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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: roiled
cipher variations:
spjmfe tqkngf urlohg vsmpih wtnqji
xuorkj yvpslk zwqtml axrunm bysvon
cztwpo dauxqp ebvyrq fcwzsr gdxats
heybut ifzcvu jgadwv khbexw licfyx
mjdgzy nkehaz olfiba pmgjcb qnhkdc

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: roiled
Cipher: ilrovw

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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: roiled

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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: roiled
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: roiled
Cipher: ebvyrq

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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: roiled
Cipher: 244342135141

Extended Methods:
Method #1

Plaintext: roiled
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
r o i l e d 
2 4 4 1 5 4 
4 3 2 3 1 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: roiled
Cipher: rduoma

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Method #3

Plaintext: roiled
method variations:
tsbxqf sbxqft bxqfts
xqftsb qftsbx ftsbxq

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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: roiled

all 720 cipher variations:
roiled roilde roield roiedl roidel roidle rolied rolide roleid roledi roldei
roldie roelid roeldi roeild roeidl roedil roedli rodlei rodlie rodeli rodeil
rodiel rodile rioled riolde rioeld rioedl riodel riodle riloed rilode rileod
riledo rildeo rildoe rielod rieldo rieold rieodl riedol riedlo ridleo ridloe
ridelo rideol ridoel ridole rlioed rliode rlieod rliedo rlideo rlidoe rloied
rloide rloeid rloedi rlodei rlodie rleoid rleodi rleiod rleido rledio rledoi
rldoei rldoie rldeoi rldeio rldieo rldioe reilod reildo reiold reiodl reidol
reidlo reliod relido reloid relodi reldoi reldio reolid reoldi reoild reoidl
reodil reodli redloi redlio redoli redoil rediol redilo rdileo rdiloe rdielo
rdieol rdioel rdiole rdlieo rdlioe rdleio rdleoi rdloei rdloie rdelio rdeloi
rdeilo rdeiol rdeoil rdeoli rdolei rdolie rdoeli rdoeil rdoiel rdoile oriled
orilde orield oriedl oridel oridle orlied orlide orleid orledi orldei orldie
orelid oreldi oreild oreidl oredil oredli ordlei ordlie ordeli ordeil ordiel
ordile oirled oirlde oireld oiredl oirdel oirdle oilred oilrde oilerd oiledr
oilder oildre oielrd oieldr oierld oierdl oiedrl oiedlr oidler oidlre oidelr
oiderl oidrel oidrle olired olirde olierd oliedr olider olidre olried olride
olreid olredi olrdei olrdie olerid olerdi oleird oleidr oledir oledri oldrei
oldrie olderi oldeir oldier oldire oeilrd oeildr oeirld oeirdl oeidrl oeidlr
oelird oelidr oelrid oelrdi oeldri oeldir oerlid oerldi oerild oeridl oerdil
oerdli oedlri oedlir oedrli oedril oedirl oedilr odiler odilre odielr odierl
odirel odirle odlier odlire odleir odleri odlrei odlrie odelir odelri odeilr
odeirl oderil oderli odrlei odrlie odreli odreil odriel odrile iorled iorlde
ioreld ioredl iordel iordle iolred iolrde iolerd ioledr iolder ioldre ioelrd
ioeldr ioerld ioerdl ioedrl ioedlr iodler iodlre iodelr ioderl iodrel iodrle
iroled irolde iroeld iroedl irodel irodle irloed irlode irleod irledo irldeo
irldoe irelod ireldo ireold ireodl iredol iredlo irdleo irdloe irdelo irdeol
irdoel irdole ilroed ilrode ilreod ilredo ilrdeo ilrdoe ilored ilorde iloerd
iloedr iloder ilodre ileord ileodr ilerod ilerdo iledro iledor ildoer ildore
ildeor ildero ildreo ildroe ierlod ierldo ierold ierodl ierdol ierdlo ielrod
ielrdo ielord ielodr ieldor ieldro ieolrd ieoldr ieorld ieordl ieodrl ieodlr
iedlor iedlro iedolr iedorl iedrol iedrlo idrleo idrloe idrelo idreol idroel
idrole idlreo idlroe idlero idleor idloer idlore idelro idelor iderlo iderol
ideorl ideolr idoler idolre idoelr idoerl idorel idorle loired loirde loierd
loiedr loider loidre loried loride loreid loredi lordei lordie loerid loerdi
loeird loeidr loedir loedri lodrei lodrie loderi lodeir lodier lodire liored
liorde lioerd lioedr lioder liodre liroed lirode lireod liredo lirdeo lirdoe
lierod lierdo lieord lieodr liedor liedro lidreo lidroe lidero lideor lidoer
lidore lrioed lriode lrieod lriedo lrideo lridoe lroied lroide lroeid lroedi
lrodei lrodie lreoid lreodi lreiod lreido lredio lredoi lrdoei lrdoie lrdeoi
lrdeio lrdieo lrdioe leirod leirdo leiord leiodr leidor leidro leriod lerido
leroid lerodi lerdoi lerdio leorid leordi leoird leoidr leodir leodri ledroi
ledrio ledori ledoir ledior lediro ldireo ldiroe ldiero ldieor ldioer ldiore
ldrieo ldrioe ldreio ldreoi ldroei ldroie lderio lderoi ldeiro ldeior ldeoir
ldeori ldorei ldorie ldoeri ldoeir ldoier ldoire eoilrd eoildr eoirld eoirdl
eoidrl eoidlr eolird eolidr eolrid eolrdi eoldri eoldir eorlid eorldi eorild
eoridl eordil eordli eodlri eodlir eodrli eodril eodirl eodilr eiolrd eioldr
eiorld eiordl eiodrl eiodlr eilord eilodr eilrod eilrdo eildro eildor eirlod
eirldo eirold eirodl eirdol eirdlo eidlro eidlor eidrlo eidrol eidorl eidolr
eliord eliodr elirod elirdo elidro elidor eloird eloidr elorid elordi elodri
elodir elroid elrodi elriod elrido elrdio elrdoi eldori eldoir eldroi eldrio
eldiro eldior erilod erildo eriold eriodl eridol eridlo erliod erlido erloid
erlodi erldoi erldio erolid eroldi eroild eroidl erodil erodli erdloi erdlio
erdoli erdoil erdiol erdilo edilro edilor edirlo edirol ediorl ediolr edliro
edlior edlrio edlroi edlori edloir edrlio edrloi edrilo edriol edroil edroli
edolri edolir edorli edoril edoirl edoilr doiler doilre doielr doierl doirel
doirle dolier dolire doleir doleri dolrei dolrie doelir doelri doeilr doeirl
doeril doerli dorlei dorlie doreli doreil doriel dorile dioler diolre dioelr
dioerl diorel diorle diloer dilore dileor dilero dilreo dilroe dielor dielro
dieolr dieorl dierol dierlo dirleo dirloe direlo direol diroel dirole dlioer
dliore dlieor dliero dlireo dliroe dloier dloire dloeir dloeri dlorei dlorie
dleoir dleori dleior dleiro dlerio dleroi dlroei dlroie dlreoi dlreio dlrieo
dlrioe deilor deilro deiolr deiorl deirol deirlo delior deliro deloir delori
delroi delrio deolir deolri deoilr deoirl deoril deorli derloi derlio deroli
deroil deriol derilo drileo driloe drielo drieol drioel driole drlieo drlioe
drleio drleoi drloei drloie drelio dreloi dreilo dreiol dreoil dreoli drolei
drolie droeli droeil droiel droile

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History of cryptography
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