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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: komppa
cipher variations:
lpnqqb mqorrc nrpssd osqtte ptruuf
qusvvg rvtwwh swuxxi txvyyj uywzzk
vzxaal waybbm xbzccn ycaddo zdbeep
aecffq bfdggr cgehhs dhfiit eigjju
fjhkkv gkillw hljmmx imknny jnlooz

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: komppa
Cipher: plnkkz

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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: komppa

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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: komppa
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: komppa
Cipher: xbzccn

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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: komppa
Cipher: 524323535311

Extended Methods:
Method #1

Plaintext: komppa
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
k o m p p a 
5 4 2 5 5 1 
2 3 3 3 3 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: komppa
Cipher: uwemnc

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Method #3

Plaintext: komppa
method variations:
rhxxcv hxxcvr xxcvrh
xcvrhx cvrhxx vrhxxc

Read more ...[RUS] , [EN]


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: komppa

all 720 cipher variations:
komppa kompap komppa kompap komapp komapp kopmpa kopmap koppma koppam kopapm
kopamp koppma koppam kopmpa kopmap kopamp kopapm koappm koapmp koappm koapmp
koampp koampp kmoppa kmopap kmoppa kmopap kmoapp kmoapp kmpopa kmpoap kmppoa
kmppao kmpapo kmpaop kmppoa kmppao kmpopa kmpoap kmpaop kmpapo kmappo kmapop
kmappo kmapop kmaopp kmaopp kpmopa kpmoap kpmpoa kpmpao kpmapo kpmaop kpompa
kpomap kpopma kpopam kpoapm kpoamp kppoma kppoam kppmoa kppmao kppamo kppaom
kpaopm kpaomp kpapom kpapmo kpampo kpamop kpmpoa kpmpao kpmopa kpmoap kpmaop
kpmapo kppmoa kppmao kppoma kppoam kppaom kppamo kpopma kpopam kpompa kpomap
kpoamp kpoapm kpapom kpapmo kpaopm kpaomp kpamop kpampo kamppo kampop kamppo
kampop kamopp kamopp kapmpo kapmop kappmo kappom kapopm kapomp kappmo kappom
kapmpo kapmop kapomp kapopm kaoppm kaopmp kaoppm kaopmp kaompp kaompp okmppa
okmpap okmppa okmpap okmapp okmapp okpmpa okpmap okppma okppam okpapm okpamp
okppma okppam okpmpa okpmap okpamp okpapm okappm okapmp okappm okapmp okampp
okampp omkppa omkpap omkppa omkpap omkapp omkapp ompkpa ompkap omppka omppak
ompapk ompakp omppka omppak ompkpa ompkap ompakp ompapk omappk omapkp omappk
omapkp omakpp omakpp opmkpa opmkap opmpka opmpak opmapk opmakp opkmpa opkmap
opkpma opkpam opkapm opkamp oppkma oppkam oppmka oppmak oppamk oppakm opakpm
opakmp opapkm opapmk opampk opamkp opmpka opmpak opmkpa opmkap opmakp opmapk
oppmka oppmak oppkma oppkam oppakm oppamk opkpma opkpam opkmpa opkmap opkamp
opkapm opapkm opapmk opakpm opakmp opamkp opampk oamppk oampkp oamppk oampkp
oamkpp oamkpp oapmpk oapmkp oappmk oappkm oapkpm oapkmp oappmk oappkm oapmpk
oapmkp oapkmp oapkpm oakppm oakpmp oakppm oakpmp oakmpp oakmpp mokppa mokpap
mokppa mokpap mokapp mokapp mopkpa mopkap moppka moppak mopapk mopakp moppka
moppak mopkpa mopkap mopakp mopapk moappk moapkp moappk moapkp moakpp moakpp
mkoppa mkopap mkoppa mkopap mkoapp mkoapp mkpopa mkpoap mkppoa mkppao mkpapo
mkpaop mkppoa mkppao mkpopa mkpoap mkpaop mkpapo mkappo mkapop mkappo mkapop
mkaopp mkaopp mpkopa mpkoap mpkpoa mpkpao mpkapo mpkaop mpokpa mpokap mpopka
mpopak mpoapk mpoakp mppoka mppoak mppkoa mppkao mppako mppaok mpaopk mpaokp
mpapok mpapko mpakpo mpakop mpkpoa mpkpao mpkopa mpkoap mpkaop mpkapo mppkoa
mppkao mppoka mppoak mppaok mppako mpopka mpopak mpokpa mpokap mpoakp mpoapk
mpapok mpapko mpaopk mpaokp mpakop mpakpo makppo makpop makppo makpop makopp
makopp mapkpo mapkop mappko mappok mapopk mapokp mappko mappok mapkpo mapkop
mapokp mapopk maoppk maopkp maoppk maopkp maokpp maokpp pomkpa pomkap pompka
pompak pomapk pomakp pokmpa pokmap pokpma pokpam pokapm pokamp popkma popkam
popmka popmak popamk popakm poakpm poakmp poapkm poapmk poampk poamkp pmokpa
pmokap pmopka pmopak pmoapk pmoakp pmkopa pmkoap pmkpoa pmkpao pmkapo pmkaop
pmpkoa pmpkao pmpoka pmpoak pmpaok pmpako pmakpo pmakop pmapko pmapok pmaopk
pmaokp pkmopa pkmoap pkmpoa pkmpao pkmapo pkmaop pkompa pkomap pkopma pkopam
pkoapm pkoamp pkpoma pkpoam pkpmoa pkpmao pkpamo pkpaom pkaopm pkaomp pkapom
pkapmo pkampo pkamop ppmkoa ppmkao ppmoka ppmoak ppmaok ppmako ppkmoa ppkmao
ppkoma ppkoam ppkaom ppkamo ppokma ppokam ppomka ppomak ppoamk ppoakm ppakom
ppakmo ppaokm ppaomk ppamok ppamko pamkpo pamkop pampko pampok pamopk pamokp
pakmpo pakmop pakpmo pakpom pakopm pakomp papkmo papkom papmko papmok papomk
papokm paokpm paokmp paopkm paopmk paompk paomkp pompka pompak pomkpa pomkap
pomakp pomapk popmka popmak popkma popkam popakm popamk pokpma pokpam pokmpa
pokmap pokamp pokapm poapkm poapmk poakpm poakmp poamkp poampk pmopka pmopak
pmokpa pmokap pmoakp pmoapk pmpoka pmpoak pmpkoa pmpkao pmpako pmpaok pmkpoa
pmkpao pmkopa pmkoap pmkaop pmkapo pmapko pmapok pmakpo pmakop pmaokp pmaopk
ppmoka ppmoak ppmkoa ppmkao ppmako ppmaok ppomka ppomak ppokma ppokam ppoakm
ppoamk ppkoma ppkoam ppkmoa ppkmao ppkamo ppkaom ppaokm ppaomk ppakom ppakmo
ppamko ppamok pkmpoa pkmpao pkmopa pkmoap pkmaop pkmapo pkpmoa pkpmao pkpoma
pkpoam pkpaom pkpamo pkopma pkopam pkompa pkomap pkoamp pkoapm pkapom pkapmo
pkaopm pkaomp pkamop pkampo pampko pampok pamkpo pamkop pamokp pamopk papmko
papmok papkmo papkom papokm papomk pakpmo pakpom pakmpo pakmop pakomp pakopm
paopkm paopmk paokpm paokmp paomkp paompk aomppk aompkp aomppk aompkp aomkpp
aomkpp aopmpk aopmkp aoppmk aoppkm aopkpm aopkmp aoppmk aoppkm aopmpk aopmkp
aopkmp aopkpm aokppm aokpmp aokppm aokpmp aokmpp aokmpp amoppk amopkp amoppk
amopkp amokpp amokpp ampopk ampokp amppok amppko ampkpo ampkop amppok amppko
ampopk ampokp ampkop ampkpo amkppo amkpop amkppo amkpop amkopp amkopp apmopk
apmokp apmpok apmpko apmkpo apmkop apompk apomkp apopmk apopkm apokpm apokmp
appomk appokm appmok appmko appkmo appkom apkopm apkomp apkpom apkpmo apkmpo
apkmop apmpok apmpko apmopk apmokp apmkop apmkpo appmok appmko appomk appokm
appkom appkmo apopmk apopkm apompk apomkp apokmp apokpm apkpom apkpmo apkopm
apkomp apkmop apkmpo akmppo akmpop akmppo akmpop akmopp akmopp akpmpo akpmop
akppmo akppom akpopm akpomp akppmo akppom akpmpo akpmop akpomp akpopm akoppm
akopmp akoppm akopmp akompp akompp

Read more ...[1] , [2] , [3]

History of cryptography
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