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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: ignore
cipher variations:
jhopsf kipqtg ljqruh mkrsvi nlstwj
omtuxk pnuvyl qovwzm rpwxan sqxybo
tryzcp uszadq vtaber wubcfs xvcdgt
ywdehu zxefiv ayfgjw bzghkx cahily
dbijmz ecjkna fdklob gelmpc hfmnqd

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: ignore
Cipher: rtmliv

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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: ignore

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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: ignore
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: ignore
Cipher: vtaber

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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: ignore
Cipher: 422233432451

Extended Methods:
Method #1

Plaintext: ignore
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
i g n o r e 
4 2 3 4 2 5 
2 2 3 3 4 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: ignore
Cipher: iswgnd

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Method #3

Plaintext: ignore
method variations:
gmshyq mshyqg shyqgm
hyqgms yqgmsh qgmshy

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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: ignore

all 720 cipher variations:
ignore ignoer ignroe ignreo ignero igneor igonre igoner igorne igoren igoern
igoenr igrone igroen igrnoe igrneo igreno igreon igeorn igeonr igeron igerno
igenro igenor ingore ingoer ingroe ingreo ingero ingeor inogre inoger inorge
inoreg inoerg inoegr inroge inroeg inrgoe inrgeo inrego inreog ineorg ineogr
inerog inergo inegro inegor iongre ionger ionrge ionreg ionerg ionegr iognre
iogner iogrne iogren iogern iogenr iorgne iorgen iornge iorneg ioreng ioregn
ioegrn ioegnr ioergn ioerng ioenrg ioengr irnoge irnoeg irngoe irngeo irnego
irneog ironge ironeg irogne irogen iroegn iroeng irgone irgoen irgnoe irgneo
irgeno irgeon ireogn ireong iregon iregno irengo irenog ienorg ienogr ienrog
ienrgo iengro iengor ieonrg ieongr ieorng ieorgn ieogrn ieognr ierong ierogn
iernog ierngo iergno iergon iegorn iegonr iegron iegrno iegnro iegnor ginore
ginoer ginroe ginreo ginero gineor gionre gioner giorne gioren gioern gioenr
girone giroen girnoe girneo gireno gireon gieorn gieonr gieron gierno gienro
gienor gniore gnioer gniroe gnireo gniero gnieor gnoire gnoier gnorie gnorei
gnoeri gnoeir gnroie gnroei gnrioe gnrieo gnreio gnreoi gneori gneoir gneroi
gnerio gneiro gneior gonire gonier gonrie gonrei goneri goneir goinre goiner
goirne goiren goiern goienr gorine gorien gornie gornei goreni gorein goeirn
goeinr goerin goerni goenri goenir grnoie grnoei grnioe grnieo grneio grneoi
gronie gronei groine groien groein groeni grione grioen grinoe grineo grieno
grieon greoin greoni greion greino grenio grenoi genori genoir genroi genrio
geniro genior geonri geonir georni georin geoirn geoinr geroni geroin gernoi
gernio gerino gerion geiorn geionr geiron geirno geinro geinor ngiore ngioer
ngiroe ngireo ngiero ngieor ngoire ngoier ngorie ngorei ngoeri ngoeir ngroie
ngroei ngrioe ngrieo ngreio ngreoi ngeori ngeoir ngeroi ngerio ngeiro ngeior
nigore nigoer nigroe nigreo nigero nigeor niogre nioger niorge nioreg nioerg
nioegr niroge niroeg nirgoe nirgeo nirego nireog nieorg nieogr nierog niergo
niegro niegor noigre noiger noirge noireg noierg noiegr nogire nogier nogrie
nogrei nogeri nogeir norgie norgei norige norieg noreig noregi noegri noegir
noergi noerig noeirg noeigr nrioge nrioeg nrigoe nrigeo nriego nrieog nroige
nroieg nrogie nrogei nroegi nroeig nrgoie nrgoei nrgioe nrgieo nrgeio nrgeoi
nreogi nreoig nregoi nregio nreigo nreiog neiorg neiogr neirog neirgo neigro
neigor neoirg neoigr neorig neorgi neogri neogir neroig nerogi neriog nerigo
nergio nergoi negori negoir negroi negrio negiro negior ognire ognier ognrie
ognrei ogneri ogneir oginre oginer ogirne ogiren ogiern ogienr ogrine ogrien
ogrnie ogrnei ogreni ogrein ogeirn ogeinr ogerin ogerni ogenri ogenir ongire
ongier ongrie ongrei ongeri ongeir onigre oniger onirge onireg onierg oniegr
onrige onrieg onrgie onrgei onregi onreig oneirg oneigr onerig onergi onegri
onegir oingre oinger oinrge oinreg oinerg oinegr oignre oigner oigrne oigren
oigern oigenr oirgne oirgen oirnge oirneg oireng oiregn oiegrn oiegnr oiergn
oierng oienrg oiengr ornige ornieg orngie orngei ornegi orneig oringe orineg
origne origen oriegn orieng orgine orgien orgnie orgnei orgeni orgein oreign
oreing oregin oregni orengi orenig oenirg oenigr oenrig oenrgi oengri oengir
oeinrg oeingr oeirng oeirgn oeigrn oeignr oering oerign oernig oerngi oergni
oergin oegirn oeginr oegrin oegrni oegnri oegnir rgnoie rgnoei rgnioe rgnieo
rgneio rgneoi rgonie rgonei rgoine rgoien rgoein rgoeni rgione rgioen rginoe
rgineo rgieno rgieon rgeoin rgeoni rgeion rgeino rgenio rgenoi rngoie rngoei
rngioe rngieo rngeio rngeoi rnogie rnogei rnoige rnoieg rnoeig rnoegi rnioge
rnioeg rnigoe rnigeo rniego rnieog rneoig rneogi rneiog rneigo rnegio rnegoi
rongie rongei ronige ronieg roneig ronegi rognie rognei rogine rogien rogein
rogeni roigne roigen roinge roineg roieng roiegn roegin roegni roeign roeing
roenig roengi rinoge rinoeg ringoe ringeo rinego rineog rionge rioneg riogne
riogen rioegn rioeng rigone rigoen rignoe rigneo rigeno rigeon rieogn rieong
riegon riegno riengo rienog renoig renogi reniog renigo rengio rengoi reonig
reongi reoing reoign reogin reogni reiong reiogn reinog reingo reigno reigon
regoin regoni region regino regnio regnoi egnori egnoir egnroi egnrio egniro
egnior egonri egonir egorni egorin egoirn egoinr egroni egroin egrnoi egrnio
egrino egrion egiorn egionr egiron egirno eginro eginor engori engoir engroi
engrio engiro engior enogri enogir enorgi enorig enoirg enoigr enrogi enroig
enrgoi enrgio enrigo enriog eniorg eniogr enirog enirgo enigro enigor eongri
eongir eonrgi eonrig eonirg eonigr eognri eognir eogrni eogrin eogirn eoginr
eorgni eorgin eorngi eornig eoring eorign eoigrn eoignr eoirgn eoirng eoinrg
eoingr ernogi ernoig erngoi erngio ernigo erniog erongi eronig erogni erogin
eroign eroing ergoni ergoin ergnoi ergnio ergino ergion eriogn eriong erigon
erigno eringo erinog einorg einogr einrog einrgo eingro eingor eionrg eiongr
eiorng eiorgn eiogrn eiognr eirong eirogn eirnog eirngo eirgno eirgon eigorn
eigonr eigron eigrno eignro eignor

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History of cryptography
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