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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: famble
cipher variations:
gbncmf hcodng idpeoh jeqfpi kfrgqj
lgshrk mhtisl niujtm ojvkun pkwlvo
qlxmwp rmynxq snzoyr toapzs upbqat
vqcrbu wrdscv xsetdw ytfuex zugvfy
avhwgz bwixha cxjyib dykzjc ezlakd

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: famble
Cipher: uznyov

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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: famble

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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: famble
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: famble
Cipher: snzoyr

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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: famble
Cipher: 121123211351

Extended Methods:
Method #1

Plaintext: famble
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
f a m b l e 
1 1 2 2 1 5 
2 1 3 1 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: famble
Cipher: agvbcc

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Method #3

Plaintext: famble
method variations:
bfhaxa fhaxab haxabf
axabfh xabfha abfhax

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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: famble

all 720 cipher variations:
famble fambel famlbe famleb famelb famebl fabmle fabmel fablme fablem fabelm
fabeml falbme falbem falmbe falmeb falemb falebm faeblm faebml faelbm faelmb
faemlb faembl fmable fmabel fmalbe fmaleb fmaelb fmaebl fmbale fmbael fmblae
fmblea fmbela fmbeal fmlbae fmlbea fmlabe fmlaeb fmleab fmleba fmebla fmebal
fmelba fmelab fmealb fmeabl fbmale fbmael fbmlae fbmlea fbmela fbmeal fbamle
fbamel fbalme fbalem fbaelm fbaeml fblame fblaem fblmae fblmea fblema fbleam
fbealm fbeaml fbelam fbelma fbemla fbemal flmbae flmbea flmabe flmaeb flmeab
flmeba flbmae flbmea flbame flbaem flbeam flbema flabme flabem flambe flameb
flaemb flaebm flebam flebma fleabm fleamb flemab flemba fembla fembal femlba
femlab femalb femabl febmla febmal feblma feblam febalm febaml felbma felbam
felmba felmab felamb felabm feablm feabml fealbm fealmb feamlb feambl afmble
afmbel afmlbe afmleb afmelb afmebl afbmle afbmel afblme afblem afbelm afbeml
aflbme aflbem aflmbe aflmeb aflemb aflebm afeblm afebml afelbm afelmb afemlb
afembl amfble amfbel amflbe amfleb amfelb amfebl ambfle ambfel amblfe amblef
ambelf ambefl amlbfe amlbef amlfbe amlfeb amlefb amlebf ameblf amebfl amelbf
amelfb ameflb amefbl abmfle abmfel abmlfe abmlef abmelf abmefl abfmle abfmel
abflme abflem abfelm abfeml ablfme ablfem ablmfe ablmef ablemf ablefm abeflm
abefml abelfm abelmf abemlf abemfl almbfe almbef almfbe almfeb almefb almebf
albmfe albmef albfme albfem albefm albemf alfbme alfbem alfmbe alfmeb alfemb
alfebm alebfm alebmf alefbm alefmb alemfb alembf aemblf aembfl aemlbf aemlfb
aemflb aemfbl aebmlf aebmfl aeblmf aeblfm aebflm aebfml aelbmf aelbfm aelmbf
aelmfb aelfmb aelfbm aefblm aefbml aeflbm aeflmb aefmlb aefmbl mafble mafbel
maflbe mafleb mafelb mafebl mabfle mabfel mablfe mablef mabelf mabefl malbfe
malbef malfbe malfeb malefb malebf maeblf maebfl maelbf maelfb maeflb maefbl
mfable mfabel mfalbe mfaleb mfaelb mfaebl mfbale mfbael mfblae mfblea mfbela
mfbeal mflbae mflbea mflabe mflaeb mfleab mfleba mfebla mfebal mfelba mfelab
mfealb mfeabl mbfale mbfael mbflae mbflea mbfela mbfeal mbafle mbafel mbalfe
mbalef mbaelf mbaefl mblafe mblaef mblfae mblfea mblefa mbleaf mbealf mbeafl
mbelaf mbelfa mbefla mbefal mlfbae mlfbea mlfabe mlfaeb mlfeab mlfeba mlbfae
mlbfea mlbafe mlbaef mlbeaf mlbefa mlabfe mlabef mlafbe mlafeb mlaefb mlaebf
mlebaf mlebfa mleabf mleafb mlefab mlefba mefbla mefbal meflba meflab mefalb
mefabl mebfla mebfal meblfa meblaf mebalf mebafl melbfa melbaf melfba melfab
melafb melabf meablf meabfl mealbf mealfb meaflb meafbl bamfle bamfel bamlfe
bamlef bamelf bamefl bafmle bafmel baflme baflem bafelm bafeml balfme balfem
balmfe balmef balemf balefm baeflm baefml baelfm baelmf baemlf baemfl bmafle
bmafel bmalfe bmalef bmaelf bmaefl bmfale bmfael bmflae bmflea bmfela bmfeal
bmlfae bmlfea bmlafe bmlaef bmleaf bmlefa bmefla bmefal bmelfa bmelaf bmealf
bmeafl bfmale bfmael bfmlae bfmlea bfmela bfmeal bfamle bfamel bfalme bfalem
bfaelm bfaeml bflame bflaem bflmae bflmea bflema bfleam bfealm bfeaml bfelam
bfelma bfemla bfemal blmfae blmfea blmafe blmaef blmeaf blmefa blfmae blfmea
blfame blfaem blfeam blfema blafme blafem blamfe blamef blaemf blaefm blefam
blefma bleafm bleamf blemaf blemfa bemfla bemfal bemlfa bemlaf bemalf bemafl
befmla befmal beflma beflam befalm befaml belfma belfam belmfa belmaf belamf
belafm beaflm beafml bealfm bealmf beamlf beamfl lambfe lambef lamfbe lamfeb
lamefb lamebf labmfe labmef labfme labfem labefm labemf lafbme lafbem lafmbe
lafmeb lafemb lafebm laebfm laebmf laefbm laefmb laemfb laembf lmabfe lmabef
lmafbe lmafeb lmaefb lmaebf lmbafe lmbaef lmbfae lmbfea lmbefa lmbeaf lmfbae
lmfbea lmfabe lmfaeb lmfeab lmfeba lmebfa lmebaf lmefba lmefab lmeafb lmeabf
lbmafe lbmaef lbmfae lbmfea lbmefa lbmeaf lbamfe lbamef lbafme lbafem lbaefm
lbaemf lbfame lbfaem lbfmae lbfmea lbfema lbfeam lbeafm lbeamf lbefam lbefma
lbemfa lbemaf lfmbae lfmbea lfmabe lfmaeb lfmeab lfmeba lfbmae lfbmea lfbame
lfbaem lfbeam lfbema lfabme lfabem lfambe lfameb lfaemb lfaebm lfebam lfebma
lfeabm lfeamb lfemab lfemba lembfa lembaf lemfba lemfab lemafb lemabf lebmfa
lebmaf lebfma lebfam lebafm lebamf lefbma lefbam lefmba lefmab lefamb lefabm
leabfm leabmf leafbm leafmb leamfb leambf eamblf eambfl eamlbf eamlfb eamflb
eamfbl eabmlf eabmfl eablmf eablfm eabflm eabfml ealbmf ealbfm ealmbf ealmfb
ealfmb ealfbm eafblm eafbml eaflbm eaflmb eafmlb eafmbl emablf emabfl emalbf
emalfb emaflb emafbl embalf embafl emblaf emblfa embfla embfal emlbaf emlbfa
emlabf emlafb emlfab emlfba emfbla emfbal emflba emflab emfalb emfabl ebmalf
ebmafl ebmlaf ebmlfa ebmfla ebmfal ebamlf ebamfl ebalmf ebalfm ebaflm ebafml
eblamf eblafm eblmaf eblmfa eblfma eblfam ebfalm ebfaml ebflam ebflma ebfmla
ebfmal elmbaf elmbfa elmabf elmafb elmfab elmfba elbmaf elbmfa elbamf elbafm
elbfam elbfma elabmf elabfm elambf elamfb elafmb elafbm elfbam elfbma elfabm
elfamb elfmab elfmba efmbla efmbal efmlba efmlab efmalb efmabl efbmla efbmal
efblma efblam efbalm efbaml eflbma eflbam eflmba eflmab eflamb eflabm efablm
efabml efalbm efalmb efamlb efambl

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History of cryptography
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