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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: besmut
cipher variations:
cftnvu dguowv ehvpxw fiwqyx gjxrzy
hkysaz ilztba jmaucb knbvdc locwed
mpdxfe nqeygf orfzhg psgaih qthbji
ruickj svjdlk twkeml uxlfnm vymgon
wznhpo xaoiqp ybpjrq zcqksr adrlts

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: besmut
Cipher: yvhnfg

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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: besmut

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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: besmut
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: besmut
Cipher: orfzhg

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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: besmut
Cipher: 215134235444

Extended Methods:
Method #1

Plaintext: besmut
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
b e s m u t 
2 5 3 2 5 4 
1 1 4 3 4 4 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: besmut
Cipher: whuaot

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Method #3

Plaintext: besmut
method variations:
vlixti lixtiv ixtivl
xtivli tivlix ivlixt

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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: besmut

all 720 cipher variations:
besmut besmtu besumt besutm bestum bestmu bemsut bemstu bemust bemuts bemtus
bemtsu beumst beumts beusmt beustm beutsm beutms betmus betmsu betums betusm
betsum betsmu bsemut bsemtu bseumt bseutm bsetum bsetmu bsmeut bsmetu bsmuet
bsmute bsmtue bsmteu bsumet bsumte bsuemt bsuetm bsutem bsutme bstmue bstmeu
bstume bstuem bsteum bstemu bmseut bmsetu bmsuet bmsute bmstue bmsteu bmesut
bmestu bmeust bmeuts bmetus bmetsu bmuest bmuets bmuset bmuste bmutse bmutes
bmteus bmtesu bmtues bmtuse bmtsue bmtseu busmet busmte busemt busetm bustem
bustme bumset bumste bumest bumets bumtes bumtse buemst buemts buesmt buestm
buetsm buetms butmes butmse butems butesm butsem butsme btsmue btsmeu btsume
btsuem btseum btsemu btmsue btmseu btmuse btmues btmeus btmesu btumse btumes
btusme btusem btuesm btuems btemus btemsu bteums bteusm btesum btesmu ebsmut
ebsmtu ebsumt ebsutm ebstum ebstmu ebmsut ebmstu ebmust ebmuts ebmtus ebmtsu
ebumst ebumts ebusmt ebustm ebutsm ebutms ebtmus ebtmsu ebtums ebtusm ebtsum
ebtsmu esbmut esbmtu esbumt esbutm esbtum esbtmu esmbut esmbtu esmubt esmutb
esmtub esmtbu esumbt esumtb esubmt esubtm esutbm esutmb estmub estmbu estumb
estubm estbum estbmu emsbut emsbtu emsubt emsutb emstub emstbu embsut embstu
embust embuts embtus embtsu emubst emubts emusbt emustb emutsb emutbs emtbus
emtbsu emtubs emtusb emtsub emtsbu eusmbt eusmtb eusbmt eusbtm eustbm eustmb
eumsbt eumstb eumbst eumbts eumtbs eumtsb eubmst eubmts eubsmt eubstm eubtsm
eubtms eutmbs eutmsb eutbms eutbsm eutsbm eutsmb etsmub etsmbu etsumb etsubm
etsbum etsbmu etmsub etmsbu etmusb etmubs etmbus etmbsu etumsb etumbs etusmb
etusbm etubsm etubms etbmus etbmsu etbums etbusm etbsum etbsmu sebmut sebmtu
sebumt sebutm sebtum sebtmu sembut sembtu semubt semutb semtub semtbu seumbt
seumtb seubmt seubtm seutbm seutmb setmub setmbu setumb setubm setbum setbmu
sbemut sbemtu sbeumt sbeutm sbetum sbetmu sbmeut sbmetu sbmuet sbmute sbmtue
sbmteu sbumet sbumte sbuemt sbuetm sbutem sbutme sbtmue sbtmeu sbtume sbtuem
sbteum sbtemu smbeut smbetu smbuet smbute smbtue smbteu smebut smebtu smeubt
smeutb smetub smetbu smuebt smuetb smubet smubte smutbe smuteb smteub smtebu
smtueb smtube smtbue smtbeu submet submte subemt subetm subtem subtme sumbet
sumbte sumebt sumetb sumteb sumtbe suembt suemtb suebmt suebtm suetbm suetmb
sutmeb sutmbe sutemb sutebm sutbem sutbme stbmue stbmeu stbume stbuem stbeum
stbemu stmbue stmbeu stmube stmueb stmeub stmebu stumbe stumeb stubme stubem
stuebm stuemb stemub stembu steumb steubm stebum stebmu mesbut mesbtu mesubt
mesutb mestub mestbu mebsut mebstu mebust mebuts mebtus mebtsu meubst meubts
meusbt meustb meutsb meutbs metbus metbsu metubs metusb metsub metsbu msebut
msebtu mseubt mseutb msetub msetbu msbeut msbetu msbuet msbute msbtue msbteu
msubet msubte msuebt msuetb msuteb msutbe mstbue mstbeu mstube mstueb msteub
mstebu mbseut mbsetu mbsuet mbsute mbstue mbsteu mbesut mbestu mbeust mbeuts
mbetus mbetsu mbuest mbuets mbuset mbuste mbutse mbutes mbteus mbtesu mbtues
mbtuse mbtsue mbtseu musbet musbte musebt musetb musteb mustbe mubset mubste
mubest mubets mubtes mubtse muebst muebts muesbt muestb muetsb muetbs mutbes
mutbse mutebs mutesb mutseb mutsbe mtsbue mtsbeu mtsube mtsueb mtseub mtsebu
mtbsue mtbseu mtbuse mtbues mtbeus mtbesu mtubse mtubes mtusbe mtuseb mtuesb
mtuebs mtebus mtebsu mteubs mteusb mtesub mtesbu uesmbt uesmtb uesbmt uesbtm
uestbm uestmb uemsbt uemstb uembst uembts uemtbs uemtsb uebmst uebmts uebsmt
uebstm uebtsm uebtms uetmbs uetmsb uetbms uetbsm uetsbm uetsmb usembt usemtb
usebmt usebtm usetbm usetmb usmebt usmetb usmbet usmbte usmtbe usmteb usbmet
usbmte usbemt usbetm usbtem usbtme ustmbe ustmeb ustbme ustbem ustebm ustemb
umsebt umsetb umsbet umsbte umstbe umsteb umesbt umestb umebst umebts umetbs
umetsb umbest umbets umbset umbste umbtse umbtes umtebs umtesb umtbes umtbse
umtsbe umtseb ubsmet ubsmte ubsemt ubsetm ubstem ubstme ubmset ubmste ubmest
ubmets ubmtes ubmtse ubemst ubemts ubesmt ubestm ubetsm ubetms ubtmes ubtmse
ubtems ubtesm ubtsem ubtsme utsmbe utsmeb utsbme utsbem utsebm utsemb utmsbe
utmseb utmbse utmbes utmebs utmesb utbmse utbmes utbsme utbsem utbesm utbems
utembs utemsb utebms utebsm utesbm utesmb tesmub tesmbu tesumb tesubm tesbum
tesbmu temsub temsbu temusb temubs tembus tembsu teumsb teumbs teusmb teusbm
teubsm teubms tebmus tebmsu tebums tebusm tebsum tebsmu tsemub tsembu tseumb
tseubm tsebum tsebmu tsmeub tsmebu tsmueb tsmube tsmbue tsmbeu tsumeb tsumbe
tsuemb tsuebm tsubem tsubme tsbmue tsbmeu tsbume tsbuem tsbeum tsbemu tmseub
tmsebu tmsueb tmsube tmsbue tmsbeu tmesub tmesbu tmeusb tmeubs tmebus tmebsu
tmuesb tmuebs tmuseb tmusbe tmubse tmubes tmbeus tmbesu tmbues tmbuse tmbsue
tmbseu tusmeb tusmbe tusemb tusebm tusbem tusbme tumseb tumsbe tumesb tumebs
tumbes tumbse tuemsb tuembs tuesmb tuesbm tuebsm tuebms tubmes tubmse tubems
tubesm tubsem tubsme tbsmue tbsmeu tbsume tbsuem tbseum tbsemu tbmsue tbmseu
tbmuse tbmues tbmeus tbmesu tbumse tbumes tbusme tbusem tbuesm tbuems tbemus
tbemsu tbeums tbeusm tbesum tbesmu

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History of cryptography
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