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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: terium
cipher variations:
ufsjvn vgtkwo whulxp xivmyq yjwnzr
zkxoas alypbt bmzqcu cnardv dobsew
epctfx fqdugy grevhz hsfwia itgxjb
juhykc kvizld lwjame mxkbnf nylcog
ozmdph paneqi qbofrj rcpgsk sdqhtl

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: terium
Cipher: gvirfn

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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: terium

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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: terium
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: terium
Cipher: grevhz

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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: terium
Cipher: 445124425423

Extended Methods:
Method #1

Plaintext: terium
method variations:

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

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Method #3

Plaintext: terium
method variations:
yftwis ftwisy twisyf
wisyft isyftw syftwi

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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: terium

all 720 cipher variations:
terium terimu teruim terumi termui termiu teirum teirmu teiurm teiumr teimur
teimru teuirm teuimr teurim teurmi teumri teumir temiur temiru temuir temuri
temrui temriu treium treimu treuim treumi tremui tremiu trieum triemu triuem
triume trimue trimeu truiem truime trueim truemi trumei trumie trmiue trmieu
trmuie trmuei trmeui trmeiu tireum tiremu tiruem tirume tirmue tirmeu tierum
tiermu tieurm tieumr tiemur tiemru tiuerm tiuemr tiurem tiurme tiumre tiumer
timeur timeru timuer timure timrue timreu turiem turime tureim turemi turmei
turmie tuirem tuirme tuierm tuiemr tuimer tuimre tueirm tueimr tuerim tuermi
tuemri tuemir tumier tumire tumeir tumeri tumrei tumrie tmriue tmrieu tmruie
tmruei tmreui tmreiu tmirue tmireu tmiure tmiuer tmieur tmieru tmuire tmuier
tmurie tmurei tmueri tmueir tmeiur tmeiru tmeuir tmeuri tmerui tmeriu etrium
etrimu etruim etrumi etrmui etrmiu etirum etirmu etiurm etiumr etimur etimru
etuirm etuimr eturim eturmi etumri etumir etmiur etmiru etmuir etmuri etmrui
etmriu ertium ertimu ertuim ertumi ertmui ertmiu eritum eritmu eriutm eriumt
erimut erimtu eruitm eruimt erutim erutmi erumti erumit ermiut ermitu ermuit
ermuti ermtui ermtiu eirtum eirtmu eirutm eirumt eirmut eirmtu eitrum eitrmu
eiturm eitumr eitmur eitmru eiutrm eiutmr eiurtm eiurmt eiumrt eiumtr eimtur
eimtru eimutr eimurt eimrut eimrtu euritm eurimt eurtim eurtmi eurmti eurmit
euirtm euirmt euitrm euitmr euimtr euimrt eutirm eutimr eutrim eutrmi eutmri
eutmir eumitr eumirt eumtir eumtri eumrti eumrit emriut emritu emruit emruti
emrtui emrtiu emirut emirtu emiurt emiutr emitur emitru emuirt emuitr emurit
emurti emutri emutir emtiur emtiru emtuir emturi emtrui emtriu retium retimu
retuim retumi retmui retmiu reitum reitmu reiutm reiumt reimut reimtu reuitm
reuimt reutim reutmi reumti reumit remiut remitu remuit remuti remtui remtiu
rteium rteimu rteuim rteumi rtemui rtemiu rtieum rtiemu rtiuem rtiume rtimue
rtimeu rtuiem rtuime rtueim rtuemi rtumei rtumie rtmiue rtmieu rtmuie rtmuei
rtmeui rtmeiu riteum ritemu rituem ritume ritmue ritmeu rietum rietmu rieutm
rieumt riemut riemtu riuetm riuemt riutem riutme riumte riumet rimeut rimetu
rimuet rimute rimtue rimteu rutiem rutime ruteim rutemi rutmei rutmie ruitem
ruitme ruietm ruiemt ruimet ruimte rueitm rueimt ruetim ruetmi ruemti ruemit
rumiet rumite rumeit rumeti rumtei rumtie rmtiue rmtieu rmtuie rmtuei rmteui
rmteiu rmitue rmiteu rmiute rmiuet rmieut rmietu rmuite rmuiet rmutie rmutei
rmueti rmueit rmeiut rmeitu rmeuit rmeuti rmetui rmetiu iertum iertmu ierutm
ierumt iermut iermtu ietrum ietrmu ieturm ietumr ietmur ietmru ieutrm ieutmr
ieurtm ieurmt ieumrt ieumtr iemtur iemtru iemutr iemurt iemrut iemrtu iretum
iretmu ireutm ireumt iremut iremtu irteum irtemu irtuem irtume irtmue irtmeu
irutem irutme iruetm iruemt irumet irumte irmtue irmteu irmute irmuet irmeut
irmetu itreum itremu itruem itrume itrmue itrmeu iterum itermu iteurm iteumr
itemur itemru ituerm ituemr iturem iturme itumre itumer itmeur itmeru itmuer
itmure itmrue itmreu iurtem iurtme iuretm iuremt iurmet iurmte iutrem iutrme
iuterm iutemr iutmer iutmre iuetrm iuetmr iuertm iuermt iuemrt iuemtr iumter
iumtre iumetr iumert iumret iumrte imrtue imrteu imrute imruet imreut imretu
imtrue imtreu imture imtuer imteur imteru imutre imuter imurte imuret imuert
imuetr imetur imetru imeutr imeurt imerut imertu ueritm uerimt uertim uertmi
uermti uermit ueirtm ueirmt ueitrm ueitmr ueimtr ueimrt uetirm uetimr uetrim
uetrmi uetmri uetmir uemitr uemirt uemtir uemtri uemrti uemrit ureitm ureimt
uretim uretmi uremti uremit urietm uriemt uritem uritme urimte urimet urtiem
urtime urteim urtemi urtmei urtmie urmite urmiet urmtie urmtei urmeti urmeit
uiretm uiremt uirtem uirtme uirmte uirmet uiertm uiermt uietrm uietmr uiemtr
uiemrt uiterm uitemr uitrem uitrme uitmre uitmer uimetr uimert uimter uimtre
uimrte uimret utriem utrime utreim utremi utrmei utrmie utirem utirme utierm
utiemr utimer utimre uteirm uteimr uterim utermi utemri utemir utmier utmire
utmeir utmeri utmrei utmrie umrite umriet umrtie umrtei umreti umreit umirte
umiret umitre umiter umietr umiert umtire umtier umtrie umtrei umteri umteir
umeitr umeirt umetir umetri umerti umerit meriut meritu meruit meruti mertui
mertiu meirut meirtu meiurt meiutr meitur meitru meuirt meuitr meurit meurti
meutri meutir metiur metiru metuir meturi metrui metriu mreiut mreitu mreuit
mreuti mretui mretiu mrieut mrietu mriuet mriute mritue mriteu mruiet mruite
mrueit mrueti mrutei mrutie mrtiue mrtieu mrtuie mrtuei mrteui mrteiu mireut
miretu miruet mirute mirtue mirteu mierut miertu mieurt mieutr mietur mietru
miuert miuetr miuret miurte miutre miuter miteur miteru mituer miture mitrue
mitreu muriet murite mureit mureti murtei murtie muiret muirte muiert muietr
muiter muitre mueirt mueitr muerit muerti muetri muetir mutier mutire muteir
muteri mutrei mutrie mtriue mtrieu mtruie mtruei mtreui mtreiu mtirue mtireu
mtiure mtiuer mtieur mtieru mtuire mtuier mturie mturei mtueri mtueir mteiur
mteiru mteuir mteuri mterui mteriu

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History of cryptography
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