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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: fstore
cipher variations:
gtupsf huvqtg ivwruh jwxsvi kxytwj
lyzuxk mzavyl nabwzm obcxan pcdybo
qdezcp refadq sfgber tghcfs uhidgt
vijehu wjkfiv xklgjw ylmhkx zmnily
anojmz bopkna cpqlob dqrmpc ersnqd

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: fstore
Cipher: uhgliv

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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: fstore

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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: fstore
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: fstore
Cipher: sfgber

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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: fstore
Cipher: 123444432451

Extended Methods:
Method #1

Plaintext: fstore
method variations:

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

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Method #3

Plaintext: fstore
method variations:
mtthya tthyam thyamt
hyamtt yamtth amtthy

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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: fstore

all 720 cipher variations:
fstore fstoer fstroe fstreo fstero fsteor fsotre fsoter fsorte fsoret fsoert
fsoetr fsrote fsroet fsrtoe fsrteo fsreto fsreot fseort fseotr fserot fserto
fsetro fsetor ftsore ftsoer ftsroe ftsreo ftsero ftseor ftosre ftoser ftorse
ftores ftoers ftoesr ftrose ftroes ftrsoe ftrseo ftreso ftreos fteors fteosr
fteros fterso ftesro ftesor fotsre fotser fotrse fotres foters fotesr fostre
foster fosrte fosret fosert fosetr forste forset fortse fortes forets forest
foesrt foestr foerst foerts foetrs foetsr frtose frtoes frtsoe frtseo frteso
frteos frotse frotes froste froset froest froets frsote frsoet frstoe frsteo
frseto frseot freost freots fresot fresto fretso fretos fetors fetosr fetros
fetrso fetsro fetsor feotrs feotsr feorts feorst feosrt feostr ferots ferost
fertos fertso fersto fersot fesort fesotr fesrot fesrto festro festor sftore
sftoer sftroe sftreo sftero sfteor sfotre sfoter sforte sforet sfoert sfoetr
sfrote sfroet sfrtoe sfrteo sfreto sfreot sfeort sfeotr sferot sferto sfetro
sfetor stfore stfoer stfroe stfreo stfero stfeor stofre stofer storfe storef
stoerf stoefr strofe stroef strfoe strfeo strefo streof steorf steofr sterof
sterfo stefro stefor sotfre sotfer sotrfe sotref soterf sotefr softre softer
sofrte sofret sofert sofetr sorfte sorfet sortfe sortef soretf soreft soefrt
soeftr soerft soertf soetrf soetfr srtofe srtoef srtfoe srtfeo srtefo srteof
srotfe srotef srofte srofet sroeft sroetf srfote srfoet srftoe srfteo srfeto
srfeot sreoft sreotf srefot srefto sretfo sretof setorf setofr setrof setrfo
setfro setfor seotrf seotfr seortf seorft seofrt seoftr serotf seroft sertof
sertfo serfto serfot sefort sefotr sefrot sefrto seftro seftor tsfore tsfoer
tsfroe tsfreo tsfero tsfeor tsofre tsofer tsorfe tsoref tsoerf tsoefr tsrofe
tsroef tsrfoe tsrfeo tsrefo tsreof tseorf tseofr tserof tserfo tsefro tsefor
tfsore tfsoer tfsroe tfsreo tfsero tfseor tfosre tfoser tforse tfores tfoers
tfoesr tfrose tfroes tfrsoe tfrseo tfreso tfreos tfeors tfeosr tferos tferso
tfesro tfesor tofsre tofser tofrse tofres tofers tofesr tosfre tosfer tosrfe
tosref toserf tosefr torsfe torsef torfse torfes torefs toresf toesrf toesfr
toersf toerfs toefrs toefsr trfose trfoes trfsoe trfseo trfeso trfeos trofse
trofes trosfe trosef troesf troefs trsofe trsoef trsfoe trsfeo trsefo trseof
treosf treofs tresof tresfo trefso trefos tefors tefosr tefros tefrso tefsro
tefsor teofrs teofsr teorfs teorsf teosrf teosfr terofs terosf terfos terfso
tersfo tersof tesorf tesofr tesrof tesrfo tesfro tesfor ostfre ostfer ostrfe
ostref osterf ostefr osftre osfter osfrte osfret osfert osfetr osrfte osrfet
osrtfe osrtef osretf osreft osefrt oseftr oserft osertf osetrf osetfr otsfre
otsfer otsrfe otsref otserf otsefr otfsre otfser otfrse otfres otfers otfesr
otrfse otrfes otrsfe otrsef otresf otrefs otefrs otefsr oterfs otersf otesrf
otesfr oftsre oftser oftrse oftres ofters oftesr ofstre ofster ofsrte ofsret
ofsert ofsetr ofrste ofrset ofrtse ofrtes ofrets ofrest ofesrt ofestr oferst
oferts ofetrs ofetsr ortfse ortfes ortsfe ortsef ortesf ortefs orftse orftes
orfste orfset orfest orfets orsfte orsfet orstfe orstef orsetf orseft orefst
orefts oresft orestf oretsf oretfs oetfrs oetfsr oetrfs oetrsf oetsrf oetsfr
oeftrs oeftsr oefrts oefrst oefsrt oefstr oerfts oerfst oertfs oertsf oerstf
oersft oesfrt oesftr oesrft oesrtf oestrf oestfr rstofe rstoef rstfoe rstfeo
rstefo rsteof rsotfe rsotef rsofte rsofet rsoeft rsoetf rsfote rsfoet rsftoe
rsfteo rsfeto rsfeot rseoft rseotf rsefot rsefto rsetfo rsetof rtsofe rtsoef
rtsfoe rtsfeo rtsefo rtseof rtosfe rtosef rtofse rtofes rtoefs rtoesf rtfose
rtfoes rtfsoe rtfseo rtfeso rtfeos rteofs rteosf rtefos rtefso rtesfo rtesof
rotsfe rotsef rotfse rotfes rotefs rotesf rostfe rostef rosfte rosfet roseft
rosetf rofste rofset roftse roftes rofets rofest roesft roestf roefst roefts
roetfs roetsf rftose rftoes rftsoe rftseo rfteso rfteos rfotse rfotes rfoste
rfoset rfoest rfoets rfsote rfsoet rfstoe rfsteo rfseto rfseot rfeost rfeots
rfesot rfesto rfetso rfetos retofs retosf retfos retfso retsfo retsof reotfs
reotsf reofts reofst reosft reostf refots refost reftos reftso refsto refsot
resoft resotf resfot resfto restfo restof estorf estofr estrof estrfo estfro
estfor esotrf esotfr esortf esorft esofrt esoftr esrotf esroft esrtof esrtfo
esrfto esrfot esfort esfotr esfrot esfrto esftro esftor etsorf etsofr etsrof
etsrfo etsfro etsfor etosrf etosfr etorsf etorfs etofrs etofsr etrosf etrofs
etrsof etrsfo etrfso etrfos etfors etfosr etfros etfrso etfsro etfsor eotsrf
eotsfr eotrsf eotrfs eotfrs eotfsr eostrf eostfr eosrtf eosrft eosfrt eosftr
eorstf eorsft eortsf eortfs eorfts eorfst eofsrt eofstr eofrst eofrts eoftrs
eoftsr ertosf ertofs ertsof ertsfo ertfso ertfos erotsf erotfs erostf erosft
erofst erofts ersotf ersoft erstof erstfo ersfto ersfot erfost erfots erfsot
erfsto erftso erftos eftors eftosr eftros eftrso eftsro eftsor efotrs efotsr
eforts eforst efosrt efostr efrots efrost efrtos efrtso efrsto efrsot efsort
efsotr efsrot efsrto efstro efstor

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History of cryptography
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