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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: kurtpc
cipher variations:
lvsuqd mwtvre nxuwsf oyvxtg pzwyuh
qaxzvi rbyawj sczbxk tdacyl uebdzm
vfcean wgdfbo xhegcp yifhdq zjgier
akhjfs blikgt cmjlhu dnkmiv eolnjw
fpmokx gqnply hroqmz isprna jtqsob

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: kurtpc
Cipher: pfigkx

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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: kurtpc

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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: kurtpc
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: kurtpc
Cipher: xhegcp

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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: kurtpc
Cipher: 525424445331

Extended Methods:
Method #1

Plaintext: kurtpc
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
k u r t p c 
5 5 2 4 5 3 
2 4 4 4 3 1 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: kurtpc
Cipher: zrprtc

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Method #3

Plaintext: kurtpc
method variations:
witynv itynvw tynvwi
ynvwit nvwity vwityn

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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: kurtpc

all 720 cipher variations:
kurtpc kurtcp kurptc kurpct kurcpt kurctp kutrpc kutrcp kutprc kutpcr kutcpr
kutcrp kuptrc kuptcr kuprtc kuprct kupcrt kupctr kuctpr kuctrp kucptr kucprt
kucrpt kucrtp krutpc krutcp kruptc krupct krucpt kructp krtupc krtucp krtpuc
krtpcu krtcpu krtcup krptuc krptcu krputc krpuct krpcut krpctu krctpu krctup
krcptu krcput krcupt krcutp ktrupc ktrucp ktrpuc ktrpcu ktrcpu ktrcup kturpc
kturcp ktuprc ktupcr ktucpr ktucrp ktpurc ktpucr ktpruc ktprcu ktpcru ktpcur
ktcupr ktcurp ktcpur ktcpru ktcrpu ktcrup kprtuc kprtcu kprutc kpruct kprcut
kprctu kptruc kptrcu kpturc kptucr kptcur kptcru kputrc kputcr kpurtc kpurct
kpucrt kpuctr kpctur kpctru kpcutr kpcurt kpcrut kpcrtu kcrtpu kcrtup kcrptu
kcrput kcrupt kcrutp kctrpu kctrup kctpru kctpur kctupr kcturp kcptru kcptur
kcprtu kcprut kcpurt kcputr kcutpr kcutrp kcuptr kcuprt kcurpt kcurtp ukrtpc
ukrtcp ukrptc ukrpct ukrcpt ukrctp uktrpc uktrcp uktprc uktpcr uktcpr uktcrp
ukptrc ukptcr ukprtc ukprct ukpcrt ukpctr ukctpr ukctrp ukcptr ukcprt ukcrpt
ukcrtp urktpc urktcp urkptc urkpct urkcpt urkctp urtkpc urtkcp urtpkc urtpck
urtcpk urtckp urptkc urptck urpktc urpkct urpckt urpctk urctpk urctkp urcptk
urcpkt urckpt urcktp utrkpc utrkcp utrpkc utrpck utrcpk utrckp utkrpc utkrcp
utkprc utkpcr utkcpr utkcrp utpkrc utpkcr utprkc utprck utpcrk utpckr utckpr
utckrp utcpkr utcprk utcrpk utcrkp uprtkc uprtck uprktc uprkct uprckt uprctk
uptrkc uptrck uptkrc uptkcr uptckr uptcrk upktrc upktcr upkrtc upkrct upkcrt
upkctr upctkr upctrk upcktr upckrt upcrkt upcrtk ucrtpk ucrtkp ucrptk ucrpkt
ucrkpt ucrktp uctrpk uctrkp uctprk uctpkr uctkpr uctkrp ucptrk ucptkr ucprtk
ucprkt ucpkrt ucpktr ucktpr ucktrp uckptr uckprt uckrpt uckrtp ruktpc ruktcp
rukptc rukpct rukcpt rukctp rutkpc rutkcp rutpkc rutpck rutcpk rutckp ruptkc
ruptck rupktc rupkct rupckt rupctk ructpk ructkp rucptk rucpkt ruckpt rucktp
rkutpc rkutcp rkuptc rkupct rkucpt rkuctp rktupc rktucp rktpuc rktpcu rktcpu
rktcup rkptuc rkptcu rkputc rkpuct rkpcut rkpctu rkctpu rkctup rkcptu rkcput
rkcupt rkcutp rtkupc rtkucp rtkpuc rtkpcu rtkcpu rtkcup rtukpc rtukcp rtupkc
rtupck rtucpk rtuckp rtpukc rtpuck rtpkuc rtpkcu rtpcku rtpcuk rtcupk rtcukp
rtcpuk rtcpku rtckpu rtckup rpktuc rpktcu rpkutc rpkuct rpkcut rpkctu rptkuc
rptkcu rptukc rptuck rptcuk rptcku rputkc rputck rpuktc rpukct rpuckt rpuctk
rpctuk rpctku rpcutk rpcukt rpckut rpcktu rcktpu rcktup rckptu rckput rckupt
rckutp rctkpu rctkup rctpku rctpuk rctupk rctukp rcptku rcptuk rcpktu rcpkut
rcpukt rcputk rcutpk rcutkp rcuptk rcupkt rcukpt rcuktp turkpc turkcp turpkc
turpck turcpk turckp tukrpc tukrcp tukprc tukpcr tukcpr tukcrp tupkrc tupkcr
tuprkc tuprck tupcrk tupckr tuckpr tuckrp tucpkr tucprk tucrpk tucrkp trukpc
trukcp trupkc trupck trucpk truckp trkupc trkucp trkpuc trkpcu trkcpu trkcup
trpkuc trpkcu trpukc trpuck trpcuk trpcku trckpu trckup trcpku trcpuk trcupk
trcukp tkrupc tkrucp tkrpuc tkrpcu tkrcpu tkrcup tkurpc tkurcp tkuprc tkupcr
tkucpr tkucrp tkpurc tkpucr tkpruc tkprcu tkpcru tkpcur tkcupr tkcurp tkcpur
tkcpru tkcrpu tkcrup tprkuc tprkcu tprukc tpruck tprcuk tprcku tpkruc tpkrcu
tpkurc tpkucr tpkcur tpkcru tpukrc tpukcr tpurkc tpurck tpucrk tpuckr tpckur
tpckru tpcukr tpcurk tpcruk tpcrku tcrkpu tcrkup tcrpku tcrpuk tcrupk tcrukp
tckrpu tckrup tckpru tckpur tckupr tckurp tcpkru tcpkur tcprku tcpruk tcpurk
tcpukr tcukpr tcukrp tcupkr tcuprk tcurpk tcurkp purtkc purtck purktc purkct
purckt purctk putrkc putrck putkrc putkcr putckr putcrk puktrc puktcr pukrtc
pukrct pukcrt pukctr puctkr puctrk pucktr puckrt pucrkt pucrtk prutkc prutck
pruktc prukct pruckt pructk prtukc prtuck prtkuc prtkcu prtcku prtcuk prktuc
prktcu prkutc prkuct prkcut prkctu prctku prctuk prcktu prckut prcukt prcutk
ptrukc ptruck ptrkuc ptrkcu ptrcku ptrcuk pturkc pturck ptukrc ptukcr ptuckr
ptucrk ptkurc ptkucr ptkruc ptkrcu ptkcru ptkcur ptcukr ptcurk ptckur ptckru
ptcrku ptcruk pkrtuc pkrtcu pkrutc pkruct pkrcut pkrctu pktruc pktrcu pkturc
pktucr pktcur pktcru pkutrc pkutcr pkurtc pkurct pkucrt pkuctr pkctur pkctru
pkcutr pkcurt pkcrut pkcrtu pcrtku pcrtuk pcrktu pcrkut pcrukt pcrutk pctrku
pctruk pctkru pctkur pctukr pcturk pcktru pcktur pckrtu pckrut pckurt pckutr
pcutkr pcutrk pcuktr pcukrt pcurkt pcurtk curtpk curtkp curptk curpkt curkpt
curktp cutrpk cutrkp cutprk cutpkr cutkpr cutkrp cuptrk cuptkr cuprtk cuprkt
cupkrt cupktr cuktpr cuktrp cukptr cukprt cukrpt cukrtp crutpk crutkp cruptk
crupkt crukpt cruktp crtupk crtukp crtpuk crtpku crtkpu crtkup crptuk crptku
crputk crpukt crpkut crpktu crktpu crktup crkptu crkput crkupt crkutp ctrupk
ctrukp ctrpuk ctrpku ctrkpu ctrkup cturpk cturkp ctuprk ctupkr ctukpr ctukrp
ctpurk ctpukr ctpruk ctprku ctpkru ctpkur ctkupr ctkurp ctkpur ctkpru ctkrpu
ctkrup cprtuk cprtku cprutk cprukt cprkut cprktu cptruk cptrku cpturk cptukr
cptkur cptkru cputrk cputkr cpurtk cpurkt cpukrt cpuktr cpktur cpktru cpkutr
cpkurt cpkrut cpkrtu ckrtpu ckrtup ckrptu ckrput ckrupt ckrutp cktrpu cktrup
cktpru cktpur cktupr ckturp ckptru ckptur ckprtu ckprut ckpurt ckputr ckutpr
ckutrp ckuptr ckuprt ckurpt ckurtp

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History of cryptography
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