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Caesar cipher

Caesar cipher, is one of the simplest and most widely known encryption techniques. The transformation can be represented by aligning two alphabets, the cipher alphabet is the plain alphabet rotated left or right by some number of positions.

When encrypting, a person looks up each letter of the message in the 'plain' line and writes down the corresponding letter in the 'cipher' line. Deciphering is done in reverse.
The encryption can also be represented using modular arithmetic by first transforming the letters into numbers, according to the scheme, A = 0, B = 1,..., Z = 25. Encryption of a letter x by a shift n can be described mathematically as

Plaintext: miscut
cipher variations:
njtdvu okuewv plvfxw qmwgyx rnxhzy
soyiaz tpzjba uqakcb vrbldc wscmed
xtdnfe yueogf zvfphg awgqih bxhrji
cyiskj dzjtlk eakuml fblvnm gcmwon
hdnxpo ieoyqp jfpzrq kgqasr lhrbts

Decryption is performed similarly,

(There are different definitions for the modulo operation. In the above, the result is in the range 0...25. I.e., if x+n or x-n are not in the range 0...25, we have to subtract or add 26.)
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Atbash Cipher

Atbash is an ancient encryption system created in the Middle East. It was originally used in the Hebrew language.
The Atbash cipher is a simple substitution cipher that relies on transposing all the letters in the alphabet such that the resulting alphabet is backwards.
The first letter is replaced with the last letter, the second with the second-last, and so on.
An example plaintext to ciphertext using Atbash:
Plain: miscut
Cipher: nrhxfg

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Baconian Cipher

To encode a message, each letter of the plaintext is replaced by a group of five of the letters 'A' or 'B'. This replacement is done according to the alphabet of the Baconian cipher, shown below.
a   AAAAA   g    AABBA     m    ABABB   s    BAAAB     y    BABBA
b   AAAAB   h    AABBB     n    ABBAA   t    BAABA     z    BABBB
c   AAABA   i    ABAAA     o    ABBAB   u    BAABB 
d   AAABB   j    BBBAA     p    ABBBA   v    BBBAB
e   AABAA   k    ABAAB     q    ABBBB   w    BABAA
f   AABAB   l    ABABA     r    BAAAA   x    BABAB

Plain: miscut

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Affine Cipher
In the affine cipher the letters of an alphabet of size m are first mapped to the integers in the range 0..m - 1. It then uses modular arithmetic to transform the integer that each plaintext letter corresponds to into another integer that correspond to a ciphertext letter. The encryption function for a single letter is

where modulus m is the size of the alphabet and a and b are the key of the cipher. The value a must be chosen such that a and m are coprime.
Considering the specific case of encrypting messages in English (i.e. m = 26), there are a total of 286 non-trivial affine ciphers, not counting the 26 trivial Caesar ciphers. This number comes from the fact there are 12 numbers that are coprime with 26 that are less than 26 (these are the possible values of a). Each value of a can have 26 different addition shifts (the b value) ; therefore, there are 12*26 or 312 possible keys.
Plaintext: miscut
cipher variations:

The decryption function is

where a - 1 is the modular multiplicative inverse of a modulo m. I.e., it satisfies the equation

The multiplicative inverse of a only exists if a and m are coprime. Hence without the restriction on a decryption might not be possible. It can be shown as follows that decryption function is the inverse of the encryption function,

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ROT13 Cipher
Applying ROT13 to a piece of text merely requires examining its alphabetic characters and replacing each one by the letter 13 places further along in the alphabet, wrapping back to the beginning if necessary. A becomes N, B becomes O, and so on up to M, which becomes Z, then the sequence continues at the beginning of the alphabet: N becomes A, O becomes B, and so on to Z, which becomes M. Only those letters which occur in the English alphabet are affected; numbers, symbols, whitespace, and all other characters are left unchanged. Because there are 26 letters in the English alphabet and 26 = 2 * 13, the ROT13 function is its own inverse:

ROT13(ROT13(x)) = x for any basic Latin-alphabet text x

An example plaintext to ciphertext using ROT13:

Plain: miscut
Cipher: zvfphg

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Polybius Square

A Polybius Square is a table that allows someone to translate letters into numbers. To give a small level of encryption, this table can be randomized and shared with the recipient. In order to fit the 26 letters of the alphabet into the 25 spots created by the table, the letters i and j are usually combined.
1 2 3 4 5
1 A B C D E
2 F G H I/J K
3 L M N O P
4 Q R S T U
5 V W X Y Z

Basic Form:
Plain: miscut
Cipher: 234234315444

Extended Methods:
Method #1

Plaintext: miscut
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
m i s c u t 
2 4 3 3 5 4 
3 2 4 1 4 4 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: miscut
Cipher: rnuhdt

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Method #3

Plaintext: miscut
method variations:
smovti movtis ovtism
vtismo tismov ismovt

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Permutation Cipher
In classical cryptography, a permutation cipher is a transposition cipher in which the key is a permutation. To apply a cipher, a random permutation of size E is generated (the larger the value of E the more secure the cipher). The plaintext is then broken into segments of size E and the letters within that segment are permuted according to this key.
In theory, any transposition cipher can be viewed as a permutation cipher where E is equal to the length of the plaintext; this is too cumbersome a generalisation to use in actual practice, however.
The idea behind a permutation cipher is to keep the plaintext characters unchanged, butalter their positions by rearrangement using a permutation
This cipher is defined as:
Let m be a positive integer, and K consist of all permutations of {1,...,m}
For a key (permutation) , define:
The encryption function
The decryption function
A small example, assuming m = 6, and the key is the permutation :

The first row is the value of i, and the second row is the corresponding value of (i)
The inverse permutation, is constructed by interchanging the two rows, andrearranging the columns so that the first row is in increasing order, Therefore, is:

Total variation formula:

e = 2,718281828 , n - plaintext length

Plaintext: miscut

all 720 cipher variations:
miscut misctu misuct misutc mistuc mistcu micsut micstu micust micuts mictus
mictsu miucst miucts miusct miustc miutsc miutcs mitcus mitcsu mitucs mitusc
mitsuc mitscu msicut msictu msiuct msiutc msituc msitcu msciut mscitu mscuit
mscuti msctui msctiu msucit msucti msuict msuitc msutic msutci mstcui mstciu
mstuci mstuic mstiuc msticu mcsiut mcsitu mcsuit mcsuti mcstui mcstiu mcisut
mcistu mciust mciuts mcitus mcitsu mcuist mcuits mcusit mcusti mcutsi mcutis
mctius mctisu mctuis mctusi mctsui mctsiu muscit muscti musict musitc mustic
mustci mucsit mucsti mucist mucits muctis muctsi muicst muicts muisct muistc
muitsc muitcs mutcis mutcsi mutics mutisc mutsic mutsci mtscui mtsciu mtsuci
mtsuic mtsiuc mtsicu mtcsui mtcsiu mtcusi mtcuis mtcius mtcisu mtucsi mtucis
mtusci mtusic mtuisc mtuics mticus mticsu mtiucs mtiusc mtisuc mtiscu imscut
imsctu imsuct imsutc imstuc imstcu imcsut imcstu imcust imcuts imctus imctsu
imucst imucts imusct imustc imutsc imutcs imtcus imtcsu imtucs imtusc imtsuc
imtscu ismcut ismctu ismuct ismutc ismtuc ismtcu iscmut iscmtu iscumt iscutm
isctum isctmu isucmt isuctm isumct isumtc isutmc isutcm istcum istcmu istucm
istumc istmuc istmcu icsmut icsmtu icsumt icsutm icstum icstmu icmsut icmstu
icmust icmuts icmtus icmtsu icumst icumts icusmt icustm icutsm icutms ictmus
ictmsu ictums ictusm ictsum ictsmu iuscmt iusctm iusmct iusmtc iustmc iustcm
iucsmt iucstm iucmst iucmts iuctms iuctsm iumcst iumcts iumsct iumstc iumtsc
iumtcs iutcms iutcsm iutmcs iutmsc iutsmc iutscm itscum itscmu itsucm itsumc
itsmuc itsmcu itcsum itcsmu itcusm itcums itcmus itcmsu itucsm itucms ituscm
itusmc itumsc itumcs itmcus itmcsu itmucs itmusc itmsuc itmscu simcut simctu
simuct simutc simtuc simtcu sicmut sicmtu sicumt sicutm sictum sictmu siucmt
siuctm siumct siumtc siutmc siutcm sitcum sitcmu situcm situmc sitmuc sitmcu
smicut smictu smiuct smiutc smituc smitcu smciut smcitu smcuit smcuti smctui
smctiu smucit smucti smuict smuitc smutic smutci smtcui smtciu smtuci smtuic
smtiuc smticu scmiut scmitu scmuit scmuti scmtui scmtiu scimut scimtu sciumt
sciutm scitum scitmu scuimt scuitm scumit scumti scutmi scutim sctium sctimu
sctuim sctumi sctmui sctmiu sumcit sumcti sumict sumitc sumtic sumtci sucmit
sucmti sucimt sucitm suctim suctmi suicmt suictm suimct suimtc suitmc suitcm
sutcim sutcmi suticm sutimc sutmic sutmci stmcui stmciu stmuci stmuic stmiuc
stmicu stcmui stcmiu stcumi stcuim stcium stcimu stucmi stucim stumci stumic
stuimc stuicm sticum sticmu stiucm stiumc stimuc stimcu cismut cismtu cisumt
cisutm cistum cistmu cimsut cimstu cimust cimuts cimtus cimtsu ciumst ciumts
ciusmt ciustm ciutsm ciutms citmus citmsu citums citusm citsum citsmu csimut
csimtu csiumt csiutm csitum csitmu csmiut csmitu csmuit csmuti csmtui csmtiu
csumit csumti csuimt csuitm csutim csutmi cstmui cstmiu cstumi cstuim cstium
cstimu cmsiut cmsitu cmsuit cmsuti cmstui cmstiu cmisut cmistu cmiust cmiuts
cmitus cmitsu cmuist cmuits cmusit cmusti cmutsi cmutis cmtius cmtisu cmtuis
cmtusi cmtsui cmtsiu cusmit cusmti cusimt cusitm custim custmi cumsit cumsti
cumist cumits cumtis cumtsi cuimst cuimts cuismt cuistm cuitsm cuitms cutmis
cutmsi cutims cutism cutsim cutsmi ctsmui ctsmiu ctsumi ctsuim ctsium ctsimu
ctmsui ctmsiu ctmusi ctmuis ctmius ctmisu ctumsi ctumis ctusmi ctusim ctuism
ctuims ctimus ctimsu ctiums ctiusm ctisum ctismu uiscmt uisctm uismct uismtc
uistmc uistcm uicsmt uicstm uicmst uicmts uictms uictsm uimcst uimcts uimsct
uimstc uimtsc uimtcs uitcms uitcsm uitmcs uitmsc uitsmc uitscm usicmt usictm
usimct usimtc usitmc usitcm uscimt uscitm uscmit uscmti usctmi usctim usmcit
usmcti usmict usmitc usmtic usmtci ustcmi ustcim ustmci ustmic ustimc usticm
ucsimt ucsitm ucsmit ucsmti ucstmi ucstim ucismt ucistm ucimst ucimts ucitms
ucitsm ucmist ucmits ucmsit ucmsti ucmtsi ucmtis uctims uctism uctmis uctmsi
uctsmi uctsim umscit umscti umsict umsitc umstic umstci umcsit umcsti umcist
umcits umctis umctsi umicst umicts umisct umistc umitsc umitcs umtcis umtcsi
umtics umtisc umtsic umtsci utscmi utscim utsmci utsmic utsimc utsicm utcsmi
utcsim utcmsi utcmis utcims utcism utmcsi utmcis utmsci utmsic utmisc utmics
uticms uticsm utimcs utimsc utismc utiscm tiscum tiscmu tisucm tisumc tismuc
tismcu ticsum ticsmu ticusm ticums ticmus ticmsu tiucsm tiucms tiuscm tiusmc
tiumsc tiumcs timcus timcsu timucs timusc timsuc timscu tsicum tsicmu tsiucm
tsiumc tsimuc tsimcu tscium tscimu tscuim tscumi tscmui tscmiu tsucim tsucmi
tsuicm tsuimc tsumic tsumci tsmcui tsmciu tsmuci tsmuic tsmiuc tsmicu tcsium
tcsimu tcsuim tcsumi tcsmui tcsmiu tcisum tcismu tciusm tciums tcimus tcimsu
tcuism tcuims tcusim tcusmi tcumsi tcumis tcmius tcmisu tcmuis tcmusi tcmsui
tcmsiu tuscim tuscmi tusicm tusimc tusmic tusmci tucsim tucsmi tucism tucims
tucmis tucmsi tuicsm tuicms tuiscm tuismc tuimsc tuimcs tumcis tumcsi tumics
tumisc tumsic tumsci tmscui tmsciu tmsuci tmsuic tmsiuc tmsicu tmcsui tmcsiu
tmcusi tmcuis tmcius tmcisu tmucsi tmucis tmusci tmusic tmuisc tmuics tmicus
tmicsu tmiucs tmiusc tmisuc tmiscu

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History of cryptography
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