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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: pincus
cipher variations:
qjodvt rkpewu slqfxv tmrgyw unshzx
votiay wpujbz xqvkca yrwldb zsxmec
atynfd buzoge cvaphf dwbqig excrjh
fydski gzetlj hafumk ibgvnl jchwom
kdixpn lejyqo mfkzrp nglasq ohmbtr

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: pincus
Cipher: krmxfh

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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: pincus

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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: pincus
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: pincus
Cipher: cvaphf

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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: pincus
Cipher: 534233315434

Extended Methods:
Method #1

Plaintext: pincus
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
p i n c u s 
5 4 3 3 5 3 
3 2 3 1 4 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: pincus
Cipher: unphct

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Method #3

Plaintext: pincus
method variations:
smnvoy mnvoys nvoysm
voysmn oysmnv ysmnvo

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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: pincus

all 720 cipher variations:
pincus pincsu pinucs pinusc pinsuc pinscu picnus picnsu picuns picusn picsun
picsnu piucns piucsn piuncs piunsc piusnc piuscn piscun piscnu pisucn pisunc
pisnuc pisncu pnicus pnicsu pniucs pniusc pnisuc pniscu pncius pncisu pncuis
pncusi pncsui pncsiu pnucis pnucsi pnuics pnuisc pnusic pnusci pnscui pnsciu
pnsuci pnsuic pnsiuc pnsicu pcnius pcnisu pcnuis pcnusi pcnsui pcnsiu pcinus
pcinsu pciuns pciusn pcisun pcisnu pcuins pcuisn pcunis pcunsi pcusni pcusin
pcsiun pcsinu pcsuin pcsuni pcsnui pcsniu puncis puncsi punics punisc punsic
punsci pucnis pucnsi pucins pucisn pucsin pucsni puicns puicsn puincs puinsc
puisnc puiscn puscin puscni pusicn pusinc pusnic pusnci psncui psnciu psnuci
psnuic psniuc psnicu pscnui pscniu pscuni pscuin psciun pscinu psucni psucin
psunci psunic psuinc psuicn psicun psicnu psiucn psiunc psinuc psincu ipncus
ipncsu ipnucs ipnusc ipnsuc ipnscu ipcnus ipcnsu ipcuns ipcusn ipcsun ipcsnu
ipucns ipucsn ipuncs ipunsc ipusnc ipuscn ipscun ipscnu ipsucn ipsunc ipsnuc
ipsncu inpcus inpcsu inpucs inpusc inpsuc inpscu incpus incpsu incups incusp
incsup incspu inucps inucsp inupcs inupsc inuspc inuscp inscup inscpu insucp
insupc inspuc inspcu icnpus icnpsu icnups icnusp icnsup icnspu icpnus icpnsu
icpuns icpusn icpsun icpsnu icupns icupsn icunps icunsp icusnp icuspn icspun
icspnu icsupn icsunp icsnup icsnpu iuncps iuncsp iunpcs iunpsc iunspc iunscp
iucnps iucnsp iucpns iucpsn iucspn iucsnp iupcns iupcsn iupncs iupnsc iupsnc
iupscn iuscpn iuscnp iuspcn iuspnc iusnpc iusncp isncup isncpu isnucp isnupc
isnpuc isnpcu iscnup iscnpu iscunp iscupn iscpun iscpnu isucnp isucpn isuncp
isunpc isupnc isupcn ispcun ispcnu ispucn ispunc ispnuc ispncu nipcus nipcsu
nipucs nipusc nipsuc nipscu nicpus nicpsu nicups nicusp nicsup nicspu niucps
niucsp niupcs niupsc niuspc niuscp niscup niscpu nisucp nisupc nispuc nispcu
npicus npicsu npiucs npiusc npisuc npiscu npcius npcisu npcuis npcusi npcsui
npcsiu npucis npucsi npuics npuisc npusic npusci npscui npsciu npsuci npsuic
npsiuc npsicu ncpius ncpisu ncpuis ncpusi ncpsui ncpsiu ncipus ncipsu nciups
nciusp ncisup ncispu ncuips ncuisp ncupis ncupsi ncuspi ncusip ncsiup ncsipu
ncsuip ncsupi ncspui ncspiu nupcis nupcsi nupics nupisc nupsic nupsci nucpis
nucpsi nucips nucisp nucsip nucspi nuicps nuicsp nuipcs nuipsc nuispc nuiscp
nuscip nuscpi nusicp nusipc nuspic nuspci nspcui nspciu nspuci nspuic nspiuc
nspicu nscpui nscpiu nscupi nscuip nsciup nscipu nsucpi nsucip nsupci nsupic
nsuipc nsuicp nsicup nsicpu nsiucp nsiupc nsipuc nsipcu cinpus cinpsu cinups
cinusp cinsup cinspu cipnus cipnsu cipuns cipusn cipsun cipsnu ciupns ciupsn
ciunps ciunsp ciusnp ciuspn cispun cispnu cisupn cisunp cisnup cisnpu cnipus
cnipsu cniups cniusp cnisup cnispu cnpius cnpisu cnpuis cnpusi cnpsui cnpsiu
cnupis cnupsi cnuips cnuisp cnusip cnuspi cnspui cnspiu cnsupi cnsuip cnsiup
cnsipu cpnius cpnisu cpnuis cpnusi cpnsui cpnsiu cpinus cpinsu cpiuns cpiusn
cpisun cpisnu cpuins cpuisn cpunis cpunsi cpusni cpusin cpsiun cpsinu cpsuin
cpsuni cpsnui cpsniu cunpis cunpsi cunips cunisp cunsip cunspi cupnis cupnsi
cupins cupisn cupsin cupsni cuipns cuipsn cuinps cuinsp cuisnp cuispn cuspin
cuspni cusipn cusinp cusnip cusnpi csnpui csnpiu csnupi csnuip csniup csnipu
cspnui cspniu cspuni cspuin cspiun cspinu csupni csupin csunpi csunip csuinp
csuipn csipun csipnu csiupn csiunp csinup csinpu uincps uincsp uinpcs uinpsc
uinspc uinscp uicnps uicnsp uicpns uicpsn uicspn uicsnp uipcns uipcsn uipncs
uipnsc uipsnc uipscn uiscpn uiscnp uispcn uispnc uisnpc uisncp unicps unicsp
unipcs unipsc unispc uniscp uncips uncisp uncpis uncpsi uncspi uncsip unpcis
unpcsi unpics unpisc unpsic unpsci unscpi unscip unspci unspic unsipc unsicp
ucnips ucnisp ucnpis ucnpsi ucnspi ucnsip ucinps ucinsp ucipns ucipsn ucispn
ucisnp ucpins ucpisn ucpnis ucpnsi ucpsni ucpsin ucsipn ucsinp ucspin ucspni
ucsnpi ucsnip upncis upncsi upnics upnisc upnsic upnsci upcnis upcnsi upcins
upcisn upcsin upcsni upicns upicsn upincs upinsc upisnc upiscn upscin upscni
upsicn upsinc upsnic upsnci usncpi usncip usnpci usnpic usnipc usnicp uscnpi
uscnip uscpni uscpin uscipn uscinp uspcni uspcin uspnci uspnic uspinc uspicn
usicpn usicnp usipcn usipnc usinpc usincp sincup sincpu sinucp sinupc sinpuc
sinpcu sicnup sicnpu sicunp sicupn sicpun sicpnu siucnp siucpn siuncp siunpc
siupnc siupcn sipcun sipcnu sipucn sipunc sipnuc sipncu snicup snicpu sniucp
sniupc snipuc snipcu snciup sncipu sncuip sncupi sncpui sncpiu snucip snucpi
snuicp snuipc snupic snupci snpcui snpciu snpuci snpuic snpiuc snpicu scniup
scnipu scnuip scnupi scnpui scnpiu scinup scinpu sciunp sciupn scipun scipnu
scuinp scuipn scunip scunpi scupni scupin scpiun scpinu scpuin scpuni scpnui
scpniu suncip suncpi sunicp sunipc sunpic sunpci sucnip sucnpi sucinp sucipn
sucpin sucpni suicnp suicpn suincp suinpc suipnc suipcn supcin supcni supicn
supinc supnic supnci spncui spnciu spnuci spnuic spniuc spnicu spcnui spcniu
spcuni spcuin spciun spcinu spucni spucin spunci spunic spuinc spuicn spicun
spicnu spiucn spiunc spinuc spincu

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History of cryptography
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