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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: maysel
cipher variations:
nbztfm ocaugn pdbvho qecwip rfdxjq
sgeykr thfzls uigamt vjhbnu wkicov
xljdpw ymkeqx znlfry aomgsz bpnhta
cqoiub drpjvc esqkwd ftrlxe gusmyf
hvtnzg iwuoah jxvpbi kywqcj lzxrdk

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: maysel
Cipher: nzbhvo

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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: maysel

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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: maysel
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: maysel
Cipher: znlfry

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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: maysel
Cipher: 231145345113

Extended Methods:
Method #1

Plaintext: maysel
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 y s e l 
2 1 4 3 5 1 
3 1 5 4 1 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: maysel
Cipher: boecul

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Method #3

Plaintext: maysel
method variations:
cqpyah qpyahc pyahcq
yahcqp ahcqpy hcqpya

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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: maysel

all 720 cipher variations:
maysel maysle mayesl mayels mayles maylse masyel masyle maseyl masely masley
maslye maesyl maesly maeysl maeyls maelys maelsy malsey malsye malesy maleys
malyes malyse myasel myasle myaesl myaels myales myalse mysael mysale myseal
mysela myslea myslae myesal myesla myeasl myeals myelas myelsa mylsea mylsae
mylesa myleas mylaes mylase msyael msyale msyeal msyela msylea msylae msayel
msayle msaeyl msaely msaley msalye mseayl msealy mseyal mseyla mselya mselay
mslaey mslaye msleay msleya mslyea mslyae meysal meysla meyasl meyals meylas
meylsa mesyal mesyla mesayl mesaly meslay meslya measyl measly meaysl meayls
mealys mealsy melsay melsya melasy melays melyas melysa mlysea mlysae mlyesa
mlyeas mlyaes mlyase mlsyea mlsyae mlseya mlseay mlsaey mlsaye mlesya mlesay
mleysa mleyas mleays mleasy mlasey mlasye mlaesy mlaeys mlayes mlayse amysel
amysle amyesl amyels amyles amylse amsyel amsyle amseyl amsely amsley amslye
amesyl amesly ameysl ameyls amelys amelsy amlsey amlsye amlesy amleys amlyes
amlyse aymsel aymsle aymesl aymels aymles aymlse aysmel aysmle ayseml ayselm
ayslem ayslme ayesml ayeslm ayemsl ayemls ayelms ayelsm aylsem aylsme aylesm
aylems aylmes aylmse asymel asymle asyeml asyelm asylem asylme asmyel asmyle
asmeyl asmely asmley asmlye asemyl asemly aseyml aseylm aselym aselmy aslmey
aslmye aslemy asleym aslyem aslyme aeysml aeyslm aeymsl aeymls aeylms aeylsm
aesyml aesylm aesmyl aesmly aeslmy aeslym aemsyl aemsly aemysl aemyls aemlys
aemlsy aelsmy aelsym aelmsy aelmys aelyms aelysm alysem alysme alyesm alyems
alymes alymse alsyem alsyme alseym alsemy alsmey alsmye alesym alesmy aleysm
aleyms alemys alemsy almsey almsye almesy almeys almyes almyse yamsel yamsle
yamesl yamels yamles yamlse yasmel yasmle yaseml yaselm yaslem yaslme yaesml
yaeslm yaemsl yaemls yaelms yaelsm yalsem yalsme yalesm yalems yalmes yalmse
ymasel ymasle ymaesl ymaels ymales ymalse ymsael ymsale ymseal ymsela ymslea
ymslae ymesal ymesla ymeasl ymeals ymelas ymelsa ymlsea ymlsae ymlesa ymleas
ymlaes ymlase ysmael ysmale ysmeal ysmela ysmlea ysmlae ysamel ysamle ysaeml
ysaelm ysalem ysalme yseaml ysealm ysemal ysemla yselma yselam yslaem yslame
ysleam yslema yslmea yslmae yemsal yemsla yemasl yemals yemlas yemlsa yesmal
yesmla yesaml yesalm yeslam yeslma yeasml yeaslm yeamsl yeamls yealms yealsm
yelsam yelsma yelasm yelams yelmas yelmsa ylmsea ylmsae ylmesa ylmeas ylmaes
ylmase ylsmea ylsmae ylsema ylseam ylsaem ylsame ylesma ylesam ylemsa ylemas
yleams yleasm ylasem ylasme ylaesm ylaems ylames ylamse saymel saymle sayeml
sayelm saylem saylme samyel samyle sameyl samely samley samlye saemyl saemly
saeyml saeylm saelym saelmy salmey salmye salemy saleym salyem salyme syamel
syamle syaeml syaelm syalem syalme symael symale symeal symela symlea symlae
syemal syemla syeaml syealm syelam syelma sylmea sylmae sylema syleam sylaem
sylame smyael smyale smyeal smyela smylea smylae smayel smayle smaeyl smaely
smaley smalye smeayl smealy smeyal smeyla smelya smelay smlaey smlaye smleay
smleya smlyea smlyae seymal seymla seyaml seyalm seylam seylma semyal semyla
semayl semaly semlay semlya seamyl seamly seayml seaylm sealym sealmy selmay
selmya selamy selaym selyam selyma slymea slymae slyema slyeam slyaem slyame
slmyea slmyae slmeya slmeay slmaey slmaye slemya slemay sleyma sleyam sleaym
sleamy slamey slamye slaemy slaeym slayem slayme eaysml eayslm eaymsl eaymls
eaylms eaylsm easyml easylm easmyl easmly easlmy easlym eamsyl eamsly eamysl
eamyls eamlys eamlsy ealsmy ealsym ealmsy ealmys ealyms ealysm eyasml eyaslm
eyamsl eyamls eyalms eyalsm eysaml eysalm eysmal eysmla eyslma eyslam eymsal
eymsla eymasl eymals eymlas eymlsa eylsma eylsam eylmsa eylmas eylams eylasm
esyaml esyalm esymal esymla esylma esylam esayml esaylm esamyl esamly esalmy
esalym esmayl esmaly esmyal esmyla esmlya esmlay eslamy eslaym eslmay eslmya
eslyma eslyam emysal emysla emyasl emyals emylas emylsa emsyal emsyla emsayl
emsaly emslay emslya emasyl emasly emaysl emayls emalys emalsy emlsay emlsya
emlasy emlays emlyas emlysa elysma elysam elymsa elymas elyams elyasm elsyma
elsyam elsmya elsmay elsamy elsaym elmsya elmsay elmysa elmyas elmays elmasy
elasmy elasym elamsy elamys elayms elaysm laysem laysme layesm layems laymes
laymse lasyem lasyme laseym lasemy lasmey lasmye laesym laesmy laeysm laeyms
laemys laemsy lamsey lamsye lamesy lameys lamyes lamyse lyasem lyasme lyaesm
lyaems lyames lyamse lysaem lysame lyseam lysema lysmea lysmae lyesam lyesma
lyeasm lyeams lyemas lyemsa lymsea lymsae lymesa lymeas lymaes lymase lsyaem
lsyame lsyeam lsyema lsymea lsymae lsayem lsayme lsaeym lsaemy lsamey lsamye
lseaym lseamy lseyam lseyma lsemya lsemay lsmaey lsmaye lsmeay lsmeya lsmyea
lsmyae leysam leysma leyasm leyams leymas leymsa lesyam lesyma lesaym lesamy
lesmay lesmya leasym leasmy leaysm leayms leamys leamsy lemsay lemsya lemasy
lemays lemyas lemysa lmysea lmysae lmyesa lmyeas lmyaes lmyase lmsyea lmsyae
lmseya lmseay lmsaey lmsaye lmesya lmesay lmeysa lmeyas lmeays lmeasy lmasey
lmasye lmaesy lmaeys lmayes lmayse

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History of cryptography
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