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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: widell
cipher variations:
xjefmm ykfgnn zlghoo amhipp bnijqq
cojkrr dpklss eqlmtt frmnuu gsnovv
htopww iupqxx jvqryy kwrszz lxstaa
mytubb nzuvcc oavwdd pbwxee qcxyff
rdyzgg sezahh tfabii ugbcjj vhcdkk

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: widell
Cipher: drwvoo

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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: widell

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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: widell
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: widell
Cipher: jvqryy

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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: widell
Cipher: 254241511313

Extended Methods:
Method #1

Plaintext: widell
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
w i d e l l 
2 4 4 5 1 1 
5 2 1 1 3 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: widell
Cipher: ryakan

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Method #3

Plaintext: widell
method variations:
urvach rvachu vachur
achurv churva hurvac

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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: widell

all 720 cipher variations:
widell widell widlel widlle widlle widlel wiedll wiedll wieldl wielld wielld
wieldl wiledl wileld wildel wildle willde willed wileld wiledl willed willde
wildle wildel wdiell wdiell wdilel wdille wdille wdilel wdeill wdeill wdelil
wdelli wdelli wdelil wdleil wdleli wdliel wdlile wdllie wdllei wdleli wdleil
wdllei wdllie wdlile wdliel wedill wedill wedlil wedlli wedlli wedlil weidll
weidll weildl weilld weilld weildl welidl welild weldil weldli welldi wellid
welild welidl wellid welldi weldli weldil wldeil wldeli wldiel wldile wldlie
wldlei wledil wledli wleidl wleild wlelid wleldi wliedl wlield wlidel wlidle
wlilde wliled wlleid wlledi wllied wllide wlldie wlldei wldeli wldeil wldlei
wldlie wldile wldiel wledli wledil wleldi wlelid wleild wleidl wlledi wlleid
wlldei wlldie wllide wllied wlield wliedl wliled wlilde wlidle wlidel iwdell
iwdell iwdlel iwdlle iwdlle iwdlel iwedll iwedll iweldl iwelld iwelld iweldl
iwledl iwleld iwldel iwldle iwllde iwlled iwleld iwledl iwlled iwllde iwldle
iwldel idwell idwell idwlel idwlle idwlle idwlel idewll idewll idelwl idellw
idellw idelwl idlewl idlelw idlwel idlwle idllwe idllew idlelw idlewl idllew
idllwe idlwle idlwel iedwll iedwll iedlwl iedllw iedllw iedlwl iewdll iewdll
iewldl iewlld iewlld iewldl ielwdl ielwld ieldwl ieldlw ielldw iellwd ielwld
ielwdl iellwd ielldw ieldlw ieldwl ildewl ildelw ildwel ildwle ildlwe ildlew
iledwl iledlw ilewdl ilewld ilelwd ileldw ilwedl ilweld ilwdel ilwdle ilwlde
ilwled illewd illedw illwed illwde illdwe illdew ildelw ildewl ildlew ildlwe
ildwle ildwel iledlw iledwl ileldw ilelwd ilewld ilewdl illedw illewd illdew
illdwe illwde illwed ilweld ilwedl ilwled ilwlde ilwdle ilwdel diwell diwell
diwlel diwlle diwlle diwlel diewll diewll dielwl diellw diellw dielwl dilewl
dilelw dilwel dilwle dillwe dillew dilelw dilewl dillew dillwe dilwle dilwel
dwiell dwiell dwilel dwille dwille dwilel dweill dweill dwelil dwelli dwelli
dwelil dwleil dwleli dwliel dwlile dwllie dwllei dwleli dwleil dwllei dwllie
dwlile dwliel dewill dewill dewlil dewlli dewlli dewlil deiwll deiwll deilwl
deillw deillw deilwl deliwl delilw delwil delwli dellwi delliw delilw deliwl
delliw dellwi delwli delwil dlweil dlweli dlwiel dlwile dlwlie dlwlei dlewil
dlewli dleiwl dleilw dleliw dlelwi dliewl dlielw dliwel dliwle dlilwe dlilew
dlleiw dllewi dlliew dlliwe dllwie dllwei dlweli dlweil dlwlei dlwlie dlwile
dlwiel dlewli dlewil dlelwi dleliw dleilw dleiwl dllewi dlleiw dllwei dllwie
dlliwe dlliew dlielw dliewl dlilew dlilwe dliwle dliwel eidwll eidwll eidlwl
eidllw eidllw eidlwl eiwdll eiwdll eiwldl eiwlld eiwlld eiwldl eilwdl eilwld
eildwl eildlw eilldw eillwd eilwld eilwdl eillwd eilldw eildlw eildwl ediwll
ediwll edilwl edillw edillw edilwl edwill edwill edwlil edwlli edwlli edwlil
edlwil edlwli edliwl edlilw edlliw edllwi edlwli edlwil edllwi edlliw edlilw
edliwl ewdill ewdill ewdlil ewdlli ewdlli ewdlil ewidll ewidll ewildl ewilld
ewilld ewildl ewlidl ewlild ewldil ewldli ewlldi ewllid ewlild ewlidl ewllid
ewlldi ewldli ewldil eldwil eldwli eldiwl eldilw eldliw eldlwi elwdil elwdli
elwidl elwild elwlid elwldi eliwdl eliwld elidwl elidlw elildw elilwd ellwid
ellwdi elliwd ellidw elldiw elldwi eldwli eldwil eldlwi eldliw eldilw eldiwl
elwdli elwdil elwldi elwlid elwild elwidl ellwdi ellwid elldwi elldiw ellidw
elliwd eliwld eliwdl elilwd elildw elidlw elidwl lidewl lidelw lidwel lidwle
lidlwe lidlew liedwl liedlw liewdl liewld lielwd lieldw liwedl liweld liwdel
liwdle liwlde liwled lilewd liledw lilwed lilwde lildwe lildew ldiewl ldielw
ldiwel ldiwle ldilwe ldilew ldeiwl ldeilw ldewil ldewli ldelwi ldeliw ldweil
ldweli ldwiel ldwile ldwlie ldwlei ldlewi ldleiw ldlwei ldlwie ldliwe ldliew
lediwl ledilw ledwil ledwli ledlwi ledliw leidwl leidlw leiwdl leiwld leilwd
leildw lewidl lewild lewdil lewdli lewldi lewlid leliwd lelidw lelwid lelwdi
leldwi leldiw lwdeil lwdeli lwdiel lwdile lwdlie lwdlei lwedil lwedli lweidl
lweild lwelid lweldi lwiedl lwield lwidel lwidle lwilde lwiled lwleid lwledi
lwlied lwlide lwldie lwldei lldewi lldeiw lldwei lldwie lldiwe lldiew lledwi
llediw llewdi llewid lleiwd lleidw llwedi llweid llwdei llwdie llwide llwied
lliewd lliedw lliwed lliwde llidwe llidew lidelw lidewl lidlew lidlwe lidwle
lidwel liedlw liedwl lieldw lielwd liewld liewdl liledw lilewd lildew lildwe
lilwde lilwed liweld liwedl liwled liwlde liwdle liwdel ldielw ldiewl ldilew
ldilwe ldiwle ldiwel ldeilw ldeiwl ldeliw ldelwi ldewli ldewil ldleiw ldlewi
ldliew ldliwe ldlwie ldlwei ldweli ldweil ldwlei ldwlie ldwile ldwiel ledilw
lediwl ledliw ledlwi ledwli ledwil leidlw leidwl leildw leilwd leiwld leiwdl
lelidw leliwd leldiw leldwi lelwdi lelwid lewild lewidl lewlid lewldi lewdli
lewdil lldeiw lldewi lldiew lldiwe lldwie lldwei llediw lledwi lleidw lleiwd
llewid llewdi lliedw lliewd llidew llidwe lliwde lliwed llweid llwedi llwied
llwide llwdie llwdei lwdeli lwdeil lwdlei lwdlie lwdile lwdiel lwedli lwedil
lweldi lwelid lweild lweidl lwledi lwleid lwldei lwldie lwlide lwlied lwield
lwiedl lwiled lwilde lwidle lwidel

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History of cryptography
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