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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: onesti
cipher variations:
poftuj qpguvk rqhvwl sriwxm tsjxyn
utkyzo vulzap wvmabq xwnbcr yxocds
zypdet azqefu barfgv cbsghw dcthix
eduijy fevjkz gfwkla hgxlmb ihymnc
jiznod kjaope lkbpqf mlcqrg nmdrsh

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: onesti
Cipher: lmvhgr

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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: onesti

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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: onesti
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: onesti
Cipher: barfgv

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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: onesti
Cipher: 433351344442

Extended Methods:
Method #1

Plaintext: onesti
method variations:

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

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Method #3

Plaintext: onesti
method variations:
nxlttr xlttrn lttrnx
ttrnxl trnxlt rnxltt

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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: onesti

all 720 cipher variations:
onesti onesit onetsi onetis oneits oneist onseti onseit onstei onstie onsite
onsiet ontsei ontsie ontesi onteis onties ontise oniste oniset onitse onites
oniets oniest oensti oensit oentsi oentis oenits oenist oesnti oesnit oestni
oestin oesitn oesint oetsni oetsin oetnsi oetnis oetins oetisn oeistn oeisnt
oeitsn oeitns oeints oeinst osenti osenit osetni osetin oseitn oseint osneti
osneit osntei osntie osnite osniet ostnei ostnie osteni ostein ostien ostine
osinte osinet ositne ositen osietn osient otesni otesin otensi otenis oteins
oteisn otseni otsein otsnei otsnie otsine otsien otnsei otnsie otnesi otneis
otnies otnise otisne otisen otinse otines otiens otiesn oiestn oiesnt oietsn
oietns oients oienst oisetn oisent oisten oistne oisnte oisnet oitsen oitsne
oitesn oitens oitnes oitnse oinste oinset ointse ointes oinets oinest noesti
noesit noetsi noetis noeits noeist noseti noseit nostei nostie nosite nosiet
notsei notsie notesi noteis noties notise noiste noiset noitse noites noiets
noiest neosti neosit neotsi neotis neoits neoist nesoti nesoit nestoi nestio
nesito nesiot netsoi netsio netosi netois netios netiso neisto neisot neitso
neitos neiots neiost nseoti nseoit nsetoi nsetio nseito nseiot nsoeti nsoeit
nsotei nsotie nsoite nsoiet nstoei nstoie nsteoi nsteio nstieo nstioe nsiote
nsioet nsitoe nsiteo nsieto nsieot ntesoi ntesio nteosi nteois nteios nteiso
ntseoi ntseio ntsoei ntsoie ntsioe ntsieo ntosei ntosie ntoesi ntoeis ntoies
ntoise ntisoe ntiseo ntiose ntioes ntieos ntieso niesto niesot nietso nietos
nieots nieost niseto niseot nisteo nistoe nisote nisoet nitseo nitsoe niteso
niteos nitoes nitose nioste nioset niotse niotes nioets nioest enosti enosit
enotsi enotis enoits enoist ensoti ensoit enstoi enstio ensito ensiot entsoi
entsio entosi entois entios entiso enisto enisot enitso enitos eniots eniost
eonsti eonsit eontsi eontis eonits eonist eosnti eosnit eostni eostin eositn
eosint eotsni eotsin eotnsi eotnis eotins eotisn eoistn eoisnt eoitsn eoitns
eoints eoinst esonti esonit esotni esotin esoitn esoint esnoti esnoit esntoi
esntio esnito esniot estnoi estnio estoni estoin estion estino esinto esinot
esitno esiton esiotn esiont etosni etosin etonsi etonis etoins etoisn etsoni
etsoin etsnoi etsnio etsino etsion etnsoi etnsio etnosi etnois etnios etniso
etisno etison etinso etinos etions etiosn eiostn eiosnt eiotsn eiotns eionts
eionst eisotn eisont eiston eistno eisnto eisnot eitson eitsno eitosn eitons
eitnos eitnso einsto einsot eintso eintos einots einost sneoti sneoit snetoi
snetio sneito sneiot snoeti snoeit snotei snotie snoite snoiet sntoei sntoie
snteoi snteio sntieo sntioe sniote snioet snitoe sniteo snieto snieot senoti
senoit sentoi sentio senito seniot seonti seonit seotni seotin seoitn seoint
setoni setoin setnoi setnio setino setion seiotn seiont seiton seitno seinto
seinot soenti soenit soetni soetin soeitn soeint soneti soneit sontei sontie
sonite soniet sotnei sotnie soteni sotein sotien sotine sointe soinet soitne
soiten soietn soient steoni steoin stenoi stenio steino steion stoeni stoein
stonei stonie stoine stoien stnoei stnoie stneoi stneio stnieo stnioe stione
stioen stinoe stineo stieno stieon sieotn sieont sieton sietno siento sienot
sioetn sioent sioten siotne sionte sionet sitoen sitone siteon siteno sitneo
sitnoe sinote sinoet sintoe sinteo sineto sineot tnesoi tnesio tneosi tneois
tneios tneiso tnseoi tnseio tnsoei tnsoie tnsioe tnsieo tnosei tnosie tnoesi
tnoeis tnoies tnoise tnisoe tniseo tniose tnioes tnieos tnieso tensoi tensio
tenosi tenois tenios teniso tesnoi tesnio tesoni tesoin tesion tesino teosni
teosin teonsi teonis teoins teoisn teison teisno teiosn teions teinos teinso
tsenoi tsenio tseoni tseoin tseion tseino tsneoi tsneio tsnoei tsnoie tsnioe
tsnieo tsonei tsonie tsoeni tsoein tsoien tsoine tsinoe tsineo tsione tsioen
tsieon tsieno toesni toesin toensi toenis toeins toeisn toseni tosein tosnei
tosnie tosine tosien tonsei tonsie tonesi toneis tonies tonise toisne toisen
toinse toines toiens toiesn tieson tiesno tieosn tieons tienos tienso tiseon
tiseno tisoen tisone tisnoe tisneo tiosen tiosne tioesn tioens tiones tionse
tinsoe tinseo tinose tinoes tineos tineso inesto inesot inetso inetos ineots
ineost inseto inseot insteo instoe insote insoet intseo intsoe inteso inteos
intoes intose inoste inoset inotse inotes inoets inoest iensto iensot ientso
ientos ienots ienost iesnto iesnot iestno ieston iesotn iesont ietsno ietson
ietnso ietnos ietons ietosn ieostn ieosnt ieotsn ieotns ieonts ieonst isento
isenot isetno iseton iseotn iseont isneto isneot isnteo isntoe isnote isnoet
istneo istnoe isteno isteon istoen istone isonte isonet isotne isoten isoetn
isoent itesno iteson itenso itenos iteons iteosn itseno itseon itsneo itsnoe
itsone itsoen itnseo itnsoe itneso itneos itnoes itnose itosne itosen itonse
itones itoens itoesn ioestn ioesnt ioetsn ioetns ioents ioenst iosetn iosent
iosten iostne iosnte iosnet iotsen iotsne iotesn iotens iotnes iotnse ionste
ionset iontse iontes ionets ionest

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History of cryptography
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