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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: kurata
cipher variations:
lvsbub mwtcvc nxudwd oyvexe pzwfyf
qaxgzg rbyhah sczibi tdajcj uebkdk
vfclel wgdmfm xhengn yifoho zjgpip
akhqjq blirkr cmjsls dnktmt eolunu
fpmvov gqnwpw hroxqx ispyry jtqzsz

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: kurata
Cipher: pfizgz

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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: kurata

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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: kurata
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: kurata
Cipher: xhengn

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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: kurata
Cipher: 525424114411

Extended Methods:
Method #1

Plaintext: kurata
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
k u r a t a 
5 5 2 1 4 1 
2 4 4 1 4 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: kurata
Cipher: zbdrdd

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Method #3

Plaintext: kurata
method variations:
widqdv idqdvw dqdvwi
qdvwid dvwidq vwidqd

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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: kurata

all 720 cipher variations:
kurata kuraat kurtaa kurtaa kurata kuraat kuarta kuarat kuatra kuatar kuaatr
kuaart kutara kutaar kutraa kutraa kutara kutaar kuaatr kuaart kuatar kuatra
kuarta kuarat kruata kruaat krutaa krutaa kruata kruaat krauta krauat kratua
kratau kraatu kraaut krtaua krtaau krtuaa krtuaa krtaua krtaau kraatu kraaut
kratau kratua krauta krauat karuta karuat kartua kartau karatu karaut kaurta
kaurat kautra kautar kauatr kauart katura katuar katrua katrau kataru kataur
kaautr kaaurt kaatur kaatru kaartu kaarut ktraua ktraau ktruaa ktruaa ktraua
ktraau ktarua ktarau ktaura ktauar ktaaur ktaaru ktuara ktuaar kturaa kturaa
ktuara ktuaar ktaaur ktaaru ktauar ktaura ktarua ktarau karatu karaut kartau
kartua karuta karuat kaartu kaarut kaatru kaatur kaautr kaaurt kataru kataur
katrau katrua katura katuar kauatr kauart kautar kautra kaurta kaurat ukrata
ukraat ukrtaa ukrtaa ukrata ukraat ukarta ukarat ukatra ukatar ukaatr ukaart
uktara uktaar uktraa uktraa uktara uktaar ukaatr ukaart ukatar ukatra ukarta
ukarat urkata urkaat urktaa urktaa urkata urkaat urakta urakat uratka uratak
uraatk uraakt urtaka urtaak urtkaa urtkaa urtaka urtaak uraatk uraakt uratak
uratka urakta urakat uarkta uarkat uartka uartak uaratk uarakt uakrta uakrat
uaktra uaktar uakatr uakart uatkra uatkar uatrka uatrak uatark uatakr uaaktr
uaakrt uaatkr uaatrk uaartk uaarkt utraka utraak utrkaa utrkaa utraka utraak
utarka utarak utakra utakar utaakr utaark utkara utkaar utkraa utkraa utkara
utkaar utaakr utaark utakar utakra utarka utarak uaratk uarakt uartak uartka
uarkta uarkat uaartk uaarkt uaatrk uaatkr uaaktr uaakrt uatark uatakr uatrak
uatrka uatkra uatkar uakatr uakart uaktar uaktra uakrta uakrat rukata rukaat
ruktaa ruktaa rukata rukaat ruakta ruakat ruatka ruatak ruaatk ruaakt rutaka
rutaak rutkaa rutkaa rutaka rutaak ruaatk ruaakt ruatak ruatka ruakta ruakat
rkuata rkuaat rkutaa rkutaa rkuata rkuaat rkauta rkauat rkatua rkatau rkaatu
rkaaut rktaua rktaau rktuaa rktuaa rktaua rktaau rkaatu rkaaut rkatau rkatua
rkauta rkauat rakuta rakuat raktua raktau rakatu rakaut raukta raukat rautka
rautak rauatk rauakt ratuka ratuak ratkua ratkau rataku ratauk raautk raaukt
raatuk raatku raaktu raakut rtkaua rtkaau rtkuaa rtkuaa rtkaua rtkaau rtakua
rtakau rtauka rtauak rtaauk rtaaku rtuaka rtuaak rtukaa rtukaa rtuaka rtuaak
rtaauk rtaaku rtauak rtauka rtakua rtakau rakatu rakaut raktau raktua rakuta
rakuat raaktu raakut raatku raatuk raautk raaukt rataku ratauk ratkau ratkua
ratuka ratuak rauatk rauakt rautak rautka raukta raukat aurkta aurkat aurtka
aurtak auratk aurakt aukrta aukrat auktra auktar aukatr aukart autkra autkar
autrka autrak autark autakr auaktr auakrt auatkr auatrk auartk auarkt arukta
arukat arutka arutak aruatk aruakt arkuta arkuat arktua arktau arkatu arkaut
artkua artkau artuka artuak artauk artaku araktu arakut aratku aratuk arautk
araukt akruta akruat akrtua akrtau akratu akraut akurta akurat akutra akutar
akuatr akuart aktura aktuar aktrua aktrau aktaru aktaur akautr akaurt akatur
akatru akartu akarut atrkua atrkau atruka atruak atrauk atraku atkrua atkrau
atkura atkuar atkaur atkaru atukra atukar aturka aturak atuark atuakr atakur
atakru ataukr ataurk ataruk atarku aarktu aarkut aartku aartuk aarutk aarukt
aakrtu aakrut aaktru aaktur aakutr aakurt aatkru aatkur aatrku aatruk aaturk
aatukr aauktr aaukrt aautkr aautrk aaurtk aaurkt turaka turaak turkaa turkaa
turaka turaak tuarka tuarak tuakra tuakar tuaakr tuaark tukara tukaar tukraa
tukraa tukara tukaar tuaakr tuaark tuakar tuakra tuarka tuarak truaka truaak
trukaa trukaa truaka truaak trauka trauak trakua trakau traaku traauk trkaua
trkaau trkuaa trkuaa trkaua trkaau traaku traauk trakau trakua trauka trauak
taruka taruak tarkua tarkau taraku tarauk taurka taurak taukra taukar tauakr
tauark takura takuar takrua takrau takaru takaur taaukr taaurk taakur taakru
taarku taaruk tkraua tkraau tkruaa tkruaa tkraua tkraau tkarua tkarau tkaura
tkauar tkaaur tkaaru tkuara tkuaar tkuraa tkuraa tkuara tkuaar tkaaur tkaaru
tkauar tkaura tkarua tkarau taraku tarauk tarkau tarkua taruka taruak taarku
taaruk taakru taakur taaukr taaurk takaru takaur takrau takrua takura takuar
tauakr tauark taukar taukra taurka taurak auratk aurakt aurtak aurtka aurkta
aurkat auartk auarkt auatrk auatkr auaktr auakrt autark autakr autrak autrka
autkra autkar aukatr aukart auktar auktra aukrta aukrat aruatk aruakt arutak
arutka arukta arukat arautk araukt aratuk aratku araktu arakut artauk artaku
artuak artuka artkua artkau arkatu arkaut arktau arktua arkuta arkuat aarutk
aarukt aartuk aartku aarktu aarkut aaurtk aaurkt aautrk aautkr aauktr aaukrt
aaturk aatukr aatruk aatrku aatkru aatkur aakutr aakurt aaktur aaktru aakrtu
aakrut atrauk atraku atruak atruka atrkua atrkau ataruk atarku ataurk ataukr
atakur atakru atuark atuakr aturak aturka atukra atukar atkaur atkaru atkuar
atkura atkrua atkrau akratu akraut akrtau akrtua akruta akruat akartu akarut
akatru akatur akautr akaurt aktaru aktaur aktrau aktrua aktura aktuar akuatr
akuart akutar akutra akurta akurat

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History of cryptography
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