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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: dygert
cipher variations:
ezhfsu faigtv gbjhuw hckivx idljwy
jemkxz kfnlya lgomzb mhpnac niqobd
ojrpce pksqdf qltreg rmusfh snvtgi
towuhj upxvik vqywjl wrzxkm xsayln
ytbzmo zucanp avdboq bwecpr cxfdqs

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: dygert
Cipher: wbtvig

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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: dygert

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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: dygert
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: dygert
Cipher: qltreg

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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: dygert
Cipher: 414522512444

Extended Methods:
Method #1

Plaintext: dygert
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
d y g e r t 
4 4 2 5 2 4 
1 5 2 1 4 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: dygert
Cipher: twrvbt

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Method #3

Plaintext: dygert
method variations:
qkwftt kwfttq wfttqk
fttqkw ttqkwf tqkwft

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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: dygert

all 720 cipher variations:
dygert dygetr dygret dygrte dygtre dygter dyegrt dyegtr dyergt dyertg dyetrg
dyetgr dyregt dyretg dyrget dyrgte dyrtge dyrteg dyterg dytegr dytreg dytrge
dytgre dytger dgyert dgyetr dgyret dgyrte dgytre dgyter dgeyrt dgeytr dgeryt
dgerty dgetry dgetyr dgreyt dgrety dgryet dgryte dgrtye dgrtey dgtery dgteyr
dgtrey dgtrye dgtyre dgtyer degyrt degytr degryt degrty degtry degtyr deygrt
deygtr deyrgt deyrtg deytrg deytgr derygt derytg dergyt dergty dertgy dertyg
detyrg detygr detryg detrgy detgry detgyr drgeyt drgety drgyet drgyte drgtye
drgtey dregyt dregty dreygt dreytg dretyg dretgy dryegt dryetg dryget drygte
drytge dryteg drteyg drtegy drtyeg drtyge drtgye drtgey dtgery dtgeyr dtgrey
dtgrye dtgyre dtgyer dtegry dtegyr dtergy dteryg dteyrg dteygr dtregy dtreyg
dtrgey dtrgye dtryge dtryeg dtyerg dtyegr dtyreg dtyrge dtygre dtyger ydgert
ydgetr ydgret ydgrte ydgtre ydgter ydegrt ydegtr ydergt ydertg ydetrg ydetgr
ydregt ydretg ydrget ydrgte ydrtge ydrteg ydterg ydtegr ydtreg ydtrge ydtgre
ydtger ygdert ygdetr ygdret ygdrte ygdtre ygdter ygedrt ygedtr ygerdt ygertd
ygetrd ygetdr ygredt ygretd ygrdet ygrdte ygrtde ygrted ygterd ygtedr ygtred
ygtrde ygtdre ygtder yegdrt yegdtr yegrdt yegrtd yegtrd yegtdr yedgrt yedgtr
yedrgt yedrtg yedtrg yedtgr yerdgt yerdtg yergdt yergtd yertgd yertdg yetdrg
yetdgr yetrdg yetrgd yetgrd yetgdr yrgedt yrgetd yrgdet yrgdte yrgtde yrgted
yregdt yregtd yredgt yredtg yretdg yretgd yrdegt yrdetg yrdget yrdgte yrdtge
yrdteg yrtedg yrtegd yrtdeg yrtdge yrtgde yrtged ytgerd ytgedr ytgred ytgrde
ytgdre ytgder ytegrd ytegdr ytergd yterdg ytedrg ytedgr ytregd ytredg ytrged
ytrgde ytrdge ytrdeg ytderg ytdegr ytdreg ytdrge ytdgre ytdger gydert gydetr
gydret gydrte gydtre gydter gyedrt gyedtr gyerdt gyertd gyetrd gyetdr gyredt
gyretd gyrdet gyrdte gyrtde gyrted gyterd gytedr gytred gytrde gytdre gytder
gdyert gdyetr gdyret gdyrte gdytre gdyter gdeyrt gdeytr gderyt gderty gdetry
gdetyr gdreyt gdrety gdryet gdryte gdrtye gdrtey gdtery gdteyr gdtrey gdtrye
gdtyre gdtyer gedyrt gedytr gedryt gedrty gedtry gedtyr geydrt geydtr geyrdt
geyrtd geytrd geytdr gerydt gerytd gerdyt gerdty gertdy gertyd getyrd getydr
getryd getrdy getdry getdyr grdeyt grdety grdyet grdyte grdtye grdtey gredyt
gredty greydt greytd gretyd gretdy gryedt gryetd grydet grydte grytde gryted
grteyd grtedy grtyed grtyde grtdye grtdey gtdery gtdeyr gtdrey gtdrye gtdyre
gtdyer gtedry gtedyr gterdy gteryd gteyrd gteydr gtredy gtreyd gtrdey gtrdye
gtryde gtryed gtyerd gtyedr gtyred gtyrde gtydre gtyder eygdrt eygdtr eygrdt
eygrtd eygtrd eygtdr eydgrt eydgtr eydrgt eydrtg eydtrg eydtgr eyrdgt eyrdtg
eyrgdt eyrgtd eyrtgd eyrtdg eytdrg eytdgr eytrdg eytrgd eytgrd eytgdr egydrt
egydtr egyrdt egyrtd egytrd egytdr egdyrt egdytr egdryt egdrty egdtry egdtyr
egrdyt egrdty egrydt egrytd egrtyd egrtdy egtdry egtdyr egtrdy egtryd egtyrd
egtydr edgyrt edgytr edgryt edgrty edgtry edgtyr edygrt edygtr edyrgt edyrtg
edytrg edytgr edrygt edrytg edrgyt edrgty edrtgy edrtyg edtyrg edtygr edtryg
edtrgy edtgry edtgyr ergdyt ergdty ergydt ergytd ergtyd ergtdy erdgyt erdgty
erdygt erdytg erdtyg erdtgy erydgt erydtg erygdt erygtd erytgd erytdg ertdyg
ertdgy ertydg ertygd ertgyd ertgdy etgdry etgdyr etgrdy etgryd etgyrd etgydr
etdgry etdgyr etdrgy etdryg etdyrg etdygr etrdgy etrdyg etrgdy etrgyd etrygd
etrydg etydrg etydgr etyrdg etyrgd etygrd etygdr rygedt rygetd rygdet rygdte
rygtde rygted ryegdt ryegtd ryedgt ryedtg ryetdg ryetgd rydegt rydetg rydget
rydgte rydtge rydteg rytedg rytegd rytdeg rytdge rytgde rytged rgyedt rgyetd
rgydet rgydte rgytde rgyted rgeydt rgeytd rgedyt rgedty rgetdy rgetyd rgdeyt
rgdety rgdyet rgdyte rgdtye rgdtey rgtedy rgteyd rgtdey rgtdye rgtyde rgtyed
regydt regytd regdyt regdty regtdy regtyd reygdt reygtd reydgt reydtg reytdg
reytgd redygt redytg redgyt redgty redtgy redtyg retydg retygd retdyg retdgy
retgdy retgyd rdgeyt rdgety rdgyet rdgyte rdgtye rdgtey rdegyt rdegty rdeygt
rdeytg rdetyg rdetgy rdyegt rdyetg rdyget rdygte rdytge rdyteg rdteyg rdtegy
rdtyeg rdtyge rdtgye rdtgey rtgedy rtgeyd rtgdey rtgdye rtgyde rtgyed rtegdy
rtegyd rtedgy rtedyg rteydg rteygd rtdegy rtdeyg rtdgey rtdgye rtdyge rtdyeg
rtyedg rtyegd rtydeg rtydge rtygde rtyged tygerd tygedr tygred tygrde tygdre
tygder tyegrd tyegdr tyergd tyerdg tyedrg tyedgr tyregd tyredg tyrged tyrgde
tyrdge tyrdeg tyderg tydegr tydreg tydrge tydgre tydger tgyerd tgyedr tgyred
tgyrde tgydre tgyder tgeyrd tgeydr tgeryd tgerdy tgedry tgedyr tgreyd tgredy
tgryed tgryde tgrdye tgrdey tgdery tgdeyr tgdrey tgdrye tgdyre tgdyer tegyrd
tegydr tegryd tegrdy tegdry tegdyr teygrd teygdr teyrgd teyrdg teydrg teydgr
terygd terydg tergyd tergdy terdgy terdyg tedyrg tedygr tedryg tedrgy tedgry
tedgyr trgeyd trgedy trgyed trgyde trgdye trgdey tregyd tregdy treygd treydg
tredyg tredgy tryegd tryedg tryged trygde trydge trydeg trdeyg trdegy trdyeg
trdyge trdgye trdgey tdgery tdgeyr tdgrey tdgrye tdgyre tdgyer tdegry tdegyr
tdergy tderyg tdeyrg tdeygr tdregy tdreyg tdrgey tdrgye tdryge tdryeg tdyerg
tdyegr tdyreg tdyrge tdygre tdyger

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History of cryptography
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