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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: malope
cipher variations:
nbmpqf ocnqrg pdorsh qepsti rfqtuj
sgruvk thsvwl uitwxm vjuxyn wkvyzo
xlwzap ymxabq znybcr aozcds bpadet
cqbefu drcfgv esdghw ftehix gufijy
hvgjkz iwhkla jxilmb kyjmnc lzknod

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: malope
Cipher: nzolkv

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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: malope

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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: malope
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: malope
Cipher: znybcr

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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: malope
Cipher: 231113435351

Extended Methods:
Method #1

Plaintext: malope
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
m a l o p e 
2 1 1 4 5 5 
3 1 3 3 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: malope
Cipher: bqzcnc

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Method #3

Plaintext: malope
method variations:
casxxf asxxfc sxxfca
xxfcas xfcasx fcasxx

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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: malope

all 720 cipher variations:
malope maloep malpoe malpeo malepo maleop maolpe maolep maople maopel maoepl
maoelp mapole mapoel maploe mapleo mapelo mapeol maeopl maeolp maepol maeplo
maelpo maelop mlaope mlaoep mlapoe mlapeo mlaepo mlaeop mloape mloaep mlopae
mlopea mloepa mloeap mlpoae mlpoea mlpaoe mlpaeo mlpeao mlpeoa mleopa mleoap
mlepoa mlepao mleapo mleaop molape molaep molpae molpea molepa moleap moalpe
moalep moaple moapel moaepl moaelp mopale mopael moplae moplea mopela mopeal
moeapl moealp moepal moepla moelpa moelap mploae mploea mplaoe mplaeo mpleao
mpleoa mpolae mpolea mpoale mpoael mpoeal mpoela mpaole mpaoel mpaloe mpaleo
mpaelo mpaeol mpeoal mpeola mpeaol mpealo mpelao mpeloa melopa meloap melpoa
melpao melapo melaop meolpa meolap meopla meopal meoapl meoalp mepola mepoal
meploa meplao mepalo mepaol meaopl meaolp meapol meaplo mealpo mealop amlope
amloep amlpoe amlpeo amlepo amleop amolpe amolep amople amopel amoepl amoelp
ampole ampoel amploe ampleo ampelo ampeol ameopl ameolp amepol ameplo amelpo
amelop almope almoep almpoe almpeo almepo almeop alompe alomep alopme alopem
aloepm aloemp alpome alpoem alpmoe alpmeo alpemo alpeom aleopm aleomp alepom
alepmo alempo alemop aolmpe aolmep aolpme aolpem aolepm aolemp aomlpe aomlep
aomple aompel aomepl aomelp aopmle aopmel aoplme aoplem aopelm aopeml aoempl
aoemlp aoepml aoeplm aoelpm aoelmp aplome aploem aplmoe aplmeo aplemo apleom
apolme apolem apomle apomel apoeml apoelm apmole apmoel apmloe apmleo apmelo
apmeol apeoml apeolm apemol apemlo apelmo apelom aelopm aelomp aelpom aelpmo
aelmpo aelmop aeolpm aeolmp aeoplm aeopml aeompl aeomlp aepolm aepoml aeplom
aeplmo aepmlo aepmol aemopl aemolp aempol aemplo aemlpo aemlop lamope lamoep
lampoe lampeo lamepo lameop laompe laomep laopme laopem laoepm laoemp lapome
lapoem lapmoe lapmeo lapemo lapeom laeopm laeomp laepom laepmo laempo laemop
lmaope lmaoep lmapoe lmapeo lmaepo lmaeop lmoape lmoaep lmopae lmopea lmoepa
lmoeap lmpoae lmpoea lmpaoe lmpaeo lmpeao lmpeoa lmeopa lmeoap lmepoa lmepao
lmeapo lmeaop lomape lomaep lompae lompea lomepa lomeap loampe loamep loapme
loapem loaepm loaemp lopame lopaem lopmae lopmea lopema lopeam loeapm loeamp
loepam loepma loempa loemap lpmoae lpmoea lpmaoe lpmaeo lpmeao lpmeoa lpomae
lpomea lpoame lpoaem lpoeam lpoema lpaome lpaoem lpamoe lpameo lpaemo lpaeom
lpeoam lpeoma lpeaom lpeamo lpemao lpemoa lemopa lemoap lempoa lempao lemapo
lemaop leompa leomap leopma leopam leoapm leoamp lepoma lepoam lepmoa lepmao
lepamo lepaom leaopm leaomp leapom leapmo leampo leamop oalmpe oalmep oalpme
oalpem oalepm oalemp oamlpe oamlep oample oampel oamepl oamelp oapmle oapmel
oaplme oaplem oapelm oapeml oaempl oaemlp oaepml oaeplm oaelpm oaelmp olampe
olamep olapme olapem olaepm olaemp olmape olmaep olmpae olmpea olmepa olmeap
olpmae olpmea olpame olpaem olpeam olpema olempa olemap olepma olepam oleapm
oleamp omlape omlaep omlpae omlpea omlepa omleap omalpe omalep omaple omapel
omaepl omaelp ompale ompael omplae omplea ompela ompeal omeapl omealp omepal
omepla omelpa omelap oplmae oplmea oplame oplaem opleam oplema opmlae opmlea
opmale opmael opmeal opmela opamle opamel opalme opalem opaelm opaeml opemal
opemla opeaml opealm opelam opelma oelmpa oelmap oelpma oelpam oelapm oelamp
oemlpa oemlap oempla oempal oemapl oemalp oepmla oepmal oeplma oeplam oepalm
oepaml oeampl oeamlp oeapml oeaplm oealpm oealmp palome paloem palmoe palmeo
palemo paleom paolme paolem paomle paomel paoeml paoelm pamole pamoel pamloe
pamleo pamelo pameol paeoml paeolm paemol paemlo paelmo paelom plaome plaoem
plamoe plameo plaemo plaeom ploame ploaem plomae plomea ploema ploeam plmoae
plmoea plmaoe plmaeo plmeao plmeoa pleoma pleoam plemoa plemao pleamo pleaom
polame polaem polmae polmea polema poleam poalme poalem poamle poamel poaeml
poaelm pomale pomael pomlae pomlea pomela pomeal poeaml poealm poemal poemla
poelma poelam pmloae pmloea pmlaoe pmlaeo pmleao pmleoa pmolae pmolea pmoale
pmoael pmoeal pmoela pmaole pmaoel pmaloe pmaleo pmaelo pmaeol pmeoal pmeola
pmeaol pmealo pmelao pmeloa peloma peloam pelmoa pelmao pelamo pelaom peolma
peolam peomla peomal peoaml peoalm pemola pemoal pemloa pemlao pemalo pemaol
peaoml peaolm peamol peamlo pealmo pealom ealopm ealomp ealpom ealpmo ealmpo
ealmop eaolpm eaolmp eaoplm eaopml eaompl eaomlp eapolm eapoml eaplom eaplmo
eapmlo eapmol eamopl eamolp eampol eamplo eamlpo eamlop elaopm elaomp elapom
elapmo elampo elamop eloapm eloamp elopam elopma elompa elomap elpoam elpoma
elpaom elpamo elpmao elpmoa elmopa elmoap elmpoa elmpao elmapo elmaop eolapm
eolamp eolpam eolpma eolmpa eolmap eoalpm eoalmp eoaplm eoapml eoampl eoamlp
eopalm eopaml eoplam eoplma eopmla eopmal eomapl eomalp eompal eompla eomlpa
eomlap eploam eploma eplaom eplamo eplmao eplmoa epolam epolma epoalm epoaml
epomal epomla epaolm epaoml epalom epalmo epamlo epamol epmoal epmola epmaol
epmalo epmlao epmloa emlopa emloap emlpoa emlpao emlapo emlaop emolpa emolap
emopla emopal emoapl emoalp empola empoal emploa emplao empalo empaol emaopl
emaolp emapol emaplo emalpo emalop

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History of cryptography
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