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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: mactwo
cipher variations:
nbduxp ocevyq pdfwzr qegxas rfhybt
sgizcu thjadv uikbew vjlcfx wkmdgy
xlnehz ymofia znpgjb aoqhkc bprild
cqsjme drtknf esulog ftvmph guwnqi
hvxorj iwypsk jxzqtl kyarum lzbsvn

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: mactwo
Cipher: nzxgdl

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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: mactwo

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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: mactwo
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: mactwo
Cipher: znpgjb

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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: mactwo
Cipher: 231131442543

Extended Methods:
Method #1

Plaintext: mactwo
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 c t w o 
2 1 3 4 2 4 
3 1 1 4 5 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: mactwo
Cipher: bsrcqp

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Method #3

Plaintext: mactwo
method variations:
clqiuh lqiuhc qiuhcl
iuhclq uhclqi hclqiu

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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: mactwo

all 720 cipher variations:
mactwo mactow macwto macwot macowt macotw matcwo matcow matwco matwoc matowc
matocw mawtco mawtoc mawcto mawcot mawoct mawotc maotwc maotcw maowtc maowct
maocwt maoctw mcatwo mcatow mcawto mcawot mcaowt mcaotw mctawo mctaow mctwao
mctwoa mctowa mctoaw mcwtao mcwtoa mcwato mcwaot mcwoat mcwota mcotwa mcotaw
mcowta mcowat mcoawt mcoatw mtcawo mtcaow mtcwao mtcwoa mtcowa mtcoaw mtacwo
mtacow mtawco mtawoc mtaowc mtaocw mtwaco mtwaoc mtwcao mtwcoa mtwoca mtwoac
mtoawc mtoacw mtowac mtowca mtocwa mtocaw mwctao mwctoa mwcato mwcaot mwcoat
mwcota mwtcao mwtcoa mwtaco mwtaoc mwtoac mwtoca mwatco mwatoc mwacto mwacot
mwaoct mwaotc mwotac mwotca mwoatc mwoact mwocat mwocta moctwa moctaw mocwta
mocwat mocawt mocatw motcwa motcaw motwca motwac motawc motacw mowtca mowtac
mowcta mowcat mowact mowatc moatwc moatcw moawtc moawct moacwt moactw amctwo
amctow amcwto amcwot amcowt amcotw amtcwo amtcow amtwco amtwoc amtowc amtocw
amwtco amwtoc amwcto amwcot amwoct amwotc amotwc amotcw amowtc amowct amocwt
amoctw acmtwo acmtow acmwto acmwot acmowt acmotw actmwo actmow actwmo actwom
actowm actomw acwtmo acwtom acwmto acwmot acwomt acwotm acotwm acotmw acowtm
acowmt acomwt acomtw atcmwo atcmow atcwmo atcwom atcowm atcomw atmcwo atmcow
atmwco atmwoc atmowc atmocw atwmco atwmoc atwcmo atwcom atwocm atwomc atomwc
atomcw atowmc atowcm atocwm atocmw awctmo awctom awcmto awcmot awcomt awcotm
awtcmo awtcom awtmco awtmoc awtomc awtocm awmtco awmtoc awmcto awmcot awmoct
awmotc awotmc awotcm awomtc awomct awocmt awoctm aoctwm aoctmw aocwtm aocwmt
aocmwt aocmtw aotcwm aotcmw aotwcm aotwmc aotmwc aotmcw aowtcm aowtmc aowctm
aowcmt aowmct aowmtc aomtwc aomtcw aomwtc aomwct aomcwt aomctw camtwo camtow
camwto camwot camowt camotw catmwo catmow catwmo catwom catowm catomw cawtmo
cawtom cawmto cawmot cawomt cawotm caotwm caotmw caowtm caowmt caomwt caomtw
cmatwo cmatow cmawto cmawot cmaowt cmaotw cmtawo cmtaow cmtwao cmtwoa cmtowa
cmtoaw cmwtao cmwtoa cmwato cmwaot cmwoat cmwota cmotwa cmotaw cmowta cmowat
cmoawt cmoatw ctmawo ctmaow ctmwao ctmwoa ctmowa ctmoaw ctamwo ctamow ctawmo
ctawom ctaowm ctaomw ctwamo ctwaom ctwmao ctwmoa ctwoma ctwoam ctoawm ctoamw
ctowam ctowma ctomwa ctomaw cwmtao cwmtoa cwmato cwmaot cwmoat cwmota cwtmao
cwtmoa cwtamo cwtaom cwtoam cwtoma cwatmo cwatom cwamto cwamot cwaomt cwaotm
cwotam cwotma cwoatm cwoamt cwomat cwomta comtwa comtaw comwta comwat comawt
comatw cotmwa cotmaw cotwma cotwam cotawm cotamw cowtma cowtam cowmta cowmat
cowamt cowatm coatwm coatmw coawtm coawmt coamwt coamtw tacmwo tacmow tacwmo
tacwom tacowm tacomw tamcwo tamcow tamwco tamwoc tamowc tamocw tawmco tawmoc
tawcmo tawcom tawocm tawomc taomwc taomcw taowmc taowcm taocwm taocmw tcamwo
tcamow tcawmo tcawom tcaowm tcaomw tcmawo tcmaow tcmwao tcmwoa tcmowa tcmoaw
tcwmao tcwmoa tcwamo tcwaom tcwoam tcwoma tcomwa tcomaw tcowma tcowam tcoawm
tcoamw tmcawo tmcaow tmcwao tmcwoa tmcowa tmcoaw tmacwo tmacow tmawco tmawoc
tmaowc tmaocw tmwaco tmwaoc tmwcao tmwcoa tmwoca tmwoac tmoawc tmoacw tmowac
tmowca tmocwa tmocaw twcmao twcmoa twcamo twcaom twcoam twcoma twmcao twmcoa
twmaco twmaoc twmoac twmoca twamco twamoc twacmo twacom twaocm twaomc twomac
twomca twoamc twoacm twocam twocma tocmwa tocmaw tocwma tocwam tocawm tocamw
tomcwa tomcaw tomwca tomwac tomawc tomacw towmca towmac towcma towcam towacm
towamc toamwc toamcw toawmc toawcm toacwm toacmw wactmo wactom wacmto wacmot
wacomt wacotm watcmo watcom watmco watmoc watomc watocm wamtco wamtoc wamcto
wamcot wamoct wamotc waotmc waotcm waomtc waomct waocmt waoctm wcatmo wcatom
wcamto wcamot wcaomt wcaotm wctamo wctaom wctmao wctmoa wctoma wctoam wcmtao
wcmtoa wcmato wcmaot wcmoat wcmota wcotma wcotam wcomta wcomat wcoamt wcoatm
wtcamo wtcaom wtcmao wtcmoa wtcoma wtcoam wtacmo wtacom wtamco wtamoc wtaomc
wtaocm wtmaco wtmaoc wtmcao wtmcoa wtmoca wtmoac wtoamc wtoacm wtomac wtomca
wtocma wtocam wmctao wmctoa wmcato wmcaot wmcoat wmcota wmtcao wmtcoa wmtaco
wmtaoc wmtoac wmtoca wmatco wmatoc wmacto wmacot wmaoct wmaotc wmotac wmotca
wmoatc wmoact wmocat wmocta woctma woctam wocmta wocmat wocamt wocatm wotcma
wotcam wotmca wotmac wotamc wotacm womtca womtac womcta womcat womact womatc
woatmc woatcm woamtc woamct woacmt woactm oactwm oactmw oacwtm oacwmt oacmwt
oacmtw oatcwm oatcmw oatwcm oatwmc oatmwc oatmcw oawtcm oawtmc oawctm oawcmt
oawmct oawmtc oamtwc oamtcw oamwtc oamwct oamcwt oamctw ocatwm ocatmw ocawtm
ocawmt ocamwt ocamtw octawm octamw octwam octwma octmwa octmaw ocwtam ocwtma
ocwatm ocwamt ocwmat ocwmta ocmtwa ocmtaw ocmwta ocmwat ocmawt ocmatw otcawm
otcamw otcwam otcwma otcmwa otcmaw otacwm otacmw otawcm otawmc otamwc otamcw
otwacm otwamc otwcam otwcma otwmca otwmac otmawc otmacw otmwac otmwca otmcwa
otmcaw owctam owctma owcatm owcamt owcmat owcmta owtcam owtcma owtacm owtamc
owtmac owtmca owatcm owatmc owactm owacmt owamct owamtc owmtac owmtca owmatc
owmact owmcat owmcta omctwa omctaw omcwta omcwat omcawt omcatw omtcwa omtcaw
omtwca omtwac omtawc omtacw omwtca omwtac omwcta omwcat omwact omwatc omatwc
omatcw omawtc omawct omacwt omactw

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History of cryptography
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