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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: uberty
cipher variations:
vcfsuz wdgtva xehuwb yfivxc zgjwyd
ahkxze bilyaf cjmzbg dknach elobdi
fmpcej gnqdfk horegl ipsfhm jqtgin
kruhjo lsvikp mtwjlq nuxkmr ovylns
pwzmot qxanpu ryboqv szcprw tadqsx

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: uberty
Cipher: fyvigb

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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: uberty

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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: uberty
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: uberty
Cipher: horegl

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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: uberty
Cipher: 542151244445

Extended Methods:
Method #1

Plaintext: uberty
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
u b e r t y 
5 2 5 2 4 4 
4 1 1 4 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: uberty
Cipher: kktdqy

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Method #3

Plaintext: uberty
method variations:
ivfttz vfttzi fttziv
ttzivf tzivft zivftt

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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: uberty

all 720 cipher variations:
uberty uberyt ubetry ubetyr ubeytr ubeyrt ubrety ubreyt ubrtey ubrtye ubryte
ubryet ubtrey ubtrye ubtery ubteyr ubtyer ubtyre ubyrte ubyret ubytre ubyter
ubyetr ubyert uebrty uebryt uebtry uebtyr uebytr uebyrt uerbty uerbyt uertby
uertyb uerytb uerybt uetrby uetryb uetbry uetbyr uetybr uetyrb ueyrtb ueyrbt
ueytrb ueytbr ueybtr ueybrt urebty urebyt uretby uretyb ureytb ureybt urbety
urbeyt urbtey urbtye urbyte urbyet urtbey urtbye urteby urteyb urtyeb urtybe
urybte urybet urytbe uryteb uryetb uryebt uterby uteryb utebry utebyr uteybr
uteyrb utreby utreyb utrbey utrbye utrybe utryeb utbrey utbrye utbery utbeyr
utbyer utbyre utyrbe utyreb utybre utyber utyebr utyerb uyertb uyerbt uyetrb
uyetbr uyebtr uyebrt uyretb uyrebt uyrteb uyrtbe uyrbte uyrbet uytreb uytrbe
uyterb uytebr uytber uytbre uybrte uybret uybtre uybter uybetr uybert buerty
bueryt buetry buetyr bueytr bueyrt burety bureyt burtey burtye buryte buryet
butrey butrye butery buteyr butyer butyre buyrte buyret buytre buyter buyetr
buyert beurty beuryt beutry beutyr beuytr beuyrt beruty beruyt bertuy bertyu
berytu beryut betruy betryu betury betuyr betyur betyru beyrtu beyrut beytru
beytur beyutr beyurt breuty breuyt bretuy bretyu breytu breyut bruety brueyt
brutey brutye bruyte bruyet brtuey brtuye brteuy brteyu brtyeu brtyue bryute
bryuet brytue bryteu bryetu bryeut bteruy bteryu bteury bteuyr bteyur bteyru
btreuy btreyu btruey btruye btryue btryeu bturey bturye btuery btueyr btuyer
btuyre btyrue btyreu btyure btyuer btyeur btyeru byertu byerut byetru byetur
byeutr byeurt byretu byreut byrteu byrtue byrute byruet bytreu bytrue byteru
byteur bytuer byture byurte byuret byutre byuter byuetr byuert eburty eburyt
ebutry ebutyr ebuytr ebuyrt ebruty ebruyt ebrtuy ebrtyu ebrytu ebryut ebtruy
ebtryu ebtury ebtuyr ebtyur ebtyru ebyrtu ebyrut ebytru ebytur ebyutr ebyurt
eubrty eubryt eubtry eubtyr eubytr eubyrt eurbty eurbyt eurtby eurtyb eurytb
eurybt eutrby eutryb eutbry eutbyr eutybr eutyrb euyrtb euyrbt euytrb euytbr
euybtr euybrt erubty erubyt erutby erutyb eruytb eruybt erbuty erbuyt erbtuy
erbtyu erbytu erbyut ertbuy ertbyu ertuby ertuyb ertyub ertybu erybtu erybut
erytbu erytub eryutb eryubt eturby eturyb etubry etubyr etuybr etuyrb etruby
etruyb etrbuy etrbyu etrybu etryub etbruy etbryu etbury etbuyr etbyur etbyru
etyrbu etyrub etybru etybur etyubr etyurb eyurtb eyurbt eyutrb eyutbr eyubtr
eyubrt eyrutb eyrubt eyrtub eyrtbu eyrbtu eyrbut eytrub eytrbu eyturb eytubr
eytbur eytbru eybrtu eybrut eybtru eybtur eybutr eyburt rbeuty rbeuyt rbetuy
rbetyu rbeytu rbeyut rbuety rbueyt rbutey rbutye rbuyte rbuyet rbtuey rbtuye
rbteuy rbteyu rbtyeu rbtyue rbyute rbyuet rbytue rbyteu rbyetu rbyeut rebuty
rebuyt rebtuy rebtyu rebytu rebyut reubty reubyt reutby reutyb reuytb reuybt
retuby retuyb retbuy retbyu retybu retyub reyutb reyubt reytub reytbu reybtu
reybut ruebty ruebyt ruetby ruetyb rueytb rueybt rubety rubeyt rubtey rubtye
rubyte rubyet rutbey rutbye ruteby ruteyb rutyeb rutybe ruybte ruybet ruytbe
ruyteb ruyetb ruyebt rteuby rteuyb rtebuy rtebyu rteybu rteyub rtueby rtueyb
rtubey rtubye rtuybe rtuyeb rtbuey rtbuye rtbeuy rtbeyu rtbyeu rtbyue rtyube
rtyueb rtybue rtybeu rtyebu rtyeub ryeutb ryeubt ryetub ryetbu ryebtu ryebut
ryuetb ryuebt ryuteb ryutbe ryubte ryubet rytueb rytube ryteub rytebu rytbeu
rytbue rybute rybuet rybtue rybteu rybetu rybeut tberuy tberyu tbeury tbeuyr
tbeyur tbeyru tbreuy tbreyu tbruey tbruye tbryue tbryeu tburey tburye tbuery
tbueyr tbuyer tbuyre tbyrue tbyreu tbyure tbyuer tbyeur tbyeru tebruy tebryu
tebury tebuyr tebyur tebyru terbuy terbyu teruby teruyb teryub terybu teurby
teuryb teubry teubyr teuybr teuyrb teyrub teyrbu teyurb teyubr teybur teybru
trebuy trebyu treuby treuyb treyub treybu trbeuy trbeyu trbuey trbuye trbyue
trbyeu trubey trubye trueby trueyb truyeb truybe trybue trybeu tryube tryueb
tryeub tryebu tuerby tueryb tuebry tuebyr tueybr tueyrb tureby tureyb turbey
turbye turybe turyeb tubrey tubrye tubery tubeyr tubyer tubyre tuyrbe tuyreb
tuybre tuyber tuyebr tuyerb tyerub tyerbu tyeurb tyeubr tyebur tyebru tyreub
tyrebu tyrueb tyrube tyrbue tyrbeu tyureb tyurbe tyuerb tyuebr tyuber tyubre
tybrue tybreu tybure tybuer tybeur tyberu ybertu yberut ybetru ybetur ybeutr
ybeurt ybretu ybreut ybrteu ybrtue ybrute ybruet ybtreu ybtrue ybteru ybteur
ybtuer ybture yburte yburet ybutre ybuter ybuetr ybuert yebrtu yebrut yebtru
yebtur yebutr yeburt yerbtu yerbut yertbu yertub yerutb yerubt yetrbu yetrub
yetbru yetbur yetubr yeturb yeurtb yeurbt yeutrb yeutbr yeubtr yeubrt yrebtu
yrebut yretbu yretub yreutb yreubt yrbetu yrbeut yrbteu yrbtue yrbute yrbuet
yrtbeu yrtbue yrtebu yrteub yrtueb yrtube yrubte yrubet yrutbe yruteb yruetb
yruebt yterbu yterub ytebru ytebur yteubr yteurb ytrebu ytreub ytrbeu ytrbue
ytrube ytrueb ytbreu ytbrue ytberu ytbeur ytbuer ytbure yturbe ytureb ytubre
ytuber ytuebr ytuerb yuertb yuerbt yuetrb yuetbr yuebtr yuebrt yuretb yurebt
yurteb yurtbe yurbte yurbet yutreb yutrbe yuterb yutebr yutber yutbre yubrte
yubret yubtre yubter yubetr yubert

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History of cryptography
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