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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: porath
cipher variations:
qpsbui rqtcvj srudwk tsvexl utwfym
vuxgzn wvyhao xwzibp yxajcq zybkdr
azcles badmft cbengu dcfohv edgpiw
fehqjx gfirky hgjslz ihktma jilunb
kjmvoc lknwpd mloxqe nmpyrf onqzsg

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: porath
Cipher: klizgs

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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: porath

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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: porath
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: porath
Cipher: cbengu

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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: porath
Cipher: 534324114432

Extended Methods:
Method #1

Plaintext: porath
method variations:

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

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Method #3

Plaintext: porath
method variations:
shdqow hdqows dqowsh
qowshd owshdq wshdqo

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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: porath

all 720 cipher variations:
porath poraht portah portha porhta porhat poarth poarht poatrh poathr poahtr
poahrt potarh potahr potrah potrha pothra pothar pohatr pohart pohtar pohtra
pohrta pohrat proath proaht protah protha prohta prohat praoth praoht pratoh
pratho prahto prahot prtaoh prtaho prtoah prtoha prthoa prthao prhato prhaot
prhtao prhtoa prhota prhoat paroth paroht partoh partho parhto parhot paorth
paorht paotrh paothr paohtr paohrt patorh patohr patroh patrho pathro pathor
pahotr pahort pahtor pahtro pahrto pahrot ptraoh ptraho ptroah ptroha ptrhoa
ptrhao ptaroh ptarho ptaorh ptaohr ptahor ptahro ptoarh ptoahr ptorah ptorha
ptohra ptohar pthaor ptharo pthoar pthora pthroa pthrao phrato phraot phrtao
phrtoa phrota phroat pharto pharot phatro phator phaotr phaort phtaro phtaor
phtrao phtroa phtora phtoar phoatr phoart photar photra phorta phorat oprath
opraht oprtah oprtha oprhta oprhat oparth oparht opatrh opathr opahtr opahrt
optarh optahr optrah optrha opthra opthar ophatr ophart ophtar ophtra ophrta
ophrat orpath orpaht orptah orptha orphta orphat orapth orapht oratph orathp
orahtp orahpt ortaph ortahp ortpah ortpha orthpa orthap orhatp orhapt orhtap
orhtpa orhpta orhpat oarpth oarpht oartph oarthp oarhtp oarhpt oaprth oaprht
oaptrh oapthr oaphtr oaphrt oatprh oatphr oatrph oatrhp oathrp oathpr oahptr
oahprt oahtpr oahtrp oahrtp oahrpt otraph otrahp otrpah otrpha otrhpa otrhap
otarph otarhp otaprh otaphr otahpr otahrp otparh otpahr otprah otprha otphra
otphar othapr otharp othpar othpra othrpa othrap ohratp ohrapt ohrtap ohrtpa
ohrpta ohrpat ohartp oharpt ohatrp ohatpr ohaptr ohaprt ohtarp ohtapr ohtrap
ohtrpa ohtpra ohtpar ohpatr ohpart ohptar ohptra ohprta ohprat ropath ropaht
roptah roptha rophta rophat roapth roapht roatph roathp roahtp roahpt rotaph
rotahp rotpah rotpha rothpa rothap rohatp rohapt rohtap rohtpa rohpta rohpat
rpoath rpoaht rpotah rpotha rpohta rpohat rpaoth rpaoht rpatoh rpatho rpahto
rpahot rptaoh rptaho rptoah rptoha rpthoa rpthao rphato rphaot rphtao rphtoa
rphota rphoat rapoth rapoht raptoh raptho raphto raphot raopth raopht raotph
raothp raohtp raohpt ratoph ratohp ratpoh ratpho rathpo rathop rahotp rahopt
rahtop rahtpo rahpto rahpot rtpaoh rtpaho rtpoah rtpoha rtphoa rtphao rtapoh
rtapho rtaoph rtaohp rtahop rtahpo rtoaph rtoahp rtopah rtopha rtohpa rtohap
rthaop rthapo rthoap rthopa rthpoa rthpao rhpato rhpaot rhptao rhptoa rhpota
rhpoat rhapto rhapot rhatpo rhatop rhaotp rhaopt rhtapo rhtaop rhtpao rhtpoa
rhtopa rhtoap rhoatp rhoapt rhotap rhotpa rhopta rhopat aorpth aorpht aortph
aorthp aorhtp aorhpt aoprth aoprht aoptrh aopthr aophtr aophrt aotprh aotphr
aotrph aotrhp aothrp aothpr aohptr aohprt aohtpr aohtrp aohrtp aohrpt aropth
aropht arotph arothp arohtp arohpt arpoth arpoht arptoh arptho arphto arphot
artpoh artpho artoph artohp arthop arthpo arhpto arhpot arhtpo arhtop arhotp
arhopt aproth aproht aprtoh aprtho aprhto aprhot aporth aporht apotrh apothr
apohtr apohrt aptorh aptohr aptroh aptrho apthro apthor aphotr aphort aphtor
aphtro aphrto aphrot atrpoh atrpho atroph atrohp atrhop atrhpo atproh atprho
atporh atpohr atphor atphro atoprh atophr atorph atorhp atohrp atohpr athpor
athpro athopr athorp athrop athrpo ahrpto ahrpot ahrtpo ahrtop ahrotp ahropt
ahprto ahprot ahptro ahptor ahpotr ahport ahtpro ahtpor ahtrpo ahtrop ahtorp
ahtopr ahoptr ahoprt ahotpr ahotrp ahortp ahorpt toraph torahp torpah torpha
torhpa torhap toarph toarhp toaprh toaphr toahpr toahrp toparh topahr toprah
toprha tophra tophar tohapr toharp tohpar tohpra tohrpa tohrap troaph troahp
tropah tropha trohpa trohap traoph traohp trapoh trapho trahpo trahop trpaoh
trpaho trpoah trpoha trphoa trphao trhapo trhaop trhpao trhpoa trhopa trhoap
taroph tarohp tarpoh tarpho tarhpo tarhop taorph taorhp taoprh taophr taohpr
taohrp taporh tapohr taproh taprho taphro taphor tahopr tahorp tahpor tahpro
tahrpo tahrop tpraoh tpraho tproah tproha tprhoa tprhao tparoh tparho tpaorh
tpaohr tpahor tpahro tpoarh tpoahr tporah tporha tpohra tpohar tphaor tpharo
tphoar tphora tphroa tphrao thrapo thraop thrpao thrpoa thropa throap tharpo
tharop thapro thapor thaopr thaorp thparo thpaor thprao thproa thpora thpoar
thoapr thoarp thopar thopra thorpa thorap horatp horapt hortap hortpa horpta
horpat hoartp hoarpt hoatrp hoatpr hoaptr hoaprt hotarp hotapr hotrap hotrpa
hotpra hotpar hopatr hopart hoptar hoptra hoprta hoprat hroatp hroapt hrotap
hrotpa hropta hropat hraotp hraopt hratop hratpo hrapto hrapot hrtaop hrtapo
hrtoap hrtopa hrtpoa hrtpao hrpato hrpaot hrptao hrptoa hrpota hrpoat harotp
haropt hartop hartpo harpto harpot haortp haorpt haotrp haotpr haoptr haoprt
hatorp hatopr hatrop hatrpo hatpro hatpor hapotr haport haptor haptro haprto
haprot htraop htrapo htroap htropa htrpoa htrpao htarop htarpo htaorp htaopr
htapor htapro htoarp htoapr htorap htorpa htopra htopar htpaor htparo htpoar
htpora htproa htprao hprato hpraot hprtao hprtoa hprota hproat hparto hparot
hpatro hpator hpaotr hpaort hptaro hptaor hptrao hptroa hptora hptoar hpoatr
hpoart hpotar hpotra hporta hporat

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History of cryptography
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