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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: gowjen
cipher variations:
hpxkfo iqylgp jrzmhq ksanir ltbojs
mucpkt nvdqlu owermv pxfsnw qygtox
rzhupy saivqz tbjwra uckxsb vdlytc
wemzud xfnave ygobwf zhpcxg aiqdyh
bjrezi cksfaj dltgbk emuhcl fnvidm

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: gowjen
Cipher: tldqvm

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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: gowjen

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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: gowjen
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: gowjen
Cipher: tbjwra

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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: gowjen
Cipher: 224325425133

Extended Methods:
Method #1

Plaintext: gowjen
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
g o w j e n 
2 4 2 4 5 3 
2 3 5 2 1 3 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: gowjen
Cipher: rrpmkl

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Method #3

Plaintext: gowjen
method variations:
rhuwlh huwlhr uwlhrh
wlhrhu lhrhuw hrhuwl

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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: gowjen

all 720 cipher variations:
gowjen gowjne gowejn gowenj gownej gownje gojwen gojwne gojewn gojenw gojnew
gojnwe goejwn goejnw goewjn goewnj goenwj goenjw gonjew gonjwe gonejw gonewj
gonwej gonwje gwojen gwojne gwoejn gwoenj gwonej gwonje gwjoen gwjone gwjeon
gwjeno gwjneo gwjnoe gwejon gwejno gweojn gweonj gwenoj gwenjo gwnjeo gwnjoe
gwnejo gwneoj gwnoej gwnoje gjwoen gjwone gjweon gjweno gjwneo gjwnoe gjowen
gjowne gjoewn gjoenw gjonew gjonwe gjeown gjeonw gjewon gjewno gjenwo gjenow
gjnoew gjnowe gjneow gjnewo gjnweo gjnwoe gewjon gewjno gewojn gewonj gewnoj
gewnjo gejwon gejwno gejown gejonw gejnow gejnwo geojwn geojnw geowjn geownj
geonwj geonjw genjow genjwo genojw genowj genwoj genwjo gnwjeo gnwjoe gnwejo
gnweoj gnwoej gnwoje gnjweo gnjwoe gnjewo gnjeow gnjoew gnjowe gnejwo gnejow
gnewjo gnewoj gneowj gneojw gnojew gnojwe gnoejw gnoewj gnowej gnowje ogwjen
ogwjne ogwejn ogwenj ogwnej ogwnje ogjwen ogjwne ogjewn ogjenw ogjnew ogjnwe
ogejwn ogejnw ogewjn ogewnj ogenwj ogenjw ognjew ognjwe ognejw ognewj ognwej
ognwje owgjen owgjne owgejn owgenj owgnej owgnje owjgen owjgne owjegn owjeng
owjneg owjnge owejgn owejng owegjn owegnj owengj owenjg ownjeg ownjge ownejg
ownegj owngej owngje ojwgen ojwgne ojwegn ojweng ojwneg ojwnge ojgwen ojgwne
ojgewn ojgenw ojgnew ojgnwe ojegwn ojegnw ojewgn ojewng ojenwg ojengw ojngew
ojngwe ojnegw ojnewg ojnweg ojnwge oewjgn oewjng oewgjn oewgnj oewngj oewnjg
oejwgn oejwng oejgwn oejgnw oejngw oejnwg oegjwn oegjnw oegwjn oegwnj oegnwj
oegnjw oenjgw oenjwg oengjw oengwj oenwgj oenwjg onwjeg onwjge onwejg onwegj
onwgej onwgje onjweg onjwge onjewg onjegw onjgew onjgwe onejwg onejgw onewjg
onewgj onegwj onegjw ongjew ongjwe ongejw ongewj ongwej ongwje wogjen wogjne
wogejn wogenj wognej wognje wojgen wojgne wojegn wojeng wojneg wojnge woejgn
woejng woegjn woegnj woengj woenjg wonjeg wonjge wonejg wonegj wongej wongje
wgojen wgojne wgoejn wgoenj wgonej wgonje wgjoen wgjone wgjeon wgjeno wgjneo
wgjnoe wgejon wgejno wgeojn wgeonj wgenoj wgenjo wgnjeo wgnjoe wgnejo wgneoj
wgnoej wgnoje wjgoen wjgone wjgeon wjgeno wjgneo wjgnoe wjogen wjogne wjoegn
wjoeng wjoneg wjonge wjeogn wjeong wjegon wjegno wjengo wjenog wjnoeg wjnoge
wjneog wjnego wjngeo wjngoe wegjon wegjno wegojn wegonj wegnoj wegnjo wejgon
wejgno wejogn wejong wejnog wejngo weojgn weojng weogjn weognj weongj weonjg
wenjog wenjgo wenojg wenogj wengoj wengjo wngjeo wngjoe wngejo wngeoj wngoej
wngoje wnjgeo wnjgoe wnjego wnjeog wnjoeg wnjoge wnejgo wnejog wnegjo wnegoj
wneogj wneojg wnojeg wnojge wnoejg wnoegj wnogej wnogje jowgen jowgne jowegn
joweng jowneg jownge jogwen jogwne jogewn jogenw jognew jognwe joegwn joegnw
joewgn joewng joenwg joengw jongew jongwe jonegw jonewg jonweg jonwge jwogen
jwogne jwoegn jwoeng jwoneg jwonge jwgoen jwgone jwgeon jwgeno jwgneo jwgnoe
jwegon jwegno jweogn jweong jwenog jwengo jwngeo jwngoe jwnego jwneog jwnoeg
jwnoge jgwoen jgwone jgweon jgweno jgwneo jgwnoe jgowen jgowne jgoewn jgoenw
jgonew jgonwe jgeown jgeonw jgewon jgewno jgenwo jgenow jgnoew jgnowe jgneow
jgnewo jgnweo jgnwoe jewgon jewgno jewogn jewong jewnog jewngo jegwon jegwno
jegown jegonw jegnow jegnwo jeogwn jeognw jeowgn jeowng jeonwg jeongw jengow
jengwo jenogw jenowg jenwog jenwgo jnwgeo jnwgoe jnwego jnweog jnwoeg jnwoge
jngweo jngwoe jngewo jngeow jngoew jngowe jnegwo jnegow jnewgo jnewog jneowg
jneogw jnogew jnogwe jnoegw jnoewg jnoweg jnowge eowjgn eowjng eowgjn eowgnj
eowngj eownjg eojwgn eojwng eojgwn eojgnw eojngw eojnwg eogjwn eogjnw eogwjn
eogwnj eognwj eognjw eonjgw eonjwg eongjw eongwj eonwgj eonwjg ewojgn ewojng
ewogjn ewognj ewongj ewonjg ewjogn ewjong ewjgon ewjgno ewjngo ewjnog ewgjon
ewgjno ewgojn ewgonj ewgnoj ewgnjo ewnjgo ewnjog ewngjo ewngoj ewnogj ewnojg
ejwogn ejwong ejwgon ejwgno ejwngo ejwnog ejowgn ejowng ejogwn ejognw ejongw
ejonwg ejgown ejgonw ejgwon ejgwno ejgnwo ejgnow ejnogw ejnowg ejngow ejngwo
ejnwgo ejnwog egwjon egwjno egwojn egwonj egwnoj egwnjo egjwon egjwno egjown
egjonw egjnow egjnwo egojwn egojnw egowjn egownj egonwj egonjw egnjow egnjwo
egnojw egnowj egnwoj egnwjo enwjgo enwjog enwgjo enwgoj enwogj enwojg enjwgo
enjwog enjgwo enjgow enjogw enjowg engjwo engjow engwjo engwoj engowj engojw
enojgw enojwg enogjw enogwj enowgj enowjg nowjeg nowjge nowejg nowegj nowgej
nowgje nojweg nojwge nojewg nojegw nojgew nojgwe noejwg noejgw noewjg noewgj
noegwj noegjw nogjew nogjwe nogejw nogewj nogwej nogwje nwojeg nwojge nwoejg
nwoegj nwogej nwogje nwjoeg nwjoge nwjeog nwjego nwjgeo nwjgoe nwejog nwejgo
nweojg nweogj nwegoj nwegjo nwgjeo nwgjoe nwgejo nwgeoj nwgoej nwgoje njwoeg
njwoge njweog njwego njwgeo njwgoe njoweg njowge njoewg njoegw njogew njogwe
njeowg njeogw njewog njewgo njegwo njegow njgoew njgowe njgeow njgewo njgweo
njgwoe newjog newjgo newojg newogj newgoj newgjo nejwog nejwgo nejowg nejogw
nejgow nejgwo neojwg neojgw neowjg neowgj neogwj neogjw negjow negjwo negojw
negowj negwoj negwjo ngwjeo ngwjoe ngwejo ngweoj ngwoej ngwoje ngjweo ngjwoe
ngjewo ngjeow ngjoew ngjowe ngejwo ngejow ngewjo ngewoj ngeowj ngeojw ngojew
ngojwe ngoejw ngoewj ngowej ngowje

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History of cryptography
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