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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: tropez
cipher variations:
uspqfa vtqrgb wurshc xvstid ywtuje
zxuvkf ayvwlg bzwxmh caxyni dbyzoj
eczapk fdabql gebcrm hfcdsn igdeto
jhefup kifgvq ljghwr mkhixs nlijyt
omjkzu pnklav qolmbw rpmncx sqnody

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: tropez
Cipher: gilkva

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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: tropez

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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: tropez
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: tropez
Cipher: gebcrm

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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: tropez
Cipher: 442443535155

Extended Methods:
Method #1

Plaintext: tropez
method variations:

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

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Method #3

Plaintext: tropez
method variations:
itxxvu txxvui xxvuit
xvuitx vuitxx uitxxv

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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: tropez

all 720 cipher variations:
tropez tropze troepz troezp trozep trozpe trpoez trpoze trpeoz trpezo trpzeo
trpzoe trepoz trepzo treopz treozp trezop trezpo trzpeo trzpoe trzepo trzeop
trzoep trzope torpez torpze torepz torezp torzep torzpe toprez toprze toperz
topezr topzer topzre toeprz toepzr toerpz toerzp toezrp toezpr tozper tozpre
tozepr tozerp tozrep tozrpe tporez tporze tpoerz tpoezr tpozer tpozre tproez
tproze tpreoz tprezo tprzeo tprzoe tperoz tperzo tpeorz tpeozr tpezor tpezro
tpzreo tpzroe tpzero tpzeor tpzoer tpzore teoprz teopzr teorpz teorzp teozrp
teozpr teporz tepozr teproz teprzo tepzro tepzor terpoz terpzo teropz terozp
terzop terzpo tezpro tezpor tezrpo tezrop tezorp tezopr tzoper tzopre tzoepr
tzoerp tzorep tzorpe tzpoer tzpore tzpeor tzpero tzpreo tzproe tzepor tzepro
tzeopr tzeorp tzerop tzerpo tzrpeo tzrpoe tzrepo tzreop tzroep tzrope rtopez
rtopze rtoepz rtoezp rtozep rtozpe rtpoez rtpoze rtpeoz rtpezo rtpzeo rtpzoe
rtepoz rtepzo rteopz rteozp rtezop rtezpo rtzpeo rtzpoe rtzepo rtzeop rtzoep
rtzope rotpez rotpze rotepz rotezp rotzep rotzpe roptez roptze ropetz ropezt
ropzet ropzte roeptz roepzt roetpz roetzp roeztp roezpt rozpet rozpte rozept
rozetp roztep roztpe rpotez rpotze rpoetz rpoezt rpozet rpozte rptoez rptoze
rpteoz rptezo rptzeo rptzoe rpetoz rpetzo rpeotz rpeozt rpezot rpezto rpzteo
rpztoe rpzeto rpzeot rpzoet rpzote reoptz reopzt reotpz reotzp reoztp reozpt
repotz repozt reptoz reptzo repzto repzot retpoz retpzo retopz retozp retzop
retzpo rezpto rezpot reztpo reztop rezotp rezopt rzopet rzopte rzoept rzoetp
rzotep rzotpe rzpoet rzpote rzpeot rzpeto rzpteo rzptoe rzepot rzepto rzeopt
rzeotp rzetop rzetpo rztpeo rztpoe rztepo rzteop rztoep rztope ortpez ortpze
ortepz ortezp ortzep ortzpe orptez orptze orpetz orpezt orpzet orpzte oreptz
orepzt oretpz oretzp oreztp orezpt orzpet orzpte orzept orzetp orztep orztpe
otrpez otrpze otrepz otrezp otrzep otrzpe otprez otprze otperz otpezr otpzer
otpzre oteprz otepzr oterpz oterzp otezrp otezpr otzper otzpre otzepr otzerp
otzrep otzrpe optrez optrze opterz optezr optzer optzre oprtez oprtze opretz
oprezt oprzet oprzte opertz operzt opetrz opetzr opeztr opezrt opzret opzrte
opzert opzetr opzter opztre oetprz oetpzr oetrpz oetrzp oetzrp oetzpr oeptrz
oeptzr oeprtz oeprzt oepzrt oepztr oerptz oerpzt oertpz oertzp oerztp oerzpt
oezprt oezptr oezrpt oezrtp oeztrp oeztpr oztper oztpre oztepr ozterp oztrep
oztrpe ozpter ozptre ozpetr ozpert ozpret ozprte ozeptr ozeprt ozetpr ozetrp
ozertp ozerpt ozrpet ozrpte ozrept ozretp ozrtep ozrtpe protez protze proetz
proezt prozet prozte prtoez prtoze prteoz prtezo prtzeo prtzoe pretoz pretzo
preotz preozt prezot prezto przteo prztoe przeto przeot przoet przote portez
portze poretz porezt porzet porzte potrez potrze poterz potezr potzer potzre
poetrz poetzr poertz poerzt poezrt poeztr pozter poztre pozetr pozert pozret
pozrte ptorez ptorze ptoerz ptoezr ptozer ptozre ptroez ptroze ptreoz ptrezo
ptrzeo ptrzoe pteroz pterzo pteorz pteozr ptezor ptezro ptzreo ptzroe ptzero
ptzeor ptzoer ptzore peotrz peotzr peortz peorzt peozrt peoztr petorz petozr
petroz petrzo petzro petzor pertoz pertzo perotz perozt perzot perzto peztro
peztor pezrto pezrot pezort pezotr pzoter pzotre pzoetr pzoert pzoret pzorte
pztoer pztore pzteor pztero pztreo pztroe pzetor pzetro pzeotr pzeort pzerot
pzerto pzrteo pzrtoe pzreto pzreot pzroet pzrote eroptz eropzt erotpz erotzp
eroztp erozpt erpotz erpozt erptoz erptzo erpzto erpzot ertpoz ertpzo ertopz
ertozp ertzop ertzpo erzpto erzpot erztpo erztop erzotp erzopt eorptz eorpzt
eortpz eortzp eorztp eorzpt eoprtz eoprzt eoptrz eoptzr eopztr eopzrt eotprz
eotpzr eotrpz eotrzp eotzrp eotzpr eozptr eozprt eoztpr eoztrp eozrtp eozrpt
eportz eporzt epotrz epotzr epoztr epozrt eprotz eprozt eprtoz eprtzo eprzto
eprzot eptroz eptrzo eptorz eptozr eptzor eptzro epzrto epzrot epztro epztor
epzotr epzort etoprz etopzr etorpz etorzp etozrp etozpr etporz etpozr etproz
etprzo etpzro etpzor etrpoz etrpzo etropz etrozp etrzop etrzpo etzpro etzpor
etzrpo etzrop etzorp etzopr ezoptr ezoprt ezotpr ezotrp ezortp ezorpt ezpotr
ezport ezptor ezptro ezprto ezprot eztpor eztpro eztopr eztorp eztrop eztrpo
ezrpto ezrpot ezrtpo ezrtop ezrotp ezropt zropet zropte zroept zroetp zrotep
zrotpe zrpoet zrpote zrpeot zrpeto zrpteo zrptoe zrepot zrepto zreopt zreotp
zretop zretpo zrtpeo zrtpoe zrtepo zrteop zrtoep zrtope zorpet zorpte zorept
zoretp zortep zortpe zopret zoprte zopert zopetr zopter zoptre zoeprt zoeptr
zoerpt zoertp zoetrp zoetpr zotper zotpre zotepr zoterp zotrep zotrpe zporet
zporte zpoert zpoetr zpoter zpotre zproet zprote zpreot zpreto zprteo zprtoe
zperot zperto zpeort zpeotr zpetor zpetro zptreo zptroe zptero zpteor zptoer
zptore zeoprt zeoptr zeorpt zeortp zeotrp zeotpr zeport zepotr zeprot zeprto
zeptro zeptor zerpot zerpto zeropt zerotp zertop zertpo zetpro zetpor zetrpo
zetrop zetorp zetopr ztoper ztopre ztoepr ztoerp ztorep ztorpe ztpoer ztpore
ztpeor ztpero ztpreo ztproe ztepor ztepro zteopr zteorp zterop zterpo ztrpeo
ztrpoe ztrepo ztreop ztroep ztrope

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History of cryptography
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