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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: leniit
cipher variations:
mfojju ngpkkv ohqllw pirmmx qjsnny
rktooz sluppa tmvqqb unwrrc voxssd
wpytte xqzuuf yravvg zsbwwh atcxxi
budyyj cvezzk dwfaal exgbbm fyhccn
gziddo hajeep ibkffq jclggr kdmhhs

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: leniit
Cipher: ovmrrg

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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: leniit

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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: leniit
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: leniit
Cipher: yravvg

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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: leniit
Cipher: 135133424244

Extended Methods:
Method #1

Plaintext: leniit
method variations:

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

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Method #3

Plaintext: leniit
method variations:
xlsrrd lsrrdx srrdxl
rrdxls rdxlsr dxlsrr

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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: leniit

all 720 cipher variations:
leniit leniti leniit leniti lentii lentii leinit leinti leiint leiitn leitin
leitni leiint leiitn leinit leinti leitni leitin letiin letini letiin letini
letnii letnii lneiit lneiti lneiit lneiti lnetii lnetii lnieit lnieti lniiet
lniite lnitie lnitei lniiet lniite lnieit lnieti lnitei lnitie lntiie lntiei
lntiie lntiei lnteii lnteii lineit lineti liniet linite lintie lintei lienit
lienti lieint lieitn lietin lietni liient liietn liinet liinte liitne liiten
litein liteni litien litine litnie litnei liniet linite lineit lineti lintei
lintie liinet liinte liient liietn liiten liitne lieint lieitn lienit lienti
lietni lietin litien litine litein liteni litnei litnie ltniie ltniei ltniie
ltniei ltneii ltneii ltinie ltinei ltiine ltiien ltiein ltieni ltiine ltiien
ltinie ltinei ltieni ltiein lteiin lteini lteiin lteini ltenii ltenii elniit
elniti elniit elniti elntii elntii elinit elinti eliint eliitn elitin elitni
eliint eliitn elinit elinti elitni elitin eltiin eltini eltiin eltini eltnii
eltnii enliit enliti enliit enliti enltii enltii enilit enilti eniilt eniitl
enitil enitli eniilt eniitl enilit enilti enitli enitil entiil entili entiil
entili entlii entlii einlit einlti einilt einitl eintil eintli eilnit eilnti
eilint eilitn eiltin eiltni eiilnt eiiltn eiinlt eiintl eiitnl eiitln eitlin
eitlni eitiln eitinl eitnil eitnli einilt einitl einlit einlti eintli eintil
eiinlt eiintl eiilnt eiiltn eiitln eiitnl eilint eilitn eilnit eilnti eiltni
eiltin eitiln eitinl eitlin eitlni eitnli eitnil etniil etnili etniil etnili
etnlii etnlii etinil etinli etiinl etiiln etilin etilni etiinl etiiln etinil
etinli etilni etilin etliin etlini etliin etlini etlnii etlnii neliit neliti
neliit neliti neltii neltii neilit neilti neiilt neiitl neitil neitli neiilt
neiitl neilit neilti neitli neitil netiil netili netiil netili netlii netlii
nleiit nleiti nleiit nleiti nletii nletii nlieit nlieti nliiet nliite nlitie
nlitei nliiet nliite nlieit nlieti nlitei nlitie nltiie nltiei nltiie nltiei
nlteii nlteii nileit nileti niliet nilite niltie niltei nielit nielti nieilt
nieitl nietil nietli niielt niietl niilet niilte niitle niitel niteil niteli
nitiel nitile nitlie nitlei niliet nilite nileit nileti niltei niltie niilet
niilte niielt niietl niitel niitle nieilt nieitl nielit nielti nietli nietil
nitiel nitile niteil niteli nitlei nitlie ntliie ntliei ntliie ntliei ntleii
ntleii ntilie ntilei ntiile ntiiel ntieil ntieli ntiile ntiiel ntilie ntilei
ntieli ntieil nteiil nteili nteiil nteili ntelii ntelii ienlit ienlti ienilt
ienitl ientil ientli ielnit ielnti ielint ielitn ieltin ieltni ieilnt ieiltn
ieinlt ieintl ieitnl ieitln ietlin ietlni ietiln ietinl ietnil ietnli inelit
inelti ineilt ineitl inetil inetli inleit inleti inliet inlite inltie inltei
inilet inilte inielt inietl initel initle intlie intlei intile intiel inteil
inteli ilneit ilneti ilniet ilnite ilntie ilntei ilenit ilenti ileint ileitn
iletin iletni ilient ilietn ilinet ilinte ilitne iliten iltein ilteni iltien
iltine iltnie iltnei iinlet iinlte iinelt iinetl iintel iintle iilnet iilnte
iilent iiletn iilten iiltne iielnt iieltn iienlt iientl iietnl iietln iitlen
iitlne iiteln iitenl iitnel iitnle itnlie itnlei itnile itniel itneil itneli
itlnie itlnei itline itlien itlein itleni itilne itilen itinle itinel itienl
itieln itelin itelni iteiln iteinl itenil itenli ienilt ienitl ienlit ienlti
ientli ientil ieinlt ieintl ieilnt ieiltn ieitln ieitnl ielint ielitn ielnit
ielnti ieltni ieltin ietiln ietinl ietlin ietlni ietnli ietnil ineilt ineitl
inelit inelti inetli inetil inielt inietl inilet inilte initle initel inliet
inlite inleit inleti inltei inltie intile intiel intlie intlei inteli inteil
iinelt iinetl iinlet iinlte iintle iintel iienlt iientl iielnt iieltn iietln
iietnl iilent iiletn iilnet iilnte iiltne iilten iiteln iitenl iitlen iitlne
iitnle iitnel ilniet ilnite ilneit ilneti ilntei ilntie ilinet ilinte ilient
ilietn iliten ilitne ileint ileitn ilenit ilenti iletni iletin iltien iltine
iltein ilteni iltnei iltnie itnile itniel itnlie itnlei itneli itneil itinle
itinel itilne itilen itieln itienl itline itlien itlnie itlnei itleni itlein
iteiln iteinl itelin itelni itenli itenil teniil tenili teniil tenili tenlii
tenlii teinil teinli teiinl teiiln teilin teilni teiinl teiiln teinil teinli
teilni teilin teliin telini teliin telini telnii telnii tneiil tneili tneiil
tneili tnelii tnelii tnieil tnieli tniiel tniile tnilie tnilei tniiel tniile
tnieil tnieli tnilei tnilie tnliie tnliei tnliie tnliei tnleii tnleii tineil
tineli tiniel tinile tinlie tinlei tienil tienli tieinl tieiln tielin tielni
tiienl tiieln tiinel tiinle tiilne tiilen tilein tileni tilien tiline tilnie
tilnei tiniel tinile tineil tineli tinlei tinlie tiinel tiinle tiienl tiieln
tiilen tiilne tieinl tieiln tienil tienli tielni tielin tilien tiline tilein
tileni tilnei tilnie tlniie tlniei tlniie tlniei tlneii tlneii tlinie tlinei
tliine tliien tliein tlieni tliine tliien tlinie tlinei tlieni tliein tleiin
tleini tleiin tleini tlenii tlenii

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History of cryptography
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