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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: colter
cipher variations:
dpmufs eqnvgt frowhu gspxiv htqyjw
iurzkx jvsaly kwtbmz lxucna myvdob
nzwepc oaxfqd pbygre qczhsf rdaitg
sebjuh tfckvi ugdlwj vhemxk wifnyl
xjgozm ykhpan zliqbo amjrcp bnksdq

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: colter
Cipher: xlogvi

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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: colter

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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: colter
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: colter
Cipher: pbygre

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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: colter
Cipher: 314313445124

Extended Methods:
Method #1

Plaintext: colter
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
c o l t e r 
3 4 1 4 5 2 
1 3 3 4 1 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: colter
Cipher: sqklsq

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Method #3

Plaintext: colter
method variations:
qcsyfo csyfoq syfoqc
yfoqcs foqcsy oqcsyf

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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: colter

all 720 cipher variations:
colter coltre coletr colert colret colrte cotler cotlre cotelr coterl cotrel
cotrle coetlr coetrl coeltr coelrt coerlt coertl cortel cortle coretl corelt
corlet corlte cloter clotre cloetr cloert cloret clorte cltoer cltore clteor
cltero cltreo cltroe cletor cletro cleotr cleort clerot clerto clrteo clrtoe
clreto clreot clroet clrote ctloer ctlore ctleor ctlero ctlreo ctlroe ctoler
ctolre ctoelr ctoerl ctorel ctorle cteolr cteorl ctelor ctelro cterlo cterol
ctroel ctrole ctreol ctrelo ctrleo ctrloe celtor celtro celotr celort celrot
celrto cetlor cetlro cetolr cetorl cetrol cetrlo ceotlr ceotrl ceoltr ceolrt
ceorlt ceortl certol certlo cerotl cerolt cerlot cerlto crlteo crltoe crleto
crleot crloet crlote crtleo crtloe crtelo crteol crtoel crtole cretlo cretol
crelto crelot creolt creotl crotel crotle croetl croelt crolet crolte oclter
ocltre ocletr oclert oclret oclrte octler octlre octelr octerl octrel octrle
ocetlr ocetrl oceltr ocelrt ocerlt ocertl ocrtel ocrtle ocretl ocrelt ocrlet
ocrlte olcter olctre olcetr olcert olcret olcrte oltcer oltcre oltecr olterc
oltrec oltrce oletcr oletrc olectr olecrt olerct olertc olrtec olrtce olretc
olrect olrcet olrcte otlcer otlcre otlecr otlerc otlrec otlrce otcler otclre
otcelr otcerl otcrel otcrle oteclr otecrl otelcr otelrc oterlc otercl otrcel
otrcle otrecl otrelc otrlec otrlce oeltcr oeltrc oelctr oelcrt oelrct oelrtc
oetlcr oetlrc oetclr oetcrl oetrcl oetrlc oectlr oectrl oecltr oeclrt oecrlt
oecrtl oertcl oertlc oerctl oerclt oerlct oerltc orltec orltce orletc orlect
orlcet orlcte ortlec ortlce ortelc ortecl ortcel ortcle oretlc oretcl oreltc
orelct oreclt orectl orctel orctle orcetl orcelt orclet orclte locter loctre
locetr locert locret locrte lotcer lotcre lotecr loterc lotrec lotrce loetcr
loetrc loectr loecrt loerct loertc lortec lortce loretc lorect lorcet lorcte
lcoter lcotre lcoetr lcoert lcoret lcorte lctoer lctore lcteor lctero lctreo
lctroe lcetor lcetro lceotr lceort lcerot lcerto lcrteo lcrtoe lcreto lcreot
lcroet lcrote ltcoer ltcore ltceor ltcero ltcreo ltcroe ltocer ltocre ltoecr
ltoerc ltorec ltorce lteocr lteorc ltecor ltecro lterco lteroc ltroec ltroce
ltreoc ltreco ltrceo ltrcoe lector lectro lecotr lecort lecrot lecrto letcor
letcro letocr letorc letroc letrco leotcr leotrc leoctr leocrt leorct leortc
lertoc lertco lerotc leroct lercot lercto lrcteo lrctoe lrceto lrceot lrcoet
lrcote lrtceo lrtcoe lrteco lrteoc lrtoec lrtoce lretco lretoc lrecto lrecot
lreoct lreotc lrotec lrotce lroetc lroect lrocet lrocte tolcer tolcre tolecr
tolerc tolrec tolrce tocler toclre tocelr tocerl tocrel tocrle toeclr toecrl
toelcr toelrc toerlc toercl torcel torcle torecl torelc torlec torlce tlocer
tlocre tloecr tloerc tlorec tlorce tlcoer tlcore tlceor tlcero tlcreo tlcroe
tlecor tlecro tleocr tleorc tleroc tlerco tlrceo tlrcoe tlreco tlreoc tlroec
tlroce tcloer tclore tcleor tclero tclreo tclroe tcoler tcolre tcoelr tcoerl
tcorel tcorle tceolr tceorl tcelor tcelro tcerlo tcerol tcroel tcrole tcreol
tcrelo tcrleo tcrloe telcor telcro telocr telorc telroc telrco teclor teclro
tecolr tecorl tecrol tecrlo teoclr teocrl teolcr teolrc teorlc teorcl tercol
terclo terocl terolc terloc terlco trlceo trlcoe trleco trleoc trloec trloce
trcleo trcloe trcelo trceol trcoel trcole treclo trecol trelco treloc treolc
treocl trocel trocle troecl troelc trolec trolce eoltcr eoltrc eolctr eolcrt
eolrct eolrtc eotlcr eotlrc eotclr eotcrl eotrcl eotrlc eoctlr eoctrl eocltr
eoclrt eocrlt eocrtl eortcl eortlc eorctl eorclt eorlct eorltc elotcr elotrc
eloctr elocrt elorct elortc eltocr eltorc eltcor eltcro eltrco eltroc elctor
elctro elcotr elcort elcrot elcrto elrtco elrtoc elrcto elrcot elroct elrotc
etlocr etlorc etlcor etlcro etlrco etlroc etolcr etolrc etoclr etocrl etorcl
etorlc etcolr etcorl etclor etclro etcrlo etcrol etrocl etrolc etrcol etrclo
etrlco etrloc ecltor ecltro eclotr eclort eclrot eclrto ectlor ectlro ectolr
ectorl ectrol ectrlo ecotlr ecotrl ecoltr ecolrt ecorlt ecortl ecrtol ecrtlo
ecrotl ecrolt ecrlot ecrlto erltco erltoc erlcto erlcot erloct erlotc ertlco
ertloc ertclo ertcol ertocl ertolc erctlo erctol erclto erclot ercolt ercotl
erotcl erotlc eroctl eroclt erolct eroltc roltec roltce roletc rolect rolcet
rolcte rotlec rotlce rotelc rotecl rotcel rotcle roetlc roetcl roeltc roelct
roeclt roectl roctel roctle rocetl rocelt roclet roclte rlotec rlotce rloetc
rloect rlocet rlocte rltoec rltoce rlteoc rlteco rltceo rltcoe rletoc rletco
rleotc rleoct rlecot rlecto rlcteo rlctoe rlceto rlceot rlcoet rlcote rtloec
rtloce rtleoc rtleco rtlceo rtlcoe rtolec rtolce rtoelc rtoecl rtocel rtocle
rteolc rteocl rteloc rtelco rteclo rtecol rtcoel rtcole rtceol rtcelo rtcleo
rtcloe reltoc reltco relotc reloct relcot relcto retloc retlco retolc retocl
retcol retclo reotlc reotcl reoltc reolct reoclt reoctl rectol rectlo recotl
recolt reclot reclto rclteo rcltoe rcleto rcleot rcloet rclote rctleo rctloe
rctelo rcteol rctoel rctole rcetlo rcetol rcelto rcelot rceolt rceotl rcotel
rcotle rcoetl rcoelt rcolet rcolte

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History of cryptography
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