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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: pugnet
cipher variations:
qvhofu rwipgv sxjqhw tykrix uzlsjy
vamtkz wbnula xcovmb ydpwnc zeqxod
afrype bgszqf chtarg diubsh ejvcti
fkwduj glxevk hmyfwl inzgxm joahyn
kpbizo lqcjap mrdkbq nselcr otfmds

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: pugnet
Cipher: kftmvg

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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: pugnet

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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: pugnet
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: pugnet
Cipher: chtarg

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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: pugnet
Cipher: 535422335144

Extended Methods:
Method #1

Plaintext: pugnet
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
p u g n e t 
5 5 2 3 5 4 
3 4 2 3 1 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: pugnet
Cipher: zmusmq

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Method #3

Plaintext: pugnet
method variations:
ximxqy imxqyx mxqyxi
xqyxim qyximx yximxq

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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: pugnet

all 720 cipher variations:
pugnet pugnte pugent pugetn pugten pugtne punget pungte punegt punetg punteg
puntge puengt puentg puegnt puegtn puetgn puetng putneg putnge puteng putegn
putgen putgne pgunet pgunte pguent pguetn pguten pgutne pgnuet pgnute pgneut
pgnetu pgnteu pgntue pgenut pgentu pgeunt pgeutn pgetun pgetnu pgtneu pgtnue
pgtenu pgteun pgtuen pgtune pnguet pngute pngeut pngetu pngteu pngtue pnuget
pnugte pnuegt pnuetg pnuteg pnutge pneugt pneutg pnegut pnegtu pnetgu pnetug
pntueg pntuge pnteug pntegu pntgeu pntgue pegnut pegntu pegunt pegutn pegtun
pegtnu pengut pengtu penugt penutg pentug pentgu peungt peuntg peugnt peugtn
peutgn peutng petnug petngu petung petugn petgun petgnu ptgneu ptgnue ptgenu
ptgeun ptguen ptgune ptngeu ptngue ptnegu ptneug ptnueg ptnuge ptengu ptenug
ptegnu ptegun pteugn pteung ptuneg ptunge ptueng ptuegn ptugen ptugne upgnet
upgnte upgent upgetn upgten upgtne upnget upngte upnegt upnetg upnteg upntge
upengt upentg upegnt upegtn upetgn upetng uptneg uptnge upteng uptegn uptgen
uptgne ugpnet ugpnte ugpent ugpetn ugpten ugptne ugnpet ugnpte ugnept ugnetp
ugntep ugntpe ugenpt ugentp ugepnt ugeptn ugetpn ugetnp ugtnep ugtnpe ugtenp
ugtepn ugtpen ugtpne ungpet ungpte ungept ungetp ungtep ungtpe unpget unpgte
unpegt unpetg unpteg unptge unepgt uneptg unegpt unegtp unetgp unetpg untpeg
untpge untepg untegp untgep untgpe uegnpt uegntp uegpnt uegptn uegtpn uegtnp
uengpt uengtp uenpgt uenptg uentpg uentgp uepngt uepntg uepgnt uepgtn ueptgn
ueptng uetnpg uetngp uetpng uetpgn uetgpn uetgnp utgnep utgnpe utgenp utgepn
utgpen utgpne utngep utngpe utnegp utnepg utnpeg utnpge utengp utenpg utegnp
utegpn utepgn utepng utpneg utpnge utpeng utpegn utpgen utpgne gupnet gupnte
gupent gupetn gupten guptne gunpet gunpte gunept gunetp guntep guntpe guenpt
guentp guepnt gueptn guetpn guetnp gutnep gutnpe gutenp gutepn gutpen gutpne
gpunet gpunte gpuent gpuetn gputen gputne gpnuet gpnute gpneut gpnetu gpnteu
gpntue gpenut gpentu gpeunt gpeutn gpetun gpetnu gptneu gptnue gptenu gpteun
gptuen gptune gnpuet gnpute gnpeut gnpetu gnpteu gnptue gnupet gnupte gnuept
gnuetp gnutep gnutpe gneupt gneutp gneput gneptu gnetpu gnetup gntuep gntupe
gnteup gntepu gntpeu gntpue gepnut gepntu gepunt geputn geptun geptnu genput
genptu genupt genutp gentup gentpu geunpt geuntp geupnt geuptn geutpn geutnp
getnup getnpu getunp getupn getpun getpnu gtpneu gtpnue gtpenu gtpeun gtpuen
gtpune gtnpeu gtnpue gtnepu gtneup gtnuep gtnupe gtenpu gtenup gtepnu gtepun
gteupn gteunp gtunep gtunpe gtuenp gtuepn gtupen gtupne nugpet nugpte nugept
nugetp nugtep nugtpe nupget nupgte nupegt nupetg nupteg nuptge nuepgt nueptg
nuegpt nuegtp nuetgp nuetpg nutpeg nutpge nutepg nutegp nutgep nutgpe ngupet
ngupte nguept nguetp ngutep ngutpe ngpuet ngpute ngpeut ngpetu ngpteu ngptue
ngeput ngeptu ngeupt ngeutp ngetup ngetpu ngtpeu ngtpue ngtepu ngteup ngtuep
ngtupe npguet npgute npgeut npgetu npgteu npgtue npuget npugte npuegt npuetg
nputeg nputge npeugt npeutg npegut npegtu npetgu npetug nptueg nptuge npteug
nptegu nptgeu nptgue negput negptu negupt negutp negtup negtpu nepgut nepgtu
nepugt neputg neptug neptgu neupgt neuptg neugpt neugtp neutgp neutpg netpug
netpgu netupg netugp netgup netgpu ntgpeu ntgpue ntgepu ntgeup ntguep ntgupe
ntpgeu ntpgue ntpegu ntpeug ntpueg ntpuge ntepgu ntepug ntegpu ntegup nteugp
nteupg ntupeg ntupge ntuepg ntuegp ntugep ntugpe eugnpt eugntp eugpnt eugptn
eugtpn eugtnp eungpt eungtp eunpgt eunptg euntpg euntgp eupngt eupntg eupgnt
eupgtn euptgn euptng eutnpg eutngp eutpng eutpgn eutgpn eutgnp egunpt eguntp
egupnt eguptn egutpn egutnp egnupt egnutp egnput egnptu egntpu egntup egpnut
egpntu egpunt egputn egptun egptnu egtnpu egtnup egtpnu egtpun egtupn egtunp
engupt engutp engput engptu engtpu engtup enugpt enugtp enupgt enuptg enutpg
enutgp enpugt enputg enpgut enpgtu enptgu enptug entupg entugp entpug entpgu
entgpu entgup epgnut epgntu epgunt epgutn epgtun epgtnu epngut epngtu epnugt
epnutg epntug epntgu epungt epuntg epugnt epugtn eputgn eputng eptnug eptngu
eptung eptugn eptgun eptgnu etgnpu etgnup etgpnu etgpun etgupn etgunp etngpu
etngup etnpgu etnpug etnupg etnugp etpngu etpnug etpgnu etpgun etpugn etpung
etunpg etungp etupng etupgn etugpn etugnp tugnep tugnpe tugenp tugepn tugpen
tugpne tungep tungpe tunegp tunepg tunpeg tunpge tuengp tuenpg tuegnp tuegpn
tuepgn tuepng tupneg tupnge tupeng tupegn tupgen tupgne tgunep tgunpe tguenp
tguepn tgupen tgupne tgnuep tgnupe tgneup tgnepu tgnpeu tgnpue tgenup tgenpu
tgeunp tgeupn tgepun tgepnu tgpneu tgpnue tgpenu tgpeun tgpuen tgpune tnguep
tngupe tngeup tngepu tngpeu tngpue tnugep tnugpe tnuegp tnuepg tnupeg tnupge
tneugp tneupg tnegup tnegpu tnepgu tnepug tnpueg tnpuge tnpeug tnpegu tnpgeu
tnpgue tegnup tegnpu tegunp tegupn tegpun tegpnu tengup tengpu tenugp tenupg
tenpug tenpgu teungp teunpg teugnp teugpn teupgn teupng tepnug tepngu tepung
tepugn tepgun tepgnu tpgneu tpgnue tpgenu tpgeun tpguen tpgune tpngeu tpngue
tpnegu tpneug tpnueg tpnuge tpengu tpenug tpegnu tpegun tpeugn tpeung tpuneg
tpunge tpueng tpuegn tpugen tpugne

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History of cryptography
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