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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: buskey
cipher variations:
cvtlfz dwumga exvnhb fywoic gzxpjd
hayqke ibzrlf jcasmg kdbtnh lecuoi
mfdvpj ngewqk ohfxrl pigysm qjhztn
rkiauo sljbvp tmkcwq unldxr vomeys
wpnfzt xqogau yrphbv zsqicw atrjdx

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: buskey
Cipher: yfhpvb

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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: buskey

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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: buskey
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: buskey
Cipher: ohfxrl

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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: buskey
Cipher: 215434525145

Extended Methods:
Method #1

Plaintext: buskey
method variations:

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

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Method #3

Plaintext: buskey
method variations:
voywqk oywqkv ywqkvo
wqkvoy qkvoyw kvoywq

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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: buskey

all 720 cipher variations:
buskey buskye buseky buseyk busyek busyke buksey buksye bukesy bukeys bukyes
bukyse bueksy buekys buesky buesyk bueysk bueyks buykes buykse buyeks buyesk
buysek buyske bsukey bsukye bsueky bsueyk bsuyek bsuyke bskuey bskuye bskeuy
bskeyu bskyeu bskyue bsekuy bsekyu bseuky bseuyk bseyuk bseyku bsykeu bsykue
bsyeku bsyeuk bsyuek bsyuke bksuey bksuye bkseuy bkseyu bksyeu bksyue bkusey
bkusye bkuesy bkueys bkuyes bkuyse bkeusy bkeuys bkesuy bkesyu bkeysu bkeyus
bkyues bkyuse bkyeus bkyesu bkyseu bkysue beskuy beskyu besuky besuyk besyuk
besyku beksuy beksyu bekusy bekuys bekyus bekysu beuksy beukys beusky beusyk
beuysk beuyks beykus beyksu beyuks beyusk beysuk beysku byskeu byskue byseku
byseuk bysuek bysuke bykseu byksue bykesu bykeus bykues bykuse byeksu byekus
byesku byesuk byeusk byeuks byukes byukse byueks byuesk byusek byuske ubskey
ubskye ubseky ubseyk ubsyek ubsyke ubksey ubksye ubkesy ubkeys ubkyes ubkyse
ubeksy ubekys ubesky ubesyk ubeysk ubeyks ubykes ubykse ubyeks ubyesk ubysek
ubyske usbkey usbkye usbeky usbeyk usbyek usbyke uskbey uskbye uskeby uskeyb
uskyeb uskybe usekby usekyb usebky usebyk useybk useykb usykeb usykbe usyekb
usyebk usybek usybke uksbey uksbye ukseby ukseyb uksyeb uksybe ukbsey ukbsye
ukbesy ukbeys ukbyes ukbyse ukebsy ukebys ukesby ukesyb ukeysb ukeybs ukybes
ukybse ukyebs ukyesb ukyseb ukysbe ueskby ueskyb uesbky uesbyk uesybk uesykb
ueksby ueksyb uekbsy uekbys uekybs uekysb uebksy uebkys uebsky uebsyk uebysk
uebyks ueykbs ueyksb ueybks ueybsk ueysbk ueyskb uyskeb uyskbe uysekb uysebk
uysbek uysbke uykseb uyksbe uykesb uykebs uykbes uykbse uyeksb uyekbs uyeskb
uyesbk uyebsk uyebks uybkes uybkse uybeks uybesk uybsek uybske subkey subkye
subeky subeyk subyek subyke sukbey sukbye sukeby sukeyb sukyeb sukybe suekby
suekyb suebky suebyk sueybk sueykb suykeb suykbe suyekb suyebk suybek suybke
sbukey sbukye sbueky sbueyk sbuyek sbuyke sbkuey sbkuye sbkeuy sbkeyu sbkyeu
sbkyue sbekuy sbekyu sbeuky sbeuyk sbeyuk sbeyku sbykeu sbykue sbyeku sbyeuk
sbyuek sbyuke skbuey skbuye skbeuy skbeyu skbyeu skbyue skubey skubye skueby
skueyb skuyeb skuybe skeuby skeuyb skebuy skebyu skeybu skeyub skyueb skyube
skyeub skyebu skybeu skybue sebkuy sebkyu sebuky sebuyk sebyuk sebyku sekbuy
sekbyu sekuby sekuyb sekyub sekybu seukby seukyb seubky seubyk seuybk seuykb
seykub seykbu seyukb seyubk seybuk seybku sybkeu sybkue sybeku sybeuk sybuek
sybuke sykbeu sykbue sykebu sykeub sykueb sykube syekbu syekub syebku syebuk
syeubk syeukb syukeb syukbe syuekb syuebk syubek syubke kusbey kusbye kuseby
kuseyb kusyeb kusybe kubsey kubsye kubesy kubeys kubyes kubyse kuebsy kuebys
kuesby kuesyb kueysb kueybs kuybes kuybse kuyebs kuyesb kuyseb kuysbe ksubey
ksubye ksueby ksueyb ksuyeb ksuybe ksbuey ksbuye ksbeuy ksbeyu ksbyeu ksbyue
ksebuy ksebyu kseuby kseuyb kseyub kseybu ksybeu ksybue ksyebu ksyeub ksyueb
ksyube kbsuey kbsuye kbseuy kbseyu kbsyeu kbsyue kbusey kbusye kbuesy kbueys
kbuyes kbuyse kbeusy kbeuys kbesuy kbesyu kbeysu kbeyus kbyues kbyuse kbyeus
kbyesu kbyseu kbysue kesbuy kesbyu kesuby kesuyb kesyub kesybu kebsuy kebsyu
kebusy kebuys kebyus kebysu keubsy keubys keusby keusyb keuysb keuybs keybus
keybsu keyubs keyusb keysub keysbu kysbeu kysbue kysebu kyseub kysueb kysube
kybseu kybsue kybesu kybeus kybues kybuse kyebsu kyebus kyesbu kyesub kyeusb
kyeubs kyubes kyubse kyuebs kyuesb kyuseb kyusbe euskby euskyb eusbky eusbyk
eusybk eusykb euksby euksyb eukbsy eukbys eukybs eukysb eubksy eubkys eubsky
eubsyk eubysk eubyks euykbs euyksb euybks euybsk euysbk euyskb esukby esukyb
esubky esubyk esuybk esuykb eskuby eskuyb eskbuy eskbyu eskybu eskyub esbkuy
esbkyu esbuky esbuyk esbyuk esbyku esykbu esykub esybku esybuk esyubk esyukb
eksuby eksuyb eksbuy eksbyu eksybu eksyub ekusby ekusyb ekubsy ekubys ekuybs
ekuysb ekbusy ekbuys ekbsuy ekbsyu ekbysu ekbyus ekyubs ekyusb ekybus ekybsu
ekysbu ekysub ebskuy ebskyu ebsuky ebsuyk ebsyuk ebsyku ebksuy ebksyu ebkusy
ebkuys ebkyus ebkysu ebuksy ebukys ebusky ebusyk ebuysk ebuyks ebykus ebyksu
ebyuks ebyusk ebysuk ebysku eyskbu eyskub eysbku eysbuk eysubk eysukb eyksbu
eyksub eykbsu eykbus eykubs eykusb eybksu eybkus eybsku eybsuk eybusk eybuks
eyukbs eyuksb eyubks eyubsk eyusbk eyuskb yuskeb yuskbe yusekb yusebk yusbek
yusbke yukseb yuksbe yukesb yukebs yukbes yukbse yueksb yuekbs yueskb yuesbk
yuebsk yuebks yubkes yubkse yubeks yubesk yubsek yubske ysukeb ysukbe ysuekb
ysuebk ysubek ysubke yskueb yskube yskeub yskebu yskbeu yskbue ysekub ysekbu
yseukb yseubk ysebuk ysebku ysbkeu ysbkue ysbeku ysbeuk ysbuek ysbuke yksueb
yksube ykseub yksebu yksbeu yksbue ykuseb ykusbe ykuesb ykuebs ykubes ykubse
ykeusb ykeubs ykesub ykesbu ykebsu ykebus ykbues ykbuse ykbeus ykbesu ykbseu
ykbsue yeskub yeskbu yesukb yesubk yesbuk yesbku yeksub yeksbu yekusb yekubs
yekbus yekbsu yeuksb yeukbs yeuskb yeusbk yeubsk yeubks yebkus yebksu yebuks
yebusk yebsuk yebsku ybskeu ybskue ybseku ybseuk ybsuek ybsuke ybkseu ybksue
ybkesu ybkeus ybkues ybkuse ybeksu ybekus ybesku ybesuk ybeusk ybeuks ybukes
ybukse ybueks ybuesk ybusek ybuske

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History of cryptography
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