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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: xterms
cipher variations:
yufsnt zvgtou awhupv bxivqw cyjwrx
dzkxsy ealytz fbmzua gcnavb hdobwc
iepcxd jfqdye kgrezf lhsfag mitgbh
njuhci okvidj plwjek qmxkfl rnylgm
sozmhn tpanio uqbojp vrcpkq wsdqlr

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: xterms
Cipher: cgvinh

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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: xterms

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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: xterms
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: xterms
Cipher: kgrezf

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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: xterms
Cipher: 354451242334

Extended Methods:
Method #1

Plaintext: xterms
method variations:

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

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Method #3

Plaintext: xterms
method variations:
uyfino yfinou finouy
inouyf nouyfi ouyfin

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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: xterms

all 720 cipher variations:
xterms xtersm xtemrs xtemsr xtesmr xtesrm xtrems xtresm xtrmes xtrmse xtrsme
xtrsem xtmres xtmrse xtmers xtmesr xtmser xtmsre xtsrme xtsrem xtsmre xtsmer
xtsemr xtserm xetrms xetrsm xetmrs xetmsr xetsmr xetsrm xertms xertsm xermts
xermst xersmt xerstm xemrts xemrst xemtrs xemtsr xemstr xemsrt xesrmt xesrtm
xesmrt xesmtr xestmr xestrm xretms xretsm xremts xremst xresmt xrestm xrtems
xrtesm xrtmes xrtmse xrtsme xrtsem xrmtes xrmtse xrmets xrmest xrmset xrmste
xrstme xrstem xrsmte xrsmet xrsemt xrsetm xmerts xmerst xmetrs xmetsr xmestr
xmesrt xmrets xmrest xmrtes xmrtse xmrste xmrset xmtres xmtrse xmters xmtesr
xmtser xmtsre xmsrte xmsret xmstre xmster xmsetr xmsert xsermt xsertm xsemrt
xsemtr xsetmr xsetrm xsremt xsretm xsrmet xsrmte xsrtme xsrtem xsmret xsmrte
xsmert xsmetr xsmter xsmtre xstrme xstrem xstmre xstmer xstemr xsterm txerms
txersm txemrs txemsr txesmr txesrm txrems txresm txrmes txrmse txrsme txrsem
txmres txmrse txmers txmesr txmser txmsre txsrme txsrem txsmre txsmer txsemr
txserm texrms texrsm texmrs texmsr texsmr texsrm terxms terxsm termxs termsx
tersmx tersxm temrxs temrsx temxrs temxsr temsxr temsrx tesrmx tesrxm tesmrx
tesmxr tesxmr tesxrm trexms trexsm tremxs tremsx tresmx tresxm trxems trxesm
trxmes trxmse trxsme trxsem trmxes trmxse trmexs trmesx trmsex trmsxe trsxme
trsxem trsmxe trsmex trsemx trsexm tmerxs tmersx tmexrs tmexsr tmesxr tmesrx
tmrexs tmresx tmrxes tmrxse tmrsxe tmrsex tmxres tmxrse tmxers tmxesr tmxser
tmxsre tmsrxe tmsrex tmsxre tmsxer tmsexr tmserx tsermx tserxm tsemrx tsemxr
tsexmr tsexrm tsremx tsrexm tsrmex tsrmxe tsrxme tsrxem tsmrex tsmrxe tsmerx
tsmexr tsmxer tsmxre tsxrme tsxrem tsxmre tsxmer tsxemr tsxerm etxrms etxrsm
etxmrs etxmsr etxsmr etxsrm etrxms etrxsm etrmxs etrmsx etrsmx etrsxm etmrxs
etmrsx etmxrs etmxsr etmsxr etmsrx etsrmx etsrxm etsmrx etsmxr etsxmr etsxrm
extrms extrsm extmrs extmsr extsmr extsrm exrtms exrtsm exrmts exrmst exrsmt
exrstm exmrts exmrst exmtrs exmtsr exmstr exmsrt exsrmt exsrtm exsmrt exsmtr
exstmr exstrm erxtms erxtsm erxmts erxmst erxsmt erxstm ertxms ertxsm ertmxs
ertmsx ertsmx ertsxm ermtxs ermtsx ermxts ermxst ermsxt ermstx erstmx erstxm
ersmtx ersmxt ersxmt ersxtm emxrts emxrst emxtrs emxtsr emxstr emxsrt emrxts
emrxst emrtxs emrtsx emrstx emrsxt emtrxs emtrsx emtxrs emtxsr emtsxr emtsrx
emsrtx emsrxt emstrx emstxr emsxtr emsxrt esxrmt esxrtm esxmrt esxmtr esxtmr
esxtrm esrxmt esrxtm esrmxt esrmtx esrtmx esrtxm esmrxt esmrtx esmxrt esmxtr
esmtxr esmtrx estrmx estrxm estmrx estmxr estxmr estxrm rtexms rtexsm rtemxs
rtemsx rtesmx rtesxm rtxems rtxesm rtxmes rtxmse rtxsme rtxsem rtmxes rtmxse
rtmexs rtmesx rtmsex rtmsxe rtsxme rtsxem rtsmxe rtsmex rtsemx rtsexm retxms
retxsm retmxs retmsx retsmx retsxm rextms rextsm rexmts rexmst rexsmt rexstm
remxts remxst remtxs remtsx remstx remsxt resxmt resxtm resmxt resmtx restmx
restxm rxetms rxetsm rxemts rxemst rxesmt rxestm rxtems rxtesm rxtmes rxtmse
rxtsme rxtsem rxmtes rxmtse rxmets rxmest rxmset rxmste rxstme rxstem rxsmte
rxsmet rxsemt rxsetm rmexts rmexst rmetxs rmetsx rmestx rmesxt rmxets rmxest
rmxtes rmxtse rmxste rmxset rmtxes rmtxse rmtexs rmtesx rmtsex rmtsxe rmsxte
rmsxet rmstxe rmstex rmsetx rmsext rsexmt rsextm rsemxt rsemtx rsetmx rsetxm
rsxemt rsxetm rsxmet rsxmte rsxtme rsxtem rsmxet rsmxte rsmext rsmetx rsmtex
rsmtxe rstxme rstxem rstmxe rstmex rstemx rstexm mterxs mtersx mtexrs mtexsr
mtesxr mtesrx mtrexs mtresx mtrxes mtrxse mtrsxe mtrsex mtxres mtxrse mtxers
mtxesr mtxser mtxsre mtsrxe mtsrex mtsxre mtsxer mtsexr mtserx metrxs metrsx
metxrs metxsr metsxr metsrx mertxs mertsx merxts merxst mersxt merstx mexrts
mexrst mextrs mextsr mexstr mexsrt mesrxt mesrtx mesxrt mesxtr mestxr mestrx
mretxs mretsx mrexts mrexst mresxt mrestx mrtexs mrtesx mrtxes mrtxse mrtsxe
mrtsex mrxtes mrxtse mrxets mrxest mrxset mrxste mrstxe mrstex mrsxte mrsxet
mrsext mrsetx mxerts mxerst mxetrs mxetsr mxestr mxesrt mxrets mxrest mxrtes
mxrtse mxrste mxrset mxtres mxtrse mxters mxtesr mxtser mxtsre mxsrte mxsret
mxstre mxster mxsetr mxsert mserxt msertx msexrt msextr msetxr msetrx msrext
msretx msrxet msrxte msrtxe msrtex msxret msxrte msxert msxetr msxter msxtre
mstrxe mstrex mstxre mstxer mstexr msterx stermx sterxm stemrx stemxr stexmr
stexrm stremx strexm strmex strmxe strxme strxem stmrex stmrxe stmerx stmexr
stmxer stmxre stxrme stxrem stxmre stxmer stxemr stxerm setrmx setrxm setmrx
setmxr setxmr setxrm sertmx sertxm sermtx sermxt serxmt serxtm semrtx semrxt
semtrx semtxr semxtr semxrt sexrmt sexrtm sexmrt sexmtr sextmr sextrm sretmx
sretxm sremtx sremxt srexmt srextm srtemx srtexm srtmex srtmxe srtxme srtxem
srmtex srmtxe srmetx srmext srmxet srmxte srxtme srxtem srxmte srxmet srxemt
srxetm smertx smerxt smetrx smetxr smextr smexrt smretx smrext smrtex smrtxe
smrxte smrxet smtrex smtrxe smterx smtexr smtxer smtxre smxrte smxret smxtre
smxter smxetr smxert sxermt sxertm sxemrt sxemtr sxetmr sxetrm sxremt sxretm
sxrmet sxrmte sxrtme sxrtem sxmret sxmrte sxmert sxmetr sxmter sxmtre sxtrme
sxtrem sxtmre sxtmer sxtemr sxterm

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History of cryptography
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