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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: brunty
cipher variations:
csvouz dtwpva euxqwb fvyrxc gwzsyd
hxatze iybuaf jzcvbg kadwch lbexdi
mcfyej ndgzfk oehagl pfibhm qgjcin
rhkdjo silekp tjmflq ukngmr vlohns
wmpiot xnqjpu yorkqv zpslrw aqtmsx

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: brunty
Cipher: yifmgb

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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: brunty

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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: brunty
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: brunty
Cipher: oehagl

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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: brunty
Cipher: 212454334445

Extended Methods:
Method #1

Plaintext: brunty
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
b r u n t y 
2 2 5 3 4 4 
1 4 4 3 4 5 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: brunty
Cipher: gptqoy

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Method #3

Plaintext: brunty
method variations:
fyostk yostkf ostkfy
stkfyo tkfyos kfyost

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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: brunty

all 720 cipher variations:
brunty brunyt brutny brutyn bruytn bruynt brnuty brnuyt brntuy brntyu brnytu
brnyut brtnuy brtnyu brtuny brtuyn brtyun brtynu bryntu brynut brytnu brytun
bryutn bryunt burnty burnyt burtny burtyn burytn burynt bunrty bunryt buntry
buntyr bunytr bunyrt butnry butnyr butrny butryn butyrn butynr buyntr buynrt
buytnr buytrn buyrtn buyrnt bnurty bnuryt bnutry bnutyr bnuytr bnuyrt bnruty
bnruyt bnrtuy bnrtyu bnrytu bnryut bntruy bntryu bntury bntuyr bntyur bntyru
bnyrtu bnyrut bnytru bnytur bnyutr bnyurt btunry btunyr bturny bturyn btuyrn
btuynr btnury btnuyr btnruy btnryu btnyru btnyur btrnuy btrnyu btruny btruyn
btryun btrynu btynru btynur btyrnu btyrun btyurn btyunr byuntr byunrt byutnr
byutrn byurtn byurnt bynutr bynurt byntur byntru bynrtu bynrut bytnur bytnru
bytunr byturn bytrun bytrnu byrntu byrnut byrtnu byrtun byrutn byrunt rbunty
rbunyt rbutny rbutyn rbuytn rbuynt rbnuty rbnuyt rbntuy rbntyu rbnytu rbnyut
rbtnuy rbtnyu rbtuny rbtuyn rbtyun rbtynu rbyntu rbynut rbytnu rbytun rbyutn
rbyunt rubnty rubnyt rubtny rubtyn rubytn rubynt runbty runbyt runtby runtyb
runytb runybt rutnby rutnyb rutbny rutbyn rutybn rutynb ruyntb ruynbt ruytnb
ruytbn ruybtn ruybnt rnubty rnubyt rnutby rnutyb rnuytb rnuybt rnbuty rnbuyt
rnbtuy rnbtyu rnbytu rnbyut rntbuy rntbyu rntuby rntuyb rntyub rntybu rnybtu
rnybut rnytbu rnytub rnyutb rnyubt rtunby rtunyb rtubny rtubyn rtuybn rtuynb
rtnuby rtnuyb rtnbuy rtnbyu rtnybu rtnyub rtbnuy rtbnyu rtbuny rtbuyn rtbyun
rtbynu rtynbu rtynub rtybnu rtybun rtyubn rtyunb ryuntb ryunbt ryutnb ryutbn
ryubtn ryubnt rynutb rynubt ryntub ryntbu rynbtu rynbut rytnub rytnbu rytunb
rytubn rytbun rytbnu rybntu rybnut rybtnu rybtun rybutn rybunt urbnty urbnyt
urbtny urbtyn urbytn urbynt urnbty urnbyt urntby urntyb urnytb urnybt urtnby
urtnyb urtbny urtbyn urtybn urtynb uryntb urynbt urytnb urytbn urybtn urybnt
ubrnty ubrnyt ubrtny ubrtyn ubrytn ubrynt ubnrty ubnryt ubntry ubntyr ubnytr
ubnyrt ubtnry ubtnyr ubtrny ubtryn ubtyrn ubtynr ubyntr ubynrt ubytnr ubytrn
ubyrtn ubyrnt unbrty unbryt unbtry unbtyr unbytr unbyrt unrbty unrbyt unrtby
unrtyb unrytb unrybt untrby untryb untbry untbyr untybr untyrb unyrtb unyrbt
unytrb unytbr unybtr unybrt utbnry utbnyr utbrny utbryn utbyrn utbynr utnbry
utnbyr utnrby utnryb utnyrb utnybr utrnby utrnyb utrbny utrbyn utrybn utrynb
utynrb utynbr utyrnb utyrbn utybrn utybnr uybntr uybnrt uybtnr uybtrn uybrtn
uybrnt uynbtr uynbrt uyntbr uyntrb uynrtb uynrbt uytnbr uytnrb uytbnr uytbrn
uytrbn uytrnb uyrntb uyrnbt uyrtnb uyrtbn uyrbtn uyrbnt nrubty nrubyt nrutby
nrutyb nruytb nruybt nrbuty nrbuyt nrbtuy nrbtyu nrbytu nrbyut nrtbuy nrtbyu
nrtuby nrtuyb nrtyub nrtybu nrybtu nrybut nrytbu nrytub nryutb nryubt nurbty
nurbyt nurtby nurtyb nurytb nurybt nubrty nubryt nubtry nubtyr nubytr nubyrt
nutbry nutbyr nutrby nutryb nutyrb nutybr nuybtr nuybrt nuytbr nuytrb nuyrtb
nuyrbt nburty nburyt nbutry nbutyr nbuytr nbuyrt nbruty nbruyt nbrtuy nbrtyu
nbrytu nbryut nbtruy nbtryu nbtury nbtuyr nbtyur nbtyru nbyrtu nbyrut nbytru
nbytur nbyutr nbyurt ntubry ntubyr nturby nturyb ntuyrb ntuybr ntbury ntbuyr
ntbruy ntbryu ntbyru ntbyur ntrbuy ntrbyu ntruby ntruyb ntryub ntrybu ntybru
ntybur ntyrbu ntyrub ntyurb ntyubr nyubtr nyubrt nyutbr nyutrb nyurtb nyurbt
nybutr nyburt nybtur nybtru nybrtu nybrut nytbur nytbru nytubr nyturb nytrub
nytrbu nyrbtu nyrbut nyrtbu nyrtub nyrutb nyrubt trunby trunyb trubny trubyn
truybn truynb trnuby trnuyb trnbuy trnbyu trnybu trnyub trbnuy trbnyu trbuny
trbuyn trbyun trbynu trynbu trynub trybnu trybun tryubn tryunb turnby turnyb
turbny turbyn turybn turynb tunrby tunryb tunbry tunbyr tunybr tunyrb tubnry
tubnyr tubrny tubryn tubyrn tubynr tuynbr tuynrb tuybnr tuybrn tuyrbn tuyrnb
tnurby tnuryb tnubry tnubyr tnuybr tnuyrb tnruby tnruyb tnrbuy tnrbyu tnrybu
tnryub tnbruy tnbryu tnbury tnbuyr tnbyur tnbyru tnyrbu tnyrub tnybru tnybur
tnyubr tnyurb tbunry tbunyr tburny tburyn tbuyrn tbuynr tbnury tbnuyr tbnruy
tbnryu tbnyru tbnyur tbrnuy tbrnyu tbruny tbruyn tbryun tbrynu tbynru tbynur
tbyrnu tbyrun tbyurn tbyunr tyunbr tyunrb tyubnr tyubrn tyurbn tyurnb tynubr
tynurb tynbur tynbru tynrbu tynrub tybnur tybnru tybunr tyburn tybrun tybrnu
tyrnbu tyrnub tyrbnu tyrbun tyrubn tyrunb yruntb yrunbt yrutnb yrutbn yrubtn
yrubnt yrnutb yrnubt yrntub yrntbu yrnbtu yrnbut yrtnub yrtnbu yrtunb yrtubn
yrtbun yrtbnu yrbntu yrbnut yrbtnu yrbtun yrbutn yrbunt yurntb yurnbt yurtnb
yurtbn yurbtn yurbnt yunrtb yunrbt yuntrb yuntbr yunbtr yunbrt yutnrb yutnbr
yutrnb yutrbn yutbrn yutbnr yubntr yubnrt yubtnr yubtrn yubrtn yubrnt ynurtb
ynurbt ynutrb ynutbr ynubtr ynubrt ynrutb ynrubt ynrtub ynrtbu ynrbtu ynrbut
yntrub yntrbu ynturb yntubr yntbur yntbru ynbrtu ynbrut ynbtru ynbtur ynbutr
ynburt ytunrb ytunbr yturnb yturbn ytubrn ytubnr ytnurb ytnubr ytnrub ytnrbu
ytnbru ytnbur ytrnub ytrnbu ytrunb ytrubn ytrbun ytrbnu ytbnru ytbnur ytbrnu
ytbrun ytburn ytbunr ybuntr ybunrt ybutnr ybutrn yburtn yburnt ybnutr ybnurt
ybntur ybntru ybnrtu ybnrut ybtnur ybtnru ybtunr ybturn ybtrun ybtrnu ybrntu
ybrnut ybrtnu ybrtun ybrutn ybrunt

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History of cryptography
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