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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: duling
cipher variations:
evmjoh fwnkpi gxolqj hypmrk izqnsl
jarotm kbspun lctqvo mdurwp nevsxq
ofwtyr pgxuzs qhyvat rizwbu sjaxcv
tkbydw ulczex vmdafy wnebgz xofcha
ypgdib zqhejc arifkd bsjgle ctkhmf

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: duling
Cipher: wformt

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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: duling

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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: duling
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: duling
Cipher: qhyvat

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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: duling
Cipher: 415413423322

Extended Methods:
Method #1

Plaintext: duling
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
d u l i n g 
4 5 1 4 3 2 
1 4 3 2 3 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: duling
Cipher: yqhqhh

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Method #3

Plaintext: duling
method variations:
vdsmhr dsmhrv smhrvd
mhrvds hrvdsm rvdsmh

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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: duling

all 720 cipher variations:
duling dulign dulnig dulngi dulgni dulgin duilng duilgn duinlg duingl duignl
duigln dunilg dunigl dunlig dunlgi dungli dungil duginl dugiln dugnil dugnli
duglni duglin dluing dluign dlunig dlungi dlugni dlugin dliung dliugn dlinug
dlingu dlignu dligun dlniug dlnigu dlnuig dlnugi dlngui dlngiu dlginu dlgiun
dlgniu dlgnui dlguni dlguin dilung dilugn dilnug dilngu dilgnu dilgun diulng
diulgn diunlg diungl diugnl diugln dinulg dinugl dinlug dinlgu dinglu dingul
digunl diguln dignul dignlu diglnu diglun dnliug dnligu dnluig dnlugi dnlgui
dnlgiu dnilug dnilgu dniulg dniugl dnigul dniglu dnuilg dnuigl dnulig dnulgi
dnugli dnugil dngiul dngilu dnguil dnguli dnglui dngliu dglinu dgliun dglniu
dglnui dgluni dgluin dgilnu dgilun dginlu dginul dgiunl dgiuln dgnilu dgniul
dgnliu dgnlui dgnuli dgnuil dguinl dguiln dgunil dgunli dgulni dgulin udling
udlign udlnig udlngi udlgni udlgin udilng udilgn udinlg udingl udignl udigln
udnilg udnigl udnlig udnlgi udngli udngil udginl udgiln udgnil udgnli udglni
udglin ulding uldign uldnig uldngi uldgni uldgin ulidng ulidgn ulindg ulingd
ulignd uligdn ulnidg ulnigd ulndig ulndgi ulngdi ulngid ulgind ulgidn ulgnid
ulgndi ulgdni ulgdin uildng uildgn uilndg uilngd uilgnd uilgdn uidlng uidlgn
uidnlg uidngl uidgnl uidgln uindlg uindgl uinldg uinlgd uingld uingdl uigdnl
uigdln uigndl uignld uiglnd uigldn unlidg unligd unldig unldgi unlgdi unlgid
unildg unilgd unidlg unidgl unigdl unigld undilg undigl undlig undlgi undgli
undgil ungidl ungild ungdil ungdli ungldi unglid uglind uglidn uglnid uglndi
ugldni ugldin ugilnd ugildn uginld ugindl ugidnl ugidln ugnild ugnidl ugnlid
ugnldi ugndli ugndil ugdinl ugdiln ugdnil ugdnli ugdlni ugdlin luding ludign
ludnig ludngi ludgni ludgin luidng luidgn luindg luingd luignd luigdn lunidg
lunigd lundig lundgi lungdi lungid lugind lugidn lugnid lugndi lugdni lugdin
lduing lduign ldunig ldungi ldugni ldugin ldiung ldiugn ldinug ldingu ldignu
ldigun ldniug ldnigu ldnuig ldnugi ldngui ldngiu ldginu ldgiun ldgniu ldgnui
ldguni ldguin lidung lidugn lidnug lidngu lidgnu lidgun liudng liudgn liundg
liungd liugnd liugdn linudg linugd lindug lindgu lingdu lingud ligund ligudn
lignud ligndu ligdnu ligdun lndiug lndigu lnduig lndugi lndgui lndgiu lnidug
lnidgu lniudg lniugd lnigud lnigdu lnuidg lnuigd lnudig lnudgi lnugdi lnugid
lngiud lngidu lnguid lngudi lngdui lngdiu lgdinu lgdiun lgdniu lgdnui lgduni
lgduin lgidnu lgidun lgindu lginud lgiund lgiudn lgnidu lgniud lgndiu lgndui
lgnudi lgnuid lguind lguidn lgunid lgundi lgudni lgudin iuldng iuldgn iulndg
iulngd iulgnd iulgdn iudlng iudlgn iudnlg iudngl iudgnl iudgln iundlg iundgl
iunldg iunlgd iungld iungdl iugdnl iugdln iugndl iugnld iuglnd iugldn iludng
iludgn ilundg ilungd ilugnd ilugdn ildung ildugn ildnug ildngu ildgnu ildgun
ilndug ilndgu ilnudg ilnugd ilngud ilngdu ilgdnu ilgdun ilgndu ilgnud ilgund
ilgudn idlung idlugn idlnug idlngu idlgnu idlgun idulng idulgn idunlg idungl
idugnl idugln idnulg idnugl idnlug idnlgu idnglu idngul idgunl idguln idgnul
idgnlu idglnu idglun inldug inldgu inludg inlugd inlgud inlgdu indlug indlgu
indulg indugl indgul indglu inudlg inudgl inuldg inulgd inugld inugdl ingdul
ingdlu ingudl inguld inglud ingldu igldnu igldun iglndu iglnud iglund igludn
igdlnu igdlun igdnlu igdnul igdunl igduln igndlu igndul ignldu ignlud ignuld
ignudl igudnl igudln igundl igunld igulnd iguldn nulidg nuligd nuldig nuldgi
nulgdi nulgid nuildg nuilgd nuidlg nuidgl nuigdl nuigld nudilg nudigl nudlig
nudlgi nudgli nudgil nugidl nugild nugdil nugdli nugldi nuglid nluidg nluigd
nludig nludgi nlugdi nlugid nliudg nliugd nlidug nlidgu nligdu nligud nldiug
nldigu nlduig nldugi nldgui nldgiu nlgidu nlgiud nlgdiu nlgdui nlgudi nlguid
niludg nilugd nildug nildgu nilgdu nilgud niuldg niulgd niudlg niudgl niugdl
niugld nidulg nidugl nidlug nidlgu nidglu nidgul nigudl niguld nigdul nigdlu
nigldu niglud ndliug ndligu ndluig ndlugi ndlgui ndlgiu ndilug ndilgu ndiulg
ndiugl ndigul ndiglu nduilg nduigl ndulig ndulgi ndugli ndugil ndgiul ndgilu
ndguil ndguli ndglui ndgliu nglidu ngliud ngldiu ngldui ngludi ngluid ngildu
ngilud ngidlu ngidul ngiudl ngiuld ngdilu ngdiul ngdliu ngdlui ngduli ngduil
nguidl nguild ngudil ngudli nguldi ngulid gulind gulidn gulnid gulndi guldni
guldin guilnd guildn guinld guindl guidnl guidln gunild gunidl gunlid gunldi
gundli gundil gudinl gudiln gudnil gudnli gudlni gudlin gluind gluidn glunid
glundi gludni gludin gliund gliudn glinud glindu glidnu glidun glniud glnidu
glnuid glnudi glndui glndiu gldinu gldiun gldniu gldnui glduni glduin gilund
giludn gilnud gilndu gildnu gildun giulnd giuldn giunld giundl giudnl giudln
ginuld ginudl ginlud ginldu gindlu gindul gidunl giduln gidnul gidnlu gidlnu
gidlun gnliud gnlidu gnluid gnludi gnldui gnldiu gnilud gnildu gniuld gniudl
gnidul gnidlu gnuild gnuidl gnulid gnuldi gnudli gnudil gndiul gndilu gnduil
gnduli gndlui gndliu gdlinu gdliun gdlniu gdlnui gdluni gdluin gdilnu gdilun
gdinlu gdinul gdiunl gdiuln gdnilu gdniul gdnliu gdnlui gdnuli gdnuil gduinl
gduiln gdunil gdunli gdulni gdulin

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History of cryptography
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