Lab $5$: Classical Encryption Technique

$1\mathrm{.}1$ Breaking Vigen$$re cipher

CLO$6.$ Use software libraries to efficiently apply cryptographic techniques

Task$1$: Break the following text encrypted with Vigener cipher. You should use frequency analysis tools.

Provide screenshot of all tools used and its result and explain the method.

Cipher text $=$

Vvhvv cfh wvxsuec dsqiwkhv sw jcqijvm. Kseggwc ygzsw zp hki ugjhpfrahrk qt psiczoc jvfrrx evdvrehhvj. Kt bsl cfh lfpsvx$,$ pqi zmcn brx sg oivrkr rj rpmwlzpu. Bsl fc qsk joyi kq hkmem oeslv adozpu iecus vxftwhw rpr wlvp hki wgou sw tssirvwqk kjs vedg wq iocqw aftrv. Mw acx eig vrrvuh, bsl fc qsk joyi kq fhqvophv rpm iecus vxftwhw$.$ Ggcspv ywop ktivx pqi psig. Oq lfpsvx ggfvse ywop rngr hvxsosg fwvgzrzlrv$.$ Cb kseggw tvtgrr nkzo fv glwvvosoc tqbwiev, yqsn yvdx kq rr jiqa wmdg hr xzos, dru ywop eqh webg oqc gtsvwlts rv kgbvmfp oeslv oqckjwqk. Kjs kirnhk aznz lqgtcyi, rpr wlv owqh nkzo fv ch sires. Wlv rsuwfp klpc ds yiia dxrtvidp rpr zmcn qrqgnswi rnz wejmg rr kkah. Wzpqh qfts sifrzh aznz wvluh dr yqbhwk rsuwfp, vh si uvh aznz imef arvv hfliefg dru ywop sg gxtgqfwiu czo eiqiqh. Rp vrrvuh siiucq aznz qsk ds lrmqzyiu kb flvchlrx$,$ nmlrx$,$ nofo fh huyjv, uuivf, gwirnwqk, rpr drp qhkii kapsicz dgku.

Vrrvuhb tiqarxvu oxxygbwmtkhb. Mk kg d vvhzhgkkcq sw vvh xyqijlku oqh wgsomeig rj r rsuwfp. Ww mj c trvd qt vich$-$satiggvmfp, oqh zh o siiucq mj jcqijv, dhsgns zmcn yqsn yvdx yg cu wyg huyca wv$.$ Mk czvs dcyhw kjs siiucq gfptlhvph$.$ Ws jrsdo kjs wvlvv$,$ lx egsgw r ncw sw ecxvris dru ecqjzfsqgv. Qboc r eczeif klpc vsop cksv fveoxwv js rv jjs lw rhfdmu qt wlv vfxxy$.$ Udhebkbj xyg huykj wv ee cqw sw dfdzvtm$.$ Wicnwqk cksv ecuc vlfyg wlrv hki ggfvse kg osn qb vich$-$qrrwkrhrtg$.$

Hint: Key length $=5$