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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: dhauri
cipher variations:
eibvsj fjcwtk gkdxul hleyvm imfzwn
jngaxo kohbyp lpiczq mqjdar nrkebs
oslfct ptmgdu qunhev rvoifw swpjgx
txqkhy uyrliz vzsmja watnkb xbuolc
ycvpmd zdwqne aexrof bfyspg cgztqh

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: dhauri
Cipher: wszfir

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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: dhauri

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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: dhauri
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: dhauri
Cipher: qunhev

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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: dhauri
Cipher: 413211542442

Extended Methods:
Method #1

Plaintext: dhauri
method variations:

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

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Method #3

Plaintext: dhauri
method variations:
lbvitr bvitrl vitrlb
itrlbv trlbvi rlbvit

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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: dhauri

all 720 cipher variations:
dhauri dhauir dharui dhariu dhairu dhaiur dhuari dhuair dhurai dhuria dhuira
dhuiar dhruai dhruia dhraui dhraiu dhriau dhriua dhiura dhiuar dhirua dhirau
dhiaru dhiaur dahuri dahuir dahrui dahriu dahiru dahiur dauhri dauhir daurhi
daurih dauirh dauihr daruhi daruih darhui darhiu darihu dariuh daiurh daiuhr
dairuh dairhu daihru daihur duahri duahir duarhi duarih duairh duaihr duhari
duhair duhrai duhria duhira duhiar durhai durhia durahi duraih duriah duriha
duihra duihar duirha duirah duiarh duiahr drauhi drauih drahui drahiu draihu
draiuh druahi druaih druhai druhia druiha druiah drhuai drhuia drhaui drhaiu
drhiau drhiua driuha driuah drihua drihau driahu driauh diaurh diauhr diaruh
diarhu diahru diahur diuarh diuahr diurah diurha diuhra diuhar diruah diruha
dirauh dirahu dirhau dirhua dihura dihuar dihrua dihrau diharu dihaur hdauri
hdauir hdarui hdariu hdairu hdaiur hduari hduair hdurai hduria hduira hduiar
hdruai hdruia hdraui hdraiu hdriau hdriua hdiura hdiuar hdirua hdirau hdiaru
hdiaur haduri haduir hadrui hadriu hadiru hadiur haudri haudir haurdi haurid
hauird hauidr harudi haruid hardui hardiu haridu hariud haiurd haiudr hairud
hairdu haidru haidur huadri huadir huardi huarid huaird huaidr hudari hudair
hudrai hudria hudira hudiar hurdai hurdia huradi huraid huriad hurida huidra
huidar huirda huirad huiard huiadr hraudi hrauid hradui hradiu hraidu hraiud
hruadi hruaid hrudai hrudia hruida hruiad hrduai hrduia hrdaui hrdaiu hrdiau
hrdiua hriuda hriuad hridua hridau hriadu hriaud hiaurd hiaudr hiarud hiardu
hiadru hiadur hiuard hiuadr hiurad hiurda hiudra hiudar hiruad hiruda hiraud
hiradu hirdau hirdua hidura hiduar hidrua hidrau hidaru hidaur ahduri ahduir
ahdrui ahdriu ahdiru ahdiur ahudri ahudir ahurdi ahurid ahuird ahuidr ahrudi
ahruid ahrdui ahrdiu ahridu ahriud ahiurd ahiudr ahirud ahirdu ahidru ahidur
adhuri adhuir adhrui adhriu adhiru adhiur aduhri aduhir adurhi adurih aduirh
aduihr adruhi adruih adrhui adrhiu adrihu adriuh adiurh adiuhr adiruh adirhu
adihru adihur audhri audhir audrhi audrih audirh audihr auhdri auhdir auhrdi
auhrid auhird auhidr aurhdi aurhid aurdhi aurdih auridh aurihd auihrd auihdr
auirhd auirdh auidrh auidhr arduhi arduih ardhui ardhiu ardihu ardiuh arudhi
arudih aruhdi aruhid aruihd aruidh arhudi arhuid arhdui arhdiu arhidu arhiud
ariuhd ariudh arihud arihdu aridhu ariduh aidurh aiduhr aidruh aidrhu aidhru
aidhur aiudrh aiudhr aiurdh aiurhd aiuhrd aiuhdr airudh airuhd airduh airdhu
airhdu airhud aihurd aihudr aihrud aihrdu aihdru aihdur uhadri uhadir uhardi
uharid uhaird uhaidr uhdari uhdair uhdrai uhdria uhdira uhdiar uhrdai uhrdia
uhradi uhraid uhriad uhrida uhidra uhidar uhirda uhirad uhiard uhiadr uahdri
uahdir uahrdi uahrid uahird uahidr uadhri uadhir uadrhi uadrih uadirh uadihr
uardhi uardih uarhdi uarhid uarihd uaridh uaidrh uaidhr uairdh uairhd uaihrd
uaihdr udahri udahir udarhi udarih udairh udaihr udhari udhair udhrai udhria
udhira udhiar udrhai udrhia udrahi udraih udriah udriha udihra udihar udirha
udirah udiarh udiahr uradhi uradih urahdi urahid uraihd uraidh urdahi urdaih
urdhai urdhia urdiha urdiah urhdai urhdia urhadi urhaid urhiad urhida uridha
uridah urihda urihad uriahd uriadh uiadrh uiadhr uiardh uiarhd uiahrd uiahdr
uidarh uidahr uidrah uidrha uidhra uidhar uirdah uirdha uiradh uirahd uirhad
uirhda uihdra uihdar uihrda uihrad uihard uihadr rhaudi rhauid rhadui rhadiu
rhaidu rhaiud rhuadi rhuaid rhudai rhudia rhuida rhuiad rhduai rhduia rhdaui
rhdaiu rhdiau rhdiua rhiuda rhiuad rhidua rhidau rhiadu rhiaud rahudi rahuid
rahdui rahdiu rahidu rahiud rauhdi rauhid raudhi raudih rauidh rauihd raduhi
raduih radhui radhiu radihu radiuh raiudh raiuhd raiduh raidhu raihdu raihud
ruahdi ruahid ruadhi ruadih ruaidh ruaihd ruhadi ruhaid ruhdai ruhdia ruhida
ruhiad rudhai rudhia rudahi rudaih rudiah rudiha ruihda ruihad ruidha ruidah
ruiadh ruiahd rdauhi rdauih rdahui rdahiu rdaihu rdaiuh rduahi rduaih rduhai
rduhia rduiha rduiah rdhuai rdhuia rdhaui rdhaiu rdhiau rdhiua rdiuha rdiuah
rdihua rdihau rdiahu rdiauh riaudh riauhd riaduh riadhu riahdu riahud riuadh
riuahd riudah riudha riuhda riuhad riduah riduha ridauh ridahu ridhau ridhua
rihuda rihuad rihdua rihdau rihadu rihaud ihaurd ihaudr iharud ihardu ihadru
ihadur ihuard ihuadr ihurad ihurda ihudra ihudar ihruad ihruda ihraud ihradu
ihrdau ihrdua ihdura ihduar ihdrua ihdrau ihdaru ihdaur iahurd iahudr iahrud
iahrdu iahdru iahdur iauhrd iauhdr iaurhd iaurdh iaudrh iaudhr iaruhd iarudh
iarhud iarhdu iardhu iarduh iadurh iaduhr iadruh iadrhu iadhru iadhur iuahrd
iuahdr iuarhd iuardh iuadrh iuadhr iuhard iuhadr iuhrad iuhrda iuhdra iuhdar
iurhad iurhda iurahd iuradh iurdah iurdha iudhra iudhar iudrha iudrah iudarh
iudahr irauhd iraudh irahud irahdu iradhu iraduh iruahd iruadh iruhad iruhda
irudha irudah irhuad irhuda irhaud irhadu irhdau irhdua irduha irduah irdhua
irdhau irdahu irdauh idaurh idauhr idaruh idarhu idahru idahur iduarh iduahr
idurah idurha iduhra iduhar idruah idruha idrauh idrahu idrhau idrhua idhura
idhuar idhrua idhrau idharu idhaur

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History of cryptography
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