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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: fremas
cipher variations:
gsfnbt htgocu iuhpdv jviqew kwjrfx
lxksgy mylthz nzmuia oanvjb pbowkc
qcpxld rdqyme serznf tfsaog ugtbph
vhucqi wivdrj xjwesk ykxftl zlygum
amzhvn bnaiwo cobjxp dpckyq eqdlzr

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: fremas
Cipher: uivnzh

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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: fremas

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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: fremas
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: fremas
Cipher: serznf

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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: fremas
Cipher: 122451231134

Extended Methods:
Method #1

Plaintext: fremas
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
f r e m a s 
1 2 5 2 1 3 
2 4 1 3 1 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: fremas
Cipher: fklrlq

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Method #3

Plaintext: fremas
method variations:
gyfcld yfcldg fcldgy
cldgyf ldgyfc dgyfcl

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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: fremas

all 720 cipher variations:
fremas fremsa freams freasm fresam fresma frmeas frmesa frmaes frmase frmsae
frmsea frames framse fraems fraesm frasem frasme frsmae frsmea frsame frsaem
frseam frsema fermas fermsa ferams ferasm fersam fersma femras femrsa femars
femasr femsar femsra feamrs feamsr fearms fearsm feasrm feasmr fesmar fesmra
fesamr fesarm fesram fesrma fmeras fmersa fmears fmeasr fmesar fmesra fmreas
fmresa fmraes fmrase fmrsae fmrsea fmares fmarse fmaers fmaesr fmaser fmasre
fmsrae fmsrea fmsare fmsaer fmsear fmsera faemrs faemsr faerms faersm faesrm
faesmr famers famesr famres famrse famsre famser farmes farmse farems faresm
farsem farsme fasmre fasmer fasrme fasrem faserm fasemr fsemar fsemra fseamr
fsearm fseram fserma fsmear fsmera fsmaer fsmare fsmrae fsmrea fsamer fsamre
fsaemr fsaerm fsarem fsarme fsrmae fsrmea fsrame fsraem fsream fsrema rfemas
rfemsa rfeams rfeasm rfesam rfesma rfmeas rfmesa rfmaes rfmase rfmsae rfmsea
rfames rfamse rfaems rfaesm rfasem rfasme rfsmae rfsmea rfsame rfsaem rfseam
rfsema refmas refmsa refams refasm refsam refsma remfas remfsa remafs remasf
remsaf remsfa reamfs reamsf reafms reafsm reasfm reasmf resmaf resmfa resamf
resafm resfam resfma rmefas rmefsa rmeafs rmeasf rmesaf rmesfa rmfeas rmfesa
rmfaes rmfase rmfsae rmfsea rmafes rmafse rmaefs rmaesf rmasef rmasfe rmsfae
rmsfea rmsafe rmsaef rmseaf rmsefa raemfs raemsf raefms raefsm raesfm raesmf
ramefs ramesf ramfes ramfse ramsfe ramsef rafmes rafmse rafems rafesm rafsem
rafsme rasmfe rasmef rasfme rasfem rasefm rasemf rsemaf rsemfa rseamf rseafm
rsefam rsefma rsmeaf rsmefa rsmaef rsmafe rsmfae rsmfea rsamef rsamfe rsaemf
rsaefm rsafem rsafme rsfmae rsfmea rsfame rsfaem rsfeam rsfema erfmas erfmsa
erfams erfasm erfsam erfsma ermfas ermfsa ermafs ermasf ermsaf ermsfa eramfs
eramsf erafms erafsm erasfm erasmf ersmaf ersmfa ersamf ersafm ersfam ersfma
efrmas efrmsa eframs efrasm efrsam efrsma efmras efmrsa efmars efmasr efmsar
efmsra efamrs efamsr efarms efarsm efasrm efasmr efsmar efsmra efsamr efsarm
efsram efsrma emfras emfrsa emfars emfasr emfsar emfsra emrfas emrfsa emrafs
emrasf emrsaf emrsfa emarfs emarsf emafrs emafsr emasfr emasrf emsraf emsrfa
emsarf emsafr emsfar emsfra eafmrs eafmsr eafrms eafrsm eafsrm eafsmr eamfrs
eamfsr eamrfs eamrsf eamsrf eamsfr earmfs earmsf earfms earfsm earsfm earsmf
easmrf easmfr easrmf easrfm easfrm easfmr esfmar esfmra esfamr esfarm esfram
esfrma esmfar esmfra esmafr esmarf esmraf esmrfa esamfr esamrf esafmr esafrm
esarfm esarmf esrmaf esrmfa esramf esrafm esrfam esrfma mrefas mrefsa mreafs
mreasf mresaf mresfa mrfeas mrfesa mrfaes mrfase mrfsae mrfsea mrafes mrafse
mraefs mraesf mrasef mrasfe mrsfae mrsfea mrsafe mrsaef mrseaf mrsefa merfas
merfsa merafs merasf mersaf mersfa mefras mefrsa mefars mefasr mefsar mefsra
meafrs meafsr mearfs mearsf measrf measfr mesfar mesfra mesafr mesarf mesraf
mesrfa mferas mfersa mfears mfeasr mfesar mfesra mfreas mfresa mfraes mfrase
mfrsae mfrsea mfares mfarse mfaers mfaesr mfaser mfasre mfsrae mfsrea mfsare
mfsaer mfsear mfsera maefrs maefsr maerfs maersf maesrf maesfr mafers mafesr
mafres mafrse mafsre mafser marfes marfse marefs maresf marsef marsfe masfre
masfer masrfe masref maserf masefr msefar msefra mseafr msearf mseraf mserfa
msfear msfera msfaer msfare msfrae msfrea msafer msafre msaefr msaerf msaref
msarfe msrfae msrfea msrafe msraef msreaf msrefa aremfs aremsf arefms arefsm
aresfm aresmf armefs armesf armfes armfse armsfe armsef arfmes arfmse arfems
arfesm arfsem arfsme arsmfe arsmef arsfme arsfem arsefm arsemf aermfs aermsf
aerfms aerfsm aersfm aersmf aemrfs aemrsf aemfrs aemfsr aemsfr aemsrf aefmrs
aefmsr aefrms aefrsm aefsrm aefsmr aesmfr aesmrf aesfmr aesfrm aesrfm aesrmf
amerfs amersf amefrs amefsr amesfr amesrf amrefs amresf amrfes amrfse amrsfe
amrsef amfres amfrse amfers amfesr amfser amfsre amsrfe amsref amsfre amsfer
amsefr amserf afemrs afemsr aferms afersm afesrm afesmr afmers afmesr afmres
afmrse afmsre afmser afrmes afrmse afrems afresm afrsem afrsme afsmre afsmer
afsrme afsrem afserm afsemr asemfr asemrf asefmr asefrm aserfm asermf asmefr
asmerf asmfer asmfre asmrfe asmref asfmer asfmre asfemr asferm asfrem asfrme
asrmfe asrmef asrfme asrfem asrefm asremf sremaf sremfa sreamf sreafm srefam
srefma srmeaf srmefa srmaef srmafe srmfae srmfea sramef sramfe sraemf sraefm
srafem srafme srfmae srfmea srfame srfaem srfeam srfema sermaf sermfa seramf
serafm serfam serfma semraf semrfa semarf semafr semfar semfra seamrf seamfr
searmf searfm seafrm seafmr sefmar sefmra sefamr sefarm sefram sefrma smeraf
smerfa smearf smeafr smefar smefra smreaf smrefa smraef smrafe smrfae smrfea
smaref smarfe smaerf smaefr smafer smafre smfrae smfrea smfare smfaer smfear
smfera saemrf saemfr saermf saerfm saefrm saefmr samerf samefr samref samrfe
samfre samfer sarmef sarmfe saremf sarefm sarfem sarfme safmre safmer safrme
safrem saferm safemr sfemar sfemra sfeamr sfearm sferam sferma sfmear sfmera
sfmaer sfmare sfmrae sfmrea sfamer sfamre sfaemr sfaerm sfarem sfarme sfrmae
sfrmea sframe sfraem sfream sfrema

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