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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: lovest
cipher variations:
mpwftu nqxguv oryhvw psziwx qtajxy
rubkyz svclza twdmab uxenbc vyfocd
wzgpde xahqef ybirfg zcjsgh adkthi
beluij cfmvjk dgnwkl ehoxlm fipymn
gjqzno hkraop ilsbpq jmtcqr knudrs

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: lovest
Cipher: olevhg

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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: lovest

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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: lovest
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: lovest
Cipher: ybirfg

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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: lovest
Cipher: 134315513444

Extended Methods:
Method #1

Plaintext: lovest
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
l o v e s t 
1 4 1 5 3 4 
3 3 5 1 4 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: lovest
Cipher: qvsnet

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Method #3

Plaintext: lovest
method variations:
sczltd czltds zltdsc
ltdscz tdsczl dsczlt

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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: lovest

all 720 cipher variations:
lovest lovets lovset lovste lovtse lovtes loevst loevts loesvt loestv loetsv
loetvs losevt losetv losvet losvte lostve lostev lotesv lotevs lotsev lotsve
lotvse lotves lvoest lvoets lvoset lvoste lvotse lvotes lveost lveots lvesot
lvesto lvetso lvetos lvseot lvseto lvsoet lvsote lvstoe lvsteo lvteso lvteos
lvtseo lvtsoe lvtose lvtoes levost levots levsot levsto levtso levtos leovst
leovts leosvt leostv leotsv leotvs lesovt lesotv lesvot lesvto lestvo lestov
letosv letovs letsov letsvo letvso letvos lsveot lsveto lsvoet lsvote lsvtoe
lsvteo lsevot lsevto lseovt lseotv lsetov lsetvo lsoevt lsoetv lsovet lsovte
lsotve lsotev lsteov lstevo lstoev lstove lstvoe lstveo ltveso ltveos ltvseo
ltvsoe ltvose ltvoes ltevso ltevos ltesvo ltesov lteosv lteovs ltsevo ltseov
ltsveo ltsvoe ltsove ltsoev ltoesv ltoevs ltosev ltosve ltovse ltoves olvest
olvets olvset olvste olvtse olvtes olevst olevts olesvt olestv oletsv oletvs
olsevt olsetv olsvet olsvte olstve olstev oltesv oltevs oltsev oltsve oltvse
oltves ovlest ovlets ovlset ovlste ovltse ovltes ovelst ovelts oveslt ovestl
ovetsl ovetls ovselt ovsetl ovslet ovslte ovstle ovstel ovtesl ovtels ovtsel
ovtsle ovtlse ovtles oevlst oevlts oevslt oevstl oevtsl oevtls oelvst oelvts
oelsvt oelstv oeltsv oeltvs oeslvt oesltv oesvlt oesvtl oestvl oestlv oetlsv
oetlvs oetslv oetsvl oetvsl oetvls osvelt osvetl osvlet osvlte osvtle osvtel
osevlt osevtl oselvt oseltv osetlv osetvl oslevt osletv oslvet oslvte osltve
osltev ostelv ostevl ostlev ostlve ostvle ostvel otvesl otvels otvsel otvsle
otvlse otvles otevsl otevls otesvl oteslv otelsv otelvs otsevl otselv otsvel
otsvle otslve otslev otlesv otlevs otlsev otlsve otlvse otlves volest volets
volset volste voltse voltes voelst voelts voeslt voestl voetsl voetls voselt
vosetl voslet voslte vostle vostel votesl votels votsel votsle votlse votles
vloest vloets vloset vloste vlotse vlotes vleost vleots vlesot vlesto vletso
vletos vlseot vlseto vlsoet vlsote vlstoe vlsteo vlteso vlteos vltseo vltsoe
vltose vltoes velost velots velsot velsto veltso veltos veolst veolts veoslt
veostl veotsl veotls vesolt vesotl veslot veslto vestlo vestol vetosl vetols
vetsol vetslo vetlso vetlos vsleot vsleto vsloet vslote vsltoe vslteo vselot
vselto vseolt vseotl vsetol vsetlo vsoelt vsoetl vsolet vsolte vsotle vsotel
vsteol vstelo vstoel vstole vstloe vstleo vtleso vtleos vtlseo vtlsoe vtlose
vtloes vtelso vtelos vteslo vtesol vteosl vteols vtselo vtseol vtsleo vtsloe
vtsole vtsoel vtoesl vtoels vtosel vtosle vtolse vtoles eovlst eovlts eovslt
eovstl eovtsl eovtls eolvst eolvts eolsvt eolstv eoltsv eoltvs eoslvt eosltv
eosvlt eosvtl eostvl eostlv eotlsv eotlvs eotslv eotsvl eotvsl eotvls evolst
evolts evoslt evostl evotsl evotls evlost evlots evlsot evlsto evltso evltos
evslot evslto evsolt evsotl evstol evstlo evtlso evtlos evtslo evtsol evtosl
evtols elvost elvots elvsot elvsto elvtso elvtos elovst elovts elosvt elostv
elotsv elotvs elsovt elsotv elsvot elsvto elstvo elstov eltosv eltovs eltsov
eltsvo eltvso eltvos esvlot esvlto esvolt esvotl esvtol esvtlo eslvot eslvto
eslovt eslotv esltov esltvo esolvt esoltv esovlt esovtl esotvl esotlv estlov
estlvo estolv estovl estvol estvlo etvlso etvlos etvslo etvsol etvosl etvols
etlvso etlvos etlsvo etlsov etlosv etlovs etslvo etslov etsvlo etsvol etsovl
etsolv etolsv etolvs etoslv etosvl etovsl etovls sovelt sovetl sovlet sovlte
sovtle sovtel soevlt soevtl soelvt soeltv soetlv soetvl solevt soletv solvet
solvte soltve soltev sotelv sotevl sotlev sotlve sotvle sotvel svoelt svoetl
svolet svolte svotle svotel sveolt sveotl svelot svelto svetlo svetol svleot
svleto svloet svlote svltoe svlteo svtelo svteol svtleo svtloe svtole svtoel
sevolt sevotl sevlot sevlto sevtlo sevtol seovlt seovtl seolvt seoltv seotlv
seotvl selovt selotv selvot selvto seltvo seltov setolv setovl setlov setlvo
setvlo setvol slveot slveto slvoet slvote slvtoe slvteo slevot slevto sleovt
sleotv sletov sletvo sloevt sloetv slovet slovte slotve slotev slteov sltevo
sltoev sltove sltvoe sltveo stvelo stveol stvleo stvloe stvole stvoel stevlo
stevol stelvo stelov steolv steovl stlevo stleov stlveo stlvoe stlove stloev
stoelv stoevl stolev stolve stovle stovel tovesl tovels tovsel tovsle tovlse
tovles toevsl toevls toesvl toeslv toelsv toelvs tosevl toselv tosvel tosvle
toslve toslev tolesv tolevs tolsev tolsve tolvse tolves tvoesl tvoels tvosel
tvosle tvolse tvoles tveosl tveols tvesol tveslo tvelso tvelos tvseol tvselo
tvsoel tvsole tvsloe tvsleo tvleso tvleos tvlseo tvlsoe tvlose tvloes tevosl
tevols tevsol tevslo tevlso tevlos teovsl teovls teosvl teoslv teolsv teolvs
tesovl tesolv tesvol tesvlo teslvo teslov telosv telovs telsov telsvo telvso
telvos tsveol tsvelo tsvoel tsvole tsvloe tsvleo tsevol tsevlo tseovl tseolv
tselov tselvo tsoevl tsoelv tsovel tsovle tsolve tsolev tsleov tslevo tsloev
tslove tslvoe tslveo tlveso tlveos tlvseo tlvsoe tlvose tlvoes tlevso tlevos
tlesvo tlesov tleosv tleovs tlsevo tlseov tlsveo tlsvoe tlsove tlsoev tloesv
tloevs tlosev tlosve tlovse tloves

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History of cryptography
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