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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: rafuse
cipher variations:
sbgvtf tchwug udixvh vejywi wfkzxj
xglayk yhmbzl zincam ajodbn bkpeco
clqfdp dmrgeq enshfr fotigs gpujht
hqvkiu irwljv jsxmkw ktynlx luzomy
mvapnz nwbqoa oxcrpb pydsqc qzetrd

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: rafuse
Cipher: izufhv

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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: rafuse

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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: rafuse
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: rafuse
Cipher: enshfr

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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: rafuse
Cipher: 241112543451

Extended Methods:
Method #1

Plaintext: rafuse
method variations:

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

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Method #3

Plaintext: rafuse
method variations:
dawoyf awoyfd woyfda
oyfdaw yfdawo fdawoy

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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: rafuse

all 720 cipher variations:
rafuse rafues rafsue rafseu rafesu rafeus raufse raufes rausfe rausef rauesf
rauefs rasufe rasuef rasfue rasfeu rasefu raseuf raeusf raeufs raesuf raesfu
raefsu raefus rfause rfaues rfasue rfaseu rfaesu rfaeus rfuase rfuaes rfusae
rfusea rfuesa rfueas rfsuae rfsuea rfsaue rfsaeu rfseau rfseua rfeusa rfeuas
rfesua rfesau rfeasu rfeaus rufase rufaes rufsae rufsea rufesa rufeas ruafse
ruafes ruasfe ruasef ruaesf ruaefs rusafe rusaef rusfae rusfea rusefa ruseaf
rueasf rueafs ruesaf ruesfa ruefsa ruefas rsfuae rsfuea rsfaue rsfaeu rsfeau
rsfeua rsufae rsufea rsuafe rsuaef rsueaf rsuefa rsaufe rsauef rsafue rsafeu
rsaefu rsaeuf rseuaf rseufa rseauf rseafu rsefau rsefua refusa refuas refsua
refsau refasu refaus reufsa reufas reusfa reusaf reuasf reuafs resufa resuaf
resfua resfau resafu resauf reausf reaufs reasuf reasfu reafsu reafus arfuse
arfues arfsue arfseu arfesu arfeus arufse arufes arusfe arusef aruesf aruefs
arsufe arsuef arsfue arsfeu arsefu arseuf areusf areufs aresuf aresfu arefsu
arefus afruse afrues afrsue afrseu afresu afreus afurse afures afusre afuser
afuesr afuers afsure afsuer afsrue afsreu afseru afseur afeusr afeurs afesur
afesru afersu aferus aufrse aufres aufsre aufser aufesr aufers aurfse aurfes
aursfe aursef auresf aurefs ausrfe ausref ausfre ausfer ausefr auserf auersf
auerfs auesrf auesfr auefsr auefrs asfure asfuer asfrue asfreu asferu asfeur
asufre asufer asurfe asuref asuerf asuefr asrufe asruef asrfue asrfeu asrefu
asreuf aseurf aseufr aseruf aserfu asefru asefur aefusr aefurs aefsur aefsru
aefrsu aefrus aeufsr aeufrs aeusfr aeusrf aeursf aeurfs aesufr aesurf aesfur
aesfru aesrfu aesruf aerusf aerufs aersuf aersfu aerfsu aerfus faruse farues
farsue farseu faresu fareus faurse faures fausre fauser fauesr fauers fasure
fasuer fasrue fasreu faseru faseur faeusr faeurs faesur faesru faersu faerus
frause fraues frasue fraseu fraesu fraeus fruase fruaes frusae frusea fruesa
frueas frsuae frsuea frsaue frsaeu frseau frseua freusa freuas fresua fresau
freasu freaus furase furaes fursae fursea furesa fureas fuarse fuares fuasre
fuaser fuaesr fuaers fusare fusaer fusrae fusrea fusera fusear fueasr fuears
fuesar fuesra fuersa fueras fsruae fsruea fsraue fsraeu fsreau fsreua fsurae
fsurea fsuare fsuaer fsuear fsuera fsaure fsauer fsarue fsareu fsaeru fsaeur
fseuar fseura fseaur fsearu fserau fserua ferusa feruas fersua fersau ferasu
feraus feursa feuras feusra feusar feuasr feuars fesura fesuar fesrua fesrau
fesaru fesaur feausr feaurs feasur feasru fearsu fearus uafrse uafres uafsre
uafser uafesr uafers uarfse uarfes uarsfe uarsef uaresf uarefs uasrfe uasref
uasfre uasfer uasefr uaserf uaersf uaerfs uaesrf uaesfr uaefsr uaefrs ufarse
ufares ufasre ufaser ufaesr ufaers ufrase ufraes ufrsae ufrsea ufresa ufreas
ufsrae ufsrea ufsare ufsaer ufsear ufsera ufersa uferas ufesra ufesar ufeasr
ufears urfase urfaes urfsae urfsea urfesa urfeas urafse urafes urasfe urasef
uraesf uraefs ursafe ursaef ursfae ursfea ursefa urseaf ureasf ureafs uresaf
uresfa urefsa urefas usfrae usfrea usfare usfaer usfear usfera usrfae usrfea
usrafe usraef usreaf usrefa usarfe usaref usafre usafer usaefr usaerf useraf
userfa usearf useafr usefar usefra uefrsa uefras uefsra uefsar uefasr uefars
uerfsa uerfas uersfa uersaf uerasf uerafs uesrfa uesraf uesfra uesfar uesafr
uesarf uearsf uearfs ueasrf ueasfr ueafsr ueafrs safure safuer safrue safreu
saferu safeur saufre saufer saurfe sauref sauerf sauefr sarufe saruef sarfue
sarfeu sarefu sareuf saeurf saeufr saeruf saerfu saefru saefur sfaure sfauer
sfarue sfareu sfaeru sfaeur sfuare sfuaer sfurae sfurea sfuera sfuear sfruae
sfruea sfraue sfraeu sfreau sfreua sfeura sfeuar sferua sferau sfearu sfeaur
sufare sufaer sufrae sufrea sufera sufear suafre suafer suarfe suaref suaerf
suaefr surafe suraef surfae surfea surefa sureaf suearf sueafr sueraf suerfa
suefra suefar srfuae srfuea srfaue srfaeu srfeau srfeua srufae srufea sruafe
sruaef srueaf sruefa sraufe srauef srafue srafeu sraefu sraeuf sreuaf sreufa
sreauf sreafu srefau srefua sefura sefuar sefrua sefrau sefaru sefaur seufra
seufar seurfa seuraf seuarf seuafr serufa seruaf serfua serfau serafu serauf
seaurf seaufr searuf searfu seafru seafur eafusr eafurs eafsur eafsru eafrsu
eafrus eaufsr eaufrs eausfr eausrf eaursf eaurfs easufr easurf easfur easfru
easrfu easruf earusf earufs earsuf earsfu earfsu earfus efausr efaurs efasur
efasru efarsu efarus efuasr efuars efusar efusra efursa efuras efsuar efsura
efsaur efsaru efsrau efsrua efrusa efruas efrsua efrsau efrasu efraus eufasr
eufars eufsar eufsra eufrsa eufras euafsr euafrs euasfr euasrf euarsf euarfs
eusafr eusarf eusfar eusfra eusrfa eusraf eurasf eurafs eursaf eursfa eurfsa
eurfas esfuar esfura esfaur esfaru esfrau esfrua esufar esufra esuafr esuarf
esuraf esurfa esaufr esaurf esafur esafru esarfu esaruf esruaf esrufa esrauf
esrafu esrfau esrfua erfusa erfuas erfsua erfsau erfasu erfaus erufsa erufas
erusfa erusaf eruasf eruafs ersufa ersuaf ersfua ersfau ersafu ersauf erausf
eraufs erasuf erasfu erafsu erafus

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History of cryptography
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