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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: micell
cipher variations:
njdfmm okegnn plfhoo qmgipp rnhjqq
soikrr tpjlss uqkmtt vrlnuu wsmovv
xtnpww yuoqxx zvpryy awqszz bxrtaa
cysubb dztvcc eauwdd fbvxee gcwyff
hdxzgg ieyahh jfzbii kgacjj lhbdkk

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: micell
Cipher: nrxvoo

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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: micell

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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: micell
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: micell
Cipher: zvpryy

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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: micell
Cipher: 234231511313

Extended Methods:
Method #1

Plaintext: micell
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
m i c e l l 
2 4 3 5 1 1 
3 2 1 1 3 3 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: micell
Cipher: rxahan

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Method #3

Plaintext: micell
method variations:
smvach mvachs vachsm
achsmv chsmva hsmvac

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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: micell

all 720 cipher variations:
micell micell miclel miclle miclle miclel miecll miecll mielcl miellc miellc
mielcl milecl milelc milcel milcle millce millec milelc milecl millec millce
milcle milcel mciell mciell mcilel mcille mcille mcilel mceill mceill mcelil
mcelli mcelli mcelil mcleil mcleli mcliel mclile mcllie mcllei mcleli mcleil
mcllei mcllie mclile mcliel mecill mecill meclil meclli meclli meclil meicll
meicll meilcl meillc meillc meilcl melicl melilc melcil melcli mellci mellic
melilc melicl mellic mellci melcli melcil mlceil mlceli mlciel mlcile mlclie
mlclei mlecil mlecli mleicl mleilc mlelic mlelci mliecl mlielc mlicel mlicle
mlilce mlilec mlleic mlleci mlliec mllice mllcie mllcei mlceli mlceil mlclei
mlclie mlcile mlciel mlecli mlecil mlelci mlelic mleilc mleicl mlleci mlleic
mllcei mllcie mllice mlliec mlielc mliecl mlilec mlilce mlicle mlicel imcell
imcell imclel imclle imclle imclel imecll imecll imelcl imellc imellc imelcl
imlecl imlelc imlcel imlcle imllce imllec imlelc imlecl imllec imllce imlcle
imlcel icmell icmell icmlel icmlle icmlle icmlel icemll icemll icelml icellm
icellm icelml icleml iclelm iclmel iclmle icllme icllem iclelm icleml icllem
icllme iclmle iclmel iecmll iecmll ieclml iecllm iecllm ieclml iemcll iemcll
iemlcl iemllc iemllc iemlcl ielmcl ielmlc ielcml ielclm iellcm iellmc ielmlc
ielmcl iellmc iellcm ielclm ielcml ilceml ilcelm ilcmel ilcmle ilclme ilclem
ilecml ileclm ilemcl ilemlc ilelmc ilelcm ilmecl ilmelc ilmcel ilmcle ilmlce
ilmlec illemc illecm illmec illmce illcme illcem ilcelm ilceml ilclem ilclme
ilcmle ilcmel ileclm ilecml ilelcm ilelmc ilemlc ilemcl illecm illemc illcem
illcme illmce illmec ilmelc ilmecl ilmlec ilmlce ilmcle ilmcel cimell cimell
cimlel cimlle cimlle cimlel ciemll ciemll cielml ciellm ciellm cielml cileml
cilelm cilmel cilmle cillme cillem cilelm cileml cillem cillme cilmle cilmel
cmiell cmiell cmilel cmille cmille cmilel cmeill cmeill cmelil cmelli cmelli
cmelil cmleil cmleli cmliel cmlile cmllie cmllei cmleli cmleil cmllei cmllie
cmlile cmliel cemill cemill cemlil cemlli cemlli cemlil ceimll ceimll ceilml
ceillm ceillm ceilml celiml celilm celmil celmli cellmi cellim celilm celiml
cellim cellmi celmli celmil clmeil clmeli clmiel clmile clmlie clmlei clemil
clemli cleiml cleilm clelim clelmi clieml clielm climel climle clilme clilem
clleim cllemi clliem cllime cllmie cllmei clmeli clmeil clmlei clmlie clmile
clmiel clemli clemil clelmi clelim cleilm cleiml cllemi clleim cllmei cllmie
cllime clliem clielm clieml clilem clilme climle climel eicmll eicmll eiclml
eicllm eicllm eiclml eimcll eimcll eimlcl eimllc eimllc eimlcl eilmcl eilmlc
eilcml eilclm eillcm eillmc eilmlc eilmcl eillmc eillcm eilclm eilcml ecimll
ecimll ecilml ecillm ecillm ecilml ecmill ecmill ecmlil ecmlli ecmlli ecmlil
eclmil eclmli ecliml eclilm ecllim ecllmi eclmli eclmil ecllmi ecllim eclilm
ecliml emcill emcill emclil emclli emclli emclil emicll emicll emilcl emillc
emillc emilcl emlicl emlilc emlcil emlcli emllci emllic emlilc emlicl emllic
emllci emlcli emlcil elcmil elcmli elciml elcilm elclim elclmi elmcil elmcli
elmicl elmilc elmlic elmlci elimcl elimlc elicml eliclm elilcm elilmc ellmic
ellmci ellimc ellicm ellcim ellcmi elcmli elcmil elclmi elclim elcilm elciml
elmcli elmcil elmlci elmlic elmilc elmicl ellmci ellmic ellcmi ellcim ellicm
ellimc elimlc elimcl elilmc elilcm eliclm elicml liceml licelm licmel licmle
liclme liclem liecml lieclm liemcl liemlc lielmc lielcm limecl limelc limcel
limcle limlce limlec lilemc lilecm lilmec lilmce lilcme lilcem lcieml lcielm
lcimel lcimle lcilme lcilem lceiml lceilm lcemil lcemli lcelmi lcelim lcmeil
lcmeli lcmiel lcmile lcmlie lcmlei lclemi lcleim lclmei lclmie lclime lcliem
leciml lecilm lecmil lecmli leclmi leclim leicml leiclm leimcl leimlc leilmc
leilcm lemicl lemilc lemcil lemcli lemlci lemlic lelimc lelicm lelmic lelmci
lelcmi lelcim lmceil lmceli lmciel lmcile lmclie lmclei lmecil lmecli lmeicl
lmeilc lmelic lmelci lmiecl lmielc lmicel lmicle lmilce lmilec lmleic lmleci
lmliec lmlice lmlcie lmlcei llcemi llceim llcmei llcmie llcime llciem llecmi
llecim llemci llemic lleimc lleicm llmeci llmeic llmcei llmcie llmice llmiec
lliemc lliecm llimec llimce llicme llicem licelm liceml liclem liclme licmle
licmel lieclm liecml lielcm lielmc liemlc liemcl lilecm lilemc lilcem lilcme
lilmce lilmec limelc limecl limlec limlce limcle limcel lcielm lcieml lcilem
lcilme lcimle lcimel lceilm lceiml lcelim lcelmi lcemli lcemil lcleim lclemi
lcliem lclime lclmie lclmei lcmeli lcmeil lcmlei lcmlie lcmile lcmiel lecilm
leciml leclim leclmi lecmli lecmil leiclm leicml leilcm leilmc leimlc leimcl
lelicm lelimc lelcim lelcmi lelmci lelmic lemilc lemicl lemlic lemlci lemcli
lemcil llceim llcemi llciem llcime llcmie llcmei llecim llecmi lleicm lleimc
llemic llemci lliecm lliemc llicem llicme llimce llimec llmeic llmeci llmiec
llmice llmcie llmcei lmceli lmceil lmclei lmclie lmcile lmciel lmecli lmecil
lmelci lmelic lmeilc lmeicl lmleci lmleic lmlcei lmlcie lmlice lmliec lmielc
lmiecl lmilec lmilce lmicle lmicel

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History of cryptography
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