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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: persyn
cipher variations:
qfstzo rgtuap shuvbq tivwcr ujwxds
vkxyet wlyzfu xmzagv ynabhw zobcix
apcdjy bqdekz crefla dsfgmb etghnc
fuhiod gvijpe hwjkqf ixklrg jylmsh
kzmnti lanouj mbopvk ncpqwl odqrxm

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: persyn
Cipher: kvihbm

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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: persyn

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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: persyn
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: persyn
Cipher: crefla

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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: persyn
Cipher: 535124344533

Extended Methods:
Method #1

Plaintext: persyn
method variations:

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

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Method #3

Plaintext: persyn
method variations:
xfotpx fotpxx otpxxf
tpxxfo pxxfot xxfotp

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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: persyn

all 720 cipher variations:
persyn persny perysn peryns pernys pernsy pesryn pesrny pesyrn pesynr pesnyr
pesnry peysrn peysnr peyrsn peyrns peynrs peynsr pensyr pensry penysr penyrs
penrys penrsy presyn presny preysn preyns prenys prensy prseyn prseny prsyen
prsyne prsnye prsney prysen prysne pryesn pryens prynes prynse prnsye prnsey
prnyse prnyes prneys prnesy psreyn psreny psryen psryne psrnye psrney pseryn
pserny pseyrn pseynr psenyr psenry psyern psyenr psyren psyrne psynre psyner
psneyr psnery psnyer psnyre psnrye psnrey pyrsen pyrsne pyresn pyrens pyrnes
pyrnse pysren pysrne pysern pysenr pysner pysnre pyesrn pyesnr pyersn pyerns
pyenrs pyensr pynser pynsre pynesr pyners pynres pynrse pnrsye pnrsey pnryse
pnryes pnreys pnresy pnsrye pnsrey pnsyre pnsyer pnseyr pnsery pnysre pnyser
pnyrse pnyres pnyers pnyesr pnesyr pnesry pneysr pneyrs pnerys pnersy eprsyn
eprsny eprysn epryns eprnys eprnsy epsryn epsrny epsyrn epsynr epsnyr epsnry
epysrn epysnr epyrsn epyrns epynrs epynsr epnsyr epnsry epnysr epnyrs epnrys
epnrsy erpsyn erpsny erpysn erpyns erpnys erpnsy erspyn erspny ersypn ersynp
ersnyp ersnpy eryspn erysnp erypsn erypns erynps erynsp ernsyp ernspy ernysp
ernyps ernpys ernpsy esrpyn esrpny esrypn esrynp esrnyp esrnpy espryn esprny
espyrn espynr espnyr espnry esyprn esypnr esyrpn esyrnp esynrp esynpr esnpyr
esnpry esnypr esnyrp esnryp esnrpy eyrspn eyrsnp eyrpsn eyrpns eyrnps eyrnsp
eysrpn eysrnp eysprn eyspnr eysnpr eysnrp eypsrn eypsnr eyprsn eyprns eypnrs
eypnsr eynspr eynsrp eynpsr eynprs eynrps eynrsp enrsyp enrspy enrysp enryps
enrpys enrpsy ensryp ensrpy ensyrp ensypr enspyr enspry enysrp enyspr enyrsp
enyrps enyprs enypsr enpsyr enpsry enpysr enpyrs enprys enprsy repsyn repsny
repysn repyns repnys repnsy respyn respny resypn resynp resnyp resnpy reyspn
reysnp reypsn reypns reynps reynsp rensyp renspy renysp renyps renpys renpsy
rpesyn rpesny rpeysn rpeyns rpenys rpensy rpseyn rpseny rpsyen rpsyne rpsnye
rpsney rpysen rpysne rpyesn rpyens rpynes rpynse rpnsye rpnsey rpnyse rpnyes
rpneys rpnesy rspeyn rspeny rspyen rspyne rspnye rspney rsepyn rsepny rseypn
rseynp rsenyp rsenpy rsyepn rsyenp rsypen rsypne rsynpe rsynep rsneyp rsnepy
rsnyep rsnype rsnpye rsnpey rypsen rypsne rypesn rypens rypnes rypnse ryspen
ryspne rysepn rysenp rysnep rysnpe ryespn ryesnp ryepsn ryepns ryenps ryensp
rynsep rynspe rynesp ryneps rynpes rynpse rnpsye rnpsey rnpyse rnpyes rnpeys
rnpesy rnspye rnspey rnsype rnsyep rnseyp rnsepy rnyspe rnysep rnypse rnypes
rnyeps rnyesp rnesyp rnespy rneysp rneyps rnepys rnepsy serpyn serpny serypn
serynp sernyp sernpy sepryn seprny sepyrn sepynr sepnyr sepnry seyprn seypnr
seyrpn seyrnp seynrp seynpr senpyr senpry senypr senyrp senryp senrpy srepyn
srepny sreypn sreynp srenyp srenpy srpeyn srpeny srpyen srpyne srpnye srpney
srypen srypne sryepn sryenp srynep srynpe srnpye srnpey srnype srnyep srneyp
srnepy spreyn spreny spryen spryne sprnye sprney speryn sperny speyrn speynr
spenyr spenry spyern spyenr spyren spyrne spynre spyner spneyr spnery spnyer
spnyre spnrye spnrey syrpen syrpne syrepn syrenp syrnep syrnpe sypren syprne
sypern sypenr sypner sypnre syeprn syepnr syerpn syernp syenrp syenpr synper
synpre synepr synerp synrep synrpe snrpye snrpey snrype snryep snreyp snrepy
snprye snprey snpyre snpyer snpeyr snpery snypre snyper snyrpe snyrep snyerp
snyepr snepyr snepry sneypr sneyrp sneryp snerpy yerspn yersnp yerpsn yerpns
yernps yernsp yesrpn yesrnp yesprn yespnr yesnpr yesnrp yepsrn yepsnr yeprsn
yeprns yepnrs yepnsr yenspr yensrp yenpsr yenprs yenrps yenrsp yrespn yresnp
yrepsn yrepns yrenps yrensp yrsepn yrsenp yrspen yrspne yrsnpe yrsnep yrpsen
yrpsne yrpesn yrpens yrpnes yrpnse yrnspe yrnsep yrnpse yrnpes yrneps yrnesp
ysrepn ysrenp ysrpen ysrpne ysrnpe ysrnep yserpn ysernp yseprn ysepnr ysenpr
ysenrp yspern yspenr yspren ysprne yspnre yspner ysnepr ysnerp ysnper ysnpre
ysnrpe ysnrep yprsen yprsne ypresn yprens yprnes yprnse ypsren ypsrne ypsern
ypsenr ypsner ypsnre ypesrn ypesnr ypersn yperns ypenrs ypensr ypnser ypnsre
ypnesr ypners ypnres ypnrse ynrspe ynrsep ynrpse ynrpes ynreps ynresp ynsrpe
ynsrep ynspre ynsper ynsepr ynserp ynpsre ynpser ynprse ynpres ynpers ynpesr
ynespr ynesrp ynepsr yneprs ynerps ynersp nersyp nerspy nerysp neryps nerpys
nerpsy nesryp nesrpy nesyrp nesypr nespyr nespry neysrp neyspr neyrsp neyrps
neyprs neypsr nepsyr nepsry nepysr nepyrs neprys neprsy nresyp nrespy nreysp
nreyps nrepys nrepsy nrseyp nrsepy nrsyep nrsype nrspye nrspey nrysep nryspe
nryesp nryeps nrypes nrypse nrpsye nrpsey nrpyse nrpyes nrpeys nrpesy nsreyp
nsrepy nsryep nsrype nsrpye nsrpey nseryp nserpy nseyrp nseypr nsepyr nsepry
nsyerp nsyepr nsyrep nsyrpe nsypre nsyper nspeyr nspery nspyer nspyre nsprye
nsprey nyrsep nyrspe nyresp nyreps nyrpes nyrpse nysrep nysrpe nyserp nysepr
nysper nyspre nyesrp nyespr nyersp nyerps nyeprs nyepsr nypser nypsre nypesr
nypers nypres nyprse nprsye nprsey npryse npryes npreys npresy npsrye npsrey
npsyre npsyer npseyr npsery npysre npyser npyrse npyres npyers npyesr npesyr
npesry npeysr npeyrs nperys npersy

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History of cryptography
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