###### findkey.zip
File size:
922 bytes
Views:
86
15. Dec 19, 2007

### lordlactose

dude you cheated with a program, come on. That takes all the fun and the skill out of it. Decoding it with a program is like not decoding it at all. Do you know how to decode a vigenere without using a program?

16. Dec 19, 2007

### dodo

You mean, measuring the distance between similar groups, and taking the GCD as a candidate for the key length. In this case, I thought it was more interesting to relate the solving to letter frequencies. It's not a brute force attack, which would be impractically long. How would you calculate letter frequencies for a substitution cypher without a program, for example?

17. Dec 19, 2007

### lordlactose

Oh well its quite easy you just count the letters. Are you saying you just used the program to save time? Can you provide the link to the program you used, the black chamber program doesn't work on this cypher becuz it has symbols. After you gathered up the frequency then how did you solve it?

Last edited: Dec 19, 2007
18. Dec 19, 2007

### dodo

The program is attached on post #14. It produces some output, which has to be sorted afterwards by column #4. The first 10 lines of the output, after sorting, are:
Code (Text):

P 2 6   0.80604 0.69821
E 3 9   0.81012 0.65658
E 0 3   0.82585 0.76514
C 10 12 0.88765 0.76796
X 1 6   0.88835 0.79568
C 4 6   0.91278 0.93505
E 3 6   0.94524 1.06175
E 6 9   0.96027 0.87800
E 3 18  0.97258 0.77753
T 5 6   1.02209 0.80147
...
Column #3 is the key length. You can see an abundance of 6 for column #3 on these first lines, as well as other multiples of 6. Column #2 is the letter position (for length=6, position=0..5), so the key EXPECT pops out immediately.

The 4th column, the one you use to sort (the one which is small on good candidates) is the sum of errors between (a) the letter frequencies in English and (b) the letter frequencies in the text for that letter, position and length. The lesser the error, the better the candidate.

19. Dec 19, 2007

### lordlactose

I am assuming that in your post p26,e39 and ect. are commonly found trigrams or three letter combos. But what are the decimal numbers for that are parallel to the trigrams? Shouldn't their abundance and space apart be represented by whole numbers? Could you have been able to gather these numbers without the software?

Last edited: Dec 19, 2007
20. Dec 22, 2007

### lordlactose

Does anyone understand how to decode the vinegre cypher?

21. Dec 27, 2007

### lordlactose

No one has a clue how to decode the vinegre cypher?

22. Nov 4, 2009

### atiekay

TXOIDSMZIG
RQZGIISISW
SMZTTSLOTR
HQYVTTIIRL
DXPTSHWZJR
GFJGJTHXCW

I think the kw is 5 letters long,
I've tried a bunch of ways but am stuck, help?

23. Dec 11, 2009

### thefrogofwar

A challenge!

See if u can decipher this famous phrase you need a (SKELETON) KEYtext for it

125 112 223 218 145 114 246 128 148 212 533 335

24. May 8, 2010

Hi guys, if you want to play with a cipher I invite you to this website:
http://toolpaq.com/en/cipher/
there is a prize for beating the cipher.
Have fun! :-)

25. Jun 8, 2010

### parazit

Hey everyone..I got something for you..I got some numbers..The open one is "2626481000" and it's close is "12122314442323121222" i mean the firts one is open form and the second one is secret/closed form..
I need the secret/closed form of "3124685300"