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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: surati
cipher variations:
tvsbuj uwtcvk vxudwl wyvexm xzwfyn
yaxgzo zbyhap aczibq bdajcr cebkds
dfclet egdmfu fhengv gifohw hjgpix
ikhqjy jlirkz kmjsla lnktmb molunc
npmvod oqnwpe proxqf qspyrg rtqzsh

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: surati
Cipher: hfizgr

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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: surati

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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: surati
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: surati
Cipher: fhengv

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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: surati
Cipher: 345424114442

Extended Methods:
Method #1

Plaintext: surati
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
s u r a t i 
3 5 2 1 4 4 
4 4 4 1 4 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: surati
Cipher: xbttdi

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Method #3

Plaintext: surati
method variations:
yidqtm idqtmy dqtmyi
qtmyid tmyidq myidqt

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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: surati

all 720 cipher variations:
surati surait surtai surtia surita suriat suarti suarit suatri suatir suaitr
suairt sutari sutair sutrai sutria sutira sutiar suiatr suiart suitar suitra
suirta suirat sruati sruait srutai srutia sruita sruiat srauti srauit sratui
sratiu sraitu sraiut srtaui srtaiu srtuai srtuia srtiua srtiau sriatu sriaut
sritau sritua sriuta sriuat saruti saruit sartui sartiu saritu sariut saurti
saurit sautri sautir sauitr sauirt saturi satuir satrui satriu satiru satiur
saiutr saiurt saitur saitru sairtu sairut straui straiu struai struia striua
striau starui stariu stauri stauir staiur stairu stuari stuair sturai sturia
stuira stuiar stiaur stiaru stiuar stiura stirua stirau siratu siraut sirtau
sirtua siruta siruat siartu siarut siatru siatur siautr siaurt sitaru sitaur
sitrau sitrua situra situar siuatr siuart siutar siutra siurta siurat usrati
usrait usrtai usrtia usrita usriat usarti usarit usatri usatir usaitr usairt
ustari ustair ustrai ustria ustira ustiar usiatr usiart usitar usitra usirta
usirat ursati ursait urstai urstia ursita ursiat urasti urasit uratsi uratis
uraits uraist urtasi urtais urtsai urtsia urtisa urtias uriats uriast uritas
uritsa urista urisat uarsti uarsit uartsi uartis uarits uarist uasrti uasrit
uastri uastir uasitr uasirt uatsri uatsir uatrsi uatris uatirs uatisr uaistr
uaisrt uaitsr uaitrs uairts uairst utrasi utrais utrsai utrsia utrisa utrias
utarsi utaris utasri utasir utaisr utairs utsari utsair utsrai utsria utsira
utsiar utiasr utiars utisar utisra utirsa utiras uirats uirast uirtas uirtsa
uirsta uirsat uiarts uiarst uiatrs uiatsr uiastr uiasrt uitars uitasr uitras
uitrsa uitsra uitsar uisatr uisart uistar uistra uisrta uisrat rusati rusait
rustai rustia rusita rusiat ruasti ruasit ruatsi ruatis ruaits ruaist rutasi
rutais rutsai rutsia rutisa rutias ruiats ruiast ruitas ruitsa ruista ruisat
rsuati rsuait rsutai rsutia rsuita rsuiat rsauti rsauit rsatui rsatiu rsaitu
rsaiut rstaui rstaiu rstuai rstuia rstiua rstiau rsiatu rsiaut rsitau rsitua
rsiuta rsiuat rasuti rasuit rastui rastiu rasitu rasiut rausti rausit rautsi
rautis rauits rauist ratusi ratuis ratsui ratsiu ratisu ratius raiuts raiust
raitus raitsu raistu raisut rtsaui rtsaiu rtsuai rtsuia rtsiua rtsiau rtasui
rtasiu rtausi rtauis rtaius rtaisu rtuasi rtuais rtusai rtusia rtuisa rtuias
rtiaus rtiasu rtiuas rtiusa rtisua rtisau risatu risaut ristau ristua risuta
risuat riastu riasut riatsu riatus riauts riaust ritasu ritaus ritsau ritsua
ritusa rituas riuats riuast riutas riutsa riusta riusat aursti aursit aurtsi
aurtis aurits aurist ausrti ausrit austri austir ausitr ausirt autsri autsir
autrsi autris autirs autisr auistr auisrt auitsr auitrs auirts auirst arusti
arusit arutsi arutis aruits aruist arsuti arsuit arstui arstiu arsitu arsiut
artsui artsiu artusi artuis artius artisu aristu arisut aritsu aritus ariuts
ariust asruti asruit asrtui asrtiu asritu asriut asurti asurit asutri asutir
asuitr asuirt asturi astuir astrui astriu astiru astiur asiutr asiurt asitur
asitru asirtu asirut atrsui atrsiu atrusi atruis atrius atrisu atsrui atsriu
atsuri atsuir atsiur atsiru atusri atusir atursi aturis atuirs atuisr atisur
atisru atiusr atiurs atirus atirsu airstu airsut airtsu airtus airuts airust
aisrtu aisrut aistru aistur aisutr aisurt aitsru aitsur aitrsu aitrus aiturs
aitusr aiustr aiusrt aiutsr aiutrs aiurts aiurst turasi turais tursai tursia
turisa turias tuarsi tuaris tuasri tuasir tuaisr tuairs tusari tusair tusrai
tusria tusira tusiar tuiasr tuiars tuisar tuisra tuirsa tuiras truasi truais
trusai trusia truisa truias trausi trauis trasui trasiu traisu traius trsaui
trsaiu trsuai trsuia trsiua trsiau triasu triaus trisau trisua triusa triuas
tarusi taruis tarsui tarsiu tarisu tarius taursi tauris tausri tausir tauisr
tauirs tasuri tasuir tasrui tasriu tasiru tasiur taiusr taiurs taisur taisru
tairsu tairus tsraui tsraiu tsruai tsruia tsriua tsriau tsarui tsariu tsauri
tsauir tsaiur tsairu tsuari tsuair tsurai tsuria tsuira tsuiar tsiaur tsiaru
tsiuar tsiura tsirua tsirau tirasu tiraus tirsau tirsua tirusa tiruas tiarsu
tiarus tiasru tiasur tiausr tiaurs tisaru tisaur tisrau tisrua tisura tisuar
tiuasr tiuars tiusar tiusra tiursa tiuras iurats iurast iurtas iurtsa iursta
iursat iuarts iuarst iuatrs iuatsr iuastr iuasrt iutars iutasr iutras iutrsa
iutsra iutsar iusatr iusart iustar iustra iusrta iusrat iruats iruast irutas
irutsa irusta irusat irauts iraust iratus iratsu irastu irasut irtaus irtasu
irtuas irtusa irtsua irtsau irsatu irsaut irstau irstua irsuta irsuat iaruts
iarust iartus iartsu iarstu iarsut iaurts iaurst iautrs iautsr iaustr iausrt
iaturs iatusr iatrus iatrsu iatsru iatsur iasutr iasurt iastur iastru iasrtu
iasrut itraus itrasu itruas itrusa itrsua itrsau itarus itarsu itaurs itausr
itasur itasru ituars ituasr ituras itursa itusra itusar itsaur itsaru itsuar
itsura itsrua itsrau isratu israut isrtau isrtua isruta isruat isartu isarut
isatru isatur isautr isaurt istaru istaur istrau istrua istura istuar isuatr
isuart isutar isutra isurta isurat

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History of cryptography
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