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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: bolich
cipher variations:
cpmjdi dqnkej erolfk fspmgl gtqnhm
huroin ivspjo jwtqkp kxurlq lyvsmr
mzwtns naxuot obyvpu pczwqv qdaxrw
rebysx sfczty tgdauz uhebva vifcwb
wjgdxc xkheyd ylifze zmjgaf ankhbg

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: bolich
Cipher: ylorxs

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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: bolich

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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: bolich
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: bolich
Cipher: obyvpu

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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: bolich
Cipher: 214313423132

Extended Methods:
Method #1

Plaintext: bolich
method variations:

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

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Method #3

Plaintext: bolich
method variations:
qcsmlg csmlgq smlgqc
mlgqcs lgqcsm gqcsml

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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: bolich

all 720 cipher variations:
bolich bolihc bolcih bolchi bolhci bolhic boilch boilhc boiclh boichl boihcl
boihlc bocilh bocihl boclih boclhi bochli bochil bohicl bohilc bohcil bohcli
bohlci bohlic bloich bloihc blocih blochi blohci blohic blioch bliohc blicoh
blicho blihco blihoc blcioh blciho blcoih blcohi blchoi blchio blhico blhioc
blhcio blhcoi blhoci blhoic biloch bilohc bilcoh bilcho bilhco bilhoc biolch
biolhc bioclh biochl biohcl biohlc bicolh bicohl bicloh biclho bichlo bichol
bihocl biholc bihcol bihclo bihlco bihloc bclioh bcliho bcloih bclohi bclhoi
bclhio bciloh bcilho bciolh bciohl bcihol bcihlo bcoilh bcoihl bcolih bcolhi
bcohli bcohil bchiol bchilo bchoil bcholi bchloi bchlio bhlico bhlioc bhlcio
bhlcoi bhloci bhloic bhilco bhiloc bhiclo bhicol bhiocl bhiolc bhcilo bhciol
bhclio bhcloi bhcoli bhcoil bhoicl bhoilc bhocil bhocli bholci bholic oblich
oblihc oblcih oblchi oblhci oblhic obilch obilhc obiclh obichl obihcl obihlc
obcilh obcihl obclih obclhi obchli obchil obhicl obhilc obhcil obhcli obhlci
obhlic olbich olbihc olbcih olbchi olbhci olbhic olibch olibhc olicbh olichb
olihcb olihbc olcibh olcihb olcbih olcbhi olchbi olchib olhicb olhibc olhcib
olhcbi olhbci olhbic oilbch oilbhc oilcbh oilchb oilhcb oilhbc oiblch oiblhc
oibclh oibchl oibhcl oibhlc oicblh oicbhl oiclbh oiclhb oichlb oichbl oihbcl
oihblc oihcbl oihclb oihlcb oihlbc oclibh oclihb oclbih oclbhi oclhbi oclhib
ocilbh ocilhb ociblh ocibhl ocihbl ocihlb ocbilh ocbihl ocblih ocblhi ocbhli
ocbhil ochibl ochilb ochbil ochbli ochlbi ochlib ohlicb ohlibc ohlcib ohlcbi
ohlbci ohlbic ohilcb ohilbc ohiclb ohicbl ohibcl ohiblc ohcilb ohcibl ohclib
ohclbi ohcbli ohcbil ohbicl ohbilc ohbcil ohbcli ohblci ohblic lobich lobihc
lobcih lobchi lobhci lobhic loibch loibhc loicbh loichb loihcb loihbc locibh
locihb locbih locbhi lochbi lochib lohicb lohibc lohcib lohcbi lohbci lohbic
lboich lboihc lbocih lbochi lbohci lbohic lbioch lbiohc lbicoh lbicho lbihco
lbihoc lbcioh lbciho lbcoih lbcohi lbchoi lbchio lbhico lbhioc lbhcio lbhcoi
lbhoci lbhoic liboch libohc libcoh libcho libhco libhoc liobch liobhc liocbh
liochb liohcb liohbc licobh licohb licboh licbho lichbo lichob lihocb lihobc
lihcob lihcbo lihbco lihboc lcbioh lcbiho lcboih lcbohi lcbhoi lcbhio lciboh
lcibho lciobh lciohb lcihob lcihbo lcoibh lcoihb lcobih lcobhi lcohbi lcohib
lchiob lchibo lchoib lchobi lchboi lchbio lhbico lhbioc lhbcio lhbcoi lhboci
lhboic lhibco lhiboc lhicbo lhicob lhiocb lhiobc lhcibo lhciob lhcbio lhcboi
lhcobi lhcoib lhoicb lhoibc lhocib lhocbi lhobci lhobic iolbch iolbhc iolcbh
iolchb iolhcb iolhbc ioblch ioblhc iobclh iobchl iobhcl iobhlc iocblh iocbhl
ioclbh ioclhb iochlb iochbl iohbcl iohblc iohcbl iohclb iohlcb iohlbc ilobch
ilobhc ilocbh ilochb ilohcb ilohbc ilboch ilbohc ilbcoh ilbcho ilbhco ilbhoc
ilcboh ilcbho ilcobh ilcohb ilchob ilchbo ilhbco ilhboc ilhcbo ilhcob ilhocb
ilhobc ibloch iblohc iblcoh iblcho iblhco iblhoc ibolch ibolhc iboclh ibochl
ibohcl ibohlc ibcolh ibcohl ibcloh ibclho ibchlo ibchol ibhocl ibholc ibhcol
ibhclo ibhlco ibhloc iclboh iclbho iclobh iclohb iclhob iclhbo icbloh icblho
icbolh icbohl icbhol icbhlo icoblh icobhl icolbh icolhb icohlb icohbl ichbol
ichblo ichobl icholb ichlob ichlbo ihlbco ihlboc ihlcbo ihlcob ihlocb ihlobc
ihblco ihbloc ihbclo ihbcol ihbocl ihbolc ihcblo ihcbol ihclbo ihclob ihcolb
ihcobl ihobcl ihoblc ihocbl ihoclb iholcb iholbc colibh colihb colbih colbhi
colhbi colhib coilbh coilhb coiblh coibhl coihbl coihlb cobilh cobihl coblih
coblhi cobhli cobhil cohibl cohilb cohbil cohbli cohlbi cohlib cloibh cloihb
clobih clobhi clohbi clohib cliobh cliohb cliboh clibho clihbo clihob clbioh
clbiho clboih clbohi clbhoi clbhio clhibo clhiob clhbio clhboi clhobi clhoib
cilobh cilohb cilboh cilbho cilhbo cilhob ciolbh ciolhb cioblh ciobhl ciohbl
ciohlb cibolh cibohl cibloh ciblho cibhlo cibhol cihobl ciholb cihbol cihblo
cihlbo cihlob cblioh cbliho cbloih cblohi cblhoi cblhio cbiloh cbilho cbiolh
cbiohl cbihol cbihlo cboilh cboihl cbolih cbolhi cbohli cbohil cbhiol cbhilo
cbhoil cbholi cbhloi cbhlio chlibo chliob chlbio chlboi chlobi chloib chilbo
chilob chiblo chibol chiobl chiolb chbilo chbiol chblio chbloi chboli chboil
choibl choilb chobil chobli cholbi cholib holicb holibc holcib holcbi holbci
holbic hoilcb hoilbc hoiclb hoicbl hoibcl hoiblc hocilb hocibl hoclib hoclbi
hocbli hocbil hobicl hobilc hobcil hobcli hoblci hoblic hloicb hloibc hlocib
hlocbi hlobci hlobic hliocb hliobc hlicob hlicbo hlibco hliboc hlciob hlcibo
hlcoib hlcobi hlcboi hlcbio hlbico hlbioc hlbcio hlbcoi hlboci hlboic hilocb
hilobc hilcob hilcbo hilbco hilboc hiolcb hiolbc hioclb hiocbl hiobcl hioblc
hicolb hicobl hiclob hiclbo hicblo hicbol hibocl hibolc hibcol hibclo hiblco
hibloc hcliob hclibo hcloib hclobi hclboi hclbio hcilob hcilbo hciolb hciobl
hcibol hciblo hcoilb hcoibl hcolib hcolbi hcobli hcobil hcbiol hcbilo hcboil
hcboli hcbloi hcblio hblico hblioc hblcio hblcoi hbloci hbloic hbilco hbiloc
hbiclo hbicol hbiocl hbiolc hbcilo hbciol hbclio hbcloi hbcoli hbcoil hboicl
hboilc hbocil hbocli hbolci hbolic

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History of cryptography
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