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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: ashton
cipher variations:
btiupo cujvqp dvkwrq ewlxsr fxmyts
gynzut hzoavu iapbwv jbqcxw kcrdyx
ldsezy metfaz nfugba ogvhcb phwidc
qixjed rjykfe skzlgf tlamhg umbnih
vncoji wodpkj xpeqlk yqfrml zrgsnm

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: ashton
Cipher: zhsglm

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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: ashton

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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: ashton
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: ashton
Cipher: nfugba

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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: ashton
Cipher: 113432444333

Extended Methods:
Method #1

Plaintext: ashton
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
a s h t o n 
1 3 3 4 4 3 
1 4 2 4 3 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: ashton
Cipher: lsoqrn

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Method #3

Plaintext: ashton
method variations:
lortnc ortncl rtnclo
tnclor nclort clortn

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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: ashton

all 720 cipher variations:
ashton ashtno ashotn ashont ashnot ashnto asthon asthno astohn astonh astnoh
astnho asothn asotnh asohtn asohnt asonht asonth asntoh asntho asnoth asnoht
asnhot asnhto ahston ahstno ahsotn ahsont ahsnot ahsnto ahtson ahtsno ahtosn
ahtons ahtnos ahtnso ahotsn ahotns ahostn ahosnt ahonst ahonts ahntos ahntso
ahnots ahnost ahnsot ahnsto athson athsno athosn athons athnos athnso atshon
atshno atsohn atsonh atsnoh atsnho atoshn atosnh atohsn atohns atonhs atonsh
atnsoh atnsho atnosh atnohs atnhos atnhso aohtsn aohtns aohstn aohsnt aohnst
aohnts aothsn aothns aotshn aotsnh aotnsh aotnhs aosthn aostnh aoshtn aoshnt
aosnht aosnth aontsh aonths aonsth aonsht aonhst aonhts anhtos anhtso anhots
anhost anhsot anhsto anthos anthso antohs antosh antsoh antsho anoths anotsh
anohts anohst anosht anosth anstoh anstho ansoth ansoht anshot anshto sahton
sahtno sahotn sahont sahnot sahnto sathon sathno satohn satonh satnoh satnho
saothn saotnh saohtn saohnt saonht saonth santoh santho sanoth sanoht sanhot
sanhto shaton shatno shaotn shaont shanot shanto shtaon shtano shtoan shtona
shtnoa shtnao shotan shotna shoatn shoant shonat shonta shntoa shntao shnota
shnoat shnaot shnato sthaon sthano sthoan sthona sthnoa sthnao stahon stahno
staohn staonh stanoh stanho stoahn stoanh stohan stohna stonha stonah stnaoh
stnaho stnoah stnoha stnhoa stnhao sohtan sohtna sohatn sohant sohnat sohnta
sothan sothna sotahn sotanh sotnah sotnha soathn soatnh soahtn soahnt soanht
soanth sontah sontha sonath sonaht sonhat sonhta snhtoa snhtao snhota snhoat
snhaot snhato snthoa snthao sntoha sntoah sntaoh sntaho snotha snotah snohta
snohat snoaht snoath snatoh snatho snaoth snaoht snahot snahto hsaton hsatno
hsaotn hsaont hsanot hsanto hstaon hstano hstoan hstona hstnoa hstnao hsotan
hsotna hsoatn hsoant hsonat hsonta hsntoa hsntao hsnota hsnoat hsnaot hsnato
haston hastno hasotn hasont hasnot hasnto hatson hatsno hatosn hatons hatnos
hatnso haotsn haotns haostn haosnt haonst haonts hantos hantso hanots hanost
hansot hansto htason htasno htaosn htaons htanos htanso htsaon htsano htsoan
htsona htsnoa htsnao htosan htosna htoasn htoans htonas htonsa htnsoa htnsao
htnosa htnoas htnaos htnaso hoatsn hoatns hoastn hoasnt hoanst hoants hotasn
hotans hotsan hotsna hotnsa hotnas hostan hostna hosatn hosant hosnat hosnta
hontsa hontas honsta honsat honast honats hnatos hnatso hnaots hnaost hnasot
hnasto hntaos hntaso hntoas hntosa hntsoa hntsao hnotas hnotsa hnoats hnoast
hnosat hnosta hnstoa hnstao hnsota hnsoat hnsaot hnsato tshaon tshano tshoan
tshona tshnoa tshnao tsahon tsahno tsaohn tsaonh tsanoh tsanho tsoahn tsoanh
tsohan tsohna tsonha tsonah tsnaoh tsnaho tsnoah tsnoha tsnhoa tsnhao thsaon
thsano thsoan thsona thsnoa thsnao thason thasno thaosn thaons thanos thanso
thoasn thoans thosan thosna thonsa thonas thnaos thnaso thnoas thnosa thnsoa
thnsao tahson tahsno tahosn tahons tahnos tahnso tashon tashno tasohn tasonh
tasnoh tasnho taoshn taosnh taohsn taohns taonhs taonsh tansoh tansho tanosh
tanohs tanhos tanhso tohasn tohans tohsan tohsna tohnsa tohnas toahsn toahns
toashn toasnh toansh toanhs tosahn tosanh toshan toshna tosnha tosnah tonash
tonahs tonsah tonsha tonhsa tonhas tnhaos tnhaso tnhoas tnhosa tnhsoa tnhsao
tnahos tnahso tnaohs tnaosh tnasoh tnasho tnoahs tnoash tnohas tnohsa tnosha
tnosah tnsaoh tnsaho tnsoah tnsoha tnshoa tnshao oshtan oshtna oshatn oshant
oshnat oshnta osthan osthna ostahn ostanh ostnah ostnha osathn osatnh osahtn
osahnt osanht osanth osntah osntha osnath osnaht osnhat osnhta ohstan ohstna
ohsatn ohsant ohsnat ohsnta ohtsan ohtsna ohtasn ohtans ohtnas ohtnsa ohatsn
ohatns ohastn ohasnt ohanst ohants ohntas ohntsa ohnats ohnast ohnsat ohnsta
othsan othsna othasn othans othnas othnsa otshan otshna otsahn otsanh otsnah
otsnha otashn otasnh otahsn otahns otanhs otansh otnsah otnsha otnash otnahs
otnhas otnhsa oahtsn oahtns oahstn oahsnt oahnst oahnts oathsn oathns oatshn
oatsnh oatnsh oatnhs oasthn oastnh oashtn oashnt oasnht oasnth oantsh oanths
oansth oansht oanhst oanhts onhtas onhtsa onhats onhast onhsat onhsta onthas
onthsa ontahs ontash ontsah ontsha onaths onatsh onahts onahst onasht onasth
onstah onstha onsath onsaht onshat onshta nshtoa nshtao nshota nshoat nshaot
nshato nsthoa nsthao nstoha nstoah nstaoh nstaho nsotha nsotah nsohta nsohat
nsoaht nsoath nsatoh nsatho nsaoth nsaoht nsahot nsahto nhstoa nhstao nhsota
nhsoat nhsaot nhsato nhtsoa nhtsao nhtosa nhtoas nhtaos nhtaso nhotsa nhotas
nhosta nhosat nhoast nhoats nhatos nhatso nhaots nhaost nhasot nhasto nthsoa
nthsao nthosa nthoas nthaos nthaso ntshoa ntshao ntsoha ntsoah ntsaoh ntsaho
ntosha ntosah ntohsa ntohas ntoahs ntoash ntasoh ntasho ntaosh ntaohs ntahos
ntahso nohtsa nohtas nohsta nohsat nohast nohats nothsa nothas notsha notsah
notash notahs nostha nostah noshta noshat nosaht nosath noatsh noaths noasth
noasht noahst noahts nahtos nahtso nahots nahost nahsot nahsto nathos nathso
natohs natosh natsoh natsho naoths naotsh naohts naohst naosht naosth nastoh
nastho nasoth nasoht nashot nashto

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History of cryptography
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