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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: plebis
cipher variations:
qmfcjt rngdku sohelv tpifmw uqjgnx
vrkhoy wslipz xtmjqa yunkrb zvolsc
awpmtd bxqnue cyrovf dzspwg eatqxh
fburyi gcvszj hdwtak iexubl jfyvcm
kgzwdn lhaxeo mibyfp njczgq okdahr

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: plebis
Cipher: kovyrh

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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: plebis

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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: plebis
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: plebis
Cipher: cyrovf

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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: plebis
Cipher: 531351214234

Extended Methods:
Method #1

Plaintext: plebis
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
p l e b i s 
5 1 5 2 4 3 
3 3 1 1 2 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: plebis
Cipher: ekonar

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Method #3

Plaintext: plebis
method variations:
cxfqmy xfqmyc fqmycx
qmycxf mycxfq ycxfqm

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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: plebis

all 720 cipher variations:
plebis plebsi pleibs pleisb plesib plesbi plbeis plbesi plbies plbise plbsie
plbsei plibes plibse pliebs pliesb pliseb plisbe plsbie plsbei plsibe plsieb
plseib plsebi pelbis pelbsi pelibs pelisb pelsib pelsbi peblis peblsi pebils
pebisl pebsil pebsli peibls peibsl peilbs peilsb peislb peisbl pesbil pesbli
pesibl pesilb peslib peslbi pbelis pbelsi pbeils pbeisl pbesil pbesli pbleis
pblesi pblies pblise pblsie pblsei pbiles pbilse pbiels pbiesl pbisel pbisle
pbslie pbslei pbsile pbsiel pbseil pbseli piebls piebsl pielbs pielsb pieslb
piesbl pibels pibesl pibles piblse pibsle pibsel pilbes pilbse pilebs pilesb
pilseb pilsbe pisble pisbel pislbe pisleb piselb pisebl psebil psebli pseibl
pseilb pselib pselbi psbeil psbeli psbiel psbile psblie psblei psibel psible
psiebl psielb psileb psilbe pslbie pslbei pslibe pslieb psleib pslebi lpebis
lpebsi lpeibs lpeisb lpesib lpesbi lpbeis lpbesi lpbies lpbise lpbsie lpbsei
lpibes lpibse lpiebs lpiesb lpiseb lpisbe lpsbie lpsbei lpsibe lpsieb lpseib
lpsebi lepbis lepbsi lepibs lepisb lepsib lepsbi lebpis lebpsi lebips lebisp
lebsip lebspi leibps leibsp leipbs leipsb leispb leisbp lesbip lesbpi lesibp
lesipb lespib lespbi lbepis lbepsi lbeips lbeisp lbesip lbespi lbpeis lbpesi
lbpies lbpise lbpsie lbpsei lbipes lbipse lbieps lbiesp lbisep lbispe lbspie
lbspei lbsipe lbsiep lbseip lbsepi liebps liebsp liepbs liepsb liespb liesbp
libeps libesp libpes libpse libspe libsep lipbes lipbse lipebs lipesb lipseb
lipsbe lisbpe lisbep lispbe lispeb lisepb lisebp lsebip lsebpi lseibp lseipb
lsepib lsepbi lsbeip lsbepi lsbiep lsbipe lsbpie lsbpei lsibep lsibpe lsiebp
lsiepb lsipeb lsipbe lspbie lspbei lspibe lspieb lspeib lspebi elpbis elpbsi
elpibs elpisb elpsib elpsbi elbpis elbpsi elbips elbisp elbsip elbspi elibps
elibsp elipbs elipsb elispb elisbp elsbip elsbpi elsibp elsipb elspib elspbi
eplbis eplbsi eplibs eplisb eplsib eplsbi epblis epblsi epbils epbisl epbsil
epbsli epibls epibsl epilbs epilsb epislb episbl epsbil epsbli epsibl epsilb
epslib epslbi ebplis ebplsi ebpils ebpisl ebpsil ebpsli eblpis eblpsi eblips
eblisp eblsip eblspi ebilps ebilsp ebipls ebipsl ebispl ebislp ebslip ebslpi
ebsilp ebsipl ebspil ebspli eipbls eipbsl eiplbs eiplsb eipslb eipsbl eibpls
eibpsl eiblps eiblsp eibslp eibspl eilbps eilbsp eilpbs eilpsb eilspb eilsbp
eisblp eisbpl eislbp eislpb eisplb eispbl espbil espbli espibl espilb esplib
esplbi esbpil esbpli esbipl esbilp esblip esblpi esibpl esiblp esipbl esiplb
esilpb esilbp eslbip eslbpi eslibp eslipb eslpib eslpbi blepis blepsi bleips
bleisp blesip blespi blpeis blpesi blpies blpise blpsie blpsei blipes blipse
blieps bliesp blisep blispe blspie blspei blsipe blsiep blseip blsepi belpis
belpsi belips belisp belsip belspi beplis beplsi bepils bepisl bepsil bepsli
beipls beipsl beilps beilsp beislp beispl bespil bespli besipl besilp beslip
beslpi bpelis bpelsi bpeils bpeisl bpesil bpesli bpleis bplesi bplies bplise
bplsie bplsei bpiles bpilse bpiels bpiesl bpisel bpisle bpslie bpslei bpsile
bpsiel bpseil bpseli biepls biepsl bielps bielsp bieslp biespl bipels bipesl
biples biplse bipsle bipsel bilpes bilpse bileps bilesp bilsep bilspe bisple
bispel bislpe bislep biselp bisepl bsepil bsepli bseipl bseilp bselip bselpi
bspeil bspeli bspiel bspile bsplie bsplei bsipel bsiple bsiepl bsielp bsilep
bsilpe bslpie bslpei bslipe bsliep bsleip bslepi ilebps ilebsp ilepbs ilepsb
ilespb ilesbp ilbeps ilbesp ilbpes ilbpse ilbspe ilbsep ilpbes ilpbse ilpebs
ilpesb ilpseb ilpsbe ilsbpe ilsbep ilspbe ilspeb ilsepb ilsebp ielbps ielbsp
ielpbs ielpsb ielspb ielsbp ieblps ieblsp iebpls iebpsl iebspl iebslp iepbls
iepbsl ieplbs ieplsb iepslb iepsbl iesbpl iesblp iespbl iesplb ieslpb ieslbp
ibelps ibelsp ibepls ibepsl ibespl ibeslp ibleps iblesp iblpes iblpse iblspe
iblsep ibples ibplse ibpels ibpesl ibpsel ibpsle ibslpe ibslep ibsple ibspel
ibsepl ibselp ipebls ipebsl ipelbs ipelsb ipeslb ipesbl ipbels ipbesl ipbles
ipblse ipbsle ipbsel iplbes iplbse iplebs iplesb iplseb iplsbe ipsble ipsbel
ipslbe ipsleb ipselb ipsebl isebpl iseblp isepbl iseplb iselpb iselbp isbepl
isbelp isbpel isbple isblpe isblep ispbel ispble ispebl ispelb ispleb isplbe
islbpe islbep islpbe islpeb islepb islebp slebip slebpi sleibp sleipb slepib
slepbi slbeip slbepi slbiep slbipe slbpie slbpei slibep slibpe sliebp sliepb
slipeb slipbe slpbie slpbei slpibe slpieb slpeib slpebi selbip selbpi selibp
selipb selpib selpbi seblip seblpi sebilp sebipl sebpil sebpli seiblp seibpl
seilbp seilpb seiplb seipbl sepbil sepbli sepibl sepilb seplib seplbi sbelip
sbelpi sbeilp sbeipl sbepil sbepli sbleip sblepi sbliep sblipe sblpie sblpei
sbilep sbilpe sbielp sbiepl sbipel sbiple sbplie sbplei sbpile sbpiel sbpeil
sbpeli sieblp siebpl sielbp sielpb sieplb siepbl sibelp sibepl siblep siblpe
sibple sibpel silbep silbpe silebp silepb silpeb silpbe sipble sipbel siplbe
sipleb sipelb sipebl spebil spebli speibl speilb spelib spelbi spbeil spbeli
spbiel spbile spblie spblei spibel spible spiebl spielb spileb spilbe splbie
splbei splibe splieb spleib splebi

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History of cryptography
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