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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: crashd
cipher variations:
dsbtie etcujf fudvkg gvewlh hwfxmi
ixgynj jyhzok kziapl lajbqm mbkcrn
ncldso odmetp penfuq qfogvr rgphws
shqixt tirjyu ujskzv vktlaw wlumbx
xmvncy ynwodz zoxpea apyqfb bqzrgc

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: crashd
Cipher: xizhsw

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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: crashd

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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: crashd
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: crashd
Cipher: penfuq

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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: crashd
Cipher: 312411343241

Extended Methods:
Method #1

Plaintext: crashd
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
c r a s h d 
3 2 1 3 3 4 
1 4 1 4 2 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: crashd
Cipher: hlsqqb

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Method #3

Plaintext: crashd
method variations:
fdlorl dlorlf lorlfd
orlfdl rlfdlo lfdlor

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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: crashd

all 720 cipher variations:
crashd crasdh crahsd crahds cradhs cradsh crsahd crsadh crshad crshda crsdha
crsdah crhsad crhsda crhasd crhads crhdas crhdsa crdsha crdsah crdhsa crdhas
crdahs crdash carshd carsdh carhsd carhds cardhs cardsh casrhd casrdh cashrd
cashdr casdhr casdrh cahsrd cahsdr cahrsd cahrds cahdrs cahdsr cadshr cadsrh
cadhsr cadhrs cadrhs cadrsh csarhd csardh csahrd csahdr csadhr csadrh csrahd
csradh csrhad csrhda csrdha csrdah cshrad cshrda cshard cshadr cshdar cshdra
csdrha csdrah csdhra csdhar csdahr csdarh chasrd chasdr charsd chards chadrs
chadsr chsard chsadr chsrad chsrda chsdra chsdar chrsad chrsda chrasd chrads
chrdas chrdsa chdsra chdsar chdrsa chdras chdars chdasr cdashr cdasrh cdahsr
cdahrs cdarhs cdarsh cdsahr cdsarh cdshar cdshra cdsrha cdsrah cdhsar cdhsra
cdhasr cdhars cdhras cdhrsa cdrsha cdrsah cdrhsa cdrhas cdrahs cdrash rcashd
rcasdh rcahsd rcahds rcadhs rcadsh rcsahd rcsadh rcshad rcshda rcsdha rcsdah
rchsad rchsda rchasd rchads rchdas rchdsa rcdsha rcdsah rcdhsa rcdhas rcdahs
rcdash racshd racsdh rachsd rachds racdhs racdsh raschd rascdh rashcd rashdc
rasdhc rasdch rahscd rahsdc rahcsd rahcds rahdcs rahdsc radshc radsch radhsc
radhcs radchs radcsh rsachd rsacdh rsahcd rsahdc rsadhc rsadch rscahd rscadh
rschad rschda rscdha rscdah rshcad rshcda rshacd rshadc rshdac rshdca rsdcha
rsdcah rsdhca rsdhac rsdahc rsdach rhascd rhasdc rhacsd rhacds rhadcs rhadsc
rhsacd rhsadc rhscad rhscda rhsdca rhsdac rhcsad rhcsda rhcasd rhcads rhcdas
rhcdsa rhdsca rhdsac rhdcsa rhdcas rhdacs rhdasc rdashc rdasch rdahsc rdahcs
rdachs rdacsh rdsahc rdsach rdshac rdshca rdscha rdscah rdhsac rdhsca rdhasc
rdhacs rdhcas rdhcsa rdcsha rdcsah rdchsa rdchas rdcahs rdcash arcshd arcsdh
archsd archds arcdhs arcdsh arschd arscdh arshcd arshdc arsdhc arsdch arhscd
arhsdc arhcsd arhcds arhdcs arhdsc ardshc ardsch ardhsc ardhcs ardchs ardcsh
acrshd acrsdh acrhsd acrhds acrdhs acrdsh acsrhd acsrdh acshrd acshdr acsdhr
acsdrh achsrd achsdr achrsd achrds achdrs achdsr acdshr acdsrh acdhsr acdhrs
acdrhs acdrsh ascrhd ascrdh aschrd aschdr ascdhr ascdrh asrchd asrcdh asrhcd
asrhdc asrdhc asrdch ashrcd ashrdc ashcrd ashcdr ashdcr ashdrc asdrhc asdrch
asdhrc asdhcr asdchr asdcrh ahcsrd ahcsdr ahcrsd ahcrds ahcdrs ahcdsr ahscrd
ahscdr ahsrcd ahsrdc ahsdrc ahsdcr ahrscd ahrsdc ahrcsd ahrcds ahrdcs ahrdsc
ahdsrc ahdscr ahdrsc ahdrcs ahdcrs ahdcsr adcshr adcsrh adchsr adchrs adcrhs
adcrsh adschr adscrh adshcr adshrc adsrhc adsrch adhscr adhsrc adhcsr adhcrs
adhrcs adhrsc adrshc adrsch adrhsc adrhcs adrchs adrcsh srachd sracdh srahcd
srahdc sradhc sradch srcahd srcadh srchad srchda srcdha srcdah srhcad srhcda
srhacd srhadc srhdac srhdca srdcha srdcah srdhca srdhac srdahc srdach sarchd
sarcdh sarhcd sarhdc sardhc sardch sacrhd sacrdh sachrd sachdr sacdhr sacdrh
sahcrd sahcdr sahrcd sahrdc sahdrc sahdcr sadchr sadcrh sadhcr sadhrc sadrhc
sadrch scarhd scardh scahrd scahdr scadhr scadrh scrahd scradh scrhad scrhda
scrdha scrdah schrad schrda schard schadr schdar schdra scdrha scdrah scdhra
scdhar scdahr scdarh shacrd shacdr sharcd shardc shadrc shadcr shcard shcadr
shcrad shcrda shcdra shcdar shrcad shrcda shracd shradc shrdac shrdca shdcra
shdcar shdrca shdrac shdarc shdacr sdachr sdacrh sdahcr sdahrc sdarhc sdarch
sdcahr sdcarh sdchar sdchra sdcrha sdcrah sdhcar sdhcra sdhacr sdharc sdhrac
sdhrca sdrcha sdrcah sdrhca sdrhac sdrahc sdrach hrascd hrasdc hracsd hracds
hradcs hradsc hrsacd hrsadc hrscad hrscda hrsdca hrsdac hrcsad hrcsda hrcasd
hrcads hrcdas hrcdsa hrdsca hrdsac hrdcsa hrdcas hrdacs hrdasc harscd harsdc
harcsd harcds hardcs hardsc hasrcd hasrdc hascrd hascdr hasdcr hasdrc hacsrd
hacsdr hacrsd hacrds hacdrs hacdsr hadscr hadsrc hadcsr hadcrs hadrcs hadrsc
hsarcd hsardc hsacrd hsacdr hsadcr hsadrc hsracd hsradc hsrcad hsrcda hsrdca
hsrdac hscrad hscrda hscard hscadr hscdar hscdra hsdrca hsdrac hsdcra hsdcar
hsdacr hsdarc hcasrd hcasdr hcarsd hcards hcadrs hcadsr hcsard hcsadr hcsrad
hcsrda hcsdra hcsdar hcrsad hcrsda hcrasd hcrads hcrdas hcrdsa hcdsra hcdsar
hcdrsa hcdras hcdars hcdasr hdascr hdasrc hdacsr hdacrs hdarcs hdarsc hdsacr
hdsarc hdscar hdscra hdsrca hdsrac hdcsar hdcsra hdcasr hdcars hdcras hdcrsa
hdrsca hdrsac hdrcsa hdrcas hdracs hdrasc drashc drasch drahsc drahcs drachs
dracsh drsahc drsach drshac drshca drscha drscah drhsac drhsca drhasc drhacs
drhcas drhcsa drcsha drcsah drchsa drchas drcahs drcash darshc darsch darhsc
darhcs darchs darcsh dasrhc dasrch dashrc dashcr daschr dascrh dahsrc dahscr
dahrsc dahrcs dahcrs dahcsr dacshr dacsrh dachsr dachrs dacrhs dacrsh dsarhc
dsarch dsahrc dsahcr dsachr dsacrh dsrahc dsrach dsrhac dsrhca dsrcha dsrcah
dshrac dshrca dsharc dshacr dshcar dshcra dscrha dscrah dschra dschar dscahr
dscarh dhasrc dhascr dharsc dharcs dhacrs dhacsr dhsarc dhsacr dhsrac dhsrca
dhscra dhscar dhrsac dhrsca dhrasc dhracs dhrcas dhrcsa dhcsra dhcsar dhcrsa
dhcras dhcars dhcasr dcashr dcasrh dcahsr dcahrs dcarhs dcarsh dcsahr dcsarh
dcshar dcshra dcsrha dcsrah dchsar dchsra dchasr dchars dchras dchrsa dcrsha
dcrsah dcrhsa dcrhas dcrahs dcrash

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History of cryptography
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