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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: schene
cipher variations:
tdifof uejgpg vfkhqh wgliri xhmjsj
yinktk zjolul akpmvm blqnwn cmroxo
dnspyp eotqzq fpurar gqvsbs hrwtct
isxudu jtyvev kuzwfw lvaxgx mwbyhy
nxcziz oydaja pzebkb qafclc rbgdmd

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: schene
Cipher: hxsvmv

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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: schene

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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: schene
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: schene
Cipher: fpurar

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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: schene
Cipher: 343132513351

Extended Methods:
Method #1

Plaintext: schene
method variations:

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

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Method #3

Plaintext: schene
method variations:
olwlxl lwlxlo wlxlol
lxlolw xlolwl lolwlx

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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: schene

all 720 cipher variations:
schene scheen schnee schnee schene scheen scehne scehen scenhe sceneh sceenh
sceehn scnehe scneeh scnhee scnhee scnehe scneeh sceenh sceehn sceneh scenhe
scehne scehen shcene shceen shcnee shcnee shcene shceen shecne shecen shence
shenec sheenc sheecn shnece shneec shncee shncee shnece shneec sheenc sheecn
shenec shence shecne shecen sehcne sehcen sehnce sehnec sehenc sehecn sechne
sechen secnhe secneh secenh secehn senche senceh senhce senhec senehc senech
seecnh seechn seench seenhc seehnc seehcn snhece snheec snhcee snhcee snhece
snheec snehce snehec sneche sneceh sneech sneehc sncehe snceeh snchee snchee
sncehe snceeh sneech sneehc sneceh sneche snehce snehec sehenc sehecn sehnec
sehnce sehcne sehcen seehnc seehcn seenhc seench seecnh seechn senehc senech
senhec senhce senche senceh secenh secehn secneh secnhe sechne sechen cshene
csheen cshnee cshnee cshene csheen csehne csehen csenhe cseneh cseenh cseehn
csnehe csneeh csnhee csnhee csnehe csneeh cseenh cseehn cseneh csenhe csehne
csehen chsene chseen chsnee chsnee chsene chseen chesne chesen chense chenes
cheens cheesn chnese chnees chnsee chnsee chnese chnees cheens cheesn chenes
chense chesne chesen cehsne cehsen cehnse cehnes cehens cehesn ceshne ceshen
cesnhe cesneh cesenh cesehn censhe censeh cenhse cenhes cenehs cenesh ceesnh
ceeshn ceensh ceenhs ceehns ceehsn cnhese cnhees cnhsee cnhsee cnhese cnhees
cnehse cnehes cneshe cneseh cneesh cneehs cnsehe cnseeh cnshee cnshee cnsehe
cnseeh cneesh cneehs cneseh cneshe cnehse cnehes cehens cehesn cehnes cehnse
cehsne cehsen ceehns ceehsn ceenhs ceensh ceesnh ceeshn cenehs cenesh cenhes
cenhse censhe censeh cesenh cesehn cesneh cesnhe ceshne ceshen hcsene hcseen
hcsnee hcsnee hcsene hcseen hcesne hcesen hcense hcenes hceens hceesn hcnese
hcnees hcnsee hcnsee hcnese hcnees hceens hceesn hcenes hcense hcesne hcesen
hscene hsceen hscnee hscnee hscene hsceen hsecne hsecen hsence hsenec hseenc
hseecn hsnece hsneec hsncee hsncee hsnece hsneec hseenc hseecn hsenec hsence
hsecne hsecen hescne hescen hesnce hesnec hesenc hesecn hecsne hecsen hecnse
hecnes hecens hecesn hencse hences hensce hensec henesc henecs heecns heecsn
heencs heensc heesnc heescn hnsece hnseec hnscee hnscee hnsece hnseec hnesce
hnesec hnecse hneces hneecs hneesc hncese hncees hncsee hncsee hncese hncees
hneecs hneesc hneces hnecse hnesce hnesec hesenc hesecn hesnec hesnce hescne
hescen heesnc heescn heensc heencs heecns heecsn henesc henecs hensec hensce
hencse hences hecens hecesn hecnes hecnse hecsne hecsen echsne echsen echnse
echnes echens echesn ecshne ecshen ecsnhe ecsneh ecsenh ecsehn ecnshe ecnseh
ecnhse ecnhes ecnehs ecnesh ecesnh eceshn ecensh ecenhs ecehns ecehsn ehcsne
ehcsen ehcnse ehcnes ehcens ehcesn ehscne ehscen ehsnce ehsnec ehsenc ehsecn
ehnsce ehnsec ehncse ehnces ehnecs ehnesc ehesnc ehescn ehensc ehencs ehecns
ehecsn eshcne eshcen eshnce eshnec eshenc eshecn eschne eschen escnhe escneh
escenh escehn esnche esnceh esnhce esnhec esnehc esnech esecnh esechn esench
esenhc esehnc esehcn enhsce enhsec enhcse enhces enhecs enhesc enshce enshec
ensche ensceh ensech ensehc encshe encseh enchse enches encehs encesh enesch
eneshc enecsh enechs enehcs enehsc eehsnc eehscn eehnsc eehncs eehcns eehcsn
eeshnc eeshcn eesnhc eesnch eescnh eeschn eenshc eensch eenhsc eenhcs eenchs
eencsh eecsnh eecshn eecnsh eecnhs eechns eechsn nchese nchees nchsee nchsee
nchese nchees ncehse ncehes nceshe nceseh nceesh nceehs ncsehe ncseeh ncshee
ncshee ncsehe ncseeh nceesh nceehs nceseh nceshe ncehse ncehes nhcese nhcees
nhcsee nhcsee nhcese nhcees nhecse nheces nhesce nhesec nheesc nheecs nhsece
nhseec nhscee nhscee nhsece nhseec nheesc nheecs nhesec nhesce nhecse nheces
nehcse nehces nehsce nehsec nehesc nehecs nechse neches necshe necseh necesh
necehs nesche nesceh neshce neshec nesehc nesech neecsh neechs neesch neeshc
neehsc neehcs nshece nsheec nshcee nshcee nshece nsheec nsehce nsehec nseche
nseceh nseech nseehc nscehe nsceeh nschee nschee nscehe nsceeh nseech nseehc
nseceh nseche nsehce nsehec nehesc nehecs nehsec nehsce nehcse nehces neehsc
neehcs neeshc neesch neecsh neechs nesehc nesech neshec neshce nesche nesceh
necesh necehs necseh necshe nechse neches echens echesn echnes echnse echsne
echsen ecehns ecehsn ecenhs ecensh ecesnh eceshn ecnehs ecnesh ecnhes ecnhse
ecnshe ecnseh ecsenh ecsehn ecsneh ecsnhe ecshne ecshen ehcens ehcesn ehcnes
ehcnse ehcsne ehcsen ehecns ehecsn ehencs ehensc ehesnc ehescn ehnecs ehnesc
ehnces ehncse ehnsce ehnsec ehsenc ehsecn ehsnec ehsnce ehscne ehscen eehcns
eehcsn eehncs eehnsc eehsnc eehscn eechns eechsn eecnhs eecnsh eecsnh eecshn
eenchs eencsh eenhcs eenhsc eenshc eensch eescnh eeschn eesnch eesnhc eeshnc
eeshcn enhecs enhesc enhces enhcse enhsce enhsec enehcs enehsc enechs enecsh
enesch eneshc encehs encesh enches enchse encshe encseh ensech ensehc ensceh
ensche enshce enshec eshenc eshecn eshnec eshnce eshcne eshcen esehnc esehcn
esenhc esench esecnh esechn esnehc esnech esnhec esnhce esnche esnceh escenh
escehn escneh escnhe eschne eschen

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History of cryptography
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