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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: dsyfko
cipher variations:
etzglp fuahmq gvbinr hwcjos ixdkpt
jyelqu kzfmrv lagnsw mbhotx ncipuy
odjqvz pekrwa qflsxb rgmtyc shnuzd
tiovae ujpwbf vkqxcg wlrydh xmszei
yntafj zoubgk apvchl bqwdim crxejn

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: dsyfko
Cipher: whbupl

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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: dsyfko

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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: dsyfko
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: dsyfko
Cipher: qflsxb

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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: dsyfko
Cipher: 413445125243

Extended Methods:
Method #1

Plaintext: dsyfko
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
d s y f k o 
4 3 4 1 5 4 
1 4 5 2 2 3 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: dsyfko
Cipher: oduqkm

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Method #3

Plaintext: dsyfko
method variations:
ltewrs tewrsl ewrslt
wrslte rsltew sltewr

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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: dsyfko

all 720 cipher variations:
dsyfko dsyfok dsykfo dsykof dsyokf dsyofk dsfyko dsfyok dsfkyo dsfkoy dsfoky
dsfoyk dskfyo dskfoy dskyfo dskyof dskoyf dskofy dsofky dsofyk dsokfy dsokyf
dsoykf dsoyfk dysfko dysfok dyskfo dyskof dysokf dysofk dyfsko dyfsok dyfkso
dyfkos dyfoks dyfosk dykfso dykfos dyksfo dyksof dykosf dykofs dyofks dyofsk
dyokfs dyoksf dyoskf dyosfk dfysko dfysok dfykso dfykos dfyoks dfyosk dfsyko
dfsyok dfskyo dfskoy dfsoky dfsoyk dfksyo dfksoy dfkyso dfkyos dfkoys dfkosy
dfosky dfosyk dfoksy dfokys dfoyks dfoysk dkyfso dkyfos dkysfo dkysof dkyosf
dkyofs dkfyso dkfyos dkfsyo dkfsoy dkfosy dkfoys dksfyo dksfoy dksyfo dksyof
dksoyf dksofy dkofsy dkofys dkosfy dkosyf dkoysf dkoyfs doyfks doyfsk doykfs
doyksf doyskf doysfk dofyks dofysk dofkys dofksy dofsky dofsyk dokfys dokfsy
dokyfs dokysf doksyf doksfy dosfky dosfyk doskfy doskyf dosykf dosyfk sdyfko
sdyfok sdykfo sdykof sdyokf sdyofk sdfyko sdfyok sdfkyo sdfkoy sdfoky sdfoyk
sdkfyo sdkfoy sdkyfo sdkyof sdkoyf sdkofy sdofky sdofyk sdokfy sdokyf sdoykf
sdoyfk sydfko sydfok sydkfo sydkof sydokf sydofk syfdko syfdok syfkdo syfkod
syfokd syfodk sykfdo sykfod sykdfo sykdof sykodf sykofd syofkd syofdk syokfd
syokdf syodkf syodfk sfydko sfydok sfykdo sfykod sfyokd sfyodk sfdyko sfdyok
sfdkyo sfdkoy sfdoky sfdoyk sfkdyo sfkdoy sfkydo sfkyod sfkoyd sfkody sfodky
sfodyk sfokdy sfokyd sfoykd sfoydk skyfdo skyfod skydfo skydof skyodf skyofd
skfydo skfyod skfdyo skfdoy skfody skfoyd skdfyo skdfoy skdyfo skdyof skdoyf
skdofy skofdy skofyd skodfy skodyf skoydf skoyfd soyfkd soyfdk soykfd soykdf
soydkf soydfk sofykd sofydk sofkyd sofkdy sofdky sofdyk sokfyd sokfdy sokyfd
sokydf sokdyf sokdfy sodfky sodfyk sodkfy sodkyf sodykf sodyfk ysdfko ysdfok
ysdkfo ysdkof ysdokf ysdofk ysfdko ysfdok ysfkdo ysfkod ysfokd ysfodk yskfdo
yskfod yskdfo yskdof yskodf yskofd ysofkd ysofdk ysokfd ysokdf ysodkf ysodfk
ydsfko ydsfok ydskfo ydskof ydsokf ydsofk ydfsko ydfsok ydfkso ydfkos ydfoks
ydfosk ydkfso ydkfos ydksfo ydksof ydkosf ydkofs ydofks ydofsk ydokfs ydoksf
ydoskf ydosfk yfdsko yfdsok yfdkso yfdkos yfdoks yfdosk yfsdko yfsdok yfskdo
yfskod yfsokd yfsodk yfksdo yfksod yfkdso yfkdos yfkods yfkosd yfoskd yfosdk
yfoksd yfokds yfodks yfodsk ykdfso ykdfos ykdsfo ykdsof ykdosf ykdofs ykfdso
ykfdos ykfsdo ykfsod ykfosd ykfods yksfdo yksfod yksdfo yksdof yksodf yksofd
ykofsd ykofds ykosfd ykosdf ykodsf ykodfs yodfks yodfsk yodkfs yodksf yodskf
yodsfk yofdks yofdsk yofkds yofksd yofskd yofsdk yokfds yokfsd yokdfs yokdsf
yoksdf yoksfd yosfkd yosfdk yoskfd yoskdf yosdkf yosdfk fsydko fsydok fsykdo
fsykod fsyokd fsyodk fsdyko fsdyok fsdkyo fsdkoy fsdoky fsdoyk fskdyo fskdoy
fskydo fskyod fskoyd fskody fsodky fsodyk fsokdy fsokyd fsoykd fsoydk fysdko
fysdok fyskdo fyskod fysokd fysodk fydsko fydsok fydkso fydkos fydoks fydosk
fykdso fykdos fyksdo fyksod fykosd fykods fyodks fyodsk fyokds fyoksd fyoskd
fyosdk fdysko fdysok fdykso fdykos fdyoks fdyosk fdsyko fdsyok fdskyo fdskoy
fdsoky fdsoyk fdksyo fdksoy fdkyso fdkyos fdkoys fdkosy fdosky fdosyk fdoksy
fdokys fdoyks fdoysk fkydso fkydos fkysdo fkysod fkyosd fkyods fkdyso fkdyos
fkdsyo fkdsoy fkdosy fkdoys fksdyo fksdoy fksydo fksyod fksoyd fksody fkodsy
fkodys fkosdy fkosyd fkoysd fkoyds foydks foydsk foykds foyksd foyskd foysdk
fodyks fodysk fodkys fodksy fodsky fodsyk fokdys fokdsy fokyds fokysd foksyd
foksdy fosdky fosdyk foskdy foskyd fosykd fosydk ksyfdo ksyfod ksydfo ksydof
ksyodf ksyofd ksfydo ksfyod ksfdyo ksfdoy ksfody ksfoyd ksdfyo ksdfoy ksdyfo
ksdyof ksdoyf ksdofy ksofdy ksofyd ksodfy ksodyf ksoydf ksoyfd kysfdo kysfod
kysdfo kysdof kysodf kysofd kyfsdo kyfsod kyfdso kyfdos kyfods kyfosd kydfso
kydfos kydsfo kydsof kydosf kydofs kyofds kyofsd kyodfs kyodsf kyosdf kyosfd
kfysdo kfysod kfydso kfydos kfyods kfyosd kfsydo kfsyod kfsdyo kfsdoy kfsody
kfsoyd kfdsyo kfdsoy kfdyso kfdyos kfdoys kfdosy kfosdy kfosyd kfodsy kfodys
kfoyds kfoysd kdyfso kdyfos kdysfo kdysof kdyosf kdyofs kdfyso kdfyos kdfsyo
kdfsoy kdfosy kdfoys kdsfyo kdsfoy kdsyfo kdsyof kdsoyf kdsofy kdofsy kdofys
kdosfy kdosyf kdoysf kdoyfs koyfds koyfsd koydfs koydsf koysdf koysfd kofyds
kofysd kofdys kofdsy kofsdy kofsyd kodfys kodfsy kodyfs kodysf kodsyf kodsfy
kosfdy kosfyd kosdfy kosdyf kosydf kosyfd osyfkd osyfdk osykfd osykdf osydkf
osydfk osfykd osfydk osfkyd osfkdy osfdky osfdyk oskfyd oskfdy oskyfd oskydf
oskdyf oskdfy osdfky osdfyk osdkfy osdkyf osdykf osdyfk oysfkd oysfdk oyskfd
oyskdf oysdkf oysdfk oyfskd oyfsdk oyfksd oyfkds oyfdks oyfdsk oykfsd oykfds
oyksfd oyksdf oykdsf oykdfs oydfks oydfsk oydkfs oydksf oydskf oydsfk ofyskd
ofysdk ofyksd ofykds ofydks ofydsk ofsykd ofsydk ofskyd ofskdy ofsdky ofsdyk
ofksyd ofksdy ofkysd ofkyds ofkdys ofkdsy ofdsky ofdsyk ofdksy ofdkys ofdyks
ofdysk okyfsd okyfds okysfd okysdf okydsf okydfs okfysd okfyds okfsyd okfsdy
okfdsy okfdys oksfyd oksfdy oksyfd oksydf oksdyf oksdfy okdfsy okdfys okdsfy
okdsyf okdysf okdyfs odyfks odyfsk odykfs odyksf odyskf odysfk odfyks odfysk
odfkys odfksy odfsky odfsyk odkfys odkfsy odkyfs odkysf odksyf odksfy odsfky
odsfyk odskfy odskyf odsykf odsyfk

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History of cryptography
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