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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: hukill
cipher variations:
ivljmm jwmknn kxnloo lyompp mzpnqq
naqorr obrpss pcsqtt qdtruu reusvv
sfvtww tgwuxx uhxvyy viywzz wjzxaa
xkaybb ylbzcc zmcadd andbee boecff
cpfdgg dqgehh erhfii fsigjj gtjhkk

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: hukill
Cipher: sfproo

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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: hukill

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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: hukill
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: hukill
Cipher: uhxvyy

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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: hukill
Cipher: 325452421313

Extended Methods:
Method #1

Plaintext: hukill
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 k i l l 
3 5 5 4 1 1 
2 4 2 2 3 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: hukill
Cipher: xuargn

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Method #3

Plaintext: hukill
method variations:
wyrbcn yrbcnw rbcnwy
bcnwyr cnwyrb nwyrbc

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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: hukill

all 720 cipher variations:
hukill hukill huklil huklli huklli huklil huikll huikll huilkl huillk huillk
huilkl hulikl hulilk hulkil hulkli hullki hullik hulilk hulikl hullik hullki
hulkli hulkil hkuill hkuill hkulil hkulli hkulli hkulil hkiull hkiull hkilul
hkillu hkillu hkilul hkliul hklilu hkluil hkluli hkllui hklliu hklilu hkliul
hklliu hkllui hkluli hkluil hikull hikull hiklul hikllu hikllu hiklul hiukll
hiukll hiulkl hiullk hiullk hiulkl hilukl hilulk hilkul hilklu hillku hilluk
hilulk hilukl hilluk hillku hilklu hilkul hlkiul hlkilu hlkuil hlkuli hlklui
hlkliu hlikul hliklu hliukl hliulk hliluk hlilku hluikl hluilk hlukil hlukli
hlulki hlulik hlliuk hlliku hlluik hlluki hllkui hllkiu hlkilu hlkiul hlkliu
hlklui hlkuli hlkuil hliklu hlikul hlilku hliluk hliulk hliukl hlliku hlliuk
hllkiu hllkui hlluki hlluik hluilk hluikl hlulik hlulki hlukli hlukil uhkill
uhkill uhklil uhklli uhklli uhklil uhikll uhikll uhilkl uhillk uhillk uhilkl
uhlikl uhlilk uhlkil uhlkli uhllki uhllik uhlilk uhlikl uhllik uhllki uhlkli
uhlkil ukhill ukhill ukhlil ukhlli ukhlli ukhlil ukihll ukihll ukilhl ukillh
ukillh ukilhl uklihl uklilh uklhil uklhli ukllhi ukllih uklilh uklihl ukllih
ukllhi uklhli uklhil uikhll uikhll uiklhl uikllh uikllh uiklhl uihkll uihkll
uihlkl uihllk uihllk uihlkl uilhkl uilhlk uilkhl uilklh uillkh uillhk uilhlk
uilhkl uillhk uillkh uilklh uilkhl ulkihl ulkilh ulkhil ulkhli ulklhi ulklih
ulikhl uliklh ulihkl ulihlk ulilhk ulilkh ulhikl ulhilk ulhkil ulhkli ulhlki
ulhlik ullihk ullikh ullhik ullhki ullkhi ullkih ulkilh ulkihl ulklih ulklhi
ulkhli ulkhil uliklh ulikhl ulilkh ulilhk ulihlk ulihkl ullikh ullihk ullkih
ullkhi ullhki ullhik ulhilk ulhikl ulhlik ulhlki ulhkli ulhkil kuhill kuhill
kuhlil kuhlli kuhlli kuhlil kuihll kuihll kuilhl kuillh kuillh kuilhl kulihl
kulilh kulhil kulhli kullhi kullih kulilh kulihl kullih kullhi kulhli kulhil
khuill khuill khulil khulli khulli khulil khiull khiull khilul khillu khillu
khilul khliul khlilu khluil khluli khllui khlliu khlilu khliul khlliu khllui
khluli khluil kihull kihull kihlul kihllu kihllu kihlul kiuhll kiuhll kiulhl
kiullh kiullh kiulhl kiluhl kilulh kilhul kilhlu killhu killuh kilulh kiluhl
killuh killhu kilhlu kilhul klhiul klhilu klhuil klhuli klhlui klhliu klihul
klihlu kliuhl kliulh kliluh klilhu kluihl kluilh kluhil kluhli klulhi klulih
klliuh kllihu klluih klluhi kllhui kllhiu klhilu klhiul klhliu klhlui klhuli
klhuil klihlu klihul klilhu kliluh kliulh kliuhl kllihu klliuh kllhiu kllhui
klluhi klluih kluilh kluihl klulih klulhi kluhli kluhil iukhll iukhll iuklhl
iukllh iukllh iuklhl iuhkll iuhkll iuhlkl iuhllk iuhllk iuhlkl iulhkl iulhlk
iulkhl iulklh iullkh iullhk iulhlk iulhkl iullhk iullkh iulklh iulkhl ikuhll
ikuhll ikulhl ikullh ikullh ikulhl ikhull ikhull ikhlul ikhllu ikhllu ikhlul
iklhul iklhlu ikluhl iklulh iklluh ikllhu iklhlu iklhul ikllhu iklluh iklulh
ikluhl ihkull ihkull ihklul ihkllu ihkllu ihklul ihukll ihukll ihulkl ihullk
ihullk ihulkl ihlukl ihlulk ihlkul ihlklu ihllku ihlluk ihlulk ihlukl ihlluk
ihllku ihlklu ihlkul ilkhul ilkhlu ilkuhl ilkulh ilkluh ilklhu ilhkul ilhklu
ilhukl ilhulk ilhluk ilhlku iluhkl iluhlk ilukhl iluklh ilulkh ilulhk illhuk
illhku illuhk illukh illkuh illkhu ilkhlu ilkhul ilklhu ilkluh ilkulh ilkuhl
ilhklu ilhkul ilhlku ilhluk ilhulk ilhukl illhku illhuk illkhu illkuh illukh
illuhk iluhlk iluhkl ilulhk ilulkh iluklh ilukhl lukihl lukilh lukhil lukhli
luklhi luklih luikhl luiklh luihkl luihlk luilhk luilkh luhikl luhilk luhkil
luhkli luhlki luhlik lulihk lulikh lulhik lulhki lulkhi lulkih lkuihl lkuilh
lkuhil lkuhli lkulhi lkulih lkiuhl lkiulh lkihul lkihlu lkilhu lkiluh lkhiul
lkhilu lkhuil lkhuli lkhlui lkhliu lklihu lkliuh lklhiu lklhui lkluhi lkluih
likuhl likulh likhul likhlu liklhu likluh liukhl liuklh liuhkl liuhlk liulhk
liulkh lihukl lihulk lihkul lihklu lihlku lihluk liluhk lilukh lilhuk lilhku
lilkhu lilkuh lhkiul lhkilu lhkuil lhkuli lhklui lhkliu lhikul lhiklu lhiukl
lhiulk lhiluk lhilku lhuikl lhuilk lhukil lhukli lhulki lhulik lhliuk lhliku
lhluik lhluki lhlkui lhlkiu llkihu llkiuh llkhiu llkhui llkuhi llkuih llikhu
llikuh llihku llihuk lliuhk lliukh llhiku llhiuk llhkiu llhkui llhuki llhuik
lluihk lluikh lluhik lluhki llukhi llukih lukilh lukihl luklih luklhi lukhli
lukhil luiklh luikhl luilkh luilhk luihlk luihkl lulikh lulihk lulkih lulkhi
lulhki lulhik luhilk luhikl luhlik luhlki luhkli luhkil lkuilh lkuihl lkulih
lkulhi lkuhli lkuhil lkiulh lkiuhl lkiluh lkilhu lkihlu lkihul lkliuh lklihu
lkluih lkluhi lklhui lklhiu lkhilu lkhiul lkhliu lkhlui lkhuli lkhuil likulh
likuhl likluh liklhu likhlu likhul liuklh liukhl liulkh liulhk liuhlk liuhkl
lilukh liluhk lilkuh lilkhu lilhku lilhuk lihulk lihukl lihluk lihlku lihklu
lihkul llkiuh llkihu llkuih llkuhi llkhui llkhiu llikuh llikhu lliukh lliuhk
llihuk llihku lluikh lluihk llukih llukhi lluhki lluhik llhiuk llhiku llhuik
llhuki llhkui llhkiu lhkilu lhkiul lhkliu lhklui lhkuli lhkuil lhiklu lhikul
lhilku lhiluk lhiulk lhiukl lhliku lhliuk lhlkiu lhlkui lhluki lhluik lhuilk
lhuikl lhulik lhulki lhukli lhukil

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History of cryptography
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