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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: rumpat
cipher variations:
svnqbu tworcv uxpsdw vyqtex wzrufy
xasvgz ybtwha zcuxib advyjc bewzkd
cfxale dgybmf ehzcng fiadoh gjbepi
hkcfqj ildgrk jmehsl knfitm logjun
mphkvo nqilwp orjmxq psknyr qtlozs

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: rumpat
Cipher: ifnkzg

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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: rumpat

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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: rumpat
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: rumpat
Cipher: ehzcng

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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: rumpat
Cipher: 245423531144

Extended Methods:
Method #1

Plaintext: rumpat
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
r u m p a t 
2 5 2 5 1 4 
4 4 3 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: rumpat
Cipher: wwqtnq

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Method #3

Plaintext: rumpat
method variations:
yixcqi ixcqiy xcqiyi
cqiyix qiyixc iyixcq

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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: rumpat

all 720 cipher variations:
rumpat rumpta rumapt rumatp rumtap rumtpa rupmat rupmta rupamt rupatm ruptam
ruptma ruapmt ruaptm ruampt ruamtp ruatmp ruatpm rutpam rutpma rutapm rutamp
rutmap rutmpa rmupat rmupta rmuapt rmuatp rmutap rmutpa rmpuat rmputa rmpaut
rmpatu rmptau rmptua rmaput rmaptu rmaupt rmautp rmatup rmatpu rmtpau rmtpua
rmtapu rmtaup rmtuap rmtupa rpmuat rpmuta rpmaut rpmatu rpmtau rpmtua rpumat
rpumta rpuamt rpuatm rputam rputma rpaumt rpautm rpamut rpamtu rpatmu rpatum
rptuam rptuma rptaum rptamu rptmau rptmua ramput ramptu ramupt ramutp ramtup
ramtpu rapmut rapmtu rapumt raputm raptum raptmu raupmt rauptm raumpt raumtp
rautmp rautpm ratpum ratpmu ratupm ratump ratmup ratmpu rtmpau rtmpua rtmapu
rtmaup rtmuap rtmupa rtpmau rtpmua rtpamu rtpaum rtpuam rtpuma rtapmu rtapum
rtampu rtamup rtaump rtaupm rtupam rtupma rtuapm rtuamp rtumap rtumpa urmpat
urmpta urmapt urmatp urmtap urmtpa urpmat urpmta urpamt urpatm urptam urptma
urapmt uraptm urampt uramtp uratmp uratpm urtpam urtpma urtapm urtamp urtmap
urtmpa umrpat umrpta umrapt umratp umrtap umrtpa umprat umprta umpart umpatr
umptar umptra umaprt umaptr umarpt umartp umatrp umatpr umtpar umtpra umtapr
umtarp umtrap umtrpa upmrat upmrta upmart upmatr upmtar upmtra uprmat uprmta
upramt upratm uprtam uprtma uparmt upartm upamrt upamtr upatmr upatrm uptram
uptrma uptarm uptamr uptmar uptmra uamprt uamptr uamrpt uamrtp uamtrp uamtpr
uapmrt uapmtr uaprmt uaprtm uaptrm uaptmr uarpmt uarptm uarmpt uarmtp uartmp
uartpm uatprm uatpmr uatrpm uatrmp uatmrp uatmpr utmpar utmpra utmapr utmarp
utmrap utmrpa utpmar utpmra utpamr utparm utpram utprma utapmr utaprm utampr
utamrp utarmp utarpm utrpam utrpma utrapm utramp utrmap utrmpa murpat murpta
murapt muratp murtap murtpa muprat muprta mupart mupatr muptar muptra muaprt
muaptr muarpt muartp muatrp muatpr mutpar mutpra mutapr mutarp mutrap mutrpa
mrupat mrupta mruapt mruatp mrutap mrutpa mrpuat mrputa mrpaut mrpatu mrptau
mrptua mraput mraptu mraupt mrautp mratup mratpu mrtpau mrtpua mrtapu mrtaup
mrtuap mrtupa mpruat mpruta mpraut mpratu mprtau mprtua mpurat mpurta mpuart
mpuatr mputar mputra mpaurt mpautr mparut mpartu mpatru mpatur mptuar mptura
mptaur mptaru mptrau mptrua marput marptu marupt marutp martup martpu maprut
maprtu mapurt maputr maptur maptru mauprt mauptr maurpt maurtp mautrp mautpr
matpur matpru matupr maturp matrup matrpu mtrpau mtrpua mtrapu mtraup mtruap
mtrupa mtprau mtprua mtparu mtpaur mtpuar mtpura mtapru mtapur mtarpu mtarup
mtaurp mtaupr mtupar mtupra mtuapr mtuarp mturap mturpa pumrat pumrta pumart
pumatr pumtar pumtra purmat purmta puramt puratm purtam purtma puarmt puartm
puamrt puamtr puatmr puatrm putram putrma putarm putamr putmar putmra pmurat
pmurta pmuart pmuatr pmutar pmutra pmruat pmruta pmraut pmratu pmrtau pmrtua
pmarut pmartu pmaurt pmautr pmatur pmatru pmtrau pmtrua pmtaru pmtaur pmtuar
pmtura prmuat prmuta prmaut prmatu prmtau prmtua prumat prumta pruamt pruatm
prutam prutma praumt prautm pramut pramtu pratmu pratum prtuam prtuma prtaum
prtamu prtmau prtmua pamrut pamrtu pamurt pamutr pamtur pamtru parmut parmtu
parumt parutm partum partmu paurmt paurtm paumrt paumtr pautmr pautrm patrum
patrmu paturm patumr patmur patmru ptmrau ptmrua ptmaru ptmaur ptmuar ptmura
ptrmau ptrmua ptramu ptraum ptruam ptruma ptarmu ptarum ptamru ptamur ptaumr
ptaurm pturam pturma ptuarm ptuamr ptumar ptumra aumprt aumptr aumrpt aumrtp
aumtrp aumtpr aupmrt aupmtr auprmt auprtm auptrm auptmr aurpmt aurptm aurmpt
aurmtp aurtmp aurtpm autprm autpmr autrpm autrmp autmrp autmpr amuprt amuptr
amurpt amurtp amutrp amutpr ampurt amputr amprut amprtu amptru amptur amrput
amrptu amrupt amrutp amrtup amrtpu amtpru amtpur amtrpu amtrup amturp amtupr
apmurt apmutr apmrut apmrtu apmtru apmtur apumrt apumtr apurmt apurtm aputrm
aputmr aprumt aprutm aprmut aprmtu aprtmu aprtum apturm aptumr aptrum aptrmu
aptmru aptmur armput armptu armupt armutp armtup armtpu arpmut arpmtu arpumt
arputm arptum arptmu arupmt aruptm arumpt arumtp arutmp arutpm artpum artpmu
artupm artump artmup artmpu atmpru atmpur atmrpu atmrup atmurp atmupr atpmru
atpmur atprmu atprum atpurm atpumr atrpmu atrpum atrmpu atrmup atrump atrupm
atuprm atupmr aturpm aturmp atumrp atumpr tumpar tumpra tumapr tumarp tumrap
tumrpa tupmar tupmra tupamr tuparm tupram tuprma tuapmr tuaprm tuampr tuamrp
tuarmp tuarpm turpam turpma turapm turamp turmap turmpa tmupar tmupra tmuapr
tmuarp tmurap tmurpa tmpuar tmpura tmpaur tmparu tmprau tmprua tmapur tmapru
tmaupr tmaurp tmarup tmarpu tmrpau tmrpua tmrapu tmraup tmruap tmrupa tpmuar
tpmura tpmaur tpmaru tpmrau tpmrua tpumar tpumra tpuamr tpuarm tpuram tpurma
tpaumr tpaurm tpamur tpamru tparmu tparum tpruam tpruma tpraum tpramu tprmau
tprmua tampur tampru tamupr tamurp tamrup tamrpu tapmur tapmru tapumr tapurm
taprum taprmu taupmr tauprm taumpr taumrp taurmp taurpm tarpum tarpmu tarupm
tarump tarmup tarmpu trmpau trmpua trmapu trmaup trmuap trmupa trpmau trpmua
trpamu trpaum trpuam trpuma trapmu trapum trampu tramup traump traupm trupam
trupma truapm truamp trumap trumpa

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History of cryptography
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