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Vigenère Cipher Issues


GeekGoneCrazy
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In my network security class we have a lab that is over different ciphers. Hoping I can get a little help figuring out what's up.

The block of Cipher text is

Fwohdwa uf gcufur isyr Cshpnab gnw ght toxk Szy ux huuks umfvylg punsekv kvzz cvr Kheaeavt em fopggxabt Uf al ljcaz hceiz gjofu Fswzy zzcfk kveoed gnwmek tstofbvt lc ouaz Jgkhvt skne sunof wa ssftgjwggnwyrw Grgjquofu suj al rggg yzoxkj cs yszg Ygar vwccrw qygaa gnsh gnwfry s kbssb gu tznsw Phz A yauo wgy fcouvmf lsiyz A rbtl yauo huk jsnygb V ylolkv vrxw oyr ksnygb Aulvvt lc fngk oal huok pegfr ako hnzlcb Hmh vzk o eksz oksige S ardaqnt uigow Vbc ah tul vrxw W ugnsaz s qyaw W orwk bal al ldwcldcc Ylscvwr bt s dbvlcc Imh ze zsrr zoq zg qeaagr uf pnic vbsw Phz lvrxwg ougnr of huk tzrtvse Gfr fugb vz owyr jsajwf Gnsh sxgnrt ucaigqgogb gnsh ukddf sw vnty ca Csggof ojgq otgab vt eoemsfvzsjvrds Fksfpnabt lgf ze dcfz kvnqwf bl koyz Kczk hsbvds prswz zzog zzsekk o jueoa zg pyges Oal W xtgk vzk al uob qgeb sgmzg Ewg ntv gbsw druhzr idovs lvnz lvrxwg n cgant lc orsar Gfr V qfcj olg ze gka jsaa lsiyz

Her clues were.

  • popular in the 80s
  • Spring break
  • Drinking was kinda hinted at.

Tried everything drinking related I could think of then thought maybe it was something to do with 80's songs. I tried a bunch of songs. None of which worked. Then I just typed in song. Using this website: http://sharkysoft.com/misc/vigenere/

Nibblin on sponge cake Watchin the sun bake All of those hgnhlfo bhhaqxp shmt khe Epqnyihg yu rbjoskujf Hz ix ydkmm bkqvt ovbzc Rfqhk mtkrx edqbyl saquqx nafbzjhg fk ahuh Vtephg mszr mczbz em fmnftdesthekeq Odtdygbzc ehd ix eaos ltwjxd ke lmhs Laid iqkoeq yktui samp saqndl m snfmj sh nhzfq Xtm U gmhi esl zkahpur ymqkm U zngf gmhi pgx dazlaj H lfwxxp ddkq wke eazlaj Mhfdhg fk raas anf pgbe xqtzz mxi pzmfkn Ugp hme w qxmh axmqsr M idquyzg oqsbq Dnp up fhf ddkq E gthamm m yknq E aeqs nnf ix yxeoyxko Lfaoiqz ng m lnifko Vgp lr tade twc ma yqnuod hz xzvw dnfq Xtm fddkqo ahavd bz pgx nhdgpaq Tzz rhaj hm ieke damwqn Samp ekavdg okmvaysbaj samp gxxlr fq dzgs km Pmosbz wvtk wftuj hg ywqzmnhmmrhexa Rxmnbaujf yan lr xkrm edzdqn ny ewkm Eklx banixa bemel mtws mtaqxe w vhywm ma xktya Anf E jgas hme ix hij ctyj etghs Rqo zgp onfq ldhbhd vxwhf fdzm fddkqo z paizg fk aemid Tzz H dzkv bfo lr asm wmim ymqkm

Google quickly turns back that this is lyrics from jimmy buffet - margaritaville. Sweet... So we know pretty much what the content is.

Frustrated I looked for a way to brute force it. Using: http://ljplawcom00.web707.discountasp.net/...gEnterText.aspx

It returned the key "ongs" Trying that...

Rjippju cr twcrhl qell Keujvmo avi tbb fbrs Ems cj uocwf ourists covered with oil Strummin my sixstring On my front porch swing Smell those shrimp theyre beginnin to boil Wastin away again in margaritaville Searching for my lost shaker of salt Some people claim that theres a woman to blame But I know its nobodys fault I dont know the reason I stayed here all season Nothin to show but this brand new tattoo But its a real beauty A mexican cutie How it got here I havent a clue I blew out my flipflop Stepped on a poptop Cut my heel had to cruise on back home But theres booze in the blender And soon it will render That frozen concoction that helps me hang on Wastin away again in margaritaville Searching for my lost shaker of salt Some people claim that theres a woman to blame But I know its my own damn fault Yes and some people claim that theres a woman to blame And I know its my own damn fault

The other part of the lyrics... lol

Nibblin on sponge cake Watchin the sun bake All of those tourists covered with oil Strummin my sixstring On my front porch swing Smell those shrimp theyre beginnin to boil Wastin away again in margaritaville Searching for my lost shaker of salt Some people claim that theres a woman to blame But I know its nobodys fault I dont know the reason I stayed here all season Nothin to show but this brand new tattoo But its a real beauty A mexican cutie How it got here I havent a clue I blew out my flipflop Stepped on a poptop Cut my heel had to cruise on back home But theres booze in the blender And soon it will render That frozen concoction that helps me hang on Wastin away again in margaritaville Searching for my lost shaker of salt Some people claim that theres a woman to blame But I know its my own damn fault Yes and some people claim that theres a woman to blame And I know its my own damn fault

So I know exactly what the message says.. Could turn this in. But not sure why exactly i'm not getting the whole thing? Or what's wrong with my key. Any Ideas?

Thanks,

Aaron

Edited by GeekGoneCrazy
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My gut instinct from your description is that it was hand enciphered and not machine enciphered. When enciphering it by hand they encipherd a letter but didn't write it down in the cipher text. We know where they made the mistake as it is at the point that the deciphering breaks.

Nibblin on sponge cake Watchin the sun bake All of those hgnhlfo bhhaq
songson gs ongson gson gsongso ngs ong song son gs ongso ngsongs ongso

Rjippju cr twcrhl qell Keujvmo avi tbb fbrs Ems cj uocwf ourists covered
ongsong so ngsong song songson gso ngs ongs ong so ngson gsongso ngsongs

In fact looking at it we can see that they dropped the character representing the letter 't' from tourists after enciphering it. So you can put in your assignment that there is a strong indication that it was either encoded by hand or altered after encoding. As it only happens once I would personally put it down to an accident in enciphering rather than a deliberate attempt to make cryptanalysis of it harder, if they were trying to make it harder to break there would have been more little mistakes like this, the sort that wouldn't be too hard for someone who knows the key to figure out but messes up frequency analysis methods by changing the mapping part way through.

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  • 1 month later...

My gut instinct from your description is that it was hand enciphered and not machine enciphered. When enciphering it by hand they encipherd a letter but didn't write it down in the cipher text. We know where they made the mistake as it is at the point that the deciphering breaks.

CODE

Nibblin on sponge cake Watchin the sun bake All of those hgnhlfo bhhaq

songson gs ongson gson gsongso ngs ong song son gs ongso ngsongs ongso

Rjippju cr twcrhl qell Keujvmo avi tbb fbrs Ems cj uocwf ourists covered

ongsong so ngsong song songson gso ngs ongs ong so ngson gsongso ngsongs

In fact looking at it we can see that they dropped the character representing the letter 't' from tourists after enciphering it. So you can put in your assignment that there is a strong indication that it was either encoded by hand or altered after encoding. As it only happens once I would personally put it down to an accident in enciphering rather than a deliberate attempt to make cryptanalysis of it harder, if they were trying to make it harder to break there would have been more little mistakes like this, the sort that wouldn't be too hard for someone who knows the key to figure out but messes up frequency analysis methods by changing the mapping part way through.

Some reason this didn't notify me of a response. But you were absolutely correct. The key was indeed just 'song'. The cypher was also missing one letter right at tourists.

The correct cypher:

Fwohdwa uf gcufur isyr Cshpnab gnw ght toxk Szy ux huuks gumfvylg punsekv kvzz cvr Kheaeavt em fopggxabt Uf al ljcaz hceiz gjofu Fswzy zzcfk kveoed gnwmek tstofbvt lc ouaz Jgkhvt skne sunof wa ssftgjwggnwyrw Grgjquofu suj al rggg yzoxkj cs yszg Ygar vwccrw qygaa gnsh gnwfry s kbssb gu tznsw Phz A yauo wgy fcouvmf lsiyz A rbtl yauo huk jsnygb V ylolkv vrxw oyr ksnygb Aulvvt lc fngk oal huok pegfr ako hnzlcb Hmh vzk o eksz oksige S ardaqnt uigow Vbc ah tul vrxw W ugnsaz s qyaw W orwk bal al ldwcldcc Ylscvwr bt s dbvlcc Imh ze zsrr zoq zg qeaagr uf pnic vbsw Phz lvrxwg ougnr of huk tzrtvse Gfr fugb vz owyr jsajwf Gnsh sxgnrt ucaigqgogb gnsh ukddf sw vnty ca Csggof ojgq otgab vt eoemsfvzsjvrds Fksfpnabt lgf ze dcfz kvnqwf bl koyz Kczk hsbvds prswz zzog zzsekk o jueoa zg pyges Oal W xtgk vzk al uob qgeb sgmzg Ewg ntv gbsw druhzr idovs lvnz lvrxwg n cgant lc orsar Gfr V qfcj olg ze gka jsaa lsiyz

Simply missing a 'g'.

Thanks for the help. I wish I would have seen it sooner. I did manage to find this out from another student before turning it in. So not all was lost.

Thanks,

Aaron

Edited by GeekGoneCrazy
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