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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: orelia
cipher variations:
psfmjb qtgnkc ruhold svipme twjqnf
uxkrog vylsph wzmtqi xanurj ybovsk
zcpwtl adqxum beryvn cfszwo dgtaxp
ehubyq fivczr gjwdas hkxebt ilyfcu
jmzgdv knahew lobifx mpcjgy nqdkhz

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: orelia
Cipher: livorz

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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: orelia

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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: orelia
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: orelia
Cipher: beryvn

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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: orelia
Cipher: 432451134211

Extended Methods:
Method #1

Plaintext: orelia
method variations:

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

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Method #3

Plaintext: orelia
method variations:
hyasbq yasbqh asbqhy
sbqhya bqhyas qhyasb

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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: orelia

all 720 cipher variations:
orelia orelai oreila oreial oreail oreali orleia orleai orliea orliae orlaie
orlaei orilea orilae oriela orieal oriael oriale oralie oralei oraile oraiel
oraeil oraeli oerlia oerlai oerila oerial oerail oerali oelria oelrai oelira
oeliar oelair oelari oeilra oeilar oeirla oeiral oeiarl oeialr oealir oealri
oeailr oeairl oearil oearli oleria olerai oleira oleiar oleair oleari olreia
olreai olriea olriae olraie olraei olirea olirae oliera oliear oliaer oliare
olarie olarei olaire olaier olaeir olaeri oielra oielar oierla oieral oiearl
oiealr oilera oilear oilrea oilrae oilare oilaer oirlea oirlae oirela oireal
oirael oirale oialre oialer oiarle oiarel oiaerl oiaelr oaelir oaelri oaeilr
oaeirl oaeril oaerli oaleir oaleri oalier oalire oalrie oalrei oailer oailre
oaielr oaierl oairel oairle oarlie oarlei oarile oariel oareil oareli roelia
roelai roeila roeial roeail roeali roleia roleai roliea roliae rolaie rolaei
roilea roilae roiela roieal roiael roiale roalie roalei roaile roaiel roaeil
roaeli reolia reolai reoila reoial reoail reoali reloia reloai relioa reliao
relaio relaoi reiloa reilao reiola reioal reiaol reialo realio realoi reailo
reaiol reaoil reaoli rleoia rleoai rleioa rleiao rleaio rleaoi rloeia rloeai
rloiea rloiae rloaie rloaei rlioea rlioae rlieoa rlieao rliaeo rliaoe rlaoie
rlaoei rlaioe rlaieo rlaeio rlaeoi rieloa rielao rieola rieoal rieaol riealo
rileoa rileao riloea riloae rilaoe rilaeo riolea riolae rioela rioeal rioael
rioale rialoe rialeo riaole riaoel riaeol riaelo raelio raeloi raeilo raeiol
raeoil raeoli raleio raleoi ralieo ralioe raloie raloei raileo railoe raielo
raieol raioel raiole raolie raolei raoile raoiel raoeil raoeli erolia erolai
eroila eroial eroail eroali erloia erloai erlioa erliao erlaio erlaoi eriloa
erilao eriola erioal eriaol erialo eralio eraloi erailo eraiol eraoil eraoli
eorlia eorlai eorila eorial eorail eorali eolria eolrai eolira eoliar eolair
eolari eoilra eoilar eoirla eoiral eoiarl eoialr eoalir eoalri eoailr eoairl
eoaril eoarli eloria elorai eloira eloiar eloair eloari elroia elroai elrioa
elriao elraio elraoi eliroa elirao eliora elioar eliaor eliaro elario elaroi
elairo elaior elaoir elaori eiolra eiolar eiorla eioral eioarl eioalr eilora
eiloar eilroa eilrao eilaro eilaor eirloa eirlao eirola eiroal eiraol eiralo
eialro eialor eiarlo eiarol eiaorl eiaolr eaolir eaolri eaoilr eaoirl eaoril
eaorli ealoir ealori ealior ealiro ealrio ealroi eailor eailro eaiolr eaiorl
eairol eairlo earlio earloi earilo eariol earoil earoli lreoia lreoai lreioa
lreiao lreaio lreaoi lroeia lroeai lroiea lroiae lroaie lroaei lrioea lrioae
lrieoa lrieao lriaeo lriaoe lraoie lraoei lraioe lraieo lraeio lraeoi leroia
leroai lerioa leriao leraio leraoi leoria leorai leoira leoiar leoair leoari
leiora leioar leiroa leirao leiaro leiaor leaoir leaori leaior leairo leario
learoi loeria loerai loeira loeiar loeair loeari loreia loreai loriea loriae
loraie loraei loirea loirae loiera loiear loiaer loiare loarie loarei loaire
loaier loaeir loaeri lieora lieoar lieroa lierao liearo lieaor lioera lioear
liorea liorae lioare lioaer liroea liroae lireoa lireao liraeo liraoe liaore
liaoer liaroe liareo liaero liaeor laeoir laeori laeior laeiro laerio laeroi
laoeir laoeri laoier laoire laorie laorei laioer laiore laieor laiero laireo
lairoe laroie laroei larioe larieo lareio lareoi ireloa irelao ireola ireoal
ireaol irealo irleoa irleao irloea irloae irlaoe irlaeo irolea irolae iroela
iroeal iroael iroale iraloe iraleo iraole iraoel iraeol iraelo ierloa ierlao
ierola ieroal ieraol ieralo ielroa ielrao ielora ieloar ielaor ielaro ieolra
ieolar ieorla ieoral ieoarl ieoalr iealor iealro ieaolr ieaorl iearol iearlo
ileroa ilerao ileora ileoar ileaor ilearo ilreoa ilreao ilroea ilroae ilraoe
ilraeo ilorea ilorae iloera iloear iloaer iloare ilaroe ilareo ilaore ilaoer
ilaeor ilaero ioelra ioelar ioerla ioeral ioearl ioealr iolera iolear iolrea
iolrae iolare iolaer iorlea iorlae iorela ioreal iorael iorale ioalre ioaler
ioarle ioarel ioaerl ioaelr iaelor iaelro iaeolr iaeorl iaerol iaerlo ialeor
ialero ialoer ialore ialroe ialreo iaoler iaolre iaoelr iaoerl iaorel iaorle
iarloe iarleo iarole iaroel iareol iarelo arelio areloi areilo areiol areoil
areoli arleio arleoi arlieo arlioe arloie arloei arileo ariloe arielo arieol
arioel ariole arolie arolei aroile aroiel aroeil aroeli aerlio aerloi aerilo
aeriol aeroil aeroli aelrio aelroi aeliro aelior aeloir aelori aeilro aeilor
aeirlo aeirol aeiorl aeiolr aeolir aeolri aeoilr aeoirl aeoril aeorli alerio
aleroi aleiro aleior aleoir aleori alreio alreoi alrieo alrioe alroie alroei
alireo aliroe aliero alieor alioer aliore alorie alorei aloire aloier aloeir
aloeri aielro aielor aierlo aierol aieorl aieolr ailero aileor ailreo ailroe
ailore ailoer airleo airloe airelo aireol airoel airole aiolre aioler aiorle
aiorel aioerl aioelr aoelir aoelri aoeilr aoeirl aoeril aoerli aoleir aoleri
aolier aolire aolrie aolrei aoiler aoilre aoielr aoierl aoirel aoirle aorlie
aorlei aorile aoriel aoreil aoreli

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History of cryptography
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