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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: nawrot
cipher variations:
obxspu pcytqv qdzurw reavsx sfbwty
tgcxuz uhdyva viezwb wjfaxc xkgbyd
ylhcze zmidaf anjebg bokfch cplgdi
dqmhej ernifk fsojgl gtpkhm huqlin
ivrmjo jwsnkp kxtolq lyupmr mzvqns

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: nawrot
Cipher: mzdilg

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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: nawrot

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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: nawrot
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: nawrot
Cipher: anjebg

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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: nawrot
Cipher: 331125244344

Extended Methods:
Method #1

Plaintext: nawrot
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
n a w r o t 
3 1 2 2 4 4 
3 1 5 4 3 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: nawrot
Cipher: cgtcus

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Method #3

Plaintext: nawrot
method variations:
cfktso fktsoc ktsocf
tsocfk socfkt ocfkts

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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: nawrot

all 720 cipher variations:
nawrot nawrto nawort nawotr nawtor nawtro narwot narwto narowt narotw nartow
nartwo naorwt naortw naowrt naowtr naotwr naotrw natrow natrwo natorw natowr
natwor natwro nwarot nwarto nwaort nwaotr nwator nwatro nwraot nwrato nwroat
nwrota nwrtoa nwrtao nworat nworta nwoart nwoatr nwotar nwotra nwtroa nwtrao
nwtora nwtoar nwtaor nwtaro nrwaot nrwato nrwoat nrwota nrwtoa nrwtao nrawot
nrawto nraowt nraotw nratow nratwo nroawt nroatw nrowat nrowta nrotwa nrotaw
nrtaow nrtawo nrtoaw nrtowa nrtwoa nrtwao nowrat nowrta nowart nowatr nowtar
nowtra norwat norwta norawt noratw nortaw nortwa noarwt noartw noawrt noawtr
noatwr noatrw notraw notrwa notarw notawr notwar notwra ntwroa ntwrao ntwora
ntwoar ntwaor ntwaro ntrwoa ntrwao ntrowa ntroaw ntraow ntrawo ntorwa ntoraw
ntowra ntowar ntoawr ntoarw ntarow ntarwo ntaorw ntaowr ntawor ntawro anwrot
anwrto anwort anwotr anwtor anwtro anrwot anrwto anrowt anrotw anrtow anrtwo
anorwt anortw anowrt anowtr anotwr anotrw antrow antrwo antorw antowr antwor
antwro awnrot awnrto awnort awnotr awntor awntro awrnot awrnto awront awrotn
awrton awrtno awornt awortn awonrt awontr awotnr awotrn awtron awtrno awtorn
awtonr awtnor awtnro arwnot arwnto arwont arwotn arwton arwtno arnwot arnwto
arnowt arnotw arntow arntwo aronwt arontw arownt arowtn arotwn arotnw artnow
artnwo artonw artown artwon artwno aowrnt aowrtn aownrt aowntr aowtnr aowtrn
aorwnt aorwtn aornwt aorntw aortnw aortwn aonrwt aonrtw aonwrt aonwtr aontwr
aontrw aotrnw aotrwn aotnrw aotnwr aotwnr aotwrn atwron atwrno atworn atwonr
atwnor atwnro atrwon atrwno atrown atronw atrnow atrnwo atorwn atornw atowrn
atownr atonwr atonrw atnrow atnrwo atnorw atnowr atnwor atnwro wanrot wanrto
wanort wanotr wantor wantro warnot warnto waront warotn warton wartno waornt
waortn waonrt waontr waotnr waotrn watron watrno watorn watonr watnor watnro
wnarot wnarto wnaort wnaotr wnator wnatro wnraot wnrato wnroat wnrota wnrtoa
wnrtao wnorat wnorta wnoart wnoatr wnotar wnotra wntroa wntrao wntora wntoar
wntaor wntaro wrnaot wrnato wrnoat wrnota wrntoa wrntao wranot wranto wraont
wraotn wraton wratno wroant wroatn wronat wronta wrotna wrotan wrtaon wrtano
wrtoan wrtona wrtnoa wrtnao wonrat wonrta wonart wonatr wontar wontra wornat
wornta worant woratn wortan wortna woarnt woartn woanrt woantr woatnr woatrn
wotran wotrna wotarn wotanr wotnar wotnra wtnroa wtnrao wtnora wtnoar wtnaor
wtnaro wtrnoa wtrnao wtrona wtroan wtraon wtrano wtorna wtoran wtonra wtonar
wtoanr wtoarn wtaron wtarno wtaorn wtaonr wtanor wtanro rawnot rawnto rawont
rawotn rawton rawtno ranwot ranwto ranowt ranotw rantow rantwo raonwt raontw
raownt raowtn raotwn raotnw ratnow ratnwo ratonw ratown ratwon ratwno rwanot
rwanto rwaont rwaotn rwaton rwatno rwnaot rwnato rwnoat rwnota rwntoa rwntao
rwonat rwonta rwoant rwoatn rwotan rwotna rwtnoa rwtnao rwtona rwtoan rwtaon
rwtano rnwaot rnwato rnwoat rnwota rnwtoa rnwtao rnawot rnawto rnaowt rnaotw
rnatow rnatwo rnoawt rnoatw rnowat rnowta rnotwa rnotaw rntaow rntawo rntoaw
rntowa rntwoa rntwao rownat rownta rowant rowatn rowtan rowtna ronwat ronwta
ronawt ronatw rontaw rontwa roanwt roantw roawnt roawtn roatwn roatnw rotnaw
rotnwa rotanw rotawn rotwan rotwna rtwnoa rtwnao rtwona rtwoan rtwaon rtwano
rtnwoa rtnwao rtnowa rtnoaw rtnaow rtnawo rtonwa rtonaw rtowna rtowan rtoawn
rtoanw rtanow rtanwo rtaonw rtaown rtawon rtawno oawrnt oawrtn oawnrt oawntr
oawtnr oawtrn oarwnt oarwtn oarnwt oarntw oartnw oartwn oanrwt oanrtw oanwrt
oanwtr oantwr oantrw oatrnw oatrwn oatnrw oatnwr oatwnr oatwrn owarnt owartn
owanrt owantr owatnr owatrn owrant owratn owrnat owrnta owrtna owrtan ownrat
ownrta ownart ownatr owntar owntra owtrna owtran owtnra owtnar owtanr owtarn
orwant orwatn orwnat orwnta orwtna orwtan orawnt orawtn oranwt orantw oratnw
oratwn ornawt ornatw ornwat ornwta orntwa orntaw ortanw ortawn ortnaw ortnwa
ortwna ortwan onwrat onwrta onwart onwatr onwtar onwtra onrwat onrwta onrawt
onratw onrtaw onrtwa onarwt onartw onawrt onawtr onatwr onatrw ontraw ontrwa
ontarw ontawr ontwar ontwra otwrna otwran otwnra otwnar otwanr otwarn otrwna
otrwan otrnwa otrnaw otranw otrawn otnrwa otnraw otnwra otnwar otnawr otnarw
otarnw otarwn otanrw otanwr otawnr otawrn tawron tawrno taworn tawonr tawnor
tawnro tarwon tarwno tarown taronw tarnow tarnwo taorwn taornw taowrn taownr
taonwr taonrw tanrow tanrwo tanorw tanowr tanwor tanwro twaron twarno twaorn
twaonr twanor twanro twraon twrano twroan twrona twrnoa twrnao tworan tworna
twoarn twoanr twonar twonra twnroa twnrao twnora twnoar twnaor twnaro trwaon
trwano trwoan trwona trwnoa trwnao trawon trawno traown traonw tranow tranwo
troawn troanw trowan trowna tronwa tronaw trnaow trnawo trnoaw trnowa trnwoa
trnwao towran towrna towarn towanr townar townra torwan torwna torawn toranw
tornaw tornwa toarwn toarnw toawrn toawnr toanwr toanrw tonraw tonrwa tonarw
tonawr tonwar tonwra tnwroa tnwrao tnwora tnwoar tnwaor tnwaro tnrwoa tnrwao
tnrowa tnroaw tnraow tnrawo tnorwa tnoraw tnowra tnowar tnoawr tnoarw tnarow
tnarwo tnaorw tnaowr tnawor tnawro

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History of cryptography
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