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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: volume
cipher variations:
wpmvnf xqnwog yroxph zspyqi atqzrj
burask cvsbtl dwtcum exudvn fyvewo
gzwfxp haxgyq ibyhzr jczias kdajbt
lebkcu mfcldv ngdmew ohenfx pifogy
qjgphz rkhqia slirjb tmjskc unktld

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: volume
Cipher: elofnv

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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: volume

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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: volume
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: volume
Cipher: ibyhzr

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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: volume
Cipher: 154313542351

Extended Methods:
Method #1

Plaintext: volume
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
v o l u m e 
1 4 1 5 2 5 
5 3 3 4 3 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: volume
Cipher: qvwpsc

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Method #3

Plaintext: volume
method variations:
ucxixa cxixau xixauc
ixaucx xaucxi aucxix

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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: volume

all 720 cipher variations:
volume voluem volmue volmeu volemu voleum voulme voulem voumle voumel voueml
vouelm vomule vomuel vomlue vomleu vomelu vomeul voeuml voeulm voemul voemlu
voelmu voelum vloume vlouem vlomue vlomeu vloemu vloeum vluome vluoem vlumoe
vlumeo vluemo vlueom vlmuoe vlmueo vlmoue vlmoeu vlmeou vlmeuo vleumo vleuom
vlemuo vlemou vleomu vleoum vulome vuloem vulmoe vulmeo vulemo vuleom vuolme
vuolem vuomle vuomel vuoeml vuoelm vumole vumoel vumloe vumleo vumelo vumeol
vueoml vueolm vuemol vuemlo vuelmo vuelom vmluoe vmlueo vmloue vmloeu vmleou
vmleuo vmuloe vmuleo vmuole vmuoel vmueol vmuelo vmoule vmouel vmolue vmoleu
vmoelu vmoeul vmeuol vmeulo vmeoul vmeolu vmelou vmeluo velumo veluom velmuo
velmou velomu veloum veulmo veulom veumlo veumol veuoml veuolm vemulo vemuol
vemluo vemlou vemolu vemoul veouml veoulm veomul veomlu veolmu veolum ovlume
ovluem ovlmue ovlmeu ovlemu ovleum ovulme ovulem ovumle ovumel ovueml ovuelm
ovmule ovmuel ovmlue ovmleu ovmelu ovmeul oveuml oveulm ovemul ovemlu ovelmu
ovelum olvume olvuem olvmue olvmeu olvemu olveum oluvme oluvem olumve olumev
oluemv oluevm olmuve olmuev olmvue olmveu olmevu olmeuv oleumv oleuvm olemuv
olemvu olevmu olevum oulvme oulvem oulmve oulmev oulemv oulevm ouvlme ouvlem
ouvmle ouvmel ouveml ouvelm oumvle oumvel oumlve oumlev oumelv oumevl ouevml
ouevlm ouemvl ouemlv ouelmv ouelvm omluve omluev omlvue omlveu omlevu omleuv
omulve omulev omuvle omuvel omuevl omuelv omvule omvuel omvlue omvleu omvelu
omveul omeuvl omeulv omevul omevlu omelvu omeluv oelumv oeluvm oelmuv oelmvu
oelvmu oelvum oeulmv oeulvm oeumlv oeumvl oeuvml oeuvlm oemulv oemuvl oemluv
oemlvu oemvlu oemvul oevuml oevulm oevmul oevmlu oevlmu oevlum lovume lovuem
lovmue lovmeu lovemu loveum louvme louvem loumve loumev louemv louevm lomuve
lomuev lomvue lomveu lomevu lomeuv loeumv loeuvm loemuv loemvu loevmu loevum
lvoume lvouem lvomue lvomeu lvoemu lvoeum lvuome lvuoem lvumoe lvumeo lvuemo
lvueom lvmuoe lvmueo lvmoue lvmoeu lvmeou lvmeuo lveumo lveuom lvemuo lvemou
lveomu lveoum luvome luvoem luvmoe luvmeo luvemo luveom luovme luovem luomve
luomev luoemv luoevm lumove lumoev lumvoe lumveo lumevo lumeov lueomv lueovm
luemov luemvo luevmo luevom lmvuoe lmvueo lmvoue lmvoeu lmveou lmveuo lmuvoe
lmuveo lmuove lmuoev lmueov lmuevo lmouve lmouev lmovue lmoveu lmoevu lmoeuv
lmeuov lmeuvo lmeouv lmeovu lmevou lmevuo levumo levuom levmuo levmou levomu
levoum leuvmo leuvom leumvo leumov leuomv leuovm lemuvo lemuov lemvuo lemvou
lemovu lemouv leoumv leouvm leomuv leomvu leovmu leovum uolvme uolvem uolmve
uolmev uolemv uolevm uovlme uovlem uovmle uovmel uoveml uovelm uomvle uomvel
uomlve uomlev uomelv uomevl uoevml uoevlm uoemvl uoemlv uoelmv uoelvm ulovme
ulovem ulomve ulomev uloemv uloevm ulvome ulvoem ulvmoe ulvmeo ulvemo ulveom
ulmvoe ulmveo ulmove ulmoev ulmeov ulmevo ulevmo ulevom ulemvo ulemov uleomv
uleovm uvlome uvloem uvlmoe uvlmeo uvlemo uvleom uvolme uvolem uvomle uvomel
uvoeml uvoelm uvmole uvmoel uvmloe uvmleo uvmelo uvmeol uveoml uveolm uvemol
uvemlo uvelmo uvelom umlvoe umlveo umlove umloev umleov umlevo umvloe umvleo
umvole umvoel umveol umvelo umovle umovel umolve umolev umoelv umoevl umevol
umevlo umeovl umeolv umelov umelvo uelvmo uelvom uelmvo uelmov uelomv uelovm
uevlmo uevlom uevmlo uevmol uevoml uevolm uemvlo uemvol uemlvo uemlov uemolv
uemovl ueovml ueovlm ueomvl ueomlv ueolmv ueolvm moluve moluev molvue molveu
molevu moleuv moulve moulev mouvle mouvel mouevl mouelv movule movuel movlue
movleu movelu moveul moeuvl moeulv moevul moevlu moelvu moeluv mlouve mlouev
mlovue mloveu mloevu mloeuv mluove mluoev mluvoe mluveo mluevo mlueov mlvuoe
mlvueo mlvoue mlvoeu mlveou mlveuo mleuvo mleuov mlevuo mlevou mleovu mleouv
mulove muloev mulvoe mulveo mulevo muleov muolve muolev muovle muovel muoevl
muoelv muvole muvoel muvloe muvleo muvelo muveol mueovl mueolv muevol muevlo
muelvo muelov mvluoe mvlueo mvloue mvloeu mvleou mvleuo mvuloe mvuleo mvuole
mvuoel mvueol mvuelo mvoule mvouel mvolue mvoleu mvoelu mvoeul mveuol mveulo
mveoul mveolu mvelou mveluo meluvo meluov melvuo melvou melovu melouv meulvo
meulov meuvlo meuvol meuovl meuolv mevulo mevuol mevluo mevlou mevolu mevoul
meouvl meoulv meovul meovlu meolvu meoluv eolumv eoluvm eolmuv eolmvu eolvmu
eolvum eoulmv eoulvm eoumlv eoumvl eouvml eouvlm eomulv eomuvl eomluv eomlvu
eomvlu eomvul eovuml eovulm eovmul eovmlu eovlmu eovlum eloumv elouvm elomuv
elomvu elovmu elovum eluomv eluovm elumov elumvo eluvmo eluvom elmuov elmuvo
elmouv elmovu elmvou elmvuo elvumo elvuom elvmuo elvmou elvomu elvoum eulomv
eulovm eulmov eulmvo eulvmo eulvom euolmv euolvm euomlv euomvl euovml euovlm
eumolv eumovl eumlov eumlvo eumvlo eumvol euvoml euvolm euvmol euvmlo euvlmo
euvlom emluov emluvo emlouv emlovu emlvou emlvuo emulov emulvo emuolv emuovl
emuvol emuvlo emoulv emouvl emoluv emolvu emovlu emovul emvuol emvulo emvoul
emvolu emvlou emvluo evlumo evluom evlmuo evlmou evlomu evloum evulmo evulom
evumlo evumol evuoml evuolm evmulo evmuol evmluo evmlou evmolu evmoul evouml
evoulm evomul evomlu evolmu evolum

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History of cryptography
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