Substitution cipher cryptanalysis Decrypt the following Cypher texts and submit

Question

Substitution cipher cryptanalysis

Decrypt the following Cypher texts and submit the plain text, the key. Submit a 1 to 2-page report detailing the cryptanalysis process, your observations and insights. There are several tools available online to help with Frequency Analysis. One such resource is http://www.simonsingh.net/The_Black_Chamber/crackingsubstitution.html

1.

papb emqgp tbmrmqu vssimpz gbjsrwubvshj m hvap lppq vedpz rw bpgwkkpqz vlwwd wq gbjsrvqvijeme kj nqywbrnqvrp vqetpb me rhvr thmip rhpbp vbp epapbviuwwz lwwde wq gbjsrwubvshj rhpbp vbp qw lwwde uwwz wb lvz wq gbjsrvqvijememr me v awmz rhvr m zwqr epp lpmqu ymiipz vqjrmkp ewwq gbjsrvqvijeme me engh
v yver-kwamqu ympiz rhvr vqj lwwd wy rpghqmxnpe twniz lp wlewiprp lpywbp mr tvesbmqrpz vqz papq my rhp lwwd gwniz ewkphwt bpkvmq gnbbpqr mr twniz zw imrriprw rpvgh gbjsrvqvijeme rhp wqij tvj rw ipvbq gbjsrvqvijeme me rhbwnuh sbvgrmgp
v ernzpqr emksij hve rw lbpvd viuwbmrhk vyrpb viuwbmrhk mqapqrmqu qpt
rpghqmxnpe vqz kwzmyjmqu pcmermqu wqpe bpvzmqu wrhpbe gbjsrvqvijeme bpenire
hpise lnr rhpbp me qw enlermrnrp ywb pcspbmpqgp vq pcgpbsr ybwk v epiy-ernzj
gwnbep mq liwgd-gmshpb gbjsrvqvijeme lj lbngp eghqpmpb uwwuip mr ywb rhp ynii vbrmgip

2.

nqaxc gytzf acudc gfuna ogyqa chavd cgfun aoxvg kcund dytcy qcjxy dcckd vqech zmyna djcvk qcddc dnqvg ytzfa cudod actyu gytzf acuqc ajyuk xvgkc udtvo lctya nsvac elovt fmana fecyw ucvdy qddfg xvdzu ywnaz uyacd agxvm mcqpc cqbyo tcqay uaycs vmfva caxyd cjcvk qcddc dayvd dndan qucty snqpa xctax cdflg fmafu caxva xvdcs ymsce vuyfq exvgk cudnd ywacq ucwcu uceay vdaxc gytzf acufq ecupu yfqea xcucn dvmyq pdavq enqpg yqauy scudo vlyfa axcac utdau fctcv qnqpn qaxnd gyqau yscud oaxca cutxv gkcun ducgm vntce logyt zfacu zuypu vttcu djxyv upfca xvana ucwcu ddntz moayd ytcyq cjnax vqves vqgce fqecu davqe nqpyw gytzf acudv qegyt zfacu qcajy ukdvq eaxva guvgk cunda xctyu cvzzu yzunv acacu twyua xydcj xyluc vknqa ygytz facud jxcax cugyt zfacu guntn qvmlm vgkxv adyug ytzfa cudcg funao chzcu ajxna cxvad lfavu cgcqa vuang mcgyq gmfec eaxva axclm vgkxv atcvq nqpda nmmzu csvnm dvtyq paxcp cqcuv mzflm ng

Explanation / Answer

Answer 1) The decrypted plain text is :

ever since writing applied cryptography i have been asked to recommend abook on cryptanalysis my unfortunate answer is that while there are severalgood books on cryptography there are no books good or bad on cryptanalysisit is a void that i dont see being filled anytime soon cryptanalysis is such a fast-moving field that any book of techniques would be obsolete before it wasprinted and even if the book could somehow remain current it would do littleto teach cryptanalysis the only way to learn cryptanalysis is through practice

a student simply has to break algorithm after algorithm inventing new techniques and modifying existing ones reading others cryptanalysis results helps but there is no substitute for experience an excerpt from a self-study course in block-cipher cryptanalysis by bruce schneier google it for the full article

The key used here for the purpose of encryption is :

abcdefghijklmnopqrstuvwxyz

vlgzpyuhmodikqwsxbernatcjf

To break a particular ciphertext, one needs to understand the concpet behind that. In substitution cipher, a particular alphabet is substituted by any other alphabet by using a key which is randomly generated. Yo decrypt a cipher text encrypted using substitution method, one needs to check the repetition of letters. The most commonly used letters in english are E, then T and then A. What we usually have to do is try and find the number of reperirion of particular alphabet and assuming that the highest repeated alphabets may be amongst those most commonly used ones.

Like in the above mentioned cipher text, the repetiton of P = 77 times, the repetition of R = 61 times and so on.

If we will assume that P in the above mentioned ciphertext is E and R is T, than it becomes easy to identify the key. This is the main thing which you need to take care of while decrypting in susbstitution cipher.

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