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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: gielow
cipher variations:
hjfmpx ikgnqy jlhorz kmipsa lnjqtb
mokruc nplsvd oqmtwe prnuxf qsovyg
rtpwzh suqxai tvrybj uwszck vxtadl
wyubem xzvcfn yawdgo zbxehp acyfiq
bdzgjr ceahks dfbilt egcjmu fhdknv

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: gielow
Cipher: trvold

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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: gielow

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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: gielow
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: gielow
Cipher: tvrybj

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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: gielow
Cipher: 224251134325

Extended Methods:
Method #1

Plaintext: gielow
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
g i e l o w 
2 4 5 1 4 2 
2 2 1 3 3 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: gielow
Cipher: reiglx

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Method #3

Plaintext: gielow
method variations:
rwashk washkr ashkrw
shkrwa hkrwas krwash

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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: gielow

all 720 cipher variations:
gielow gielwo gieolw gieowl giewol giewlo gileow gilewo giloew gilowe gilwoe
gilweo giolew giolwe gioelw gioewl giowel giowle giwloe giwleo giwole giwoel
giweol giwelo geilow geilwo geiolw geiowl geiwol geiwlo geliow geliwo geloiw
gelowi gelwoi gelwio geoliw geolwi geoilw geoiwl geowil geowli gewloi gewlio
gewoli gewoil gewiol gewilo gleiow gleiwo gleoiw gleowi glewoi glewio glieow
gliewo glioew gliowe gliwoe gliweo gloiew gloiwe gloeiw gloewi glowei glowie
glwioe glwieo glwoie glwoei glweoi glweio goeliw goelwi goeilw goeiwl goewil
goewli goleiw golewi goliew goliwe golwie golwei goilew goilwe goielw goiewl
goiwel goiwle gowlie gowlei gowile gowiel goweil goweli gweloi gwelio gweoli
gweoil gweiol gweilo gwleoi gwleio gwloei gwloie gwlioe gwlieo gwolei gwolie
gwoeli gwoeil gwoiel gwoile gwiloe gwileo gwiole gwioel gwieol gwielo igelow
igelwo igeolw igeowl igewol igewlo igleow iglewo igloew iglowe iglwoe iglweo
igolew igolwe igoelw igoewl igowel igowle igwloe igwleo igwole igwoel igweol
igwelo ieglow ieglwo iegolw iegowl iegwol iegwlo ielgow ielgwo ielogw ielowg
ielwog ielwgo ieolgw ieolwg ieoglw ieogwl ieowgl ieowlg iewlog iewlgo iewolg
iewogl iewgol iewglo ilegow ilegwo ileogw ileowg ilewog ilewgo ilgeow ilgewo
ilgoew ilgowe ilgwoe ilgweo ilogew ilogwe iloegw iloewg iloweg ilowge ilwgoe
ilwgeo ilwoge ilwoeg ilweog ilwego ioelgw ioelwg ioeglw ioegwl ioewgl ioewlg
iolegw iolewg iolgew iolgwe iolwge iolweg ioglew ioglwe iogelw iogewl iogwel
iogwle iowlge iowleg iowgle iowgel iowegl iowelg iwelog iwelgo iweolg iweogl
iwegol iweglo iwleog iwlego iwloeg iwloge iwlgoe iwlgeo iwoleg iwolge iwoelg
iwoegl iwogel iwogle iwgloe iwgleo iwgole iwgoel iwgeol iwgelo eiglow eiglwo
eigolw eigowl eigwol eigwlo eilgow eilgwo eilogw eilowg eilwog eilwgo eiolgw
eiolwg eioglw eiogwl eiowgl eiowlg eiwlog eiwlgo eiwolg eiwogl eiwgol eiwglo
egilow egilwo egiolw egiowl egiwol egiwlo egliow egliwo egloiw eglowi eglwoi
eglwio egoliw egolwi egoilw egoiwl egowil egowli egwloi egwlio egwoli egwoil
egwiol egwilo elgiow elgiwo elgoiw elgowi elgwoi elgwio eligow eligwo eliogw
eliowg eliwog eliwgo eloigw eloiwg elogiw elogwi elowgi elowig elwiog elwigo
elwoig elwogi elwgoi elwgio eogliw eoglwi eogilw eogiwl eogwil eogwli eolgiw
eolgwi eoligw eoliwg eolwig eolwgi eoilgw eoilwg eoiglw eoigwl eoiwgl eoiwlg
eowlig eowlgi eowilg eowigl eowgil eowgli ewgloi ewglio ewgoli ewgoil ewgiol
ewgilo ewlgoi ewlgio ewlogi ewloig ewliog ewligo ewolgi ewolig ewogli ewogil
ewoigl ewoilg ewilog ewilgo ewiolg ewiogl ewigol ewiglo liegow liegwo lieogw
lieowg liewog liewgo ligeow ligewo ligoew ligowe ligwoe ligweo liogew liogwe
lioegw lioewg lioweg liowge liwgoe liwgeo liwoge liwoeg liweog liwego leigow
leigwo leiogw leiowg leiwog leiwgo legiow legiwo legoiw legowi legwoi legwio
leogiw leogwi leoigw leoiwg leowig leowgi lewgoi lewgio lewogi lewoig lewiog
lewigo lgeiow lgeiwo lgeoiw lgeowi lgewoi lgewio lgieow lgiewo lgioew lgiowe
lgiwoe lgiweo lgoiew lgoiwe lgoeiw lgoewi lgowei lgowie lgwioe lgwieo lgwoie
lgwoei lgweoi lgweio loegiw loegwi loeigw loeiwg loewig loewgi logeiw logewi
logiew logiwe logwie logwei loigew loigwe loiegw loiewg loiweg loiwge lowgie
lowgei lowige lowieg loweig lowegi lwegoi lwegio lweogi lweoig lweiog lweigo
lwgeoi lwgeio lwgoei lwgoie lwgioe lwgieo lwogei lwogie lwoegi lwoeig lwoieg
lwoige lwigoe lwigeo lwioge lwioeg lwieog lwiego oielgw oielwg oieglw oiegwl
oiewgl oiewlg oilegw oilewg oilgew oilgwe oilwge oilweg oiglew oiglwe oigelw
oigewl oigwel oigwle oiwlge oiwleg oiwgle oiwgel oiwegl oiwelg oeilgw oeilwg
oeiglw oeigwl oeiwgl oeiwlg oeligw oeliwg oelgiw oelgwi oelwgi oelwig oegliw
oeglwi oegilw oegiwl oegwil oegwli oewlgi oewlig oewgli oewgil oewigl oewilg
oleigw oleiwg olegiw olegwi olewgi olewig oliegw oliewg oligew oligwe oliwge
oliweg olgiew olgiwe olgeiw olgewi olgwei olgwie olwige olwieg olwgie olwgei
olwegi olweig ogeliw ogelwi ogeilw ogeiwl ogewil ogewli ogleiw oglewi ogliew
ogliwe oglwie oglwei ogilew ogilwe ogielw ogiewl ogiwel ogiwle ogwlie ogwlei
ogwile ogwiel ogweil ogweli owelgi owelig owegli owegil oweigl oweilg owlegi
owleig owlgei owlgie owlige owlieg owglei owglie owgeli owgeil owgiel owgile
owilge owileg owigle owigel owiegl owielg wielog wielgo wieolg wieogl wiegol
wieglo wileog wilego wiloeg wiloge wilgoe wilgeo wioleg wiolge wioelg wioegl
wiogel wiogle wigloe wigleo wigole wigoel wigeol wigelo weilog weilgo weiolg
weiogl weigol weiglo weliog weligo weloig welogi welgoi welgio weolig weolgi
weoilg weoigl weogil weogli wegloi weglio wegoli wegoil wegiol wegilo wleiog
wleigo wleoig wleogi wlegoi wlegio wlieog wliego wlioeg wlioge wligoe wligeo
wloieg wloige wloeig wloegi wlogei wlogie wlgioe wlgieo wlgoie wlgoei wlgeoi
wlgeio woelig woelgi woeilg woeigl woegil woegli woleig wolegi wolieg wolige
wolgie wolgei woileg woilge woielg woiegl woigel woigle woglie woglei wogile
wogiel wogeil wogeli wgeloi wgelio wgeoli wgeoil wgeiol wgeilo wgleoi wgleio
wgloei wgloie wglioe wglieo wgolei wgolie wgoeli wgoeil wgoiel wgoile wgiloe
wgileo wgiole wgioel wgieol wgielo

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History of cryptography
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