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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: bohman
cipher variations:
cpinbo dqjocp erkpdq fslqer gtmrfs
hunsgt ivothu jwpuiv kxqvjw lyrwkx
mzsxly natymz obuzna pcvaob qdwbpc
rexcqd sfydre tgzesf uhaftg vibguh
wjchvi xkdiwj ylejxk zmfkyl anglzm

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: bohman
Cipher: ylsnzm

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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: bohman

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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: bohman
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: bohman
Cipher: obuzna

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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: bohman
Cipher: 214332231133

Extended Methods:
Method #1

Plaintext: bohman
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
b o h m a n 
2 4 3 2 1 3 
1 3 2 3 1 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: bohman
Cipher: rhllml

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Method #3

Plaintext: bohman
method variations:
qngclh ngclhq gclhqn
clhqng lhqngc hqngcl

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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: bohman

all 720 cipher variations:
bohman bohmna bohamn bohanm bohnam bohnma bomhan bomhna bomahn bomanh bomnah
bomnha boamhn boamnh boahmn boahnm boanhm boanmh bonmah bonmha bonamh bonahm
bonham bonhma bhoman bhomna bhoamn bhoanm bhonam bhonma bhmoan bhmona bhmaon
bhmano bhmnao bhmnoa bhamon bhamno bhaomn bhaonm bhanom bhanmo bhnmao bhnmoa
bhnamo bhnaom bhnoam bhnoma bmhoan bmhona bmhaon bmhano bmhnao bmhnoa bmohan
bmohna bmoahn bmoanh bmonah bmonha bmaohn bmaonh bmahon bmahno bmanho bmanoh
bmnoah bmnoha bmnaoh bmnaho bmnhao bmnhoa bahmon bahmno bahomn bahonm bahnom
bahnmo bamhon bamhno bamohn bamonh bamnoh bamnho baomhn baomnh baohmn baohnm
baonhm baonmh banmoh banmho banomh banohm banhom banhmo bnhmao bnhmoa bnhamo
bnhaom bnhoam bnhoma bnmhao bnmhoa bnmaho bnmaoh bnmoah bnmoha bnamho bnamoh
bnahmo bnahom bnaohm bnaomh bnomah bnomha bnoamh bnoahm bnoham bnohma obhman
obhmna obhamn obhanm obhnam obhnma obmhan obmhna obmahn obmanh obmnah obmnha
obamhn obamnh obahmn obahnm obanhm obanmh obnmah obnmha obnamh obnahm obnham
obnhma ohbman ohbmna ohbamn ohbanm ohbnam ohbnma ohmban ohmbna ohmabn ohmanb
ohmnab ohmnba ohambn ohamnb ohabmn ohabnm ohanbm ohanmb ohnmab ohnmba ohnamb
ohnabm ohnbam ohnbma omhban omhbna omhabn omhanb omhnab omhnba ombhan ombhna
ombahn ombanh ombnah ombnha omabhn omabnh omahbn omahnb omanhb omanbh omnbah
omnbha omnabh omnahb omnhab omnhba oahmbn oahmnb oahbmn oahbnm oahnbm oahnmb
oamhbn oamhnb oambhn oambnh oamnbh oamnhb oabmhn oabmnh oabhmn oabhnm oabnhm
oabnmh oanmbh oanmhb oanbmh oanbhm oanhbm oanhmb onhmab onhmba onhamb onhabm
onhbam onhbma onmhab onmhba onmahb onmabh onmbah onmbha onamhb onambh onahmb
onahbm onabhm onabmh onbmah onbmha onbamh onbahm onbham onbhma hobman hobmna
hobamn hobanm hobnam hobnma homban hombna homabn homanb homnab homnba hoambn
hoamnb hoabmn hoabnm hoanbm hoanmb honmab honmba honamb honabm honbam honbma
hboman hbomna hboamn hboanm hbonam hbonma hbmoan hbmona hbmaon hbmano hbmnao
hbmnoa hbamon hbamno hbaomn hbaonm hbanom hbanmo hbnmao hbnmoa hbnamo hbnaom
hbnoam hbnoma hmboan hmbona hmbaon hmbano hmbnao hmbnoa hmoban hmobna hmoabn
hmoanb hmonab hmonba hmaobn hmaonb hmabon hmabno hmanbo hmanob hmnoab hmnoba
hmnaob hmnabo hmnbao hmnboa habmon habmno habomn habonm habnom habnmo hambon
hambno hamobn hamonb hamnob hamnbo haombn haomnb haobmn haobnm haonbm haonmb
hanmob hanmbo hanomb hanobm hanbom hanbmo hnbmao hnbmoa hnbamo hnbaom hnboam
hnboma hnmbao hnmboa hnmabo hnmaob hnmoab hnmoba hnambo hnamob hnabmo hnabom
hnaobm hnaomb hnomab hnomba hnoamb hnoabm hnobam hnobma mohban mohbna mohabn
mohanb mohnab mohnba mobhan mobhna mobahn mobanh mobnah mobnha moabhn moabnh
moahbn moahnb moanhb moanbh monbah monbha monabh monahb monhab monhba mhoban
mhobna mhoabn mhoanb mhonab mhonba mhboan mhbona mhbaon mhbano mhbnao mhbnoa
mhabon mhabno mhaobn mhaonb mhanob mhanbo mhnbao mhnboa mhnabo mhnaob mhnoab
mhnoba mbhoan mbhona mbhaon mbhano mbhnao mbhnoa mbohan mbohna mboahn mboanh
mbonah mbonha mbaohn mbaonh mbahon mbahno mbanho mbanoh mbnoah mbnoha mbnaoh
mbnaho mbnhao mbnhoa mahbon mahbno mahobn mahonb mahnob mahnbo mabhon mabhno
mabohn mabonh mabnoh mabnho maobhn maobnh maohbn maohnb maonhb maonbh manboh
manbho manobh manohb manhob manhbo mnhbao mnhboa mnhabo mnhaob mnhoab mnhoba
mnbhao mnbhoa mnbaho mnbaoh mnboah mnboha mnabho mnaboh mnahbo mnahob mnaohb
mnaobh mnobah mnobha mnoabh mnoahb mnohab mnohba aohmbn aohmnb aohbmn aohbnm
aohnbm aohnmb aomhbn aomhnb aombhn aombnh aomnbh aomnhb aobmhn aobmnh aobhmn
aobhnm aobnhm aobnmh aonmbh aonmhb aonbmh aonbhm aonhbm aonhmb ahombn ahomnb
ahobmn ahobnm ahonbm ahonmb ahmobn ahmonb ahmbon ahmbno ahmnbo ahmnob ahbmon
ahbmno ahbomn ahbonm ahbnom ahbnmo ahnmbo ahnmob ahnbmo ahnbom ahnobm ahnomb
amhobn amhonb amhbon amhbno amhnbo amhnob amohbn amohnb amobhn amobnh amonbh
amonhb ambohn ambonh ambhon ambhno ambnho ambnoh amnobh amnohb amnboh amnbho
amnhbo amnhob abhmon abhmno abhomn abhonm abhnom abhnmo abmhon abmhno abmohn
abmonh abmnoh abmnho abomhn abomnh abohmn abohnm abonhm abonmh abnmoh abnmho
abnomh abnohm abnhom abnhmo anhmbo anhmob anhbmo anhbom anhobm anhomb anmhbo
anmhob anmbho anmboh anmobh anmohb anbmho anbmoh anbhmo anbhom anbohm anbomh
anombh anomhb anobmh anobhm anohbm anohmb nohmab nohmba nohamb nohabm nohbam
nohbma nomhab nomhba nomahb nomabh nombah nombha noamhb noambh noahmb noahbm
noabhm noabmh nobmah nobmha nobamh nobahm nobham nobhma nhomab nhomba nhoamb
nhoabm nhobam nhobma nhmoab nhmoba nhmaob nhmabo nhmbao nhmboa nhamob nhambo
nhaomb nhaobm nhabom nhabmo nhbmao nhbmoa nhbamo nhbaom nhboam nhboma nmhoab
nmhoba nmhaob nmhabo nmhbao nmhboa nmohab nmohba nmoahb nmoabh nmobah nmobha
nmaohb nmaobh nmahob nmahbo nmabho nmaboh nmboah nmboha nmbaoh nmbaho nmbhao
nmbhoa nahmob nahmbo nahomb nahobm nahbom nahbmo namhob namhbo namohb namobh
namboh nambho naomhb naombh naohmb naohbm naobhm naobmh nabmoh nabmho nabomh
nabohm nabhom nabhmo nbhmao nbhmoa nbhamo nbhaom nbhoam nbhoma nbmhao nbmhoa
nbmaho nbmaoh nbmoah nbmoha nbamho nbamoh nbahmo nbahom nbaohm nbaomh nbomah
nbomha nboamh nboahm nboham nbohma

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History of cryptography
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