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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: stobie
cipher variations:
tupcjf uvqdkg vwrelh wxsfmi xytgnj
yzuhok zavipl abwjqm bcxkrn cdylso
dezmtp efanuq fgbovr ghcpws hidqxt
ijeryu jkfszv klgtaw lmhubx mnivcy
nojwdz opkxea pqlyfb qrmzgc rsnahd

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: stobie
Cipher: hglyrv

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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: stobie

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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: stobie
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: stobie
Cipher: fgbovr

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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: stobie
Cipher: 344443214251

Extended Methods:
Method #1

Plaintext: stobie
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
s t o b i e 
3 4 4 2 4 5 
4 4 3 1 2 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: stobie
Cipher: siytcb

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Method #3

Plaintext: stobie
method variations:
tthqwl thqwlt hqwltt
qwltth wltthq ltthqw

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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: stobie

all 720 cipher variations:
stobie stobei stoibe stoieb stoeib stoebi stboie stboei stbioe stbieo stbeio
stbeoi stiboe stibeo stiobe stioeb stieob stiebo stebio steboi steibo steiob
steoib steobi sotbie sotbei sotibe sotieb soteib sotebi sobtie sobtei sobite
sobiet sobeit sobeti soibte soibet soitbe soiteb soietb soiebt soebit soebti
soeibt soeitb soetib soetbi sbotie sbotei sboite sboiet sboeit sboeti sbtoie
sbtoei sbtioe sbtieo sbteio sbteoi sbitoe sbiteo sbiote sbioet sbieot sbieto
sbetio sbetoi sbeito sbeiot sbeoit sbeoti siobte siobet siotbe sioteb sioetb
sioebt sibote siboet sibtoe sibteo sibeto sibeot sitboe sitbeo sitobe sitoeb
siteob sitebo siebto siebot sietbo sietob sieotb sieobt seobit seobti seoibt
seoitb seotib seotbi seboit seboti sebiot sebito sebtio sebtoi seibot seibto
seiobt seiotb seitob seitbo setbio setboi setibo setiob setoib setobi tsobie
tsobei tsoibe tsoieb tsoeib tsoebi tsboie tsboei tsbioe tsbieo tsbeio tsbeoi
tsiboe tsibeo tsiobe tsioeb tsieob tsiebo tsebio tseboi tseibo tseiob tseoib
tseobi tosbie tosbei tosibe tosieb toseib tosebi tobsie tobsei tobise tobies
tobeis tobesi toibse toibes toisbe toiseb toiesb toiebs toebis toebsi toeibs
toeisb toesib toesbi tbosie tbosei tboise tboies tboeis tboesi tbsoie tbsoei
tbsioe tbsieo tbseio tbseoi tbisoe tbiseo tbiose tbioes tbieos tbieso tbesio
tbesoi tbeiso tbeios tbeois tbeosi tiobse tiobes tiosbe tioseb tioesb tioebs
tibose tiboes tibsoe tibseo tibeso tibeos tisboe tisbeo tisobe tisoeb tiseob
tisebo tiebso tiebos tiesbo tiesob tieosb tieobs teobis teobsi teoibs teoisb
teosib teosbi tebois tebosi tebios tebiso tebsio tebsoi teibos teibso teiobs
teiosb teisob teisbo tesbio tesboi tesibo tesiob tesoib tesobi otsbie otsbei
otsibe otsieb otseib otsebi otbsie otbsei otbise otbies otbeis otbesi otibse
otibes otisbe otiseb otiesb otiebs otebis otebsi oteibs oteisb otesib otesbi
ostbie ostbei ostibe ostieb osteib ostebi osbtie osbtei osbite osbiet osbeit
osbeti osibte osibet ositbe ositeb osietb osiebt osebit osebti oseibt oseitb
osetib osetbi obstie obstei obsite obsiet obseit obseti obtsie obtsei obtise
obties obteis obtesi obitse obites obiste obiset obiest obiets obetis obetsi
obeits obeist obesit obesti oisbte oisbet oistbe oisteb oisetb oisebt oibste
oibset oibtse oibtes oibets oibest oitbse oitbes oitsbe oitseb oitesb oitebs
oiebts oiebst oietbs oietsb oiestb oiesbt oesbit oesbti oesibt oesitb oestib
oestbi oebsit oebsti oebist oebits oebtis oebtsi oeibst oeibts oeisbt oeistb
oeitsb oeitbs oetbis oetbsi oetibs oetisb oetsib oetsbi btosie btosei btoise
btoies btoeis btoesi btsoie btsoei btsioe btsieo btseio btseoi btisoe btiseo
btiose btioes btieos btieso btesio btesoi bteiso bteios bteois bteosi botsie
botsei botise boties boteis botesi bostie bostei bosite bosiet boseit boseti
boiste boiset boitse boites boiets boiest boesit boesti boeist boeits boetis
boetsi bsotie bsotei bsoite bsoiet bsoeit bsoeti bstoie bstoei bstioe bstieo
bsteio bsteoi bsitoe bsiteo bsiote bsioet bsieot bsieto bsetio bsetoi bseito
bseiot bseoit bseoti bioste bioset biotse biotes bioets bioest bisote bisoet
bistoe bisteo biseto biseot bitsoe bitseo bitose bitoes biteos biteso biesto
biesot bietso bietos bieots bieost beosit beosti beoist beoits beotis beotsi
besoit besoti besiot besito bestio bestoi beisot beisto beiost beiots beitos
beitso betsio betsoi betiso betios betois betosi itobse itobes itosbe itoseb
itoesb itoebs itbose itboes itbsoe itbseo itbeso itbeos itsboe itsbeo itsobe
itsoeb itseob itsebo itebso itebos itesbo itesob iteosb iteobs iotbse iotbes
iotsbe iotseb iotesb iotebs iobtse iobtes iobste iobset iobest iobets iosbte
iosbet iostbe iosteb iosetb iosebt ioebst ioebts ioesbt ioestb ioetsb ioetbs
ibotse ibotes iboste iboset iboest iboets ibtose ibtoes ibtsoe ibtseo ibteso
ibteos ibstoe ibsteo ibsote ibsoet ibseot ibseto ibetso ibetos ibesto ibesot
ibeost ibeots isobte isobet isotbe isoteb isoetb isoebt isbote isboet isbtoe
isbteo isbeto isbeot istboe istbeo istobe istoeb isteob istebo isebto isebot
isetbo isetob iseotb iseobt ieobst ieobts ieosbt ieostb ieotsb ieotbs iebost
iebots iebsot iebsto iebtso iebtos iesbot iesbto iesobt iesotb iestob iestbo
ietbso ietbos ietsbo ietsob ietosb ietobs etobis etobsi etoibs etoisb etosib
etosbi etbois etbosi etbios etbiso etbsio etbsoi etibos etibso etiobs etiosb
etisob etisbo etsbio etsboi etsibo etsiob etsoib etsobi eotbis eotbsi eotibs
eotisb eotsib eotsbi eobtis eobtsi eobits eobist eobsit eobsti eoibts eoibst
eoitbs eoitsb eoistb eoisbt eosbit eosbti eosibt eositb eostib eostbi ebotis
ebotsi eboits eboist ebosit ebosti ebtois ebtosi ebtios ebtiso ebtsio ebtsoi
ebitos ebitso ebiots ebiost ebisot ebisto ebstio ebstoi ebsito ebsiot ebsoit
ebsoti eiobts eiobst eiotbs eiotsb eiostb eiosbt eibots eibost eibtos eibtso
eibsto eibsot eitbos eitbso eitobs eitosb eitsob eitsbo eisbto eisbot eistbo
eistob eisotb eisobt esobit esobti esoibt esoitb esotib esotbi esboit esboti
esbiot esbito esbtio esbtoi esibot esibto esiobt esiotb esitob esitbo estbio
estboi estibo estiob estoib estobi

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History of cryptography
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