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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: hungpc
cipher variations:
ivohqd jwpire kxqjsf lyrktg mzsluh
natmvi obunwj pcvoxk qdwpyl rexqzm
sfyran tgzsbo uhatcp vibudq wjcver
xkdwfs ylexgt zmfyhu angziv bohajw
cpibkx dqjcly erkdmz fslena gtmfob

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: hungpc
Cipher: sfmtkx

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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: hungpc

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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: hungpc
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: hungpc
Cipher: uhatcp

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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: hungpc
Cipher: 325433225331

Extended Methods:
Method #1

Plaintext: hungpc
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
h u n g p c 
3 5 3 2 5 3 
2 4 3 2 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: hungpc
Cipher: xhprhc

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Method #3

Plaintext: hungpc
method variations:
wohwnl ohwnlw hwnlwo
wnlwoh nlwohw lwohwn

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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: hungpc

all 720 cipher variations:
hungpc hungcp hunpgc hunpcg huncpg huncgp hugnpc hugncp hugpnc hugpcn hugcpn
hugcnp hupgnc hupgcn hupngc hupncg hupcng hupcgn hucgpn hucgnp hucpgn hucpng
hucnpg hucngp hnugpc hnugcp hnupgc hnupcg hnucpg hnucgp hngupc hngucp hngpuc
hngpcu hngcpu hngcup hnpguc hnpgcu hnpugc hnpucg hnpcug hnpcgu hncgpu hncgup
hncpgu hncpug hncupg hncugp hgnupc hgnucp hgnpuc hgnpcu hgncpu hgncup hgunpc
hguncp hgupnc hgupcn hgucpn hgucnp hgpunc hgpucn hgpnuc hgpncu hgpcnu hgpcun
hgcupn hgcunp hgcpun hgcpnu hgcnpu hgcnup hpnguc hpngcu hpnugc hpnucg hpncug
hpncgu hpgnuc hpgncu hpgunc hpgucn hpgcun hpgcnu hpugnc hpugcn hpungc hpuncg
hpucng hpucgn hpcgun hpcgnu hpcugn hpcung hpcnug hpcngu hcngpu hcngup hcnpgu
hcnpug hcnupg hcnugp hcgnpu hcgnup hcgpnu hcgpun hcgupn hcgunp hcpgnu hcpgun
hcpngu hcpnug hcpung hcpugn hcugpn hcugnp hcupgn hcupng hcunpg hcungp uhngpc
uhngcp uhnpgc uhnpcg uhncpg uhncgp uhgnpc uhgncp uhgpnc uhgpcn uhgcpn uhgcnp
uhpgnc uhpgcn uhpngc uhpncg uhpcng uhpcgn uhcgpn uhcgnp uhcpgn uhcpng uhcnpg
uhcngp unhgpc unhgcp unhpgc unhpcg unhcpg unhcgp unghpc unghcp ungphc ungpch
ungcph ungchp unpghc unpgch unphgc unphcg unpchg unpcgh uncgph uncghp uncpgh
uncphg unchpg unchgp ugnhpc ugnhcp ugnphc ugnpch ugncph ugnchp ughnpc ughncp
ughpnc ughpcn ughcpn ughcnp ugphnc ugphcn ugpnhc ugpnch ugpcnh ugpchn ugchpn
ugchnp ugcphn ugcpnh ugcnph ugcnhp upnghc upngch upnhgc upnhcg upnchg upncgh
upgnhc upgnch upghnc upghcn upgchn upgcnh uphgnc uphgcn uphngc uphncg uphcng
uphcgn upcghn upcgnh upchgn upchng upcnhg upcngh ucngph ucnghp ucnpgh ucnphg
ucnhpg ucnhgp ucgnph ucgnhp ucgpnh ucgphn ucghpn ucghnp ucpgnh ucpghn ucpngh
ucpnhg ucphng ucphgn uchgpn uchgnp uchpgn uchpng uchnpg uchngp nuhgpc nuhgcp
nuhpgc nuhpcg nuhcpg nuhcgp nughpc nughcp nugphc nugpch nugcph nugchp nupghc
nupgch nuphgc nuphcg nupchg nupcgh nucgph nucghp nucpgh nucphg nuchpg nuchgp
nhugpc nhugcp nhupgc nhupcg nhucpg nhucgp nhgupc nhgucp nhgpuc nhgpcu nhgcpu
nhgcup nhpguc nhpgcu nhpugc nhpucg nhpcug nhpcgu nhcgpu nhcgup nhcpgu nhcpug
nhcupg nhcugp nghupc nghucp nghpuc nghpcu nghcpu nghcup nguhpc nguhcp nguphc
ngupch ngucph nguchp ngpuhc ngpuch ngphuc ngphcu ngpchu ngpcuh ngcuph ngcuhp
ngcpuh ngcphu ngchpu ngchup nphguc nphgcu nphugc nphucg nphcug nphcgu npghuc
npghcu npguhc npguch npgcuh npgchu npughc npugch npuhgc npuhcg npuchg npucgh
npcguh npcghu npcugh npcuhg npchug npchgu nchgpu nchgup nchpgu nchpug nchupg
nchugp ncghpu ncghup ncgphu ncgpuh ncguph ncguhp ncpghu ncpguh ncphgu ncphug
ncpuhg ncpugh ncugph ncughp ncupgh ncuphg ncuhpg ncuhgp gunhpc gunhcp gunphc
gunpch guncph gunchp guhnpc guhncp guhpnc guhpcn guhcpn guhcnp guphnc guphcn
gupnhc gupnch gupcnh gupchn guchpn guchnp gucphn gucpnh gucnph gucnhp gnuhpc
gnuhcp gnuphc gnupch gnucph gnuchp gnhupc gnhucp gnhpuc gnhpcu gnhcpu gnhcup
gnphuc gnphcu gnpuhc gnpuch gnpcuh gnpchu gnchpu gnchup gncphu gncpuh gncuph
gncuhp ghnupc ghnucp ghnpuc ghnpcu ghncpu ghncup ghunpc ghuncp ghupnc ghupcn
ghucpn ghucnp ghpunc ghpucn ghpnuc ghpncu ghpcnu ghpcun ghcupn ghcunp ghcpun
ghcpnu ghcnpu ghcnup gpnhuc gpnhcu gpnuhc gpnuch gpncuh gpnchu gphnuc gphncu
gphunc gphucn gphcun gphcnu gpuhnc gpuhcn gpunhc gpunch gpucnh gpuchn gpchun
gpchnu gpcuhn gpcunh gpcnuh gpcnhu gcnhpu gcnhup gcnphu gcnpuh gcnuph gcnuhp
gchnpu gchnup gchpnu gchpun gchupn gchunp gcphnu gcphun gcpnhu gcpnuh gcpunh
gcpuhn gcuhpn gcuhnp gcuphn gcupnh gcunph gcunhp punghc pungch punhgc punhcg
punchg puncgh pugnhc pugnch pughnc pughcn pugchn pugcnh puhgnc puhgcn puhngc
puhncg puhcng puhcgn pucghn pucgnh puchgn puchng pucnhg pucngh pnughc pnugch
pnuhgc pnuhcg pnuchg pnucgh pnguhc pnguch pnghuc pnghcu pngchu pngcuh pnhguc
pnhgcu pnhugc pnhucg pnhcug pnhcgu pncghu pncguh pnchgu pnchug pncuhg pncugh
pgnuhc pgnuch pgnhuc pgnhcu pgnchu pgncuh pgunhc pgunch pguhnc pguhcn pguchn
pgucnh pghunc pghucn pghnuc pghncu pghcnu pghcun pgcuhn pgcunh pgchun pgchnu
pgcnhu pgcnuh phnguc phngcu phnugc phnucg phncug phncgu phgnuc phgncu phgunc
phgucn phgcun phgcnu phugnc phugcn phungc phuncg phucng phucgn phcgun phcgnu
phcugn phcung phcnug phcngu pcnghu pcnguh pcnhgu pcnhug pcnuhg pcnugh pcgnhu
pcgnuh pcghnu pcghun pcguhn pcgunh pchgnu pchgun pchngu pchnug pchung pchugn
pcughn pcugnh pcuhgn pcuhng pcunhg pcungh cungph cunghp cunpgh cunphg cunhpg
cunhgp cugnph cugnhp cugpnh cugphn cughpn cughnp cupgnh cupghn cupngh cupnhg
cuphng cuphgn cuhgpn cuhgnp cuhpgn cuhpng cuhnpg cuhngp cnugph cnughp cnupgh
cnuphg cnuhpg cnuhgp cnguph cnguhp cngpuh cngphu cnghpu cnghup cnpguh cnpghu
cnpugh cnpuhg cnphug cnphgu cnhgpu cnhgup cnhpgu cnhpug cnhupg cnhugp cgnuph
cgnuhp cgnpuh cgnphu cgnhpu cgnhup cgunph cgunhp cgupnh cguphn cguhpn cguhnp
cgpunh cgpuhn cgpnuh cgpnhu cgphnu cgphun cghupn cghunp cghpun cghpnu cghnpu
cghnup cpnguh cpnghu cpnugh cpnuhg cpnhug cpnhgu cpgnuh cpgnhu cpgunh cpguhn
cpghun cpghnu cpugnh cpughn cpungh cpunhg cpuhng cpuhgn cphgun cphgnu cphugn
cphung cphnug cphngu chngpu chngup chnpgu chnpug chnupg chnugp chgnpu chgnup
chgpnu chgpun chgupn chgunp chpgnu chpgun chpngu chpnug chpung chpugn chugpn
chugnp chupgn chupng chunpg chungp

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History of cryptography
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