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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: iungar
cipher variations:
jvohbs kwpict lxqjdu myrkev nzslfw
oatmgx pbunhy qcvoiz rdwpja sexqkb
tfyrlc ugzsmd vhatne wibuof xjcvpg
ykdwqh zlexri amfysj bngztk cohaul
dpibvm eqjcwn frkdxo gsleyp htmfzq

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: iungar
Cipher: rfmtzi

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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: iungar

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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: iungar
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: iungar
Cipher: vhatne

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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: iungar
Cipher: 425433221124

Extended Methods:
Method #1

Plaintext: iungar
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
i u n g a r 
4 5 3 2 1 2 
2 4 3 2 1 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: iungar
Cipher: yhfrhq

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Method #3

Plaintext: iungar
method variations:
wohbft ohbftw hbftwo
bftwoh ftwohb twohbf

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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: iungar

all 720 cipher variations:
iungar iungra iunagr iunarg iunrag iunrga iugnar iugnra iuganr iugarn iugran
iugrna iuagnr iuagrn iuangr iuanrg iuarng iuargn iurgan iurgna iuragn iurang
iurnag iurnga inugar inugra inuagr inuarg inurag inurga inguar ingura ingaur
ingaru ingrau ingrua inagur inagru inaugr inaurg inarug inargu inrgau inrgua
inragu inraug inruag inruga ignuar ignura ignaur ignaru ignrau ignrua igunar
igunra iguanr iguarn iguran igurna igaunr igaurn iganur iganru igarnu igarun
igruan igruna igraun igranu igrnau igrnua iangur iangru ianugr ianurg ianrug
ianrgu iagnur iagnru iagunr iagurn iagrun iagrnu iaugnr iaugrn iaungr iaunrg
iaurng iaurgn iargun iargnu iarugn iarung iarnug iarngu irngau irngua irnagu
irnaug irnuag irnuga irgnau irgnua irganu irgaun irguan irguna iragnu iragun
irangu iranug iraung iraugn irugan irugna iruagn iruang irunag irunga uingar
uingra uinagr uinarg uinrag uinrga uignar uignra uiganr uigarn uigran uigrna
uiagnr uiagrn uiangr uianrg uiarng uiargn uirgan uirgna uiragn uirang uirnag
uirnga unigar unigra uniagr uniarg unirag unirga ungiar ungira ungair ungari
ungrai ungria unagir unagri unaigr unairg unarig unargi unrgai unrgia unragi
unraig unriag unriga ugniar ugnira ugnair ugnari ugnrai ugnria uginar uginra
ugianr ugiarn ugiran ugirna ugainr ugairn uganir uganri ugarni ugarin ugrian
ugrina ugrain ugrani ugrnai ugrnia uangir uangri uanigr uanirg uanrig uanrgi
uagnir uagnri uaginr uagirn uagrin uagrni uaignr uaigrn uaingr uainrg uairng
uairgn uargin uargni uarign uaring uarnig uarngi urngai urngia urnagi urnaig
urniag urniga urgnai urgnia urgani urgain urgian urgina uragni uragin urangi
uranig uraing uraign urigan urigna uriagn uriang urinag uringa nuigar nuigra
nuiagr nuiarg nuirag nuirga nugiar nugira nugair nugari nugrai nugria nuagir
nuagri nuaigr nuairg nuarig nuargi nurgai nurgia nuragi nuraig nuriag nuriga
niugar niugra niuagr niuarg niurag niurga niguar nigura nigaur nigaru nigrau
nigrua niagur niagru niaugr niaurg niarug niargu nirgau nirgua niragu niraug
niruag niruga ngiuar ngiura ngiaur ngiaru ngirau ngirua nguiar nguira nguair
nguari ngurai nguria ngauir ngauri ngaiur ngairu ngariu ngarui ngruai ngruia
ngraui ngraiu ngriau ngriua naigur naigru naiugr naiurg nairug nairgu nagiur
nagiru naguir naguri nagrui nagriu naugir naugri nauigr nauirg naurig naurgi
nargui nargiu narugi naruig nariug narigu nrigau nrigua nriagu nriaug nriuag
nriuga nrgiau nrgiua nrgaiu nrgaui nrguai nrguia nragiu nragui nraigu nraiug
nrauig nraugi nrugai nrugia nruagi nruaig nruiag nruiga guniar gunira gunair
gunari gunrai gunria guinar guinra guianr guiarn guiran guirna guainr guairn
guanir guanri guarni guarin gurian gurina gurain gurani gurnai gurnia gnuiar
gnuira gnuair gnuari gnurai gnuria gniuar gniura gniaur gniaru gnirau gnirua
gnaiur gnairu gnauir gnauri gnarui gnariu gnriau gnriua gnraiu gnraui gnruai
gnruia ginuar ginura ginaur ginaru ginrau ginrua giunar giunra giuanr giuarn
giuran giurna giaunr giaurn gianur gianru giarnu giarun giruan giruna giraun
giranu girnau girnua ganiur ganiru ganuir ganuri ganrui ganriu gainur gainru
gaiunr gaiurn gairun gairnu gauinr gauirn gaunir gaunri gaurni gaurin gariun
garinu garuin garuni garnui garniu grniau grniua grnaiu grnaui grnuai grnuia
grinau grinua grianu griaun griuan griuna grainu graiun graniu granui grauni
grauin gruian gruina gruain gruani grunai grunia aungir aungri aunigr aunirg
aunrig aunrgi augnir augnri auginr augirn augrin augrni auignr auigrn auingr
auinrg auirng auirgn aurgin aurgni aurign auring aurnig aurngi anugir anugri
anuigr anuirg anurig anurgi anguir anguri angiur angiru angriu angrui anigur
anigru aniugr aniurg anirug anirgu anrgiu anrgui anrigu anriug anruig anrugi
agnuir agnuri agniur agniru agnriu agnrui agunir agunri aguinr aguirn agurin
agurni agiunr agiurn aginur aginru agirnu agirun agruin agruni agriun agrinu
agrniu agrnui aingur aingru ainugr ainurg ainrug ainrgu aignur aignru aigunr
aigurn aigrun aigrnu aiugnr aiugrn aiungr aiunrg aiurng aiurgn airgun airgnu
airugn airung airnug airngu arngiu arngui arnigu arniug arnuig arnugi argniu
argnui arginu argiun arguin arguni arignu arigun aringu arinug ariung ariugn
arugin arugni aruign aruing arunig arungi rungai rungia runagi runaig runiag
runiga rugnai rugnia rugani rugain rugian rugina ruagni ruagin ruangi ruanig
ruaing ruaign ruigan ruigna ruiagn ruiang ruinag ruinga rnugai rnugia rnuagi
rnuaig rnuiag rnuiga rnguai rnguia rngaui rngaiu rngiau rngiua rnagui rnagiu
rnaugi rnauig rnaiug rnaigu rnigau rnigua rniagu rniaug rniuag rniuga rgnuai
rgnuia rgnaui rgnaiu rgniau rgniua rgunai rgunia rguani rguain rguian rguina
rgauni rgauin rganui rganiu rgainu rgaiun rgiuan rgiuna rgiaun rgianu rginau
rginua rangui rangiu ranugi ranuig raniug ranigu ragnui ragniu raguni raguin
ragiun raginu raugni raugin raungi raunig rauing rauign raigun raignu raiugn
raiung rainug raingu ringau ringua rinagu rinaug rinuag rinuga rignau rignua
riganu rigaun riguan riguna riagnu riagun riangu rianug riaung riaugn riugan
riugna riuagn riuang riunag riunga

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History of cryptography
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