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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: juliao
cipher variations:
kvmjbp lwnkcq mxoldr nypmes ozqnft
parogu qbsphv rctqiw sdurjx tevsky
ufwtlz vgxuma whyvnb xizwoc yjaxpd
zkbyqe alczrf bmdasg cnebth dofcui
epgdvj fqhewk grifxl hsjgym itkhzn

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: juliao
Cipher: qforzl

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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: juliao

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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: juliao
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: juliao
Cipher: whyvnb

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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: juliao
Cipher: 425413421143

Extended Methods:
Method #1

Plaintext: juliao
method variations:

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

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Method #3

Plaintext: juliao
method variations:
wdsbqs dsbqsw sbqswd
bqswds qswdsb swdsbq

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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: juliao

all 720 cipher variations:
juliao julioa julaio julaoi juloai juloia juilao juiloa juialo juiaol juioal
juiola juailo juaiol jualio jualoi juaoli juaoil juoial juoila juoail juoali
juolai juolia jluiao jluioa jluaio jluaoi jluoai jluoia jliuao jliuoa jliauo
jliaou jlioau jlioua jlaiuo jlaiou jlauio jlauoi jlaoui jlaoiu jloiau jloiua
jloaiu jloaui jlouai jlouia jiluao jiluoa jilauo jilaou jiloau jiloua jiulao
jiuloa jiualo jiuaol jiuoal jiuola jiaulo jiauol jialuo jialou jiaolu jiaoul
jioual jioula jioaul jioalu jiolau jiolua jaliuo jaliou jaluio jaluoi jaloui
jaloiu jailuo jailou jaiulo jaiuol jaioul jaiolu jauilo jauiol jaulio jauloi
jauoli jauoil jaoiul jaoilu jaouil jaouli jaolui jaoliu joliau joliua jolaiu
jolaui joluai joluia joilau joilua joialu joiaul joiual joiula joailu joaiul
joaliu joalui joauli joauil jouial jouila jouail jouali joulai joulia ujliao
ujlioa ujlaio ujlaoi ujloai ujloia ujilao ujiloa ujialo ujiaol ujioal ujiola
ujailo ujaiol ujalio ujaloi ujaoli ujaoil ujoial ujoila ujoail ujoali ujolai
ujolia uljiao uljioa uljaio uljaoi uljoai uljoia ulijao ulijoa uliajo uliaoj
ulioaj ulioja ulaijo ulaioj ulajio ulajoi ulaoji ulaoij uloiaj uloija uloaij
uloaji ulojai ulojia uiljao uiljoa uilajo uilaoj uiloaj uiloja uijlao uijloa
uijalo uijaol uijoal uijola uiajlo uiajol uialjo uialoj uiaolj uiaojl uiojal
uiojla uioajl uioalj uiolaj uiolja ualijo ualioj ualjio ualjoi ualoji ualoij
uailjo uailoj uaijlo uaijol uaiojl uaiolj uajilo uajiol uajlio uajloi uajoli
uajoil uaoijl uaoilj uaojil uaojli uaolji uaolij uoliaj uolija uolaij uolaji
uoljai uoljia uoilaj uoilja uoialj uoiajl uoijal uoijla uoailj uoaijl uoalij
uoalji uoajli uoajil uojial uojila uojail uojali uojlai uojlia lujiao lujioa
lujaio lujaoi lujoai lujoia luijao luijoa luiajo luiaoj luioaj luioja luaijo
luaioj luajio luajoi luaoji luaoij luoiaj luoija luoaij luoaji luojai luojia
ljuiao ljuioa ljuaio ljuaoi ljuoai ljuoia ljiuao ljiuoa ljiauo ljiaou ljioau
ljioua ljaiuo ljaiou ljauio ljauoi ljaoui ljaoiu ljoiau ljoiua ljoaiu ljoaui
ljouai ljouia lijuao lijuoa lijauo lijaou lijoau lijoua liujao liujoa liuajo
liuaoj liuoaj liuoja liaujo liauoj liajuo liajou liaoju liaouj liouaj liouja
lioauj lioaju liojau liojua lajiuo lajiou lajuio lajuoi lajoui lajoiu laijuo
laijou laiujo laiuoj laiouj laioju lauijo lauioj laujio laujoi lauoji lauoij
laoiuj laoiju laouij laouji laojui laojiu lojiau lojiua lojaiu lojaui lojuai
lojuia loijau loijua loiaju loiauj loiuaj loiuja loaiju loaiuj loajiu loajui
loauji loauij louiaj louija louaij louaji loujai loujia iuljao iuljoa iulajo
iulaoj iuloaj iuloja iujlao iujloa iujalo iujaol iujoal iujola iuajlo iuajol
iualjo iualoj iuaolj iuaojl iuojal iuojla iuoajl iuoalj iuolaj iuolja ilujao
ilujoa iluajo iluaoj iluoaj iluoja iljuao iljuoa iljauo iljaou iljoau iljoua
ilajuo ilajou ilaujo ilauoj ilaouj ilaoju ilojau ilojua iloaju iloauj ilouaj
ilouja ijluao ijluoa ijlauo ijlaou ijloau ijloua ijulao ijuloa ijualo ijuaol
ijuoal ijuola ijaulo ijauol ijaluo ijalou ijaolu ijaoul ijoual ijoula ijoaul
ijoalu ijolau ijolua ialjuo ialjou ialujo ialuoj ialouj ialoju iajluo iajlou
iajulo iajuol iajoul iajolu iaujlo iaujol iauljo iauloj iauolj iauojl iaojul
iaojlu iaoujl iaoulj iaoluj iaolju ioljau ioljua iolaju iolauj ioluaj ioluja
iojlau iojlua iojalu iojaul iojual iojula ioajlu ioajul ioalju ioaluj ioaulj
ioaujl ioujal ioujla iouajl ioualj ioulaj ioulja aulijo aulioj auljio auljoi
auloji auloij auiljo auiloj auijlo auijol auiojl auiolj aujilo aujiol aujlio
aujloi aujoli aujoil auoijl auoilj auojil auojli auolji auolij aluijo aluioj
alujio alujoi aluoji aluoij aliujo aliuoj alijuo alijou alioju aliouj aljiuo
aljiou aljuio aljuoi aljoui aljoiu aloiju aloiuj alojiu alojui alouji alouij
ailujo ailuoj ailjuo ailjou ailoju ailouj aiuljo aiuloj aiujlo aiujol aiuojl
aiuolj aijulo aijuol aijluo aijlou aijolu aijoul aioujl aioulj aiojul aiojlu
aiolju aioluj ajliuo ajliou ajluio ajluoi ajloui ajloiu ajiluo ajilou ajiulo
ajiuol ajioul ajiolu ajuilo ajuiol ajulio ajuloi ajuoli ajuoil ajoiul ajoilu
ajouil ajouli ajolui ajoliu aoliju aoliuj aoljiu aoljui aoluji aoluij aoilju
aoiluj aoijlu aoijul aoiujl aoiulj aojilu aojiul aojliu aojlui aojuli aojuil
aouijl aouilj aoujil aoujli aoulji aoulij ouliaj oulija oulaij oulaji ouljai
ouljia ouilaj ouilja ouialj ouiajl ouijal ouijla ouailj ouaijl oualij oualji
ouajli ouajil oujial oujila oujail oujali oujlai oujlia oluiaj oluija oluaij
oluaji olujai olujia oliuaj oliuja oliauj oliaju olijau olijua olaiuj olaiju
olauij olauji olajui olajiu oljiau oljiua oljaiu oljaui oljuai oljuia oiluaj
oiluja oilauj oilaju oiljau oiljua oiulaj oiulja oiualj oiuajl oiujal oiujla
oiaulj oiaujl oialuj oialju oiajlu oiajul oijual oijula oijaul oijalu oijlau
oijlua oaliuj oaliju oaluij oaluji oaljui oaljiu oailuj oailju oaiulj oaiujl
oaijul oaijlu oauilj oauijl oaulij oaulji oaujli oaujil oajiul oajilu oajuil
oajuli oajlui oajliu ojliau ojliua ojlaiu ojlaui ojluai ojluia ojilau ojilua
ojialu ojiaul ojiual ojiula ojailu ojaiul ojaliu ojalui ojauli ojauil ojuial
ojuila ojuail ojuali ojulai ojulia

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History of cryptography
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