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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: hamric
cipher variations:
ibnsjd jcotke kdpulf leqvmg mfrwnh
ngsxoi ohtypj piuzqk qjvarl rkwbsm
slxctn tmyduo unzevp voafwq wpbgxr
xqchys yrdizt zsejau atfkbv buglcw
cvhmdx dwiney exjofz fykpga gzlqhb

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: hamric
Cipher: sznirx

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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: hamric

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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: hamric
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: hamric
Cipher: unzevp

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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: hamric
Cipher: 321123244231

Extended Methods:
Method #1

Plaintext: hamric
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
h a m r i c 
3 1 2 2 4 3 
2 1 3 4 2 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: hamric
Cipher: cgobsb

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Method #3

Plaintext: hamric
method variations:
bfhtml fhtmlb htmlbf
tmlbfh mlbfht lbfhtm

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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: hamric

all 720 cipher variations:
hamric hamrci hamirc hamicr hamcir hamcri harmic harmci harimc haricm harcim
harcmi hairmc haircm haimrc haimcr haicmr haicrm hacrim hacrmi hacirm hacimr
hacmir hacmri hmaric hmarci hmairc hmaicr hmacir hmacri hmraic hmraci hmriac
hmrica hmrcia hmrcai hmirac hmirca hmiarc hmiacr hmicar hmicra hmcria hmcrai
hmcira hmciar hmcair hmcari hrmaic hrmaci hrmiac hrmica hrmcia hrmcai hramic
hramci hraimc hraicm hracim hracmi hriamc hriacm hrimac hrimca hricma hricam
hrcaim hrcami hrciam hrcima hrcmia hrcmai himrac himrca himarc himacr himcar
himcra hirmac hirmca hiramc hiracm hircam hircma hiarmc hiarcm hiamrc hiamcr
hiacmr hiacrm hicram hicrma hicarm hicamr hicmar hicmra hcmria hcmrai hcmira
hcmiar hcmair hcmari hcrmia hcrmai hcrima hcriam hcraim hcrami hcirma hciram
hcimra hcimar hciamr hciarm hcarim hcarmi hcairm hcaimr hcamir hcamri ahmric
ahmrci ahmirc ahmicr ahmcir ahmcri ahrmic ahrmci ahrimc ahricm ahrcim ahrcmi
ahirmc ahircm ahimrc ahimcr ahicmr ahicrm ahcrim ahcrmi ahcirm ahcimr ahcmir
ahcmri amhric amhrci amhirc amhicr amhcir amhcri amrhic amrhci amrihc amrich
amrcih amrchi amirhc amirch amihrc amihcr amichr amicrh amcrih amcrhi amcirh
amcihr amchir amchri armhic armhci armihc armich armcih armchi arhmic arhmci
arhimc arhicm arhcim arhcmi arihmc arihcm arimhc arimch aricmh arichm archim
archmi arcihm arcimh arcmih arcmhi aimrhc aimrch aimhrc aimhcr aimchr aimcrh
airmhc airmch airhmc airhcm airchm aircmh aihrmc aihrcm aihmrc aihmcr aihcmr
aihcrm aicrhm aicrmh aichrm aichmr aicmhr aicmrh acmrih acmrhi acmirh acmihr
acmhir acmhri acrmih acrmhi acrimh acrihm acrhim acrhmi acirmh acirhm acimrh
acimhr acihmr acihrm achrim achrmi achirm achimr achmir achmri mahric mahrci
mahirc mahicr mahcir mahcri marhic marhci marihc marich marcih marchi mairhc
mairch maihrc maihcr maichr maicrh macrih macrhi macirh macihr machir machri
mharic mharci mhairc mhaicr mhacir mhacri mhraic mhraci mhriac mhrica mhrcia
mhrcai mhirac mhirca mhiarc mhiacr mhicar mhicra mhcria mhcrai mhcira mhciar
mhcair mhcari mrhaic mrhaci mrhiac mrhica mrhcia mrhcai mrahic mrahci mraihc
mraich mracih mrachi mriahc mriach mrihac mrihca mricha mricah mrcaih mrcahi
mrciah mrciha mrchia mrchai mihrac mihrca miharc mihacr mihcar mihcra mirhac
mirhca mirahc mirach mircah mircha miarhc miarch miahrc miahcr miachr miacrh
micrah micrha micarh micahr michar michra mchria mchrai mchira mchiar mchair
mchari mcrhia mcrhai mcriha mcriah mcraih mcrahi mcirha mcirah mcihra mcihar
mciahr mciarh mcarih mcarhi mcairh mcaihr mcahir mcahri ramhic ramhci ramihc
ramich ramcih ramchi rahmic rahmci rahimc rahicm rahcim rahcmi raihmc raihcm
raimhc raimch raicmh raichm rachim rachmi racihm racimh racmih racmhi rmahic
rmahci rmaihc rmaich rmacih rmachi rmhaic rmhaci rmhiac rmhica rmhcia rmhcai
rmihac rmihca rmiahc rmiach rmicah rmicha rmchia rmchai rmciha rmciah rmcaih
rmcahi rhmaic rhmaci rhmiac rhmica rhmcia rhmcai rhamic rhamci rhaimc rhaicm
rhacim rhacmi rhiamc rhiacm rhimac rhimca rhicma rhicam rhcaim rhcami rhciam
rhcima rhcmia rhcmai rimhac rimhca rimahc rimach rimcah rimcha rihmac rihmca
rihamc rihacm rihcam rihcma riahmc riahcm riamhc riamch riacmh riachm richam
richma ricahm ricamh ricmah ricmha rcmhia rcmhai rcmiha rcmiah rcmaih rcmahi
rchmia rchmai rchima rchiam rchaim rchami rcihma rciham rcimha rcimah rciamh
rciahm rcahim rcahmi rcaihm rcaimh rcamih rcamhi iamrhc iamrch iamhrc iamhcr
iamchr iamcrh iarmhc iarmch iarhmc iarhcm iarchm iarcmh iahrmc iahrcm iahmrc
iahmcr iahcmr iahcrm iacrhm iacrmh iachrm iachmr iacmhr iacmrh imarhc imarch
imahrc imahcr imachr imacrh imrahc imrach imrhac imrhca imrcha imrcah imhrac
imhrca imharc imhacr imhcar imhcra imcrha imcrah imchra imchar imcahr imcarh
irmahc irmach irmhac irmhca irmcha irmcah iramhc iramch irahmc irahcm irachm
iracmh irhamc irhacm irhmac irhmca irhcma irhcam ircahm ircamh ircham irchma
ircmha ircmah ihmrac ihmrca ihmarc ihmacr ihmcar ihmcra ihrmac ihrmca ihramc
ihracm ihrcam ihrcma iharmc iharcm ihamrc ihamcr ihacmr ihacrm ihcram ihcrma
ihcarm ihcamr ihcmar ihcmra icmrha icmrah icmhra icmhar icmahr icmarh icrmha
icrmah icrhma icrham icrahm icramh ichrma ichram ichmra ichmar ichamr icharm
icarhm icarmh icahrm icahmr icamhr icamrh camrih camrhi camirh camihr camhir
camhri carmih carmhi carimh carihm carhim carhmi cairmh cairhm caimrh caimhr
caihmr caihrm cahrim cahrmi cahirm cahimr cahmir cahmri cmarih cmarhi cmairh
cmaihr cmahir cmahri cmraih cmrahi cmriah cmriha cmrhia cmrhai cmirah cmirha
cmiarh cmiahr cmihar cmihra cmhria cmhrai cmhira cmhiar cmhair cmhari crmaih
crmahi crmiah crmiha crmhia crmhai cramih cramhi craimh craihm crahim crahmi
criamh criahm crimah crimha crihma criham crhaim crhami crhiam crhima crhmia
crhmai cimrah cimrha cimarh cimahr cimhar cimhra cirmah cirmha ciramh cirahm
cirham cirhma ciarmh ciarhm ciamrh ciamhr ciahmr ciahrm cihram cihrma ciharm
cihamr cihmar cihmra chmria chmrai chmira chmiar chmair chmari chrmia chrmai
chrima chriam chraim chrami chirma chiram chimra chimar chiamr chiarm charim
charmi chairm chaimr chamir chamri

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History of cryptography
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