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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: borwen
cipher variations:
cpsxfo dqtygp eruzhq fsvair gtwbjs
huxckt ivydlu jwzemv kxafnw lybgox
mzchpy nadiqz obejra pcfksb qdgltc
rehmud sfinve tgjowf uhkpxg vilqyh
wjmrzi xknsaj ylotbk zmpucl anqvdm

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: borwen
Cipher: ylidvm

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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: borwen

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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: borwen
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: borwen
Cipher: obejra

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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: borwen
Cipher: 214324255133

Extended Methods:
Method #1

Plaintext: borwen
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
b o r w e n 
2 4 2 2 5 3 
1 3 4 5 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: borwen
Cipher: rgplyl

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Method #3

Plaintext: borwen
method variations:
qhizlh hizlhq izlhqh
zlhqhi lhqhiz hqhizl

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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: borwen

all 720 cipher variations:
borwen borwne borewn borenw bornew bornwe bowren bowrne bowern bowenr bowner
bownre boewrn boewnr boerwn boernw boenrw boenwr bonwer bonwre bonewr bonerw
bonrew bonrwe browen browne broewn broenw bronew bronwe brwoen brwone brweon
brweno brwneo brwnoe brewon brewno breown breonw brenow brenwo brnweo brnwoe
brnewo brneow brnoew brnowe bwroen bwrone bwreon bwreno bwrneo bwrnoe bworen
bworne bwoern bwoenr bwoner bwonre bweorn bweonr bweron bwerno bwenro bwenor
bwnoer bwnore bwneor bwnero bwnreo bwnroe berwon berwno berown beronw bernow
bernwo bewron bewrno beworn bewonr bewnor bewnro beowrn beownr beorwn beornw
beonrw beonwr benwor benwro benowr benorw benrow benrwo bnrweo bnrwoe bnrewo
bnreow bnroew bnrowe bnwreo bnwroe bnwero bnweor bnwoer bnwore bnewro bnewor
bnerwo bnerow bneorw bneowr bnower bnowre bnoewr bnoerw bnorew bnorwe obrwen
obrwne obrewn obrenw obrnew obrnwe obwren obwrne obwern obwenr obwner obwnre
obewrn obewnr oberwn obernw obenrw obenwr obnwer obnwre obnewr obnerw obnrew
obnrwe orbwen orbwne orbewn orbenw orbnew orbnwe orwben orwbne orwebn orwenb
orwneb orwnbe orewbn orewnb orebwn orebnw orenbw orenwb ornweb ornwbe ornewb
ornebw ornbew ornbwe owrben owrbne owrebn owrenb owrneb owrnbe owbren owbrne
owbern owbenr owbner owbnre owebrn owebnr owerbn owernb owenrb owenbr ownber
ownbre ownebr ownerb ownreb ownrbe oerwbn oerwnb oerbwn oerbnw oernbw oernwb
oewrbn oewrnb oewbrn oewbnr oewnbr oewnrb oebwrn oebwnr oebrwn oebrnw oebnrw
oebnwr oenwbr oenwrb oenbwr oenbrw oenrbw oenrwb onrweb onrwbe onrewb onrebw
onrbew onrbwe onwreb onwrbe onwerb onwebr onwber onwbre onewrb onewbr onerwb
onerbw onebrw onebwr onbwer onbwre onbewr onberw onbrew onbrwe robwen robwne
robewn robenw robnew robnwe rowben rowbne rowebn rowenb rowneb rownbe roewbn
roewnb roebwn roebnw roenbw roenwb ronweb ronwbe ronewb ronebw ronbew ronbwe
rbowen rbowne rboewn rboenw rbonew rbonwe rbwoen rbwone rbweon rbweno rbwneo
rbwnoe rbewon rbewno rbeown rbeonw rbenow rbenwo rbnweo rbnwoe rbnewo rbneow
rbnoew rbnowe rwboen rwbone rwbeon rwbeno rwbneo rwbnoe rwoben rwobne rwoebn
rwoenb rwoneb rwonbe rweobn rweonb rwebon rwebno rwenbo rwenob rwnoeb rwnobe
rwneob rwnebo rwnbeo rwnboe rebwon rebwno rebown rebonw rebnow rebnwo rewbon
rewbno rewobn rewonb rewnob rewnbo reowbn reownb reobwn reobnw reonbw reonwb
renwob renwbo renowb renobw renbow renbwo rnbweo rnbwoe rnbewo rnbeow rnboew
rnbowe rnwbeo rnwboe rnwebo rnweob rnwoeb rnwobe rnewbo rnewob rnebwo rnebow
rneobw rneowb rnoweb rnowbe rnoewb rnoebw rnobew rnobwe worben worbne worebn
worenb worneb wornbe wobren wobrne wobern wobenr wobner wobnre woebrn woebnr
woerbn woernb woenrb woenbr wonber wonbre wonebr wonerb wonreb wonrbe wroben
wrobne wroebn wroenb wroneb wronbe wrboen wrbone wrbeon wrbeno wrbneo wrbnoe
wrebon wrebno wreobn wreonb wrenob wrenbo wrnbeo wrnboe wrnebo wrneob wrnoeb
wrnobe wbroen wbrone wbreon wbreno wbrneo wbrnoe wboren wborne wboern wboenr
wboner wbonre wbeorn wbeonr wberon wberno wbenro wbenor wbnoer wbnore wbneor
wbnero wbnreo wbnroe werbon werbno werobn weronb wernob wernbo webron webrno
weborn webonr webnor webnro weobrn weobnr weorbn weornb weonrb weonbr wenbor
wenbro wenobr wenorb wenrob wenrbo wnrbeo wnrboe wnrebo wnreob wnroeb wnrobe
wnbreo wnbroe wnbero wnbeor wnboer wnbore wnebro wnebor wnerbo wnerob wneorb
wneobr wnober wnobre wnoebr wnoerb wnoreb wnorbe eorwbn eorwnb eorbwn eorbnw
eornbw eornwb eowrbn eowrnb eowbrn eowbnr eownbr eownrb eobwrn eobwnr eobrwn
eobrnw eobnrw eobnwr eonwbr eonwrb eonbwr eonbrw eonrbw eonrwb erowbn erownb
erobwn erobnw eronbw eronwb erwobn erwonb erwbon erwbno erwnbo erwnob erbwon
erbwno erbown erbonw erbnow erbnwo ernwbo ernwob ernbwo ernbow ernobw ernowb
ewrobn ewronb ewrbon ewrbno ewrnbo ewrnob eworbn ewornb ewobrn ewobnr ewonbr
ewonrb ewborn ewbonr ewbron ewbrno ewbnro ewbnor ewnobr ewnorb ewnbor ewnbro
ewnrbo ewnrob ebrwon ebrwno ebrown ebronw ebrnow ebrnwo ebwron ebwrno ebworn
ebwonr ebwnor ebwnro ebowrn ebownr eborwn ebornw ebonrw ebonwr ebnwor ebnwro
ebnowr ebnorw ebnrow ebnrwo enrwbo enrwob enrbwo enrbow enrobw enrowb enwrbo
enwrob enwbro enwbor enwobr enworb enbwro enbwor enbrwo enbrow enborw enbowr
enowbr enowrb enobwr enobrw enorbw enorwb norweb norwbe norewb norebw norbew
norbwe nowreb nowrbe nowerb nowebr nowber nowbre noewrb noewbr noerwb noerbw
noebrw noebwr nobwer nobwre nobewr noberw nobrew nobrwe nroweb nrowbe nroewb
nroebw nrobew nrobwe nrwoeb nrwobe nrweob nrwebo nrwbeo nrwboe nrewob nrewbo
nreowb nreobw nrebow nrebwo nrbweo nrbwoe nrbewo nrbeow nrboew nrbowe nwroeb
nwrobe nwreob nwrebo nwrbeo nwrboe nworeb nworbe nwoerb nwoebr nwober nwobre
nweorb nweobr nwerob nwerbo nwebro nwebor nwboer nwbore nwbeor nwbero nwbreo
nwbroe nerwob nerwbo nerowb nerobw nerbow nerbwo newrob newrbo neworb newobr
newbor newbro neowrb neowbr neorwb neorbw neobrw neobwr nebwor nebwro nebowr
neborw nebrow nebrwo nbrweo nbrwoe nbrewo nbreow nbroew nbrowe nbwreo nbwroe
nbwero nbweor nbwoer nbwore nbewro nbewor nberwo nberow nbeorw nbeowr nbower
nbowre nboewr nboerw nborew nborwe

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History of cryptography
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