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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: smoyer
cipher variations:
tnpzfs uoqagt vprbhu wqsciv xrtdjw
ysuekx ztvfly auwgmz bvxhna cwyiob
dxzjpc eyakqd fzblre gacmsf hbdntg
iceouh jdfpvi kegqwj lfhrxk mgisyl
nhjtzm oikuan pjlvbo qkmwcp rlnxdq

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: smoyer
Cipher: hnlbvi

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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: smoyer

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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: smoyer
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: smoyer
Cipher: fzblre

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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: smoyer
Cipher: 342343455124

Extended Methods:
Method #1

Plaintext: smoyer
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
s m o y e r 
3 2 4 4 5 2 
4 3 3 5 1 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: smoyer
Cipher: htkoxq

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Method #3

Plaintext: smoyer
method variations:
isszfo sszfoi szfois
zfoiss foissz oisszf

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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: smoyer

all 720 cipher variations:
smoyer smoyre smoeyr smoery smorey smorye smyoer smyore smyeor smyero smyreo
smyroe smeyor smeyro smeoyr smeory smeroy smeryo smryeo smryoe smreyo smreoy
smroey smroye somyer somyre someyr somery somrey somrye soymer soymre soyemr
soyerm soyrem soyrme soeymr soeyrm soemyr soemry soermy soerym soryem soryme
soreym soremy sormey sormye syomer syomre syoemr syoerm syorem syorme symoer
symore symeor symero symreo symroe syemor syemro syeomr syeorm syerom syermo
syrmeo syrmoe syremo syreom syroem syrome seoymr seoyrm seomyr seomry seormy
seorym seyomr seyorm seymor seymro seyrmo seyrom semyor semyro semoyr semory
semroy semryo serymo seryom sermyo sermoy seromy seroym sroyem sroyme sroeym
sroemy sromey sromye sryoem sryome sryeom sryemo srymeo srymoe sreyom sreymo
sreoym sreomy sremoy sremyo srmyeo srmyoe srmeyo srmeoy srmoey srmoye msoyer
msoyre msoeyr msoery msorey msorye msyoer msyore msyeor msyero msyreo msyroe
mseyor mseyro mseoyr mseory mseroy mseryo msryeo msryoe msreyo msreoy msroey
msroye mosyer mosyre moseyr mosery mosrey mosrye moyser moysre moyesr moyers
moyres moyrse moeysr moeyrs moesyr moesry moersy moerys moryes moryse moreys
moresy morsey morsye myoser myosre myoesr myoers myores myorse mysoer mysore
myseor mysero mysreo mysroe myesor myesro myeosr myeors myeros myerso myrseo
myrsoe myreso myreos myroes myrose meoysr meoyrs meosyr meosry meorsy meorys
meyosr meyors meysor meysro meyrso meyros mesyor mesyro mesoyr mesory mesroy
mesryo meryso meryos mersyo mersoy merosy meroys mroyes mroyse mroeys mroesy
mrosey mrosye mryoes mryose mryeos mryeso mryseo mrysoe mreyos mreyso mreoys
mreosy mresoy mresyo mrsyeo mrsyoe mrseyo mrseoy mrsoey mrsoye omsyer omsyre
omseyr omsery omsrey omsrye omyser omysre omyesr omyers omyres omyrse omeysr
omeyrs omesyr omesry omersy omerys omryes omryse omreys omresy omrsey omrsye
osmyer osmyre osmeyr osmery osmrey osmrye osymer osymre osyemr osyerm osyrem
osyrme oseymr oseyrm osemyr osemry osermy oserym osryem osryme osreym osremy
osrmey osrmye oysmer oysmre oysemr oyserm oysrem oysrme oymser oymsre oymesr
oymers oymres oymrse oyemsr oyemrs oyesmr oyesrm oyersm oyerms oyrmes oyrmse
oyrems oyresm oyrsem oyrsme oesymr oesyrm oesmyr oesmry oesrmy oesrym oeysmr
oeysrm oeymsr oeymrs oeyrms oeyrsm oemysr oemyrs oemsyr oemsry oemrsy oemrys
oeryms oerysm oermys oermsy oersmy oersym orsyem orsyme orseym orsemy orsmey
orsmye orysem orysme oryesm oryems orymes orymse oreysm oreyms oresym oresmy
oremsy oremys ormyes ormyse ormeys ormesy ormsey ormsye ymoser ymosre ymoesr
ymoers ymores ymorse ymsoer ymsore ymseor ymsero ymsreo ymsroe ymesor ymesro
ymeosr ymeors ymeros ymerso ymrseo ymrsoe ymreso ymreos ymroes ymrose yomser
yomsre yomesr yomers yomres yomrse yosmer yosmre yosemr yoserm yosrem yosrme
yoesmr yoesrm yoemsr yoemrs yoerms yoersm yorsem yorsme yoresm yorems yormes
yormse ysomer ysomre ysoemr ysoerm ysorem ysorme ysmoer ysmore ysmeor ysmero
ysmreo ysmroe ysemor ysemro yseomr yseorm yserom ysermo ysrmeo ysrmoe ysremo
ysreom ysroem ysrome yeosmr yeosrm yeomsr yeomrs yeorms yeorsm yesomr yesorm
yesmor yesmro yesrmo yesrom yemsor yemsro yemosr yemors yemros yemrso yersmo
yersom yermso yermos yeroms yerosm yrosem yrosme yroesm yroems yromes yromse
yrsoem yrsome yrseom yrsemo yrsmeo yrsmoe yresom yresmo yreosm yreoms yremos
yremso yrmseo yrmsoe yrmeso yrmeos yrmoes yrmose emoysr emoyrs emosyr emosry
emorsy emorys emyosr emyors emysor emysro emyrso emyros emsyor emsyro emsoyr
emsory emsroy emsryo emryso emryos emrsyo emrsoy emrosy emroys eomysr eomyrs
eomsyr eomsry eomrsy eomrys eoymsr eoymrs eoysmr eoysrm eoyrsm eoyrms eosymr
eosyrm eosmyr eosmry eosrmy eosrym eorysm eoryms eorsym eorsmy eormsy eormys
eyomsr eyomrs eyosmr eyosrm eyorsm eyorms eymosr eymors eymsor eymsro eymrso
eymros eysmor eysmro eysomr eysorm eysrom eysrmo eyrmso eyrmos eyrsmo eyrsom
eyrosm eyroms esoymr esoyrm esomyr esomry esormy esorym esyomr esyorm esymor
esymro esyrmo esyrom esmyor esmyro esmoyr esmory esmroy esmryo esrymo esryom
esrmyo esrmoy esromy esroym eroysm eroyms erosym erosmy eromsy eromys eryosm
eryoms erysom erysmo erymso erymos ersyom ersymo ersoym ersomy ersmoy ersmyo
ermyso ermyos ermsyo ermsoy ermosy ermoys rmoyes rmoyse rmoeys rmoesy rmosey
rmosye rmyoes rmyose rmyeos rmyeso rmyseo rmysoe rmeyos rmeyso rmeoys rmeosy
rmesoy rmesyo rmsyeo rmsyoe rmseyo rmseoy rmsoey rmsoye romyes romyse romeys
romesy romsey romsye roymes roymse royems royesm roysem roysme roeyms roeysm
roemys roemsy roesmy roesym rosyem rosyme roseym rosemy rosmey rosmye ryomes
ryomse ryoems ryoesm ryosem ryosme rymoes rymose rymeos rymeso rymseo rymsoe
ryemos ryemso ryeoms ryeosm ryesom ryesmo rysmeo rysmoe rysemo ryseom rysoem
rysome reoyms reoysm reomys reomsy reosmy reosym reyoms reyosm reymos reymso
reysmo reysom remyos remyso remoys remosy remsoy remsyo resymo resyom resmyo
resmoy resomy resoym rsoyem rsoyme rsoeym rsoemy rsomey rsomye rsyoem rsyome
rsyeom rsyemo rsymeo rsymoe rseyom rseymo rseoym rseomy rsemoy rsemyo rsmyeo
rsmyoe rsmeyo rsmeoy rsmoey rsmoye

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History of cryptography
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