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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: pairoj
cipher variations:
qbjspk rcktql sdlurm temvsn ufnwto
vgoxup whpyvq xiqzwr yjraxs zksbyt
altczu bmudav cnvebw dowfcx epxgdy
fqyhez grzifa hsajgb itbkhc juclid
kvdmje lwenkf mxfolg nygpmh ozhqni

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: pairoj
Cipher: kzrilq

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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: pairoj

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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: pairoj
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: pairoj
Cipher: cnvebw

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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: pairoj
Cipher: 531142244342

Extended Methods:
Method #1

Plaintext: pairoj
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
p a i r o j 
5 1 4 2 4 4 
3 1 2 4 3 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: pairoj
Cipher: eitcrh

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Method #3

Plaintext: pairoj
method variations:
cqgtsw qgtswc gtswcq
tswcqg swcqgt wcqgts

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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: pairoj

all 720 cipher variations:
pairoj pairjo paiorj paiojr paijor paijro parioj parijo paroij paroji parjoi
parjio paorij paorji paoirj paoijr paojir paojri pajroi pajrio pajori pajoir
pajior pajiro piaroj piarjo piaorj piaojr piajor piajro piraoj pirajo piroaj
piroja pirjoa pirjao pioraj piorja pioarj pioajr piojar piojra pijroa pijrao
pijora pijoar pijaor pijaro priaoj priajo prioaj prioja prijoa prijao praioj
praijo praoij praoji prajoi prajio proaij proaji proiaj proija projia projai
prjaoi prjaio prjoai prjoia prjioa prjiao poiraj poirja poiarj poiajr poijar
poijra poriaj porija poraij poraji porjai porjia poarij poarji poairj poaijr
poajir poajri pojrai pojria pojari pojair pojiar pojira pjiroa pjirao pjiora
pjioar pjiaor pjiaro pjrioa pjriao pjroia pjroai pjraoi pjraio pjoria pjorai
pjoira pjoiar pjoair pjoari pjaroi pjario pjaori pjaoir pjaior pjairo apiroj
apirjo apiorj apiojr apijor apijro aprioj aprijo aproij aproji aprjoi aprjio
aporij aporji apoirj apoijr apojir apojri apjroi apjrio apjori apjoir apjior
apjiro aiproj aiprjo aiporj aipojr aipjor aipjro airpoj airpjo airopj airojp
airjop airjpo aiorpj aiorjp aioprj aiopjr aiojpr aiojrp aijrop aijrpo aijorp
aijopr aijpor aijpro aripoj aripjo ariopj ariojp arijop arijpo arpioj arpijo
arpoij arpoji arpjoi arpjio aropij aropji aroipj aroijp arojip arojpi arjpoi
arjpio arjopi arjoip arjiop arjipo aoirpj aoirjp aoiprj aoipjr aoijpr aoijrp
aoripj aorijp aorpij aorpji aorjpi aorjip aoprij aoprji aopirj aopijr aopjir
aopjri aojrpi aojrip aojpri aojpir aojipr aojirp ajirop ajirpo ajiorp ajiopr
ajipor ajipro ajriop ajripo ajroip ajropi ajrpoi ajrpio ajorip ajorpi ajoirp
ajoipr ajopir ajopri ajproi ajprio ajpori ajpoir ajpior ajpiro iaproj iaprjo
iaporj iapojr iapjor iapjro iarpoj iarpjo iaropj iarojp iarjop iarjpo iaorpj
iaorjp iaoprj iaopjr iaojpr iaojrp iajrop iajrpo iajorp iajopr iajpor iajpro
iparoj iparjo ipaorj ipaojr ipajor ipajro ipraoj iprajo iproaj iproja iprjoa
iprjao iporaj iporja ipoarj ipoajr ipojar ipojra ipjroa ipjrao ipjora ipjoar
ipjaor ipjaro irpaoj irpajo irpoaj irpoja irpjoa irpjao irapoj irapjo iraopj
iraojp irajop irajpo iroapj iroajp iropaj iropja irojpa irojap irjaop irjapo
irjoap irjopa irjpoa irjpao iopraj ioprja ioparj iopajr iopjar iopjra iorpaj
iorpja iorapj iorajp iorjap iorjpa ioarpj ioarjp ioaprj ioapjr ioajpr ioajrp
iojrap iojrpa iojarp iojapr iojpar iojpra ijproa ijprao ijpora ijpoar ijpaor
ijparo ijrpoa ijrpao ijropa ijroap ijraop ijrapo ijorpa ijorap ijopra ijopar
ijoapr ijoarp ijarop ijarpo ijaorp ijaopr ijapor ijapro raipoj raipjo raiopj
raiojp raijop raijpo rapioj rapijo rapoij rapoji rapjoi rapjio raopij raopji
raoipj raoijp raojip raojpi rajpoi rajpio rajopi rajoip rajiop rajipo riapoj
riapjo riaopj riaojp riajop riajpo ripaoj ripajo ripoaj ripoja ripjoa ripjao
riopaj riopja rioapj rioajp riojap riojpa rijpoa rijpao rijopa rijoap rijaop
rijapo rpiaoj rpiajo rpioaj rpioja rpijoa rpijao rpaioj rpaijo rpaoij rpaoji
rpajoi rpajio rpoaij rpoaji rpoiaj rpoija rpojia rpojai rpjaoi rpjaio rpjoai
rpjoia rpjioa rpjiao roipaj roipja roiapj roiajp roijap roijpa ropiaj ropija
ropaij ropaji ropjai ropjia roapij roapji roaipj roaijp roajip roajpi rojpai
rojpia rojapi rojaip rojiap rojipa rjipoa rjipao rjiopa rjioap rjiaop rjiapo
rjpioa rjpiao rjpoia rjpoai rjpaoi rjpaio rjopia rjopai rjoipa rjoiap rjoaip
rjoapi rjapoi rjapio rjaopi rjaoip rjaiop rjaipo oairpj oairjp oaiprj oaipjr
oaijpr oaijrp oaripj oarijp oarpij oarpji oarjpi oarjip oaprij oaprji oapirj
oapijr oapjir oapjri oajrpi oajrip oajpri oajpir oajipr oajirp oiarpj oiarjp
oiaprj oiapjr oiajpr oiajrp oirapj oirajp oirpaj oirpja oirjpa oirjap oipraj
oiprja oiparj oipajr oipjar oipjra oijrpa oijrap oijpra oijpar oijapr oijarp
oriapj oriajp oripaj oripja orijpa orijap oraipj oraijp orapij orapji orajpi
orajip orpaij orpaji orpiaj orpija orpjia orpjai orjapi orjaip orjpai orjpia
orjipa orjiap opiraj opirja opiarj opiajr opijar opijra opriaj oprija opraij
opraji oprjai oprjia oparij oparji opairj opaijr opajir opajri opjrai opjria
opjari opjair opjiar opjira ojirpa ojirap ojipra ojipar ojiapr ojiarp ojripa
ojriap ojrpia ojrpai ojrapi ojraip ojpria ojprai ojpira ojpiar ojpair ojpari
ojarpi ojarip ojapri ojapir ojaipr ojairp jairop jairpo jaiorp jaiopr jaipor
jaipro jariop jaripo jaroip jaropi jarpoi jarpio jaorip jaorpi jaoirp jaoipr
jaopir jaopri japroi japrio japori japoir japior japiro jiarop jiarpo jiaorp
jiaopr jiapor jiapro jiraop jirapo jiroap jiropa jirpoa jirpao jiorap jiorpa
jioarp jioapr jiopar jiopra jiproa jiprao jipora jipoar jipaor jiparo jriaop
jriapo jrioap jriopa jripoa jripao jraiop jraipo jraoip jraopi jrapoi jrapio
jroaip jroapi jroiap jroipa jropia jropai jrpaoi jrpaio jrpoai jrpoia jrpioa
jrpiao joirap joirpa joiarp joiapr joipar joipra joriap joripa joraip jorapi
jorpai jorpia joarip joarpi joairp joaipr joapir joapri joprai jopria jopari
jopair jopiar jopira jpiroa jpirao jpiora jpioar jpiaor jpiaro jprioa jpriao
jproia jproai jpraoi jpraio jporia jporai jpoira jpoiar jpoair jpoari jparoi
jpario jpaori jpaoir jpaior jpairo

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History of cryptography
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