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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: rohuna
cipher variations:
spivob tqjwpc urkxqd vslyre wtmzsf
xunatg yvobuh zwpcvi axqdwj byrexk
czsfyl datgzm ebuhan fcvibo gdwjcp
hexkdq ifyler jgzmfs khangt libohu
mjcpiv nkdqjw olerkx pmfsly qngtmz

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: rohuna
Cipher: ilsfmz

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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: rohuna

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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: rohuna
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: rohuna
Cipher: ebuhan

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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: rohuna
Cipher: 244332543311

Extended Methods:
Method #1

Plaintext: rohuna
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
r o h u n a 
2 4 3 5 3 1 
4 3 2 4 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: rohuna
Cipher: rxcorc

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Method #3

Plaintext: rohuna
method variations:
tnwocf nwocft wocftn
ocftnw cftnwo ftnwoc

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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: rohuna

all 720 cipher variations:
rohuna rohuan rohnua rohnau rohanu rohaun rouhna rouhan rounha rounah rouanh
rouahn ronuha ronuah ronhua ronhau ronahu ronauh roaunh roauhn roanuh roanhu
roahnu roahun rhouna rhouan rhonua rhonau rhoanu rhoaun rhuona rhuoan rhunoa
rhunao rhuano rhuaon rhnuoa rhnuao rhnoua rhnoau rhnaou rhnauo rhauno rhauon
rhanuo rhanou rhaonu rhaoun ruhona ruhoan ruhnoa ruhnao ruhano ruhaon ruohna
ruohan ruonha ruonah ruoanh ruoahn runoha runoah runhoa runhao runaho runaoh
ruaonh ruaohn ruanoh ruanho ruahno ruahon rnhuoa rnhuao rnhoua rnhoau rnhaou
rnhauo rnuhoa rnuhao rnuoha rnuoah rnuaoh rnuaho rnouha rnouah rnohua rnohau
rnoahu rnoauh rnauoh rnauho rnaouh rnaohu rnahou rnahuo rahuno rahuon rahnuo
rahnou rahonu rahoun rauhno rauhon raunho raunoh rauonh rauohn ranuho ranuoh
ranhuo ranhou ranohu ranouh raounh raouhn raonuh raonhu raohnu raohun orhuna
orhuan orhnua orhnau orhanu orhaun oruhna oruhan orunha orunah oruanh oruahn
ornuha ornuah ornhua ornhau ornahu ornauh oraunh orauhn oranuh oranhu orahnu
orahun ohruna ohruan ohrnua ohrnau ohranu ohraun ohurna ohuran ohunra ohunar
ohuanr ohuarn ohnura ohnuar ohnrua ohnrau ohnaru ohnaur ohaunr ohaurn ohanur
ohanru oharnu oharun ouhrna ouhran ouhnra ouhnar ouhanr ouharn ourhna ourhan
ournha ournah ouranh ourahn ounrha ounrah ounhra ounhar ounahr ounarh ouarnh
ouarhn ouanrh ouanhr ouahnr ouahrn onhura onhuar onhrua onhrau onharu onhaur
onuhra onuhar onurha onurah onuarh onuahr onruha onruah onrhua onrhau onrahu
onrauh onaurh onauhr onaruh onarhu onahru onahur oahunr oahurn oahnur oahnru
oahrnu oahrun oauhnr oauhrn oaunhr oaunrh oaurnh oaurhn oanuhr oanurh oanhur
oanhru oanrhu oanruh oarunh oaruhn oarnuh oarnhu oarhnu oarhun horuna horuan
hornua hornau horanu horaun hourna houran hounra hounar houanr houarn honura
honuar honrua honrau honaru honaur hoaunr hoaurn hoanur hoanru hoarnu hoarun
hrouna hrouan hronua hronau hroanu hroaun hruona hruoan hrunoa hrunao hruano
hruaon hrnuoa hrnuao hrnoua hrnoau hrnaou hrnauo hrauno hrauon hranuo hranou
hraonu hraoun hurona huroan hurnoa hurnao hurano huraon huorna huoran huonra
huonar huoanr huoarn hunora hunoar hunroa hunrao hunaro hunaor huaonr huaorn
huanor huanro huarno huaron hnruoa hnruao hnroua hnroau hnraou hnrauo hnuroa
hnurao hnuora hnuoar hnuaor hnuaro hnoura hnouar hnorua hnorau hnoaru hnoaur
hnauor hnauro hnaour hnaoru hnarou hnaruo haruno haruon harnuo harnou haronu
haroun haurno hauron haunro haunor hauonr hauorn hanuro hanuor hanruo hanrou
hanoru hanour haounr haourn haonur haonru haornu haorun uohrna uohran uohnra
uohnar uohanr uoharn uorhna uorhan uornha uornah uoranh uorahn uonrha uonrah
uonhra uonhar uonahr uonarh uoarnh uoarhn uoanrh uoanhr uoahnr uoahrn uhorna
uhoran uhonra uhonar uhoanr uhoarn uhrona uhroan uhrnoa uhrnao uhrano uhraon
uhnroa uhnrao uhnora uhnoar uhnaor uhnaro uharno uharon uhanro uhanor uhaonr
uhaorn urhona urhoan urhnoa urhnao urhano urhaon urohna urohan uronha uronah
uroanh uroahn urnoha urnoah urnhoa urnhao urnaho urnaoh uraonh uraohn uranoh
uranho urahno urahon unhroa unhrao unhora unhoar unhaor unharo unrhoa unrhao
unroha unroah unraoh unraho unorha unorah unohra unohar unoahr unoarh unaroh
unarho unaorh unaohr unahor unahro uahrno uahron uahnro uahnor uahonr uahorn
uarhno uarhon uarnho uarnoh uaronh uarohn uanrho uanroh uanhro uanhor uanohr
uanorh uaornh uaorhn uaonrh uaonhr uaohnr uaohrn nohura nohuar nohrua nohrau
noharu nohaur nouhra nouhar nourha nourah nouarh nouahr noruha noruah norhua
norhau norahu norauh noaurh noauhr noaruh noarhu noahru noahur nhoura nhouar
nhorua nhorau nhoaru nhoaur nhuora nhuoar nhuroa nhurao nhuaro nhuaor nhruoa
nhruao nhroua nhroau nhraou nhrauo nhauro nhauor nharuo nharou nhaoru nhaour
nuhora nuhoar nuhroa nuhrao nuharo nuhaor nuohra nuohar nuorha nuorah nuoarh
nuoahr nuroha nuroah nurhoa nurhao nuraho nuraoh nuaorh nuaohr nuaroh nuarho
nuahro nuahor nrhuoa nrhuao nrhoua nrhoau nrhaou nrhauo nruhoa nruhao nruoha
nruoah nruaoh nruaho nrouha nrouah nrohua nrohau nroahu nroauh nrauoh nrauho
nraouh nraohu nrahou nrahuo nahuro nahuor nahruo nahrou nahoru nahour nauhro
nauhor naurho nauroh nauorh nauohr naruho naruoh narhuo narhou narohu narouh
naourh naouhr naoruh naorhu naohru naohur aohunr aohurn aohnur aohnru aohrnu
aohrun aouhnr aouhrn aounhr aounrh aournh aourhn aonuhr aonurh aonhur aonhru
aonrhu aonruh aorunh aoruhn aornuh aornhu aorhnu aorhun ahounr ahourn ahonur
ahonru ahornu ahorun ahuonr ahuorn ahunor ahunro ahurno ahuron ahnuor ahnuro
ahnour ahnoru ahnrou ahnruo ahruno ahruon ahrnuo ahrnou ahronu ahroun auhonr
auhorn auhnor auhnro auhrno auhron auohnr auohrn auonhr auonrh auornh auorhn
aunohr aunorh aunhor aunhro aunrho aunroh auronh aurohn aurnoh aurnho aurhno
aurhon anhuor anhuro anhour anhoru anhrou anhruo anuhor anuhro anuohr anuorh
anuroh anurho anouhr anourh anohur anohru anorhu anoruh anruoh anruho anrouh
anrohu anrhou anrhuo arhuno arhuon arhnuo arhnou arhonu arhoun aruhno aruhon
arunho arunoh aruonh aruohn arnuho arnuoh arnhuo arnhou arnohu arnouh arounh
arouhn aronuh aronhu arohnu arohun

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History of cryptography
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