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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: hyonil
cipher variations:
izpojm jaqpkn kbrqlo lcsrmp mdtsnq
neutor ofvups pgwvqt qhxwru riyxsv
sjzytw tkazux ulbavy vmcbwz wndcxa
xoedyb ypfezc zqgfad arhgbe bsihcf
ctjidg dukjeh evlkfi fwmlgj gxnmhk

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: hyonil
Cipher: sblmro

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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: hyonil

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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: hyonil
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: hyonil
Cipher: ulbavy

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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: hyonil
Cipher: 324543334213

Extended Methods:
Method #1

Plaintext: hyonil
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
h y o n i l 
3 4 4 3 4 1 
2 5 3 3 2 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: hyonil
Cipher: sodwnm

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Method #3

Plaintext: hyonil
method variations:
runsbn unsbnr nsbnru
sbnrun bnruns nrunsb

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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: hyonil

all 720 cipher variations:
hyonil hyonli hyoinl hyoiln hyolin hyolni hynoil hynoli hyniol hynilo hynlio
hynloi hyinol hyinlo hyionl hyioln hyilon hyilno hylnio hylnoi hylino hylion
hyloin hyloni hoynil hoynli hoyinl hoyiln hoylin hoylni honyil honyli honiyl
honily honliy honlyi hoinyl hoinly hoiynl hoiyln hoilyn hoilny holniy holnyi
holiny holiyn holyin holyni hnoyil hnoyli hnoiyl hnoily hnoliy hnolyi hnyoil
hnyoli hnyiol hnyilo hnylio hnyloi hniyol hniylo hnioyl hnioly hniloy hnilyo
hnlyio hnlyoi hnliyo hnlioy hnloiy hnloyi hionyl hionly hioynl hioyln hiolyn
hiolny hinoyl hinoly hinyol hinylo hinlyo hinloy hiynol hiynlo hiyonl hiyoln
hiylon hiylno hilnyo hilnoy hilyno hilyon hiloyn hilony hloniy hlonyi hloiny
hloiyn hloyin hloyni hlnoiy hlnoyi hlnioy hlniyo hlnyio hlnyoi hlinoy hlinyo
hliony hlioyn hliyon hliyno hlynio hlynoi hlyino hlyion hlyoin hlyoni yhonil
yhonli yhoinl yhoiln yholin yholni yhnoil yhnoli yhniol yhnilo yhnlio yhnloi
yhinol yhinlo yhionl yhioln yhilon yhilno yhlnio yhlnoi yhlino yhlion yhloin
yhloni yohnil yohnli yohinl yohiln yohlin yohlni yonhil yonhli yonihl yonilh
yonlih yonlhi yoinhl yoinlh yoihnl yoihln yoilhn yoilnh yolnih yolnhi yolinh
yolihn yolhin yolhni ynohil ynohli ynoihl ynoilh ynolih ynolhi ynhoil ynholi
ynhiol ynhilo ynhlio ynhloi ynihol ynihlo yniohl yniolh yniloh ynilho ynlhio
ynlhoi ynliho ynlioh ynloih ynlohi yionhl yionlh yiohnl yiohln yiolhn yiolnh
yinohl yinolh yinhol yinhlo yinlho yinloh yihnol yihnlo yihonl yiholn yihlon
yihlno yilnho yilnoh yilhno yilhon yilohn yilonh ylonih ylonhi yloinh yloihn
ylohin ylohni ylnoih ylnohi ylnioh ylniho ylnhio ylnhoi ylinoh ylinho ylionh
yliohn ylihon ylihno ylhnio ylhnoi ylhino ylhion ylhoin ylhoni oyhnil oyhnli
oyhinl oyhiln oyhlin oyhlni oynhil oynhli oynihl oynilh oynlih oynlhi oyinhl
oyinlh oyihnl oyihln oyilhn oyilnh oylnih oylnhi oylinh oylihn oylhin oylhni
ohynil ohynli ohyinl ohyiln ohylin ohylni ohnyil ohnyli ohniyl ohnily ohnliy
ohnlyi ohinyl ohinly ohiynl ohiyln ohilyn ohilny ohlniy ohlnyi ohliny ohliyn
ohlyin ohlyni onhyil onhyli onhiyl onhily onhliy onhlyi onyhil onyhli onyihl
onyilh onylih onylhi oniyhl oniylh onihyl onihly onilhy onilyh onlyih onlyhi
onliyh onlihy onlhiy onlhyi oihnyl oihnly oihynl oihyln oihlyn oihlny oinhyl
oinhly oinyhl oinylh oinlyh oinlhy oiynhl oiynlh oiyhnl oiyhln oiylhn oiylnh
oilnyh oilnhy oilynh oilyhn oilhyn oilhny olhniy olhnyi olhiny olhiyn olhyin
olhyni olnhiy olnhyi olnihy olniyh olnyih olnyhi olinhy olinyh olihny olihyn
oliyhn oliynh olynih olynhi olyinh olyihn olyhin olyhni nyohil nyohli nyoihl
nyoilh nyolih nyolhi nyhoil nyholi nyhiol nyhilo nyhlio nyhloi nyihol nyihlo
nyiohl nyiolh nyiloh nyilho nylhio nylhoi nyliho nylioh nyloih nylohi noyhil
noyhli noyihl noyilh noylih noylhi nohyil nohyli nohiyl nohily nohliy nohlyi
noihyl noihly noiyhl noiylh noilyh noilhy nolhiy nolhyi nolihy noliyh nolyih
nolyhi nhoyil nhoyli nhoiyl nhoily nholiy nholyi nhyoil nhyoli nhyiol nhyilo
nhylio nhyloi nhiyol nhiylo nhioyl nhioly nhiloy nhilyo nhlyio nhlyoi nhliyo
nhlioy nhloiy nhloyi niohyl niohly nioyhl nioylh niolyh niolhy nihoyl niholy
nihyol nihylo nihlyo nihloy niyhol niyhlo niyohl niyolh niyloh niylho nilhyo
nilhoy nilyho nilyoh niloyh nilohy nlohiy nlohyi nloihy nloiyh nloyih nloyhi
nlhoiy nlhoyi nlhioy nlhiyo nlhyio nlhyoi nlihoy nlihyo nliohy nlioyh nliyoh
nliyho nlyhio nlyhoi nlyiho nlyioh nlyoih nlyohi iyonhl iyonlh iyohnl iyohln
iyolhn iyolnh iynohl iynolh iynhol iynhlo iynlho iynloh iyhnol iyhnlo iyhonl
iyholn iyhlon iyhlno iylnho iylnoh iylhno iylhon iylohn iylonh ioynhl ioynlh
ioyhnl ioyhln ioylhn ioylnh ionyhl ionylh ionhyl ionhly ionlhy ionlyh iohnyl
iohnly iohynl iohyln iohlyn iohlny iolnhy iolnyh iolhny iolhyn iolyhn iolynh
inoyhl inoylh inohyl inohly inolhy inolyh inyohl inyolh inyhol inyhlo inylho
inyloh inhyol inhylo inhoyl inholy inhloy inhlyo inlyho inlyoh inlhyo inlhoy
inlohy inloyh ihonyl ihonly ihoynl ihoyln iholyn iholny ihnoyl ihnoly ihnyol
ihnylo ihnlyo ihnloy ihynol ihynlo ihyonl ihyoln ihylon ihylno ihlnyo ihlnoy
ihlyno ihlyon ihloyn ihlony ilonhy ilonyh ilohny ilohyn iloyhn iloynh ilnohy
ilnoyh ilnhoy ilnhyo ilnyho ilnyoh ilhnoy ilhnyo ilhony ilhoyn ilhyon ilhyno
ilynho ilynoh ilyhno ilyhon ilyohn ilyonh lyonih lyonhi lyoinh lyoihn lyohin
lyohni lynoih lynohi lynioh lyniho lynhio lynhoi lyinoh lyinho lyionh lyiohn
lyihon lyihno lyhnio lyhnoi lyhino lyhion lyhoin lyhoni loynih loynhi loyinh
loyihn loyhin loyhni lonyih lonyhi loniyh lonihy lonhiy lonhyi loinyh loinhy
loiynh loiyhn loihyn loihny lohniy lohnyi lohiny lohiyn lohyin lohyni lnoyih
lnoyhi lnoiyh lnoihy lnohiy lnohyi lnyoih lnyohi lnyioh lnyiho lnyhio lnyhoi
lniyoh lniyho lnioyh lniohy lnihoy lnihyo lnhyio lnhyoi lnhiyo lnhioy lnhoiy
lnhoyi lionyh lionhy lioynh lioyhn liohyn liohny linoyh linohy linyoh linyho
linhyo linhoy liynoh liynho liyonh liyohn liyhon liyhno lihnyo lihnoy lihyno
lihyon lihoyn lihony lhoniy lhonyi lhoiny lhoiyn lhoyin lhoyni lhnoiy lhnoyi
lhnioy lhniyo lhnyio lhnyoi lhinoy lhinyo lhiony lhioyn lhiyon lhiyno lhynio
lhynoi lhyino lhyion lhyoin lhyoni

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History of cryptography
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