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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: thujyl
cipher variations:
uivkzm vjwlan wkxmbo xlyncp ymzodq
znaper aobqfs bpcrgt cqdshu dretiv
esfujw ftgvkx guhwly hvixmz iwjyna
jxkzob kylapc lzmbqd mancre nbodsf
ocpetg pdqfuh qergvi rfshwj sgtixk

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: thujyl
Cipher: gsfqbo

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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: thujyl

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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: thujyl
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: thujyl
Cipher: guhwly

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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: thujyl
Cipher: 443254424513

Extended Methods:
Method #1

Plaintext: thujyl
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
t h u j y l 
4 3 5 4 4 1 
4 2 4 2 5 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: thujyl
Cipher: oudiip

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Method #3

Plaintext: thujyl
method variations:
owtres wtreso tresow
resowt esowtr sowtre

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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: thujyl

all 720 cipher variations:
thujyl thujly thuyjl thuylj thulyj thuljy thjuyl thjuly thjyul thjylu thjlyu
thjluy thyjul thyjlu thyujl thyulj thyluj thylju thljyu thljuy thlyju thlyuj
thluyj thlujy tuhjyl tuhjly tuhyjl tuhylj tuhlyj tuhljy tujhyl tujhly tujyhl
tujylh tujlyh tujlhy tuyjhl tuyjlh tuyhjl tuyhlj tuylhj tuyljh tuljyh tuljhy
tulyjh tulyhj tulhyj tulhjy tjuhyl tjuhly tjuyhl tjuylh tjulyh tjulhy tjhuyl
tjhuly tjhyul tjhylu tjhlyu tjhluy tjyhul tjyhlu tjyuhl tjyulh tjyluh tjylhu
tjlhyu tjlhuy tjlyhu tjlyuh tjluyh tjluhy tyujhl tyujlh tyuhjl tyuhlj tyulhj
tyuljh tyjuhl tyjulh tyjhul tyjhlu tyjlhu tyjluh tyhjul tyhjlu tyhujl tyhulj
tyhluj tyhlju tyljhu tyljuh tylhju tylhuj tyluhj tylujh tlujyh tlujhy tluyjh
tluyhj tluhyj tluhjy tljuyh tljuhy tljyuh tljyhu tljhyu tljhuy tlyjuh tlyjhu
tlyujh tlyuhj tlyhuj tlyhju tlhjyu tlhjuy tlhyju tlhyuj tlhuyj tlhujy htujyl
htujly htuyjl htuylj htulyj htuljy htjuyl htjuly htjyul htjylu htjlyu htjluy
htyjul htyjlu htyujl htyulj htyluj htylju htljyu htljuy htlyju htlyuj htluyj
htlujy hutjyl hutjly hutyjl hutylj hutlyj hutljy hujtyl hujtly hujytl hujylt
hujlyt hujlty huyjtl huyjlt huytjl huytlj huyltj huyljt huljyt huljty hulyjt
hulytj hultyj hultjy hjutyl hjutly hjuytl hjuylt hjulyt hjulty hjtuyl hjtuly
hjtyul hjtylu hjtlyu hjtluy hjytul hjytlu hjyutl hjyult hjylut hjyltu hjltyu
hjltuy hjlytu hjlyut hjluyt hjluty hyujtl hyujlt hyutjl hyutlj hyultj hyuljt
hyjutl hyjult hyjtul hyjtlu hyjltu hyjlut hytjul hytjlu hytujl hytulj hytluj
hytlju hyljtu hyljut hyltju hyltuj hylutj hylujt hlujyt hlujty hluyjt hluytj
hlutyj hlutjy hljuyt hljuty hljyut hljytu hljtyu hljtuy hlyjut hlyjtu hlyujt
hlyutj hlytuj hlytju hltjyu hltjuy hltyju hltyuj hltuyj hltujy uhtjyl uhtjly
uhtyjl uhtylj uhtlyj uhtljy uhjtyl uhjtly uhjytl uhjylt uhjlyt uhjlty uhyjtl
uhyjlt uhytjl uhytlj uhyltj uhyljt uhljyt uhljty uhlyjt uhlytj uhltyj uhltjy
uthjyl uthjly uthyjl uthylj uthlyj uthljy utjhyl utjhly utjyhl utjylh utjlyh
utjlhy utyjhl utyjlh utyhjl utyhlj utylhj utyljh utljyh utljhy utlyjh utlyhj
utlhyj utlhjy ujthyl ujthly ujtyhl ujtylh ujtlyh ujtlhy ujhtyl ujhtly ujhytl
ujhylt ujhlyt ujhlty ujyhtl ujyhlt ujythl ujytlh ujylth ujylht ujlhyt ujlhty
ujlyht ujlyth ujltyh ujlthy uytjhl uytjlh uythjl uythlj uytlhj uytljh uyjthl
uyjtlh uyjhtl uyjhlt uyjlht uyjlth uyhjtl uyhjlt uyhtjl uyhtlj uyhltj uyhljt
uyljht uyljth uylhjt uylhtj uylthj uyltjh ultjyh ultjhy ultyjh ultyhj ulthyj
ulthjy uljtyh uljthy uljyth uljyht uljhyt uljhty ulyjth ulyjht ulytjh ulythj
ulyhtj ulyhjt ulhjyt ulhjty ulhyjt ulhytj ulhtyj ulhtjy jhutyl jhutly jhuytl
jhuylt jhulyt jhulty jhtuyl jhtuly jhtyul jhtylu jhtlyu jhtluy jhytul jhytlu
jhyutl jhyult jhylut jhyltu jhltyu jhltuy jhlytu jhlyut jhluyt jhluty juhtyl
juhtly juhytl juhylt juhlyt juhlty juthyl juthly jutyhl jutylh jutlyh jutlhy
juythl juytlh juyhtl juyhlt juylht juylth jultyh julthy julyth julyht julhyt
julhty jtuhyl jtuhly jtuyhl jtuylh jtulyh jtulhy jthuyl jthuly jthyul jthylu
jthlyu jthluy jtyhul jtyhlu jtyuhl jtyulh jtyluh jtylhu jtlhyu jtlhuy jtlyhu
jtlyuh jtluyh jtluhy jyuthl jyutlh jyuhtl jyuhlt jyulht jyulth jytuhl jytulh
jythul jythlu jytlhu jytluh jyhtul jyhtlu jyhutl jyhult jyhlut jyhltu jylthu
jyltuh jylhtu jylhut jyluht jyluth jlutyh jluthy jluyth jluyht jluhyt jluhty
jltuyh jltuhy jltyuh jltyhu jlthyu jlthuy jlytuh jlythu jlyuth jlyuht jlyhut
jlyhtu jlhtyu jlhtuy jlhytu jlhyut jlhuyt jlhuty yhujtl yhujlt yhutjl yhutlj
yhultj yhuljt yhjutl yhjult yhjtul yhjtlu yhjltu yhjlut yhtjul yhtjlu yhtujl
yhtulj yhtluj yhtlju yhljtu yhljut yhltju yhltuj yhlutj yhlujt yuhjtl yuhjlt
yuhtjl yuhtlj yuhltj yuhljt yujhtl yujhlt yujthl yujtlh yujlth yujlht yutjhl
yutjlh yuthjl yuthlj yutlhj yutljh yuljth yuljht yultjh yulthj yulhtj yulhjt
yjuhtl yjuhlt yjuthl yjutlh yjulth yjulht yjhutl yjhult yjhtul yjhtlu yjhltu
yjhlut yjthul yjthlu yjtuhl yjtulh yjtluh yjtlhu yjlhtu yjlhut yjlthu yjltuh
yjluth yjluht ytujhl ytujlh ytuhjl ytuhlj ytulhj ytuljh ytjuhl ytjulh ytjhul
ytjhlu ytjlhu ytjluh ythjul ythjlu ythujl ythulj ythluj ythlju ytljhu ytljuh
ytlhju ytlhuj ytluhj ytlujh ylujth ylujht ylutjh yluthj yluhtj yluhjt yljuth
yljuht yljtuh yljthu yljhtu yljhut yltjuh yltjhu yltujh yltuhj ylthuj ylthju
ylhjtu ylhjut ylhtju ylhtuj ylhutj ylhujt lhujyt lhujty lhuyjt lhuytj lhutyj
lhutjy lhjuyt lhjuty lhjyut lhjytu lhjtyu lhjtuy lhyjut lhyjtu lhyujt lhyutj
lhytuj lhytju lhtjyu lhtjuy lhtyju lhtyuj lhtuyj lhtujy luhjyt luhjty luhyjt
luhytj luhtyj luhtjy lujhyt lujhty lujyht lujyth lujtyh lujthy luyjht luyjth
luyhjt luyhtj luythj luytjh lutjyh lutjhy lutyjh lutyhj luthyj luthjy ljuhyt
ljuhty ljuyht ljuyth ljutyh ljuthy ljhuyt ljhuty ljhyut ljhytu ljhtyu ljhtuy
ljyhut ljyhtu ljyuht ljyuth ljytuh ljythu ljthyu ljthuy ljtyhu ljtyuh ljtuyh
ljtuhy lyujht lyujth lyuhjt lyuhtj lyuthj lyutjh lyjuht lyjuth lyjhut lyjhtu
lyjthu lyjtuh lyhjut lyhjtu lyhujt lyhutj lyhtuj lyhtju lytjhu lytjuh lythju
lythuj lytuhj lytujh ltujyh ltujhy ltuyjh ltuyhj ltuhyj ltuhjy ltjuyh ltjuhy
ltjyuh ltjyhu ltjhyu ltjhuy ltyjuh ltyjhu ltyujh ltyuhj ltyhuj ltyhju lthjyu
lthjuy lthyju lthyuj lthuyj lthujy

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History of cryptography
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