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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: cyprum
cipher variations:
dzqsvn eartwo fbsuxp gctvyq hduwzr
ievxas jfwybt kgxzcu lhyadv mizbew
njacfx okbdgy plcehz qmdfia rnegjb
sofhkc tpgild uqhjme vriknf wsjlog
xtkmph yulnqi zvmorj awnpsk bxoqtl

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: cyprum
Cipher: xbkifn

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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: cyprum

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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: cyprum
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: cyprum
Cipher: plcehz

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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: cyprum
Cipher: 314553245423

Extended Methods:
Method #1

Plaintext: cyprum
method variations:

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

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Method #3

Plaintext: cyprum
method variations:
qzhyin zhyinq hyinqz
yinqzh inqzhy nqzhyi

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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: cyprum

all 720 cipher variations:
cyprum cyprmu cypurm cypumr cypmur cypmru cyrpum cyrpmu cyrupm cyrump cyrmup
cyrmpu cyurpm cyurmp cyuprm cyupmr cyumpr cyumrp cymrup cymrpu cymurp cymupr
cympur cympru cpyrum cpyrmu cpyurm cpyumr cpymur cpymru cpryum cprymu cpruym
cprumy cprmuy cprmyu cpurym cpurmy cpuyrm cpuymr cpumyr cpumry cpmruy cpmryu
cpmury cpmuyr cpmyur cpmyru crpyum crpymu crpuym crpumy crpmuy crpmyu crypum
crypmu cryupm cryump crymup crympu cruypm cruymp crupym crupmy crumpy crumyp
crmyup crmypu crmuyp crmupy crmpuy crmpyu cuprym cuprmy cupyrm cupymr cupmyr
cupmry curpym curpmy curypm curymp curmyp curmpy cuyrpm cuyrmp cuyprm cuypmr
cuympr cuymrp cumryp cumrpy cumyrp cumypr cumpyr cumpry cmpruy cmpryu cmpury
cmpuyr cmpyur cmpyru cmrpuy cmrpyu cmrupy cmruyp cmryup cmrypu cmurpy cmuryp
cmupry cmupyr cmuypr cmuyrp cmyrup cmyrpu cmyurp cmyupr cmypur cmypru ycprum
ycprmu ycpurm ycpumr ycpmur ycpmru ycrpum ycrpmu ycrupm ycrump ycrmup ycrmpu
ycurpm ycurmp ycuprm ycupmr ycumpr ycumrp ycmrup ycmrpu ycmurp ycmupr ycmpur
ycmpru ypcrum ypcrmu ypcurm ypcumr ypcmur ypcmru yprcum yprcmu yprucm yprumc
yprmuc yprmcu ypurcm ypurmc ypucrm ypucmr ypumcr ypumrc ypmruc ypmrcu ypmurc
ypmucr ypmcur ypmcru yrpcum yrpcmu yrpucm yrpumc yrpmuc yrpmcu yrcpum yrcpmu
yrcupm yrcump yrcmup yrcmpu yrucpm yrucmp yrupcm yrupmc yrumpc yrumcp yrmcup
yrmcpu yrmucp yrmupc yrmpuc yrmpcu yuprcm yuprmc yupcrm yupcmr yupmcr yupmrc
yurpcm yurpmc yurcpm yurcmp yurmcp yurmpc yucrpm yucrmp yucprm yucpmr yucmpr
yucmrp yumrcp yumrpc yumcrp yumcpr yumpcr yumprc ympruc ymprcu ympurc ympucr
ympcur ympcru ymrpuc ymrpcu ymrupc ymrucp ymrcup ymrcpu ymurpc ymurcp ymuprc
ymupcr ymucpr ymucrp ymcrup ymcrpu ymcurp ymcupr ymcpur ymcpru pycrum pycrmu
pycurm pycumr pycmur pycmru pyrcum pyrcmu pyrucm pyrumc pyrmuc pyrmcu pyurcm
pyurmc pyucrm pyucmr pyumcr pyumrc pymruc pymrcu pymurc pymucr pymcur pymcru
pcyrum pcyrmu pcyurm pcyumr pcymur pcymru pcryum pcrymu pcruym pcrumy pcrmuy
pcrmyu pcurym pcurmy pcuyrm pcuymr pcumyr pcumry pcmruy pcmryu pcmury pcmuyr
pcmyur pcmyru prcyum prcymu prcuym prcumy prcmuy prcmyu prycum prycmu pryucm
pryumc prymuc prymcu pruycm pruymc prucym prucmy prumcy prumyc prmyuc prmycu
prmuyc prmucy prmcuy prmcyu pucrym pucrmy pucyrm pucymr pucmyr pucmry purcym
purcmy purycm purymc purmyc purmcy puyrcm puyrmc puycrm puycmr puymcr puymrc
pumryc pumrcy pumyrc pumycr pumcyr pumcry pmcruy pmcryu pmcury pmcuyr pmcyur
pmcyru pmrcuy pmrcyu pmrucy pmruyc pmryuc pmrycu pmurcy pmuryc pmucry pmucyr
pmuycr pmuyrc pmyruc pmyrcu pmyurc pmyucr pmycur pmycru rypcum rypcmu rypucm
rypumc rypmuc rypmcu rycpum rycpmu rycupm rycump rycmup rycmpu ryucpm ryucmp
ryupcm ryupmc ryumpc ryumcp rymcup rymcpu rymucp rymupc rympuc rympcu rpycum
rpycmu rpyucm rpyumc rpymuc rpymcu rpcyum rpcymu rpcuym rpcumy rpcmuy rpcmyu
rpucym rpucmy rpuycm rpuymc rpumyc rpumcy rpmcuy rpmcyu rpmucy rpmuyc rpmyuc
rpmycu rcpyum rcpymu rcpuym rcpumy rcpmuy rcpmyu rcypum rcypmu rcyupm rcyump
rcymup rcympu rcuypm rcuymp rcupym rcupmy rcumpy rcumyp rcmyup rcmypu rcmuyp
rcmupy rcmpuy rcmpyu rupcym rupcmy rupycm rupymc rupmyc rupmcy rucpym rucpmy
rucypm rucymp rucmyp rucmpy ruycpm ruycmp ruypcm ruypmc ruympc ruymcp rumcyp
rumcpy rumycp rumypc rumpyc rumpcy rmpcuy rmpcyu rmpucy rmpuyc rmpyuc rmpycu
rmcpuy rmcpyu rmcupy rmcuyp rmcyup rmcypu rmucpy rmucyp rmupcy rmupyc rmuypc
rmuycp rmycup rmycpu rmyucp rmyupc rmypuc rmypcu uyprcm uyprmc uypcrm uypcmr
uypmcr uypmrc uyrpcm uyrpmc uyrcpm uyrcmp uyrmcp uyrmpc uycrpm uycrmp uycprm
uycpmr uycmpr uycmrp uymrcp uymrpc uymcrp uymcpr uympcr uymprc upyrcm upyrmc
upycrm upycmr upymcr upymrc uprycm uprymc uprcym uprcmy uprmcy uprmyc upcrym
upcrmy upcyrm upcymr upcmyr upcmry upmrcy upmryc upmcry upmcyr upmycr upmyrc
urpycm urpymc urpcym urpcmy urpmcy urpmyc urypcm urypmc urycpm urycmp urymcp
urympc urcypm urcymp urcpym urcpmy urcmpy urcmyp urmycp urmypc urmcyp urmcpy
urmpcy urmpyc ucprym ucprmy ucpyrm ucpymr ucpmyr ucpmry ucrpym ucrpmy ucrypm
ucrymp ucrmyp ucrmpy ucyrpm ucyrmp ucyprm ucypmr ucympr ucymrp ucmryp ucmrpy
ucmyrp ucmypr ucmpyr ucmpry umprcy umpryc umpcry umpcyr umpycr umpyrc umrpcy
umrpyc umrcpy umrcyp umrycp umrypc umcrpy umcryp umcpry umcpyr umcypr umcyrp
umyrcp umyrpc umycrp umycpr umypcr umyprc mypruc myprcu mypurc mypucr mypcur
mypcru myrpuc myrpcu myrupc myrucp myrcup myrcpu myurpc myurcp myuprc myupcr
myucpr myucrp mycrup mycrpu mycurp mycupr mycpur mycpru mpyruc mpyrcu mpyurc
mpyucr mpycur mpycru mpryuc mprycu mpruyc mprucy mprcuy mprcyu mpuryc mpurcy
mpuyrc mpuycr mpucyr mpucry mpcruy mpcryu mpcury mpcuyr mpcyur mpcyru mrpyuc
mrpycu mrpuyc mrpucy mrpcuy mrpcyu mrypuc mrypcu mryupc mryucp mrycup mrycpu
mruypc mruycp mrupyc mrupcy mrucpy mrucyp mrcyup mrcypu mrcuyp mrcupy mrcpuy
mrcpyu mupryc muprcy mupyrc mupycr mupcyr mupcry murpyc murpcy murypc murycp
murcyp murcpy muyrpc muyrcp muyprc muypcr muycpr muycrp mucryp mucrpy mucyrp
mucypr mucpyr mucpry mcpruy mcpryu mcpury mcpuyr mcpyur mcpyru mcrpuy mcrpyu
mcrupy mcruyp mcryup mcrypu mcurpy mcuryp mcupry mcupyr mcuypr mcuyrp mcyrup
mcyrpu mcyurp mcyupr mcypur mcypru

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History of cryptography
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