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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: sairve
cipher variations:
tbjswf ucktxg vdluyh wemvzi xfnwaj
ygoxbk zhpycl aiqzdm bjraen cksbfo
dltcgp emudhq fnveir gowfjs hpxgkt
iqyhlu jrzimv ksajnw ltbkox muclpy
nvdmqz owenra pxfosb qygptc rzhqud

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: sairve
Cipher: hzriev

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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: sairve

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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: sairve
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: sairve
Cipher: fnveir

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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: sairve
Cipher: 341142241551

Extended Methods:
Method #1

Plaintext: sairve
method variations:

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

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Method #3

Plaintext: sairve
method variations:
dqgdzl qgdzld gdzldq
dzldqg zldqgd ldqgdz

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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: sairve

all 720 cipher variations:
sairve sairev saivre saiver saievr saierv sarive sariev sarvie sarvei sarevi
sareiv savrie savrei savire savier saveir saveri saervi saeriv saevri saevir
saeivr saeirv siarve siarev siavre siaver siaevr siaerv sirave siraev sirvae
sirvea sireva sireav sivrae sivrea sivare sivaer sivear sivera sierva sierav
sievra sievar sieavr siearv sriave sriaev srivae srivea srieva srieav sraive
sraiev sravie sravei sraevi sraeiv srvaie srvaei srviae srviea srveia srveai
sreavi sreaiv srevai srevia sreiva sreiav svirae svirea sviare sviaer sviear
sviera svriae svriea svraie svraei svreai svreia svarie svarei svaire svaier
svaeir svaeri sverai sveria sveari sveair sveiar sveira seirva seirav seivra
seivar seiavr seiarv seriva seriav servia servai seravi seraiv sevria sevrai
sevira seviar sevair sevari searvi seariv seavri seavir seaivr seairv asirve
asirev asivre asiver asievr asierv asrive asriev asrvie asrvei asrevi asreiv
asvrie asvrei asvire asvier asveir asveri aservi aseriv asevri asevir aseivr
aseirv aisrve aisrev aisvre aisver aisevr aiserv airsve airsev airvse airves
airevs airesv aivrse aivres aivsre aivser aivesr aivers aiervs aiersv aievrs
aievsr aiesvr aiesrv arisve arisev arivse arives arievs ariesv arsive arsiev
arsvie arsvei arsevi arseiv arvsie arvsei arvise arvies arveis arvesi aresvi
aresiv arevsi arevis areivs areisv avirse avires avisre aviser aviesr aviers
avrise avries avrsie avrsei avresi avreis avsrie avsrei avsire avsier avseir
avseri aversi averis avesri avesir aveisr aveirs aeirvs aeirsv aeivrs aeivsr
aeisvr aeisrv aerivs aerisv aervis aervsi aersvi aersiv aevris aevrsi aevirs
aevisr aevsir aevsri aesrvi aesriv aesvri aesvir aesivr aesirv iasrve iasrev
iasvre iasver iasevr iaserv iarsve iarsev iarvse iarves iarevs iaresv iavrse
iavres iavsre iavser iavesr iavers iaervs iaersv iaevrs iaevsr iaesvr iaesrv
isarve isarev isavre isaver isaevr isaerv israve israev isrvae isrvea isreva
isreav isvrae isvrea isvare isvaer isvear isvera iserva iserav isevra isevar
iseavr isearv irsave irsaev irsvae irsvea irseva irseav irasve irasev iravse
iraves iraevs iraesv irvase irvaes irvsae irvsea irvesa irveas ireavs ireasv
irevas irevsa iresva iresav ivsrae ivsrea ivsare ivsaer ivsear ivsera ivrsae
ivrsea ivrase ivraes ivreas ivresa ivarse ivares ivasre ivaser ivaesr ivaers
iveras iversa ivears iveasr ivesar ivesra iesrva iesrav iesvra iesvar iesavr
iesarv iersva iersav iervsa iervas ieravs ierasv ievrsa ievras ievsra ievsar
ievasr ievars iearvs iearsv ieavrs ieavsr ieasvr ieasrv raisve raisev raivse
raives raievs raiesv rasive rasiev rasvie rasvei rasevi raseiv ravsie ravsei
ravise ravies raveis ravesi raesvi raesiv raevsi raevis raeivs raeisv riasve
riasev riavse riaves riaevs riaesv risave risaev risvae risvea riseva riseav
rivsae rivsea rivase rivaes riveas rivesa riesva riesav rievsa rievas rieavs
rieasv rsiave rsiaev rsivae rsivea rsieva rsieav rsaive rsaiev rsavie rsavei
rsaevi rsaeiv rsvaie rsvaei rsviae rsviea rsveia rsveai rseavi rseaiv rsevai
rsevia rseiva rseiav rvisae rvisea rviase rviaes rvieas rviesa rvsiae rvsiea
rvsaie rvsaei rvseai rvseia rvasie rvasei rvaise rvaies rvaeis rvaesi rvesai
rvesia rveasi rveais rveias rveisa reisva reisav reivsa reivas reiavs reiasv
resiva resiav resvia resvai resavi resaiv revsia revsai revisa revias revais
revasi reasvi reasiv reavsi reavis reaivs reaisv vairse vaires vaisre vaiser
vaiesr vaiers varise varies varsie varsei varesi vareis vasrie vasrei vasire
vasier vaseir vaseri vaersi vaeris vaesri vaesir vaeisr vaeirs viarse viares
viasre viaser viaesr viaers virase viraes virsae virsea viresa vireas visrae
visrea visare visaer visear visera viersa vieras viesra viesar vieasr viears
vriase vriaes vrisae vrisea vriesa vrieas vraise vraies vrasie vrasei vraesi
vraeis vrsaie vrsaei vrsiae vrsiea vrseia vrseai vreasi vreais vresai vresia
vreisa vreias vsirae vsirea vsiare vsiaer vsiear vsiera vsriae vsriea vsraie
vsraei vsreai vsreia vsarie vsarei vsaire vsaier vsaeir vsaeri vserai vseria
vseari vseair vseiar vseira veirsa veiras veisra veisar veiasr veiars verisa
verias versia versai verasi verais vesria vesrai vesira vesiar vesair vesari
vearsi vearis veasri veasir veaisr veairs eairvs eairsv eaivrs eaivsr eaisvr
eaisrv earivs earisv earvis earvsi earsvi earsiv eavris eavrsi eavirs eavisr
eavsir eavsri easrvi easriv easvri easvir easivr easirv eiarvs eiarsv eiavrs
eiavsr eiasvr eiasrv eiravs eirasv eirvas eirvsa eirsva eirsav eivras eivrsa
eivars eivasr eivsar eivsra eisrva eisrav eisvra eisvar eisavr eisarv eriavs
eriasv erivas erivsa erisva erisav eraivs eraisv eravis eravsi erasvi erasiv
ervais ervasi ervias ervisa ervsia ervsai ersavi ersaiv ersvai ersvia ersiva
ersiav eviras evirsa eviars eviasr evisar evisra evrias evrisa evrais evrasi
evrsai evrsia evaris evarsi evairs evaisr evasir evasri evsrai evsria evsari
evsair evsiar evsira esirva esirav esivra esivar esiavr esiarv esriva esriav
esrvia esrvai esravi esraiv esvria esvrai esvira esviar esvair esvari esarvi
esariv esavri esavir esaivr esairv

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History of cryptography
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