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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: malben
cipher variations:
nbmcfo ocndgp pdoehq qepfir rfqgjs
sgrhkt thsilu uitjmv vjuknw wkvlox
xlwmpy ymxnqz znyora aozpsb bpaqtc
cqbrud drcsve esdtwf fteuxg gufvyh
hvgwzi iwhxaj jxiybk kyjzcl lzkadm

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: malben
Cipher: nzoyvm

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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: malben

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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: malben
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: malben
Cipher: znyora

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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: malben
Cipher: 231113215133

Extended Methods:
Method #1

Plaintext: malben
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
m a l b e n 
2 1 1 2 5 3 
3 1 3 1 1 3 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: malben
Cipher: bfpccl

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Method #3

Plaintext: malben
method variations:
cahvlh ahvlhc hvlhca
vlhcah lhcahv hcahvl

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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: malben

all 720 cipher variations:
malben malbne malebn malenb malneb malnbe mablen mablne mabeln mabenl mabnel
mabnle maebln maebnl maelbn maelnb maenlb maenbl manbel manble manebl manelb
manleb manlbe mlaben mlabne mlaebn mlaenb mlaneb mlanbe mlbaen mlbane mlbean
mlbena mlbnea mlbnae mleban mlebna mleabn mleanb mlenab mlenba mlnbea mlnbae
mlneba mlneab mlnaeb mlnabe mblaen mblane mblean mblena mblnea mblnae mbalen
mbalne mbaeln mbaenl mbanel mbanle mbealn mbeanl mbelan mbelna mbenla mbenal
mbnael mbnale mbneal mbnela mbnlea mbnlae melban melbna melabn melanb melnab
melnba meblan meblna mebaln mebanl mebnal mebnla meabln meabnl mealbn mealnb
meanlb meanbl menbal menbla menabl menalb menlab menlba mnlbea mnlbae mnleba
mnleab mnlaeb mnlabe mnblea mnblae mnbela mnbeal mnbael mnbale mnebla mnebal
mnelba mnelab mnealb mneabl mnabel mnable mnaebl mnaelb mnaleb mnalbe amlben
amlbne amlebn amlenb amlneb amlnbe amblen amblne ambeln ambenl ambnel ambnle
amebln amebnl amelbn amelnb amenlb amenbl amnbel amnble amnebl amnelb amnleb
amnlbe almben almbne almebn almenb almneb almnbe albmen albmne albemn albenm
albnem albnme alebmn alebnm alembn alemnb alenmb alenbm alnbem alnbme alnebm
alnemb alnmeb alnmbe ablmen ablmne ablemn ablenm ablnem ablnme abmlen abmlne
abmeln abmenl abmnel abmnle abemln abemnl abelmn abelnm abenlm abenml abnmel
abnmle abneml abnelm abnlem abnlme aelbmn aelbnm aelmbn aelmnb aelnmb aelnbm
aeblmn aeblnm aebmln aebmnl aebnml aebnlm aembln aembnl aemlbn aemlnb aemnlb
aemnbl aenbml aenblm aenmbl aenmlb aenlmb aenlbm anlbem anlbme anlebm anlemb
anlmeb anlmbe anblem anblme anbelm anbeml anbmel anbmle aneblm anebml anelbm
anelmb anemlb anembl anmbel anmble anmebl anmelb anmleb anmlbe lamben lambne
lamebn lamenb lamneb lamnbe labmen labmne labemn labenm labnem labnme laebmn
laebnm laembn laemnb laenmb laenbm lanbem lanbme lanebm lanemb lanmeb lanmbe
lmaben lmabne lmaebn lmaenb lmaneb lmanbe lmbaen lmbane lmbean lmbena lmbnea
lmbnae lmeban lmebna lmeabn lmeanb lmenab lmenba lmnbea lmnbae lmneba lmneab
lmnaeb lmnabe lbmaen lbmane lbmean lbmena lbmnea lbmnae lbamen lbamne lbaemn
lbaenm lbanem lbanme lbeamn lbeanm lbeman lbemna lbenma lbenam lbnaem lbname
lbneam lbnema lbnmea lbnmae lemban lembna lemabn lemanb lemnab lemnba lebman
lebmna lebamn lebanm lebnam lebnma leabmn leabnm leambn leamnb leanmb leanbm
lenbam lenbma lenabm lenamb lenmab lenmba lnmbea lnmbae lnmeba lnmeab lnmaeb
lnmabe lnbmea lnbmae lnbema lnbeam lnbaem lnbame lnebma lnebam lnemba lnemab
lneamb lneabm lnabem lnabme lnaebm lnaemb lnameb lnambe balmen balmne balemn
balenm balnem balnme bamlen bamlne bameln bamenl bamnel bamnle baemln baemnl
baelmn baelnm baenlm baenml banmel banmle baneml banelm banlem banlme blamen
blamne blaemn blaenm blanem blanme blmaen blmane blmean blmena blmnea blmnae
bleman blemna bleamn bleanm blenam blenma blnmea blnmae blnema blneam blnaem
blname bmlaen bmlane bmlean bmlena bmlnea bmlnae bmalen bmalne bmaeln bmaenl
bmanel bmanle bmealn bmeanl bmelan bmelna bmenla bmenal bmnael bmnale bmneal
bmnela bmnlea bmnlae belman belmna belamn belanm belnam belnma bemlan bemlna
bemaln bemanl bemnal bemnla beamln beamnl bealmn bealnm beanlm beanml benmal
benmla benaml benalm benlam benlma bnlmea bnlmae bnlema bnleam bnlaem bnlame
bnmlea bnmlae bnmela bnmeal bnmael bnmale bnemla bnemal bnelma bnelam bnealm
bneaml bnamel bnamle bnaeml bnaelm bnalem bnalme ealbmn ealbnm ealmbn ealmnb
ealnmb ealnbm eablmn eablnm eabmln eabmnl eabnml eabnlm eambln eambnl eamlbn
eamlnb eamnlb eamnbl eanbml eanblm eanmbl eanmlb eanlmb eanlbm elabmn elabnm
elambn elamnb elanmb elanbm elbamn elbanm elbman elbmna elbnma elbnam elmban
elmbna elmabn elmanb elmnab elmnba elnbma elnbam elnmba elnmab elnamb elnabm
eblamn eblanm eblman eblmna eblnma eblnam ebalmn ebalnm ebamln ebamnl ebanml
ebanlm ebmaln ebmanl ebmlan ebmlna ebmnla ebmnal ebnaml ebnalm ebnmal ebnmla
ebnlma ebnlam emlban emlbna emlabn emlanb emlnab emlnba emblan emblna embaln
embanl embnal embnla emabln emabnl emalbn emalnb emanlb emanbl emnbal emnbla
emnabl emnalb emnlab emnlba enlbma enlbam enlmba enlmab enlamb enlabm enblma
enblam enbmla enbmal enbaml enbalm enmbla enmbal enmlba enmlab enmalb enmabl
enabml enablm enambl enamlb enalmb enalbm nalbem nalbme nalebm nalemb nalmeb
nalmbe nablem nablme nabelm nabeml nabmel nabmle naeblm naebml naelbm naelmb
naemlb naembl nambel namble namebl namelb namleb namlbe nlabem nlabme nlaebm
nlaemb nlameb nlambe nlbaem nlbame nlbeam nlbema nlbmea nlbmae nlebam nlebma
nleabm nleamb nlemab nlemba nlmbea nlmbae nlmeba nlmeab nlmaeb nlmabe nblaem
nblame nbleam nblema nblmea nblmae nbalem nbalme nbaelm nbaeml nbamel nbamle
nbealm nbeaml nbelam nbelma nbemla nbemal nbmael nbmale nbmeal nbmela nbmlea
nbmlae nelbam nelbma nelabm nelamb nelmab nelmba neblam neblma nebalm nebaml
nebmal nebmla neablm neabml nealbm nealmb neamlb neambl nembal nembla nemabl
nemalb nemlab nemlba nmlbea nmlbae nmleba nmleab nmlaeb nmlabe nmblea nmblae
nmbela nmbeal nmbael nmbale nmebla nmebal nmelba nmelab nmealb nmeabl nmabel
nmable nmaebl nmaelb nmaleb nmalbe

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History of cryptography
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