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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: feasts
cipher variations:
gfbtut hgcuvu ihdvwv jiewxw kjfxyx
lkgyzy mlhzaz nmiaba onjbcb pokcdc
qplded rqmefe srnfgf tsoghg utphih
vuqiji wvrjkj xwsklk yxtlml zyumnm
azvnon bawopo cbxpqp dcyqrq edzrsr

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: feasts
Cipher: uvzhgh

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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: feasts

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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: feasts
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: feasts
Cipher: srnfgf

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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: feasts
Cipher: 125111344434

Extended Methods:
Method #1

Plaintext: feasts
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
f e a s t s 
1 5 1 3 4 3 
2 1 1 4 4 4 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: feasts
Cipher: vlobqt

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Method #3

Plaintext: feasts
method variations:
waltod altodw ltodwa
todwal odwalt dwalto

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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: feasts

all 720 cipher variations:
feasts feasst featss featss feasts feasst fesats fesast festas festsa fessta
fessat fetsas fetssa fetass fetass fetsas fetssa fessta fessat festsa festas
fesats fesast faests faesst faetss faetss faests faesst fasets fasest fastes
fastse fasste fasset fatses fatsse fatess fatess fatses fatsse fasste fasset
fastse fastes fasets fasest fsaets fsaest fsates fsatse fsaste fsaset fseats
fseast fsetas fsetsa fsesta fsesat fsteas fstesa fstaes fstase fstsae fstsea
fsseta fsseat fsstea fsstae fssate fssaet ftases ftasse ftaess ftaess ftases
ftasse ftsaes ftsase ftseas ftsesa ftssea ftssae ftesas ftessa fteass fteass
ftesas ftessa ftssea ftssae ftsesa ftseas ftsaes ftsase fsaste fsaset fsatse
fsates fsaets fsaest fssate fssaet fsstae fsstea fsseta fsseat fstsae fstsea
fstase fstaes fsteas fstesa fsesta fsesat fsetsa fsetas fseats fseast efasts
efasst efatss efatss efasts efasst efsats efsast efstas efstsa efssta efssat
eftsas eftssa eftass eftass eftsas eftssa efssta efssat efstsa efstas efsats
efsast eafsts eafsst eaftss eaftss eafsts eafsst easfts easfst eastfs eastsf
easstf eassft eatsfs eatssf eatfss eatfss eatsfs eatssf easstf eassft eastsf
eastfs easfts easfst esafts esafst esatfs esatsf esastf esasft esfats esfast
esftas esftsa esfsta esfsat estfas estfsa estafs estasf estsaf estsfa essfta
essfat esstfa esstaf essatf essaft etasfs etassf etafss etafss etasfs etassf
etsafs etsasf etsfas etsfsa etssfa etssaf etfsas etfssa etfass etfass etfsas
etfssa etssfa etssaf etsfsa etsfas etsafs etsasf esastf esasft esatsf esatfs
esafts esafst essatf essaft esstaf esstfa essfta essfat estsaf estsfa estasf
estafs estfas estfsa esfsta esfsat esftsa esftas esfats esfast aefsts aefsst
aeftss aeftss aefsts aefsst aesfts aesfst aestfs aestsf aesstf aessft aetsfs
aetssf aetfss aetfss aetsfs aetssf aesstf aessft aestsf aestfs aesfts aesfst
afests afesst afetss afetss afests afesst afsets afsest afstes afstse afsste
afsset aftses aftsse aftess aftess aftses aftsse afsste afsset afstse afstes
afsets afsest asfets asfest asftes asftse asfste asfset asefts asefst asetfs
asetsf asestf asesft astefs astesf astfes astfse astsfe astsef assetf asseft
asstef asstfe assfte assfet atfses atfsse atfess atfess atfses atfsse atsfes
atsfse atsefs atsesf atssef atssfe atesfs atessf atefss atefss atesfs atessf
atssef atssfe atsesf atsefs atsfes atsfse asfste asfset asftse asftes asfets
asfest assfte assfet asstfe asstef assetf asseft astsfe astsef astfse astfes
astefs astesf asestf asesft asetsf asetfs asefts asefst seafts seafst seatfs
seatsf seastf seasft sefats sefast seftas seftsa sefsta sefsat setfas setfsa
setafs setasf setsaf setsfa sesfta sesfat sestfa sestaf sesatf sesaft saefts
saefst saetfs saetsf saestf saesft safets safest saftes saftse safste safset
satfes satfse satefs satesf satsef satsfe sasfte sasfet sastfe sastef sasetf
saseft sfaets sfaest sfates sfatse sfaste sfaset sfeats sfeast sfetas sfetsa
sfesta sfesat sfteas sftesa sftaes sftase sftsae sftsea sfseta sfseat sfstea
sfstae sfsate sfsaet stafes stafse staefs staesf stasef stasfe stfaes stfase
stfeas stfesa stfsea stfsae stefas stefsa steafs steasf stesaf stesfa stsfea
stsfae stsefa stseaf stsaef stsafe ssafte ssafet ssatfe ssatef ssaetf ssaeft
ssfate ssfaet ssftae ssftea ssfeta ssfeat sstfae sstfea sstafe sstaef ssteaf
sstefa ssefta ssefat ssetfa ssetaf sseatf sseaft teasfs teassf teafss teafss
teasfs teassf tesafs tesasf tesfas tesfsa tessfa tessaf tefsas tefssa tefass
tefass tefsas tefssa tessfa tessaf tesfsa tesfas tesafs tesasf taesfs taessf
taefss taefss taesfs taessf tasefs tasesf tasfes tasfse tassfe tassef tafses
tafsse tafess tafess tafses tafsse tassfe tassef tasfse tasfes tasefs tasesf
tsaefs tsaesf tsafes tsafse tsasfe tsasef tseafs tseasf tsefas tsefsa tsesfa
tsesaf tsfeas tsfesa tsfaes tsfase tsfsae tsfsea tssefa tsseaf tssfea tssfae
tssafe tssaef tfases tfasse tfaess tfaess tfases tfasse tfsaes tfsase tfseas
tfsesa tfssea tfssae tfesas tfessa tfeass tfeass tfesas tfessa tfssea tfssae
tfsesa tfseas tfsaes tfsase tsasfe tsasef tsafse tsafes tsaefs tsaesf tssafe
tssaef tssfae tssfea tssefa tsseaf tsfsae tsfsea tsfase tsfaes tsfeas tsfesa
tsesfa tsesaf tsefsa tsefas tseafs tseasf seastf seasft seatsf seatfs seafts
seafst sesatf sesaft sestaf sestfa sesfta sesfat setsaf setsfa setasf setafs
setfas setfsa sefsta sefsat seftsa seftas sefats sefast saestf saesft saetsf
saetfs saefts saefst sasetf saseft sastef sastfe sasfte sasfet satsef satsfe
satesf satefs satfes satfse safste safset saftse saftes safets safest ssaetf
ssaeft ssatef ssatfe ssafte ssafet sseatf sseaft ssetaf ssetfa ssefta ssefat
ssteaf sstefa sstaef sstafe sstfae sstfea ssfeta ssfeat ssftea ssftae ssfate
ssfaet stasef stasfe staesf staefs stafes stafse stsaef stsafe stseaf stsefa
stsfea stsfae stesaf stesfa steasf steafs stefas stefsa stfsea stfsae stfesa
stfeas stfaes stfase sfaste sfaset sfatse sfates sfaets sfaest sfsate sfsaet
sfstae sfstea sfseta sfseat sftsae sftsea sftase sftaes sfteas sftesa sfesta
sfesat sfetsa sfetas sfeats sfeast

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