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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: cresap
cipher variations:
dsftbq etgucr fuhvds gviwet hwjxfu
ixkygv jylzhw kzmaix lanbjy mbockz
ncpdla odqemb perfnc qfsgod rgthpe
shuiqf tivjrg ujwksh vkxlti wlymuj
xmznvk ynaowl zobpxm apcqyn bqdrzo

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: cresap
Cipher: xivhzk

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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: cresap

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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: cresap
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: cresap
Cipher: perfnc

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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: cresap
Cipher: 312451341153

Extended Methods:
Method #1

Plaintext: cresap
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
c r e s a p 
3 2 5 3 1 5 
1 4 1 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: cresap
Cipher: hpvqql

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Method #3

Plaintext: cresap
method variations:
fyldvn yldvnf ldvnfy
dvnfyl vnfyld nfyldv

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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: cresap

all 720 cipher variations:
cresap crespa creasp creaps crepas crepsa crseap crsepa crsaep crsape crspae
crspea crasep craspe craesp craeps crapes crapse crpsae crpsea crpase crpaes
crpeas crpesa cersap cerspa cerasp ceraps cerpas cerpsa cesrap cesrpa cesarp
cesapr cespar cespra ceasrp ceaspr cearsp cearps ceaprs ceapsr cepsar cepsra
cepasr cepars cepras ceprsa cserap cserpa csearp cseapr csepar csepra csreap
csrepa csraep csrape csrpae csrpea csarep csarpe csaerp csaepr csaper csapre
csprae csprea cspare cspaer cspear cspera caesrp caespr caersp caerps caeprs
caepsr caserp casepr casrep casrpe caspre casper carsep carspe caresp careps
carpes carpse capsre capser caprse capres capers capesr cpesar cpesra cpeasr
cpears cperas cpersa cpsear cpsera cpsaer cpsare cpsrae cpsrea cpaser cpasre
cpaesr cpaers cpares cparse cprsae cprsea cprase cpraes cpreas cpresa rcesap
rcespa rceasp rceaps rcepas rcepsa rcseap rcsepa rcsaep rcsape rcspae rcspea
rcasep rcaspe rcaesp rcaeps rcapes rcapse rcpsae rcpsea rcpase rcpaes rcpeas
rcpesa recsap recspa recasp recaps recpas recpsa rescap rescpa resacp resapc
respac respca reascp reaspc reacsp reacps reapcs reapsc repsac repsca repasc
repacs repcas repcsa rsecap rsecpa rseacp rseapc rsepac rsepca rsceap rscepa
rscaep rscape rscpae rscpea rsacep rsacpe rsaecp rsaepc rsapec rsapce rspcae
rspcea rspace rspaec rspeac rspeca raescp raespc raecsp raecps raepcs raepsc
rasecp rasepc rascep rascpe raspce raspec racsep racspe racesp raceps racpes
racpse rapsce rapsec rapcse rapces rapecs rapesc rpesac rpesca rpeasc rpeacs
rpecas rpecsa rpseac rpseca rpsaec rpsace rpscae rpscea rpasec rpasce rpaesc
rpaecs rpaces rpacse rpcsae rpcsea rpcase rpcaes rpceas rpcesa ercsap ercspa
ercasp ercaps ercpas ercpsa erscap erscpa ersacp ersapc erspac erspca erascp
eraspc eracsp eracps erapcs erapsc erpsac erpsca erpasc erpacs erpcas erpcsa
ecrsap ecrspa ecrasp ecraps ecrpas ecrpsa ecsrap ecsrpa ecsarp ecsapr ecspar
ecspra ecasrp ecaspr ecarsp ecarps ecaprs ecapsr ecpsar ecpsra ecpasr ecpars
ecpras ecprsa escrap escrpa escarp escapr escpar escpra esrcap esrcpa esracp
esrapc esrpac esrpca esarcp esarpc esacrp esacpr esapcr esaprc esprac esprca
esparc espacr espcar espcra eacsrp eacspr eacrsp eacrps eacprs eacpsr eascrp
eascpr easrcp easrpc easprc easpcr earscp earspc earcsp earcps earpcs earpsc
eapsrc eapscr eaprsc eaprcs eapcrs eapcsr epcsar epcsra epcasr epcars epcras
epcrsa epscar epscra epsacr epsarc epsrac epsrca epascr epasrc epacsr epacrs
eparcs eparsc eprsac eprsca eprasc epracs eprcas eprcsa srecap srecpa sreacp
sreapc srepac srepca srceap srcepa srcaep srcape srcpae srcpea sracep sracpe
sraecp sraepc srapec srapce srpcae srpcea srpace srpaec srpeac srpeca sercap
sercpa seracp serapc serpac serpca secrap secrpa secarp secapr secpar secpra
seacrp seacpr searcp searpc seaprc seapcr sepcar sepcra sepacr separc seprac
seprca scerap scerpa scearp sceapr scepar scepra screap screpa scraep scrape
scrpae scrpea scarep scarpe scaerp scaepr scaper scapre scprae scprea scpare
scpaer scpear scpera saecrp saecpr saercp saerpc saeprc saepcr sacerp sacepr
sacrep sacrpe sacpre sacper sarcep sarcpe sarecp sarepc sarpec sarpce sapcre
sapcer saprce saprec saperc sapecr specar specra speacr spearc sperac sperca
spcear spcera spcaer spcare spcrae spcrea spacer spacre spaecr spaerc sparec
sparce sprcae sprcea sprace spraec spreac spreca arescp arespc arecsp arecps
arepcs arepsc arsecp arsepc arscep arscpe arspce arspec arcsep arcspe arcesp
arceps arcpes arcpse arpsce arpsec arpcse arpces arpecs arpesc aerscp aerspc
aercsp aercps aerpcs aerpsc aesrcp aesrpc aescrp aescpr aespcr aesprc aecsrp
aecspr aecrsp aecrps aecprs aecpsr aepscr aepsrc aepcsr aepcrs aeprcs aeprsc
asercp aserpc asecrp asecpr asepcr aseprc asrecp asrepc asrcep asrcpe asrpce
asrpec ascrep ascrpe ascerp ascepr ascper ascpre asprce asprec aspcre aspcer
aspecr asperc acesrp acespr acersp acerps aceprs acepsr acserp acsepr acsrep
acsrpe acspre acsper acrsep acrspe acresp acreps acrpes acrpse acpsre acpser
acprse acpres acpers acpesr apescr apesrc apecsr apecrs apercs apersc apsecr
apserc apscer apscre apsrce apsrec apcser apcsre apcesr apcers apcres apcrse
aprsce aprsec aprcse aprces aprecs apresc presac presca preasc preacs precas
precsa prseac prseca prsaec prsace prscae prscea prasec prasce praesc praecs
praces pracse prcsae prcsea prcase prcaes prceas prcesa persac persca perasc
peracs percas percsa pesrac pesrca pesarc pesacr pescar pescra peasrc peascr
pearsc pearcs peacrs peacsr pecsar pecsra pecasr pecars pecras pecrsa pserac
pserca psearc pseacr psecar psecra psreac psreca psraec psrace psrcae psrcea
psarec psarce psaerc psaecr psacer psacre pscrae pscrea pscare pscaer pscear
pscera paesrc paescr paersc paercs paecrs paecsr paserc pasecr pasrec pasrce
pascre pascer parsec parsce paresc parecs parces parcse pacsre pacser pacrse
pacres pacers pacesr pcesar pcesra pceasr pcears pceras pcersa pcsear pcsera
pcsaer pcsare pcsrae pcsrea pcaser pcasre pcaesr pcaers pcares pcarse pcrsae
pcrsea pcrase pcraes pcreas pcresa

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History of cryptography
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