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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: dwarfs
cipher variations:
exbsgt fycthu gzduiv haevjw ibfwkx
jcgxly kdhymz leizna mfjaob ngkbpc
ohlcqd pimdre qjnesf rkoftg slpguh
tmqhvi unriwj vosjxk wptkyl xqulzm
yrvman zswnbo atxocp buypdq cvzqer

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: dwarfs
Cipher: wdziuh

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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: dwarfs

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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: dwarfs
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: dwarfs
Cipher: qjnesf

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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: dwarfs
Cipher: 412511241234

Extended Methods:
Method #1

Plaintext: dwarfs
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
d w a r f s 
4 2 1 2 1 3 
1 5 1 4 2 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: dwarfs
Cipher: iflvqr

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Method #3

Plaintext: dwarfs
method variations:
fefdmt efdmtf fdmtfe
dmtfef mtfefd tfefdm

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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: dwarfs

all 720 cipher variations:
dwarfs dwarsf dwafrs dwafsr dwasfr dwasrf dwrafs dwrasf dwrfas dwrfsa dwrsfa
dwrsaf dwfras dwfrsa dwfars dwfasr dwfsar dwfsra dwsrfa dwsraf dwsfra dwsfar
dwsafr dwsarf dawrfs dawrsf dawfrs dawfsr dawsfr dawsrf darwfs darwsf darfws
darfsw darsfw darswf dafrws dafrsw dafwrs dafwsr dafswr dafsrw dasrfw dasrwf
dasfrw dasfwr daswfr daswrf drawfs drawsf drafws drafsw drasfw draswf drwafs
drwasf drwfas drwfsa drwsfa drwsaf drfwas drfwsa drfaws drfasw drfsaw drfswa
drswfa drswaf drsfwa drsfaw drsafw drsawf dfarws dfarsw dfawrs dfawsr dfaswr
dfasrw dfraws dfrasw dfrwas dfrwsa dfrswa dfrsaw dfwras dfwrsa dfwars dfwasr
dfwsar dfwsra dfsrwa dfsraw dfswra dfswar dfsawr dfsarw dsarfw dsarwf dsafrw
dsafwr dsawfr dsawrf dsrafw dsrawf dsrfaw dsrfwa dsrwfa dsrwaf dsfraw dsfrwa
dsfarw dsfawr dsfwar dsfwra dswrfa dswraf dswfra dswfar dswafr dswarf wdarfs
wdarsf wdafrs wdafsr wdasfr wdasrf wdrafs wdrasf wdrfas wdrfsa wdrsfa wdrsaf
wdfras wdfrsa wdfars wdfasr wdfsar wdfsra wdsrfa wdsraf wdsfra wdsfar wdsafr
wdsarf wadrfs wadrsf wadfrs wadfsr wadsfr wadsrf wardfs wardsf warfds warfsd
warsfd warsdf wafrds wafrsd wafdrs wafdsr wafsdr wafsrd wasrfd wasrdf wasfrd
wasfdr wasdfr wasdrf wradfs wradsf wrafds wrafsd wrasfd wrasdf wrdafs wrdasf
wrdfas wrdfsa wrdsfa wrdsaf wrfdas wrfdsa wrfads wrfasd wrfsad wrfsda wrsdfa
wrsdaf wrsfda wrsfad wrsafd wrsadf wfards wfarsd wfadrs wfadsr wfasdr wfasrd
wfrads wfrasd wfrdas wfrdsa wfrsda wfrsad wfdras wfdrsa wfdars wfdasr wfdsar
wfdsra wfsrda wfsrad wfsdra wfsdar wfsadr wfsard wsarfd wsardf wsafrd wsafdr
wsadfr wsadrf wsrafd wsradf wsrfad wsrfda wsrdfa wsrdaf wsfrad wsfrda wsfard
wsfadr wsfdar wsfdra wsdrfa wsdraf wsdfra wsdfar wsdafr wsdarf awdrfs awdrsf
awdfrs awdfsr awdsfr awdsrf awrdfs awrdsf awrfds awrfsd awrsfd awrsdf awfrds
awfrsd awfdrs awfdsr awfsdr awfsrd awsrfd awsrdf awsfrd awsfdr awsdfr awsdrf
adwrfs adwrsf adwfrs adwfsr adwsfr adwsrf adrwfs adrwsf adrfws adrfsw adrsfw
adrswf adfrws adfrsw adfwrs adfwsr adfswr adfsrw adsrfw adsrwf adsfrw adsfwr
adswfr adswrf ardwfs ardwsf ardfws ardfsw ardsfw ardswf arwdfs arwdsf arwfds
arwfsd arwsfd arwsdf arfwds arfwsd arfdws arfdsw arfsdw arfswd arswfd arswdf
arsfwd arsfdw arsdfw arsdwf afdrws afdrsw afdwrs afdwsr afdswr afdsrw afrdws
afrdsw afrwds afrwsd afrswd afrsdw afwrds afwrsd afwdrs afwdsr afwsdr afwsrd
afsrwd afsrdw afswrd afswdr afsdwr afsdrw asdrfw asdrwf asdfrw asdfwr asdwfr
asdwrf asrdfw asrdwf asrfdw asrfwd asrwfd asrwdf asfrdw asfrwd asfdrw asfdwr
asfwdr asfwrd aswrfd aswrdf aswfrd aswfdr aswdfr aswdrf rwadfs rwadsf rwafds
rwafsd rwasfd rwasdf rwdafs rwdasf rwdfas rwdfsa rwdsfa rwdsaf rwfdas rwfdsa
rwfads rwfasd rwfsad rwfsda rwsdfa rwsdaf rwsfda rwsfad rwsafd rwsadf rawdfs
rawdsf rawfds rawfsd rawsfd rawsdf radwfs radwsf radfws radfsw radsfw radswf
rafdws rafdsw rafwds rafwsd rafswd rafsdw rasdfw rasdwf rasfdw rasfwd raswfd
raswdf rdawfs rdawsf rdafws rdafsw rdasfw rdaswf rdwafs rdwasf rdwfas rdwfsa
rdwsfa rdwsaf rdfwas rdfwsa rdfaws rdfasw rdfsaw rdfswa rdswfa rdswaf rdsfwa
rdsfaw rdsafw rdsawf rfadws rfadsw rfawds rfawsd rfaswd rfasdw rfdaws rfdasw
rfdwas rfdwsa rfdswa rfdsaw rfwdas rfwdsa rfwads rfwasd rfwsad rfwsda rfsdwa
rfsdaw rfswda rfswad rfsawd rfsadw rsadfw rsadwf rsafdw rsafwd rsawfd rsawdf
rsdafw rsdawf rsdfaw rsdfwa rsdwfa rsdwaf rsfdaw rsfdwa rsfadw rsfawd rsfwad
rsfwda rswdfa rswdaf rswfda rswfad rswafd rswadf fwards fwarsd fwadrs fwadsr
fwasdr fwasrd fwrads fwrasd fwrdas fwrdsa fwrsda fwrsad fwdras fwdrsa fwdars
fwdasr fwdsar fwdsra fwsrda fwsrad fwsdra fwsdar fwsadr fwsard fawrds fawrsd
fawdrs fawdsr fawsdr fawsrd farwds farwsd fardws fardsw farsdw farswd fadrws
fadrsw fadwrs fadwsr fadswr fadsrw fasrdw fasrwd fasdrw fasdwr faswdr faswrd
frawds frawsd fradws fradsw frasdw fraswd frwads frwasd frwdas frwdsa frwsda
frwsad frdwas frdwsa frdaws frdasw frdsaw frdswa frswda frswad frsdwa frsdaw
frsadw frsawd fdarws fdarsw fdawrs fdawsr fdaswr fdasrw fdraws fdrasw fdrwas
fdrwsa fdrswa fdrsaw fdwras fdwrsa fdwars fdwasr fdwsar fdwsra fdsrwa fdsraw
fdswra fdswar fdsawr fdsarw fsardw fsarwd fsadrw fsadwr fsawdr fsawrd fsradw
fsrawd fsrdaw fsrdwa fsrwda fsrwad fsdraw fsdrwa fsdarw fsdawr fsdwar fsdwra
fswrda fswrad fswdra fswdar fswadr fsward swarfd swardf swafrd swafdr swadfr
swadrf swrafd swradf swrfad swrfda swrdfa swrdaf swfrad swfrda swfard swfadr
swfdar swfdra swdrfa swdraf swdfra swdfar swdafr swdarf sawrfd sawrdf sawfrd
sawfdr sawdfr sawdrf sarwfd sarwdf sarfwd sarfdw sardfw sardwf safrwd safrdw
safwrd safwdr safdwr safdrw sadrfw sadrwf sadfrw sadfwr sadwfr sadwrf srawfd
srawdf srafwd srafdw sradfw sradwf srwafd srwadf srwfad srwfda srwdfa srwdaf
srfwad srfwda srfawd srfadw srfdaw srfdwa srdwfa srdwaf srdfwa srdfaw srdafw
srdawf sfarwd sfardw sfawrd sfawdr sfadwr sfadrw sfrawd sfradw sfrwad sfrwda
sfrdwa sfrdaw sfwrad sfwrda sfward sfwadr sfwdar sfwdra sfdrwa sfdraw sfdwra
sfdwar sfdawr sfdarw sdarfw sdarwf sdafrw sdafwr sdawfr sdawrf sdrafw sdrawf
sdrfaw sdrfwa sdrwfa sdrwaf sdfraw sdfrwa sdfarw sdfawr sdfwar sdfwra sdwrfa
sdwraf sdwfra sdwfar sdwafr sdwarf

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History of cryptography
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