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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: janick
cipher variations:
kbojdl lcpkem mdqlfn nermgo ofsnhp
pgtoiq qhupjr rivqks sjwrlt tkxsmu
ulytnv vmzuow wnavpx xobwqy ypcxrz
zqdysa areztb bsfauc ctgbvd duhcwe
evidxf fwjeyg gxkfzh hylgai izmhbj

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: janick
Cipher: qzmrxp

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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: janick

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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: janick
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: janick
Cipher: wnavpx

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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: janick
Cipher: 421133423152

Extended Methods:
Method #1

Plaintext: janick
method variations:

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

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Method #3

Plaintext: janick
method variations:
blsmvr lsmvrb smvrbl
mvrbls vrblsm rblsmv

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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: janick

all 720 cipher variations:
janick janikc jancik jancki jankci jankic jainck jainkc jaicnk jaickn jaikcn
jaiknc jacink jacikn jacnik jacnki jackni jackin jakicn jakinc jakcin jakcni
jaknci jaknic jnaick jnaikc jnacik jnacki jnakci jnakic jniack jniakc jnicak
jnicka jnikca jnikac jnciak jncika jncaik jncaki jnckai jnckia jnkica jnkiac
jnkcia jnkcai jnkaci jnkaic jinack jinakc jincak jincka jinkca jinkac jianck
jiankc jiacnk jiackn jiakcn jiaknc jicank jicakn jicnak jicnka jickna jickan
jikacn jikanc jikcan jikcna jiknca jiknac jcniak jcnika jcnaik jcnaki jcnkai
jcnkia jcinak jcinka jciank jciakn jcikan jcikna jcaink jcaikn jcanik jcanki
jcakni jcakin jckian jckina jckain jckani jcknai jcknia jknica jkniac jkncia
jkncai jknaci jknaic jkinca jkinac jkicna jkican jkiacn jkianc jkcina jkcian
jkcnia jkcnai jkcani jkcain jkaicn jkainc jkacin jkacni jkanci jkanic ajnick
ajnikc ajncik ajncki ajnkci ajnkic ajinck ajinkc ajicnk ajickn ajikcn ajiknc
ajcink ajcikn ajcnik ajcnki ajckni ajckin ajkicn ajkinc ajkcin ajkcni ajknci
ajknic anjick anjikc anjcik anjcki anjkci anjkic anijck anijkc anicjk anickj
anikcj anikjc ancijk ancikj ancjik ancjki anckji anckij ankicj ankijc ankcij
ankcji ankjci ankjic ainjck ainjkc aincjk ainckj ainkcj ainkjc aijnck aijnkc
aijcnk aijckn aijkcn aijknc aicjnk aicjkn aicnjk aicnkj aicknj aickjn aikjcn
aikjnc aikcjn aikcnj aikncj aiknjc acnijk acnikj acnjik acnjki acnkji acnkij
acinjk acinkj acijnk acijkn acikjn aciknj acjink acjikn acjnik acjnki acjkni
acjkin ackijn ackinj ackjin ackjni acknji acknij aknicj aknijc akncij akncji
aknjci aknjic akincj akinjc akicnj akicjn akijcn akijnc akcinj akcijn akcnij
akcnji akcjni akcjin akjicn akjinc akjcin akjcni akjnci akjnic najick najikc
najcik najcki najkci najkic naijck naijkc naicjk naickj naikcj naikjc nacijk
nacikj nacjik nacjki nackji nackij nakicj nakijc nakcij nakcji nakjci nakjic
njaick njaikc njacik njacki njakci njakic njiack njiakc njicak njicka njikca
njikac njciak njcika njcaik njcaki njckai njckia njkica njkiac njkcia njkcai
njkaci njkaic nijack nijakc nijcak nijcka nijkca nijkac niajck niajkc niacjk
niackj niakcj niakjc nicajk nicakj nicjak nicjka nickja nickaj nikacj nikajc
nikcaj nikcja nikjca nikjac ncjiak ncjika ncjaik ncjaki ncjkai ncjkia ncijak
ncijka nciajk nciakj ncikaj ncikja ncaijk ncaikj ncajik ncajki ncakji ncakij
nckiaj nckija nckaij nckaji nckjai nckjia nkjica nkjiac nkjcia nkjcai nkjaci
nkjaic nkijca nkijac nkicja nkicaj nkiacj nkiajc nkcija nkciaj nkcjia nkcjai
nkcaji nkcaij nkaicj nkaijc nkacij nkacji nkajci nkajic ianjck ianjkc iancjk
ianckj iankcj iankjc iajnck iajnkc iajcnk iajckn iajkcn iajknc iacjnk iacjkn
iacnjk iacnkj iacknj iackjn iakjcn iakjnc iakcjn iakcnj iakncj iaknjc inajck
inajkc inacjk inackj inakcj inakjc injack injakc injcak injcka injkca injkac
incjak incjka incajk incakj inckaj inckja inkjca inkjac inkcja inkcaj inkacj
inkajc ijnack ijnakc ijncak ijncka ijnkca ijnkac ijanck ijankc ijacnk ijackn
ijakcn ijaknc ijcank ijcakn ijcnak ijcnka ijckna ijckan ijkacn ijkanc ijkcan
ijkcna ijknca ijknac icnjak icnjka icnajk icnakj icnkaj icnkja icjnak icjnka
icjank icjakn icjkan icjkna icajnk icajkn icanjk icankj icaknj icakjn ickjan
ickjna ickajn ickanj icknaj icknja iknjca iknjac ikncja ikncaj iknacj iknajc
ikjnca ikjnac ikjcna ikjcan ikjacn ikjanc ikcjna ikcjan ikcnja ikcnaj ikcanj
ikcajn ikajcn ikajnc ikacjn ikacnj ikancj ikanjc canijk canikj canjik canjki
cankji cankij cainjk cainkj caijnk caijkn caikjn caiknj cajink cajikn cajnik
cajnki cajkni cajkin cakijn cakinj cakjin cakjni caknji caknij cnaijk cnaikj
cnajik cnajki cnakji cnakij cniajk cniakj cnijak cnijka cnikja cnikaj cnjiak
cnjika cnjaik cnjaki cnjkai cnjkia cnkija cnkiaj cnkjia cnkjai cnkaji cnkaij
cinajk cinakj cinjak cinjka cinkja cinkaj cianjk ciankj ciajnk ciajkn ciakjn
ciaknj cijank cijakn cijnak cijnka cijkna cijkan cikajn cikanj cikjan cikjna
ciknja ciknaj cjniak cjnika cjnaik cjnaki cjnkai cjnkia cjinak cjinka cjiank
cjiakn cjikan cjikna cjaink cjaikn cjanik cjanki cjakni cjakin cjkian cjkina
cjkain cjkani cjknai cjknia cknija ckniaj cknjia cknjai cknaji cknaij ckinja
ckinaj ckijna ckijan ckiajn ckianj ckjina ckjian ckjnia ckjnai ckjani ckjain
ckaijn ckainj ckajin ckajni ckanji ckanij kanicj kanijc kancij kancji kanjci
kanjic kaincj kainjc kaicnj kaicjn kaijcn kaijnc kacinj kacijn kacnij kacnji
kacjni kacjin kajicn kajinc kajcin kajcni kajnci kajnic knaicj knaijc knacij
knacji knajci knajic kniacj kniajc knicaj knicja knijca knijac knciaj kncija
kncaij kncaji kncjai kncjia knjica knjiac knjcia knjcai knjaci knjaic kinacj
kinajc kincaj kincja kinjca kinjac kiancj kianjc kiacnj kiacjn kiajcn kiajnc
kicanj kicajn kicnaj kicnja kicjna kicjan kijacn kijanc kijcan kijcna kijnca
kijnac kcniaj kcnija kcnaij kcnaji kcnjai kcnjia kcinaj kcinja kcianj kciajn
kcijan kcijna kcainj kcaijn kcanij kcanji kcajni kcajin kcjian kcjina kcjain
kcjani kcjnai kcjnia kjnica kjniac kjncia kjncai kjnaci kjnaic kjinca kjinac
kjicna kjican kjiacn kjianc kjcina kjcian kjcnia kjcnai kjcani kjcain kjaicn
kjainc kjacin kjacni kjanci kjanic

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History of cryptography
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