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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: krelos
cipher variations:
lsfmpt mtgnqu nuhorv ovipsw pwjqtx
qxkruy rylsvz szmtwa tanuxb ubovyc
vcpwzd wdqxae xerybf yfszcg zgtadh
ahubei bivcfj cjwdgk dkxehl elyfim
fmzgjn gnahko hobilp ipcjmq jqdknr

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: krelos
Cipher: pivolh

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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: krelos

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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: krelos
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: krelos
Cipher: xerybf

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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: krelos
Cipher: 522451134334

Extended Methods:
Method #1

Plaintext: krelos
method variations:

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

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Method #3

Plaintext: krelos
method variations:
gyasny yasnyg asnygy
snygya nygyas ygyasn

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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: krelos

all 720 cipher variations:
krelos krelso kreols kreosl kresol kreslo krleos krleso krloes krlose krlsoe
krlseo kroles krolse kroels kroesl krosel krosle krsloe krsleo krsole krsoel
krseol krselo kerlos kerlso kerols kerosl kersol kerslo kelros kelrso kelors
kelosr kelsor kelsro keolrs keolsr keorls keorsl keosrl keoslr keslor keslro
kesolr kesorl kesrol kesrlo kleros klerso kleors kleosr klesor klesro klreos
klreso klroes klrose klrsoe klrseo klores klorse kloers kloesr kloser klosre
klsroe klsreo klsore klsoer klseor klsero koelrs koelsr koerls koersl koesrl
koeslr kolers kolesr kolres kolrse kolsre kolser korles korlse korels koresl
korsel korsle koslre kosler kosrle kosrel koserl koselr kselor kselro kseolr
kseorl kserol kserlo ksleor kslero ksloer kslore kslroe kslreo ksoler ksolre
ksoelr ksoerl ksorel ksorle ksrloe ksrleo ksrole ksroel ksreol ksrelo rkelos
rkelso rkeols rkeosl rkesol rkeslo rkleos rkleso rkloes rklose rklsoe rklseo
rkoles rkolse rkoels rkoesl rkosel rkosle rksloe rksleo rksole rksoel rkseol
rkselo reklos reklso rekols rekosl reksol rekslo relkos relkso reloks relosk
relsok relsko reolks reolsk reokls reoksl reoskl reoslk reslok reslko resolk
resokl reskol resklo rlekos rlekso rleoks rleosk rlesok rlesko rlkeos rlkeso
rlkoes rlkose rlksoe rlkseo rlokes rlokse rloeks rloesk rlosek rloske rlskoe
rlskeo rlsoke rlsoek rlseok rlseko roelks roelsk roekls roeksl roeskl roeslk
roleks rolesk rolkes rolkse rolske rolsek rokles roklse rokels rokesl roksel
roksle roslke roslek roskle roskel rosekl roselk rselok rselko rseolk rseokl
rsekol rseklo rsleok rsleko rsloek rsloke rslkoe rslkeo rsolek rsolke rsoelk
rsoekl rsokel rsokle rskloe rskleo rskole rskoel rskeol rskelo erklos erklso
erkols erkosl erksol erkslo erlkos erlkso erloks erlosk erlsok erlsko erolks
erolsk erokls eroksl eroskl eroslk erslok erslko ersolk ersokl erskol ersklo
ekrlos ekrlso ekrols ekrosl ekrsol ekrslo eklros eklrso eklors eklosr eklsor
eklsro ekolrs ekolsr ekorls ekorsl ekosrl ekoslr ekslor ekslro eksolr eksorl
eksrol eksrlo elkros elkrso elkors elkosr elksor elksro elrkos elrkso elroks
elrosk elrsok elrsko elorks elorsk elokrs eloksr eloskr elosrk elsrok elsrko
elsork elsokr elskor elskro eoklrs eoklsr eokrls eokrsl eoksrl eokslr eolkrs
eolksr eolrks eolrsk eolsrk eolskr eorlks eorlsk eorkls eorksl eorskl eorslk
eoslrk eoslkr eosrlk eosrkl eoskrl eosklr esklor esklro eskolr eskorl eskrol
eskrlo eslkor eslkro eslokr eslork eslrok eslrko esolkr esolrk esoklr esokrl
esorkl esorlk esrlok esrlko esrolk esrokl esrkol esrklo lrekos lrekso lreoks
lreosk lresok lresko lrkeos lrkeso lrkoes lrkose lrksoe lrkseo lrokes lrokse
lroeks lroesk lrosek lroske lrskoe lrskeo lrsoke lrsoek lrseok lrseko lerkos
lerkso leroks lerosk lersok lersko lekros lekrso lekors lekosr leksor leksro
leokrs leoksr leorks leorsk leosrk leoskr leskor leskro lesokr lesork lesrok
lesrko lkeros lkerso lkeors lkeosr lkesor lkesro lkreos lkreso lkroes lkrose
lkrsoe lkrseo lkores lkorse lkoers lkoesr lkoser lkosre lksroe lksreo lksore
lksoer lkseor lksero loekrs loeksr loerks loersk loesrk loeskr lokers lokesr
lokres lokrse loksre lokser lorkes lorkse loreks loresk lorsek lorske loskre
losker losrke losrek loserk losekr lsekor lsekro lseokr lseork lserok lserko
lskeor lskero lskoer lskore lskroe lskreo lsoker lsokre lsoekr lsoerk lsorek
lsorke lsrkoe lsrkeo lsroke lsroek lsreok lsreko orelks orelsk orekls oreksl
oreskl oreslk orleks orlesk orlkes orlkse orlske orlsek orkles orklse orkels
orkesl orksel orksle orslke orslek orskle orskel orsekl orselk oerlks oerlsk
oerkls oerksl oerskl oerslk oelrks oelrsk oelkrs oelksr oelskr oelsrk oeklrs
oeklsr oekrls oekrsl oeksrl oekslr oeslkr oeslrk oesklr oeskrl oesrkl oesrlk
olerks olersk olekrs oleksr oleskr olesrk olreks olresk olrkes olrkse olrske
olrsek olkres olkrse olkers olkesr olkser olksre olsrke olsrek olskre olsker
olsekr olserk okelrs okelsr okerls okersl okesrl okeslr oklers oklesr oklres
oklrse oklsre oklser okrles okrlse okrels okresl okrsel okrsle okslre oksler
oksrle oksrel okserl okselr oselkr oselrk oseklr osekrl oserkl oserlk oslekr
oslerk oslker oslkre oslrke oslrek oskler osklre oskelr oskerl oskrel oskrle
osrlke osrlek osrkle osrkel osrekl osrelk srelok srelko sreolk sreokl srekol
sreklo srleok srleko srloek srloke srlkoe srlkeo srolek srolke sroelk sroekl
srokel srokle srkloe srkleo srkole srkoel srkeol srkelo serlok serlko serolk
serokl serkol serklo selrok selrko selork selokr selkor selkro seolrk seolkr
seorlk seorkl seokrl seoklr seklor seklro sekolr sekorl sekrol sekrlo slerok
slerko sleork sleokr slekor slekro slreok slreko slroek slroke slrkoe slrkeo
slorek slorke sloerk sloekr sloker slokre slkroe slkreo slkore slkoer slkeor
slkero soelrk soelkr soerlk soerkl soekrl soeklr solerk solekr solrek solrke
solkre solker sorlek sorlke sorelk sorekl sorkel sorkle soklre sokler sokrle
sokrel sokerl sokelr skelor skelro skeolr skeorl skerol skerlo skleor sklero
skloer sklore sklroe sklreo skoler skolre skoelr skoerl skorel skorle skrloe
skrleo skrole skroel skreol skrelo

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History of cryptography
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