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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: viator
cipher variations:
wjbups xkcvqt yldwru zmexsv anfytw
bogzux cphavy dqibwz erjcxa fskdyb
gtlezc humfad ivngbe jwohcf kxpidg
lyqjeh mzrkfi naslgj obtmhk pcunil
qdvojm rewpkn sfxqlo tgyrmp uhzsnq

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: viator
Cipher: erzgli

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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: viator

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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: viator
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: viator
Cipher: ivngbe

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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: viator
Cipher: 154211444324

Extended Methods:
Method #1

Plaintext: viator
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
v i a t o r 
1 4 1 4 4 2 
5 2 1 4 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: viator
Cipher: qqikqs

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Method #3

Plaintext: viator
method variations:
ubqthd bqthdu qthdub
thdubq hdubqt dubqth

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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: viator

all 720 cipher variations:
viator viatro viaotr viaort viarot viarto vitaor vitaro vitoar vitora vitroa
vitrao viotar viotra vioatr vioart viorat viorta virtoa virtao virota viroat
viraot virato vaitor vaitro vaiotr vaiort vairot vairto vatior vatiro vatoir
vatori vatroi vatrio vaotir vaotri vaoitr vaoirt vaorit vaorti vartoi vartio
varoti varoit variot varito vtaior vtairo vtaoir vtaori vtaroi vtario vtiaor
vtiaro vtioar vtiora vtiroa vtirao vtoiar vtoira vtoair vtoari vtorai vtoria
vtrioa vtriao vtroia vtroai vtraoi vtraio voatir voatri voaitr voairt voarit
voarti votair votari votiar votira votria votrai voitar voitra voiatr voiart
voirat voirta vortia vortai vorita voriat vorait vorati vratoi vratio vraoti
vraoit vraiot vraito vrtaoi vrtaio vrtoai vrtoia vrtioa vrtiao vrotai vrotia
vroati vroait vroiat vroita vritoa vritao vriota vrioat vriaot vriato ivator
ivatro ivaotr ivaort ivarot ivarto ivtaor ivtaro ivtoar ivtora ivtroa ivtrao
ivotar ivotra ivoatr ivoart ivorat ivorta ivrtoa ivrtao ivrota ivroat ivraot
ivrato iavtor iavtro iavotr iavort iavrot iavrto iatvor iatvro iatovr iatorv
iatrov iatrvo iaotvr iaotrv iaovtr iaovrt iaorvt iaortv iartov iartvo iarotv
iarovt iarvot iarvto itavor itavro itaovr itaorv itarov itarvo itvaor itvaro
itvoar itvora itvroa itvrao itovar itovra itoavr itoarv itorav itorva itrvoa
itrvao itrova itroav itraov itravo ioatvr ioatrv ioavtr ioavrt ioarvt ioartv
iotavr iotarv iotvar iotvra iotrva iotrav iovtar iovtra iovatr iovart iovrat
iovrta iortva iortav iorvta iorvat ioravt ioratv iratov iratvo iraotv iraovt
iravot iravto irtaov irtavo irtoav irtova irtvoa irtvao irotav irotva iroatv
iroavt irovat irovta irvtoa irvtao irvota irvoat irvaot irvato aivtor aivtro
aivotr aivort aivrot aivrto aitvor aitvro aitovr aitorv aitrov aitrvo aiotvr
aiotrv aiovtr aiovrt aiorvt aiortv airtov airtvo airotv airovt airvot airvto
avitor avitro aviotr aviort avirot avirto avtior avtiro avtoir avtori avtroi
avtrio avotir avotri avoitr avoirt avorit avorti avrtoi avrtio avroti avroit
avriot avrito atvior atviro atvoir atvori atvroi atvrio ativor ativro atiovr
atiorv atirov atirvo atoivr atoirv atovir atovri atorvi atoriv atriov atrivo
atroiv atrovi atrvoi atrvio aovtir aovtri aovitr aovirt aovrit aovrti aotvir
aotvri aotivr aotirv aotriv aotrvi aoitvr aoitrv aoivtr aoivrt aoirvt aoirtv
aortiv aortvi aoritv aorivt aorvit aorvti arvtoi arvtio arvoti arvoit arviot
arvito artvoi artvio artovi artoiv artiov artivo arotvi arotiv arovti arovit
aroivt aroitv aritov aritvo ariotv ariovt arivot arivto tiavor tiavro tiaovr
tiaorv tiarov tiarvo tivaor tivaro tivoar tivora tivroa tivrao tiovar tiovra
tioavr tioarv tiorav tiorva tirvoa tirvao tirova tiroav tiraov tiravo taivor
taivro taiovr taiorv tairov tairvo tavior taviro tavoir tavori tavroi tavrio
taovir taovri taoivr taoirv taoriv taorvi tarvoi tarvio tarovi taroiv tariov
tarivo tvaior tvairo tvaoir tvaori tvaroi tvario tviaor tviaro tvioar tviora
tviroa tvirao tvoiar tvoira tvoair tvoari tvorai tvoria tvrioa tvriao tvroia
tvroai tvraoi tvraio toavir toavri toaivr toairv toariv toarvi tovair tovari
toviar tovira tovria tovrai toivar toivra toiavr toiarv toirav toirva torvia
torvai toriva toriav toraiv toravi travoi travio traovi traoiv traiov traivo
trvaoi trvaio trvoai trvoia trvioa trviao trovai trovia troavi troaiv troiav
troiva trivoa trivao triova trioav triaov triavo oiatvr oiatrv oiavtr oiavrt
oiarvt oiartv oitavr oitarv oitvar oitvra oitrva oitrav oivtar oivtra oivatr
oivart oivrat oivrta oirtva oirtav oirvta oirvat oiravt oiratv oaitvr oaitrv
oaivtr oaivrt oairvt oairtv oativr oatirv oatvir oatvri oatrvi oatriv oavtir
oavtri oavitr oavirt oavrit oavrti oartvi oartiv oarvti oarvit oarivt oaritv
otaivr otairv otavir otavri otarvi otariv otiavr otiarv otivar otivra otirva
otirav otviar otvira otvair otvari otvrai otvria otriva otriav otrvia otrvai
otravi otraiv ovatir ovatri ovaitr ovairt ovarit ovarti ovtair ovtari ovtiar
ovtira ovtria ovtrai ovitar ovitra oviatr oviart ovirat ovirta ovrtia ovrtai
ovrita ovriat ovrait ovrati oratvi orativ oravti oravit oraivt oraitv ortavi
ortaiv ortvai ortvia ortiva ortiav orvtai orvtia orvati orvait orviat orvita
oritva oritav orivta orivat oriavt oriatv riatov riatvo riaotv riaovt riavot
riavto ritaov ritavo ritoav ritova ritvoa ritvao riotav riotva rioatv rioavt
riovat riovta rivtoa rivtao rivota rivoat rivaot rivato raitov raitvo raiotv
raiovt raivot raivto ratiov rativo ratoiv ratovi ratvoi ratvio raotiv raotvi
raoitv raoivt raovit raovti ravtoi ravtio ravoti ravoit raviot ravito rtaiov
rtaivo rtaoiv rtaovi rtavoi rtavio rtiaov rtiavo rtioav rtiova rtivoa rtivao
rtoiav rtoiva rtoaiv rtoavi rtovai rtovia rtvioa rtviao rtvoia rtvoai rtvaoi
rtvaio roativ roatvi roaitv roaivt roavit roavti rotaiv rotavi rotiav rotiva
rotvia rotvai roitav roitva roiatv roiavt roivat roivta rovtia rovtai rovita
roviat rovait rovati rvatoi rvatio rvaoti rvaoit rvaiot rvaito rvtaoi rvtaio
rvtoai rvtoia rvtioa rvtiao rvotai rvotia rvoati rvoait rvoiat rvoita rvitoa
rvitao rviota rvioat rviaot rviato

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History of cryptography
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