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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: wisper
cipher variations:
xjtqfs ykurgt zlvshu amwtiv bnxujw
coyvkx dpzwly eqaxmz frbyna gsczob
htdapc iuebqd jvfcre kwgdsf lxhetg
myifuh nzjgvi oakhwj pblixk qcmjyl
rdnkzm seolan tfpmbo ugqncp vhrodq

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: wisper
Cipher: drhkvi

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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: wisper

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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: wisper
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: wisper
Cipher: jvfcre

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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: wisper
Cipher: 254234535124

Extended Methods:
Method #1

Plaintext: wisper
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
w i s p e r 
2 4 3 5 5 2 
5 2 4 3 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: wisper
Cipher: rxkkoq

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Method #3

Plaintext: wisper
method variations:
umyxfi myxfiu yxfium
xfiumy fiumyx iumyxf

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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: wisper

all 720 cipher variations:
wisper wispre wisepr wiserp wisrep wisrpe wipser wipsre wipesr wipers wipres
wiprse wiepsr wieprs wiespr wiesrp wiersp wierps wirpes wirpse wireps wiresp
wirsep wirspe wsiper wsipre wsiepr wsierp wsirep wsirpe wspier wspire wspeir
wsperi wsprei wsprie wsepir wsepri wseipr wseirp wserip wserpi wsrpei wsrpie
wsrepi wsreip wsriep wsripe wpsier wpsire wpseir wpseri wpsrei wpsrie wpiser
wpisre wpiesr wpiers wpires wpirse wpeisr wpeirs wpesir wpesri wpersi wperis
wpries wprise wpreis wpresi wprsei wprsie wespir wespri wesipr wesirp wesrip
wesrpi wepsir wepsri wepisr wepirs wepris weprsi weipsr weiprs weispr weisrp
weirsp weirps werpis werpsi werips werisp wersip werspi wrspei wrspie wrsepi
wrseip wrsiep wrsipe wrpsei wrpsie wrpesi wrpeis wrpies wrpise wrepsi wrepis
wrespi wresip wreisp wreips wripes wripse wrieps wriesp wrisep wrispe iwsper
iwspre iwsepr iwserp iwsrep iwsrpe iwpser iwpsre iwpesr iwpers iwpres iwprse
iwepsr iweprs iwespr iwesrp iwersp iwerps iwrpes iwrpse iwreps iwresp iwrsep
iwrspe iswper iswpre iswepr iswerp iswrep iswrpe ispwer ispwre ispewr isperw
isprew isprwe isepwr iseprw isewpr isewrp iserwp iserpw isrpew isrpwe isrepw
isrewp isrwep isrwpe ipswer ipswre ipsewr ipserw ipsrew ipsrwe ipwser ipwsre
ipwesr ipwers ipwres ipwrse ipewsr ipewrs ipeswr ipesrw ipersw iperws iprwes
iprwse iprews ipresw iprsew iprswe iespwr iesprw ieswpr ieswrp iesrwp iesrpw
iepswr iepsrw iepwsr iepwrs ieprws ieprsw iewpsr iewprs iewspr iewsrp iewrsp
iewrps ierpws ierpsw ierwps ierwsp ierswp ierspw irspew irspwe irsepw irsewp
irswep irswpe irpsew irpswe irpesw irpews irpwes irpwse irepsw irepws irespw
ireswp irewsp irewps irwpes irwpse irweps irwesp irwsep irwspe siwper siwpre
siwepr siwerp siwrep siwrpe sipwer sipwre sipewr siperw siprew siprwe siepwr
sieprw siewpr siewrp sierwp sierpw sirpew sirpwe sirepw sirewp sirwep sirwpe
swiper swipre swiepr swierp swirep swirpe swpier swpire swpeir swperi swprei
swprie swepir swepri sweipr sweirp swerip swerpi swrpei swrpie swrepi swreip
swriep swripe spwier spwire spweir spweri spwrei spwrie spiwer spiwre spiewr
spierw spirew spirwe speiwr speirw spewir spewri sperwi speriw spriew spriwe
spreiw sprewi sprwei sprwie sewpir sewpri sewipr sewirp sewrip sewrpi sepwir
sepwri sepiwr sepirw sepriw seprwi seipwr seiprw seiwpr seiwrp seirwp seirpw
serpiw serpwi seripw seriwp serwip serwpi srwpei srwpie srwepi srweip srwiep
srwipe srpwei srpwie srpewi srpeiw srpiew srpiwe srepwi srepiw srewpi srewip
sreiwp sreipw sripew sripwe sriepw sriewp sriwep sriwpe piswer piswre pisewr
piserw pisrew pisrwe piwser piwsre piwesr piwers piwres piwrse piewsr piewrs
pieswr piesrw piersw pierws pirwes pirwse pirews piresw pirsew pirswe psiwer
psiwre psiewr psierw psirew psirwe pswier pswire psweir psweri pswrei pswrie
psewir psewri pseiwr pseirw pseriw pserwi psrwei psrwie psrewi psreiw psriew
psriwe pwsier pwsire pwseir pwseri pwsrei pwsrie pwiser pwisre pwiesr pwiers
pwires pwirse pweisr pweirs pwesir pwesri pwersi pweris pwries pwrise pwreis
pwresi pwrsei pwrsie peswir peswri pesiwr pesirw pesriw pesrwi pewsir pewsri
pewisr pewirs pewris pewrsi peiwsr peiwrs peiswr peisrw peirsw peirws perwis
perwsi periws perisw persiw perswi prswei prswie prsewi prseiw prsiew prsiwe
prwsei prwsie prwesi prweis prwies prwise prewsi prewis preswi presiw preisw
preiws priwes priwse priews priesw prisew priswe eispwr eisprw eiswpr eiswrp
eisrwp eisrpw eipswr eipsrw eipwsr eipwrs eiprws eiprsw eiwpsr eiwprs eiwspr
eiwsrp eiwrsp eiwrps eirpws eirpsw eirwps eirwsp eirswp eirspw esipwr esiprw
esiwpr esiwrp esirwp esirpw espiwr espirw espwir espwri esprwi espriw eswpir
eswpri eswipr eswirp eswrip eswrpi esrpwi esrpiw esrwpi esrwip esriwp esripw
epsiwr epsirw epswir epswri epsrwi epsriw episwr episrw epiwsr epiwrs epirws
epirsw epwisr epwirs epwsir epwsri epwrsi epwris epriws eprisw eprwis eprwsi
eprswi eprsiw ewspir ewspri ewsipr ewsirp ewsrip ewsrpi ewpsir ewpsri ewpisr
ewpirs ewpris ewprsi ewipsr ewiprs ewispr ewisrp ewirsp ewirps ewrpis ewrpsi
ewrips ewrisp ewrsip ewrspi erspwi erspiw erswpi erswip ersiwp ersipw erpswi
erpsiw erpwsi erpwis erpiws erpisw erwpsi erwpis erwspi erwsip erwisp erwips
eripws eripsw eriwps eriwsp eriswp erispw rispew rispwe risepw risewp riswep
riswpe ripsew ripswe ripesw ripews ripwes ripwse riepsw riepws riespw rieswp
riewsp riewps riwpes riwpse riweps riwesp riwsep riwspe rsipew rsipwe rsiepw
rsiewp rsiwep rsiwpe rspiew rspiwe rspeiw rspewi rspwei rspwie rsepiw rsepwi
rseipw rseiwp rsewip rsewpi rswpei rswpie rswepi rsweip rswiep rswipe rpsiew
rpsiwe rpseiw rpsewi rpswei rpswie rpisew rpiswe rpiesw rpiews rpiwes rpiwse
rpeisw rpeiws rpesiw rpeswi rpewsi rpewis rpwies rpwise rpweis rpwesi rpwsei
rpwsie respiw respwi resipw resiwp reswip reswpi repsiw repswi repisw repiws
repwis repwsi reipsw reipws reispw reiswp reiwsp reiwps rewpis rewpsi rewips
rewisp rewsip rewspi rwspei rwspie rwsepi rwseip rwsiep rwsipe rwpsei rwpsie
rwpesi rwpeis rwpies rwpise rwepsi rwepis rwespi rwesip rweisp rweips rwipes
rwipse rwieps rwiesp rwisep rwispe

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History of cryptography
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