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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: botega
cipher variations:
cpufhb dqvgic erwhjd fsxike gtyjlf
huzkmg ivalnh jwbmoi kxcnpj lydoqk
mzeprl nafqsm obgrtn pchsuo qditvp
rejuwq sfkvxr tglwys uhmxzt vinyau
wjozbv xkpacw ylqbdx zmrcey ansdfz

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: botega
Cipher: ylgvtz

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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: botega

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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: botega
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: botega
Cipher: obgrtn

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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: botega
Cipher: 214344512211

Extended Methods:
Method #1

Plaintext: botega
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
b o t e g a 
2 4 4 5 2 1 
1 3 4 1 2 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: botega
Cipher: rybldb

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Method #3

Plaintext: botega
method variations:
qsyfbf syfbfq yfbfqs
fbfqsy bfqsyf fqsyfb

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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: botega

all 720 cipher variations:
botega boteag botgea botgae botage botaeg boetga boetag boegta boegat boeagt
boeatg bogeta bogeat bogtea bogtae bogate bogaet boaegt boaetg boaget boagte
boatge boateg btoega btoeag btogea btogae btoage btoaeg bteoga bteoag btegoa
btegao bteago bteaog btgeoa btgeao btgoea btgoae btgaoe btgaeo btaego btaeog
btageo btagoe btaoge btaoeg betoga betoag betgoa betgao betago betaog beotga
beotag beogta beogat beoagt beoatg begota begoat begtoa begtao begato begaot
beaogt beaotg beagot beagto beatgo beatog bgteoa bgteao bgtoea bgtoae bgtaoe
bgtaeo bgetoa bgetao bgeota bgeoat bgeaot bgeato bgoeta bgoeat bgotea bgotae
bgoate bgoaet bgaeot bgaeto bgaoet bgaote bgatoe bgateo batego bateog batgeo
batgoe batoge batoeg baetgo baetog baegto baegot baeogt baeotg bageto bageot
bagteo bagtoe bagote bagoet baoegt baoetg baoget baogte baotge baoteg obtega
obteag obtgea obtgae obtage obtaeg obetga obetag obegta obegat obeagt obeatg
obgeta obgeat obgtea obgtae obgate obgaet obaegt obaetg obaget obagte obatge
obateg otbega otbeag otbgea otbgae otbage otbaeg otebga otebag otegba otegab
oteagb oteabg otgeba otgeab otgbea otgbae otgabe otgaeb otaegb otaebg otageb
otagbe otabge otabeg oetbga oetbag oetgba oetgab oetagb oetabg oebtga oebtag
oebgta oebgat oebagt oebatg oegbta oegbat oegtba oegtab oegatb oegabt oeabgt
oeabtg oeagbt oeagtb oeatgb oeatbg ogteba ogteab ogtbea ogtbae ogtabe ogtaeb
ogetba ogetab ogebta ogebat ogeabt ogeatb ogbeta ogbeat ogbtea ogbtae ogbate
ogbaet ogaebt ogaetb ogabet ogabte ogatbe ogateb oategb oatebg oatgeb oatgbe
oatbge oatbeg oaetgb oaetbg oaegtb oaegbt oaebgt oaebtg oagetb oagebt oagteb
oagtbe oagbte oagbet oabegt oabetg oabget oabgte oabtge oabteg tobega tobeag
tobgea tobgae tobage tobaeg toebga toebag toegba toegab toeagb toeabg togeba
togeab togbea togbae togabe togaeb toaegb toaebg toageb toagbe toabge toabeg
tboega tboeag tbogea tbogae tboage tboaeg tbeoga tbeoag tbegoa tbegao tbeago
tbeaog tbgeoa tbgeao tbgoea tbgoae tbgaoe tbgaeo tbaego tbaeog tbageo tbagoe
tbaoge tbaoeg teboga teboag tebgoa tebgao tebago tebaog teobga teobag teogba
teogab teoagb teoabg tegoba tegoab tegboa tegbao tegabo tegaob teaogb teaobg
teagob teagbo teabgo teabog tgbeoa tgbeao tgboea tgboae tgbaoe tgbaeo tgeboa
tgebao tgeoba tgeoab tgeaob tgeabo tgoeba tgoeab tgobea tgobae tgoabe tgoaeb
tgaeob tgaebo tgaoeb tgaobe tgaboe tgabeo tabego tabeog tabgeo tabgoe taboge
taboeg taebgo taebog taegbo taegob taeogb taeobg tagebo tageob tagbeo tagboe
tagobe tagoeb taoegb taoebg taogeb taogbe taobge taobeg eotbga eotbag eotgba
eotgab eotagb eotabg eobtga eobtag eobgta eobgat eobagt eobatg eogbta eogbat
eogtba eogtab eogatb eogabt eoabgt eoabtg eoagbt eoagtb eoatgb eoatbg etobga
etobag etogba etogab etoagb etoabg etboga etboag etbgoa etbgao etbago etbaog
etgboa etgbao etgoba etgoab etgaob etgabo etabgo etabog etagbo etagob etaogb
etaobg ebtoga ebtoag ebtgoa ebtgao ebtago ebtaog ebotga ebotag ebogta ebogat
eboagt eboatg ebgota ebgoat ebgtoa ebgtao ebgato ebgaot ebaogt ebaotg ebagot
ebagto ebatgo ebatog egtboa egtbao egtoba egtoab egtaob egtabo egbtoa egbtao
egbota egboat egbaot egbato egobta egobat egotba egotab egoatb egoabt egabot
egabto egaobt egaotb egatob egatbo eatbgo eatbog eatgbo eatgob eatogb eatobg
eabtgo eabtog eabgto eabgot eabogt eabotg eagbto eagbot eagtbo eagtob eagotb
eagobt eaobgt eaobtg eaogbt eaogtb eaotgb eaotbg goteba goteab gotbea gotbae
gotabe gotaeb goetba goetab goebta goebat goeabt goeatb gobeta gobeat gobtea
gobtae gobate gobaet goaebt goaetb goabet goabte goatbe goateb gtoeba gtoeab
gtobea gtobae gtoabe gtoaeb gteoba gteoab gteboa gtebao gteabo gteaob gtbeoa
gtbeao gtboea gtboae gtbaoe gtbaeo gtaebo gtaeob gtabeo gtaboe gtaobe gtaoeb
getoba getoab getboa getbao getabo getaob geotba geotab geobta geobat geoabt
geoatb gebota geboat gebtoa gebtao gebato gebaot geaobt geaotb geabot geabto
geatbo geatob gbteoa gbteao gbtoea gbtoae gbtaoe gbtaeo gbetoa gbetao gbeota
gbeoat gbeaot gbeato gboeta gboeat gbotea gbotae gboate gboaet gbaeot gbaeto
gbaoet gbaote gbatoe gbateo gatebo gateob gatbeo gatboe gatobe gatoeb gaetbo
gaetob gaebto gaebot gaeobt gaeotb gabeto gabeot gabteo gabtoe gabote gaboet
gaoebt gaoetb gaobet gaobte gaotbe gaoteb aotegb aotebg aotgeb aotgbe aotbge
aotbeg aoetgb aoetbg aoegtb aoegbt aoebgt aoebtg aogetb aogebt aogteb aogtbe
aogbte aogbet aobegt aobetg aobget aobgte aobtge aobteg atoegb atoebg atogeb
atogbe atobge atobeg ateogb ateobg ategob ategbo atebgo atebog atgeob atgebo
atgoeb atgobe atgboe atgbeo atbego atbeog atbgeo atbgoe atboge atboeg aetogb
aetobg aetgob aetgbo aetbgo aetbog aeotgb aeotbg aeogtb aeogbt aeobgt aeobtg
aegotb aegobt aegtob aegtbo aegbto aegbot aebogt aebotg aebgot aebgto aebtgo
aebtog agteob agtebo agtoeb agtobe agtboe agtbeo agetob agetbo ageotb ageobt
agebot agebto agoetb agoebt agoteb agotbe agobte agobet agbeot agbeto agboet
agbote agbtoe agbteo abtego abteog abtgeo abtgoe abtoge abtoeg abetgo abetog
abegto abegot abeogt abeotg abgeto abgeot abgteo abgtoe abgote abgoet aboegt
aboetg aboget abogte abotge aboteg

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History of cryptography
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