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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: verbal
cipher variations:
wfscbm xgtdcn yhuedo zivfep ajwgfq
bkxhgr clyihs dmzjit enakju foblkv
gpcmlw hqdnmx ireony jsfpoz ktgqpa
luhrqb mvisrc nwjtsd oxkute pylvuf
qzmwvg ranxwh sboyxi tcpzyj udqazk

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: verbal
Cipher: eviyzo

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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: verbal

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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: verbal
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: verbal
Cipher: ireony

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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: verbal
Cipher: 155124211113

Extended Methods:
Method #1

Plaintext: verbal
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
v e r b a l 
1 5 2 2 1 1 
5 1 4 1 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: verbal
Cipher: vgaedl

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Method #3

Plaintext: verbal
method variations:
zfiaac fiaacz iaaczf
aaczfi aczfia czfiaa

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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: verbal

all 720 cipher variations:
verbal verbla verabl veralb verlab verlba vebral vebrla vebarl vebalr veblar
veblra veabrl veablr vearbl vearlb vealrb vealbr velbar velbra velabr velarb
velrab velrba vrebal vrebla vreabl vrealb vrelab vrelba vrbeal vrbela vrbael
vrbale vrblae vrblea vrabel vrable vraebl vraelb vraleb vralbe vrlbae vrlbea
vrlabe vrlaeb vrleab vrleba vbreal vbrela vbrael vbrale vbrlae vbrlea vberal
vberla vbearl vbealr vbelar vbelra vbaerl vbaelr vbarel vbarle vbalre vbaler
vblear vblera vblaer vblare vblrae vblrea varbel varble varebl varelb varleb
varlbe vabrel vabrle vaberl vabelr vabler vablre vaebrl vaeblr vaerbl vaerlb
vaelrb vaelbr valber valbre valebr valerb valreb valrbe vlrbae vlrbea vlrabe
vlraeb vlreab vlreba vlbrae vlbrea vlbare vlbaer vlbear vlbera vlabre vlaber
vlarbe vlareb vlaerb vlaebr vlebar vlebra vleabr vlearb vlerab vlerba evrbal
evrbla evrabl evralb evrlab evrlba evbral evbrla evbarl evbalr evblar evblra
evabrl evablr evarbl evarlb evalrb evalbr evlbar evlbra evlabr evlarb evlrab
evlrba ervbal ervbla ervabl ervalb ervlab ervlba erbval erbvla erbavl erbalv
erblav erblva erabvl erablv eravbl eravlb eralvb eralbv erlbav erlbva erlabv
erlavb erlvab erlvba ebrval ebrvla ebravl ebralv ebrlav ebrlva ebvral ebvrla
ebvarl ebvalr ebvlar ebvlra ebavrl ebavlr ebarvl ebarlv ebalrv ebalvr eblvar
eblvra eblavr eblarv eblrav eblrva earbvl earblv earvbl earvlb earlvb earlbv
eabrvl eabrlv eabvrl eabvlr eablvr eablrv eavbrl eavblr eavrbl eavrlb eavlrb
eavlbr ealbvr ealbrv ealvbr ealvrb ealrvb ealrbv elrbav elrbva elrabv elravb
elrvab elrvba elbrav elbrva elbarv elbavr elbvar elbvra elabrv elabvr elarbv
elarvb elavrb elavbr elvbar elvbra elvabr elvarb elvrab elvrba revbal revbla
revabl revalb revlab revlba rebval rebvla rebavl rebalv reblav reblva reabvl
reablv reavbl reavlb realvb realbv relbav relbva relabv relavb relvab relvba
rvebal rvebla rveabl rvealb rvelab rvelba rvbeal rvbela rvbael rvbale rvblae
rvblea rvabel rvable rvaebl rvaelb rvaleb rvalbe rvlbae rvlbea rvlabe rvlaeb
rvleab rvleba rbveal rbvela rbvael rbvale rbvlae rbvlea rbeval rbevla rbeavl
rbealv rbelav rbelva rbaevl rbaelv rbavel rbavle rbalve rbalev rbleav rbleva
rblaev rblave rblvae rblvea ravbel ravble ravebl ravelb ravleb ravlbe rabvel
rabvle rabevl rabelv rablev rablve raebvl raeblv raevbl raevlb raelvb raelbv
ralbev ralbve ralebv ralevb ralveb ralvbe rlvbae rlvbea rlvabe rlvaeb rlveab
rlveba rlbvae rlbvea rlbave rlbaev rlbeav rlbeva rlabve rlabev rlavbe rlaveb
rlaevb rlaebv rlebav rlebva rleabv rleavb rlevab rlevba berval bervla beravl
beralv berlav berlva bevral bevrla bevarl bevalr bevlar bevlra beavrl beavlr
bearvl bearlv bealrv bealvr belvar belvra belavr belarv belrav belrva breval
brevla breavl brealv brelav brelva brveal brvela brvael brvale brvlae brvlea
bravel bravle braevl braelv bralev bralve brlvae brlvea brlave brlaev brleav
brleva bvreal bvrela bvrael bvrale bvrlae bvrlea bveral bverla bvearl bvealr
bvelar bvelra bvaerl bvaelr bvarel bvarle bvalre bvaler bvlear bvlera bvlaer
bvlare bvlrae bvlrea barvel barvle barevl barelv barlev barlve bavrel bavrle
baverl bavelr bavler bavlre baevrl baevlr baervl baerlv baelrv baelvr balver
balvre balevr balerv balrev balrve blrvae blrvea blrave blraev blreav blreva
blvrae blvrea blvare blvaer blvear blvera blavre blaver blarve blarev blaerv
blaevr blevar blevra bleavr blearv blerav blerva aerbvl aerblv aervbl aervlb
aerlvb aerlbv aebrvl aebrlv aebvrl aebvlr aeblvr aeblrv aevbrl aevblr aevrbl
aevrlb aevlrb aevlbr aelbvr aelbrv aelvbr aelvrb aelrvb aelrbv arebvl areblv
arevbl arevlb arelvb arelbv arbevl arbelv arbvel arbvle arblve arblev arvbel
arvble arvebl arvelb arvleb arvlbe arlbve arlbev arlvbe arlveb arlevb arlebv
abrevl abrelv abrvel abrvle abrlve abrlev abervl aberlv abevrl abevlr abelvr
abelrv abverl abvelr abvrel abvrle abvlre abvler ablevr ablerv ablver ablvre
ablrve ablrev avrbel avrble avrebl avrelb avrleb avrlbe avbrel avbrle avberl
avbelr avbler avblre avebrl aveblr averbl averlb avelrb avelbr avlber avlbre
avlebr avlerb avlreb avlrbe alrbve alrbev alrvbe alrveb alrevb alrebv albrve
albrev albvre albver albevr alberv alvbre alvber alvrbe alvreb alverb alvebr
alebvr alebrv alevbr alevrb alervb alerbv lerbav lerbva lerabv leravb lervab
lervba lebrav lebrva lebarv lebavr lebvar lebvra leabrv leabvr learbv learvb
leavrb leavbr levbar levbra levabr levarb levrab levrba lrebav lrebva lreabv
lreavb lrevab lrevba lrbeav lrbeva lrbaev lrbave lrbvae lrbvea lrabev lrabve
lraebv lraevb lraveb lravbe lrvbae lrvbea lrvabe lrvaeb lrveab lrveba lbreav
lbreva lbraev lbrave lbrvae lbrvea lberav lberva lbearv lbeavr lbevar lbevra
lbaerv lbaevr lbarev lbarve lbavre lbaver lbvear lbvera lbvaer lbvare lbvrae
lbvrea larbev larbve larebv larevb larveb larvbe labrev labrve laberv labevr
labver labvre laebrv laebvr laerbv laervb laevrb laevbr lavber lavbre lavebr
laverb lavreb lavrbe lvrbae lvrbea lvrabe lvraeb lvreab lvreba lvbrae lvbrea
lvbare lvbaer lvbear lvbera lvabre lvaber lvarbe lvareb lvaerb lvaebr lvebar
lvebra lveabr lvearb lverab lverba

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History of cryptography
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