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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: girten
cipher variations:
hjsufo iktvgp jluwhq kmvxir lnwyjs
moxzkt npyalu oqzbmv pracnw qsbdox
rtcepy sudfqz tvegra uwfhsb vxgitc
wyhjud xzikve yajlwf zbkmxg aclnyh
bdmozi cenpaj dfoqbk egprcl fhqsdm

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: girten
Cipher: trigvm

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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: girten

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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: girten
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: girten
Cipher: tvegra

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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: girten
Cipher: 224224445133

Extended Methods:
Method #1

Plaintext: girten
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
g i r t e n 
2 4 2 4 5 3 
2 2 4 4 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: girten
Cipher: rrpgtl

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Method #3

Plaintext: girten
method variations:
rgtylh gtylhr tylhrg
ylhrgt lhrgty hrgtyl

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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: girten

all 720 cipher variations:
girten girtne giretn girent girnet girnte gitren gitrne gitern gitenr gitner
gitnre gietrn gietnr giertn giernt gienrt gientr ginter gintre ginetr ginert
ginret ginrte griten gritne grietn grient grinet grinte grtien grtine grtein
grteni grtnei grtnie gretin gretni greitn greint grenit grenti grntei grntie
grneti grneit grniet grnite gtrien gtrine gtrein gtreni gtrnei gtrnie gtiren
gtirne gtiern gtienr gtiner gtinre gteirn gteinr gterin gterni gtenri gtenir
gtnier gtnire gtneir gtneri gtnrei gtnrie gertin gertni geritn gerint gernit
gernti getrin getrni getirn getinr getnir getnri geitrn geitnr geirtn geirnt
geinrt geintr gentir gentri genitr genirt genrit genrti gnrtei gnrtie gnreti
gnreit gnriet gnrite gntrei gntrie gnteri gnteir gntier gntire gnetri gnetir
gnerti gnerit gneirt gneitr gniter gnitre gnietr gniert gniret gnirte igrten
igrtne igretn igrent igrnet igrnte igtren igtrne igtern igtenr igtner igtnre
igetrn igetnr igertn igernt igenrt igentr ignter igntre ignetr ignert ignret
ignrte irgten irgtne irgetn irgent irgnet irgnte irtgen irtgne irtegn irteng
irtneg irtnge iretgn iretng iregtn iregnt irengt irentg irnteg irntge irnetg
irnegt irnget irngte itrgen itrgne itregn itreng itrneg itrnge itgren itgrne
itgern itgenr itgner itgnre itegrn itegnr itergn iterng itenrg itengr itnger
itngre itnegr itnerg itnreg itnrge iertgn iertng iergtn iergnt ierngt ierntg
ietrgn ietrng ietgrn ietgnr ietngr ietnrg iegtrn iegtnr iegrtn iegrnt iegnrt
iegntr ientgr ientrg iengtr iengrt ienrgt ienrtg inrteg inrtge inretg inregt
inrget inrgte intreg intrge interg integr intger intgre inetrg inetgr inertg
inergt inegrt inegtr ingter ingtre ingetr ingert ingret ingrte rigten rigtne
rigetn rigent rignet rignte ritgen ritgne ritegn riteng ritneg ritnge rietgn
rietng riegtn riegnt riengt rientg rinteg rintge rinetg rinegt ringet ringte
rgiten rgitne rgietn rgient rginet rginte rgtien rgtine rgtein rgteni rgtnei
rgtnie rgetin rgetni rgeitn rgeint rgenit rgenti rgntei rgntie rgneti rgneit
rgniet rgnite rtgien rtgine rtgein rtgeni rtgnei rtgnie rtigen rtigne rtiegn
rtieng rtineg rtinge rteign rteing rtegin rtegni rtengi rtenig rtnieg rtnige
rtneig rtnegi rtngei rtngie regtin regtni regitn regint regnit regnti retgin
retgni retign reting retnig retngi reitgn reitng reigtn reignt reingt reintg
rentig rentgi renitg renigt rengit rengti rngtei rngtie rngeti rngeit rngiet
rngite rntgei rntgie rntegi rnteig rntieg rntige rnetgi rnetig rnegti rnegit
rneigt rneitg rniteg rnitge rnietg rniegt rniget rnigte tirgen tirgne tiregn
tireng tirneg tirnge tigren tigrne tigern tigenr tigner tignre tiegrn tiegnr
tiergn tierng tienrg tiengr tinger tingre tinegr tinerg tinreg tinrge trigen
trigne triegn trieng trineg tringe trgien trgine trgein trgeni trgnei trgnie
tregin tregni treign treing trenig trengi trngei trngie trnegi trneig trnieg
trnige tgrien tgrine tgrein tgreni tgrnei tgrnie tgiren tgirne tgiern tgienr
tginer tginre tgeirn tgeinr tgerin tgerni tgenri tgenir tgnier tgnire tgneir
tgneri tgnrei tgnrie tergin tergni terign tering ternig terngi tegrin tegrni
tegirn teginr tegnir tegnri teigrn teignr teirgn teirng teinrg teingr tengir
tengri tenigr tenirg tenrig tenrgi tnrgei tnrgie tnregi tnreig tnrieg tnrige
tngrei tngrie tngeri tngeir tngier tngire tnegri tnegir tnergi tnerig tneirg
tneigr tniger tnigre tniegr tnierg tnireg tnirge eirtgn eirtng eirgtn eirgnt
eirngt eirntg eitrgn eitrng eitgrn eitgnr eitngr eitnrg eigtrn eigtnr eigrtn
eigrnt eignrt eigntr eintgr eintrg eingtr eingrt einrgt einrtg eritgn eritng
erigtn erignt eringt erintg ertign erting ertgin ertgni ertngi ertnig ergtin
ergtni ergitn ergint ergnit ergnti erntgi erntig erngti erngit ernigt ernitg
etrign etring etrgin etrgni etrngi etrnig etirgn etirng etigrn etignr etingr
etinrg etgirn etginr etgrin etgrni etgnri etgnir etnigr etnirg etngir etngri
etnrgi etnrig egrtin egrtni egritn egrint egrnit egrnti egtrin egtrni egtirn
egtinr egtnir egtnri egitrn egitnr egirtn egirnt eginrt egintr egntir egntri
egnitr egnirt egnrit egnrti enrtgi enrtig enrgti enrgit enrigt enritg entrgi
entrig entgri entgir entigr entirg engtri engtir engrti engrit engirt engitr
enitgr enitrg enigtr enigrt enirgt enirtg nirteg nirtge niretg niregt nirget
nirgte nitreg nitrge niterg nitegr nitger nitgre nietrg nietgr niertg niergt
niegrt niegtr nigter nigtre nigetr nigert nigret nigrte nriteg nritge nrietg
nriegt nriget nrigte nrtieg nrtige nrteig nrtegi nrtgei nrtgie nretig nretgi
nreitg nreigt nregit nregti nrgtei nrgtie nrgeti nrgeit nrgiet nrgite ntrieg
ntrige ntreig ntregi ntrgei ntrgie ntireg ntirge ntierg ntiegr ntiger ntigre
nteirg nteigr nterig ntergi ntegri ntegir ntgier ntgire ntgeir ntgeri ntgrei
ntgrie nertig nertgi neritg nerigt nergit nergti netrig netrgi netirg netigr
netgir netgri neitrg neitgr neirtg neirgt neigrt neigtr negtir negtri negitr
negirt negrit negrti ngrtei ngrtie ngreti ngreit ngriet ngrite ngtrei ngtrie
ngteri ngteir ngtier ngtire ngetri ngetir ngerti ngerit ngeirt ngeitr ngiter
ngitre ngietr ngiert ngiret ngirte

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History of cryptography
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