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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: tyriis
cipher variations:
uzsjjt vatkku wbullv xcvmmw ydwnnx
zexooy afyppz bgzqqa charrb dibssc
ejcttd fkduue glevvf hmfwwg ingxxh
johyyi kpizzj lqjaak mrkbbl nslccm
otmddn puneeo qvoffp rwpggq sxqhhr

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: tyriis
Cipher: gbirrh

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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: tyriis

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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: tyriis
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: tyriis
Cipher: glevvf

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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: tyriis
Cipher: 444524424234

Extended Methods:
Method #1

Plaintext: tyriis
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
t y r i i s 
4 4 2 4 4 3 
4 5 4 2 2 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: tyriis
Cipher: troyir

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Method #3

Plaintext: tyriis
method variations:
tktrmt ktrmtt trmttk
rmttkt mttktr ttktrm

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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: tyriis

all 720 cipher variations:
tyriis tyrisi tyriis tyrisi tyrsii tyrsii tyiris tyirsi tyiirs tyiisr tyisir
tyisri tyiirs tyiisr tyiris tyirsi tyisri tyisir tysiir tysiri tysiir tysiri
tysrii tysrii tryiis tryisi tryiis tryisi trysii trysii triyis triysi triiys
triisy trisiy trisyi triiys triisy triyis triysi trisyi trisiy trsiiy trsiyi
trsiiy trsiyi trsyii trsyii tiryis tirysi tiriys tirisy tirsiy tirsyi tiyris
tiyrsi tiyirs tiyisr tiysir tiysri tiiyrs tiiysr tiirys tiirsy tiisry tiisyr
tisyir tisyri tisiyr tisiry tisriy tisryi tiriys tirisy tiryis tirysi tirsyi
tirsiy tiirys tiirsy tiiyrs tiiysr tiisyr tiisry tiyirs tiyisr tiyris tiyrsi
tiysri tiysir tisiyr tisiry tisyir tisyri tisryi tisriy tsriiy tsriyi tsriiy
tsriyi tsryii tsryii tsiriy tsiryi tsiiry tsiiyr tsiyir tsiyri tsiiry tsiiyr
tsiriy tsiryi tsiyri tsiyir tsyiir tsyiri tsyiir tsyiri tsyrii tsyrii ytriis
ytrisi ytriis ytrisi ytrsii ytrsii ytiris ytirsi ytiirs ytiisr ytisir ytisri
ytiirs ytiisr ytiris ytirsi ytisri ytisir ytsiir ytsiri ytsiir ytsiri ytsrii
ytsrii yrtiis yrtisi yrtiis yrtisi yrtsii yrtsii yritis yritsi yriits yriist
yrisit yristi yriits yriist yritis yritsi yristi yrisit yrsiit yrsiti yrsiit
yrsiti yrstii yrstii yirtis yirtsi yirits yirist yirsit yirsti yitris yitrsi
yitirs yitisr yitsir yitsri yiitrs yiitsr yiirts yiirst yiisrt yiistr yistir
yistri yisitr yisirt yisrit yisrti yirits yirist yirtis yirtsi yirsti yirsit
yiirts yiirst yiitrs yiitsr yiistr yiisrt yitirs yitisr yitris yitrsi yitsri
yitsir yisitr yisirt yistir yistri yisrti yisrit ysriit ysriti ysriit ysriti
ysrtii ysrtii ysirit ysirti ysiirt ysiitr ysitir ysitri ysiirt ysiitr ysirit
ysirti ysitri ysitir ystiir ystiri ystiir ystiri ystrii ystrii rytiis rytisi
rytiis rytisi rytsii rytsii ryitis ryitsi ryiits ryiist ryisit ryisti ryiits
ryiist ryitis ryitsi ryisti ryisit rysiit rysiti rysiit rysiti rystii rystii
rtyiis rtyisi rtyiis rtyisi rtysii rtysii rtiyis rtiysi rtiiys rtiisy rtisiy
rtisyi rtiiys rtiisy rtiyis rtiysi rtisyi rtisiy rtsiiy rtsiyi rtsiiy rtsiyi
rtsyii rtsyii rityis ritysi ritiys ritisy ritsiy ritsyi riytis riytsi riyits
riyist riysit riysti riiyts riiyst riitys riitsy riisty riisyt risyit risyti
risiyt risity ristiy ristyi ritiys ritisy rityis ritysi ritsyi ritsiy riitys
riitsy riiyts riiyst riisyt riisty riyits riyist riytis riytsi riysti riysit
risiyt risity risyit risyti ristyi ristiy rstiiy rstiyi rstiiy rstiyi rstyii
rstyii rsitiy rsityi rsiity rsiiyt rsiyit rsiyti rsiity rsiiyt rsitiy rsityi
rsiyti rsiyit rsyiit rsyiti rsyiit rsyiti rsytii rsytii iyrtis iyrtsi iyrits
iyrist iyrsit iyrsti iytris iytrsi iytirs iytisr iytsir iytsri iyitrs iyitsr
iyirts iyirst iyisrt iyistr iystir iystri iysitr iysirt iysrit iysrti irytis
irytsi iryits iryist irysit irysti irtyis irtysi irtiys irtisy irtsiy irtsyi
iritys iritsy iriyts iriyst irisyt iristy irstiy irstyi irsity irsiyt irsyit
irsyti itryis itrysi itriys itrisy itrsiy itrsyi ityris ityrsi ityirs ityisr
itysir itysri itiyrs itiysr itirys itirsy itisry itisyr itsyir itsyri itsiyr
itsiry itsriy itsryi iirtys iirtsy iiryts iiryst iirsyt iirsty iitrys iitrsy
iityrs iitysr iitsyr iitsry iiytrs iiytsr iiyrts iiyrst iiysrt iiystr iistyr
iistry iisytr iisyrt iisryt iisrty isrtiy isrtyi isrity isriyt isryit isryti
istriy istryi istiry istiyr istyir istyri isitry isityr isirty isiryt isiyrt
isiytr isytir isytri isyitr isyirt isyrit isyrti iyrits iyrist iyrtis iyrtsi
iyrsti iyrsit iyirts iyirst iyitrs iyitsr iyistr iyisrt iytirs iytisr iytris
iytrsi iytsri iytsir iysitr iysirt iystir iystri iysrti iysrit iryits iryist
irytis irytsi irysti irysit iriyts iriyst iritys iritsy iristy irisyt irtiys
irtisy irtyis irtysi irtsyi irtsiy irsity irsiyt irstiy irstyi irsyti irsyit
iiryts iiryst iirtys iirtsy iirsty iirsyt iiyrts iiyrst iiytrs iiytsr iiystr
iiysrt iityrs iitysr iitrys iitrsy iitsry iitsyr iisytr iisyrt iistyr iistry
iisrty iisryt itriys itrisy itryis itrysi itrsyi itrsiy itirys itirsy itiyrs
itiysr itisyr itisry ityirs ityisr ityris ityrsi itysri itysir itsiyr itsiry
itsyir itsyri itsryi itsriy isrity isriyt isrtiy isrtyi isryti isryit isirty
isiryt isitry isityr isiytr isiyrt istiry istiyr istriy istryi istyri istyir
isyitr isyirt isytir isytri isyrti isyrit syriit syriti syriit syriti syrtii
syrtii syirit syirti syiirt syiitr syitir syitri syiirt syiitr syirit syirti
syitri syitir sytiir sytiri sytiir sytiri sytrii sytrii sryiit sryiti sryiit
sryiti srytii srytii sriyit sriyti sriiyt sriity sritiy srityi sriiyt sriity
sriyit sriyti srityi sritiy srtiiy srtiyi srtiiy srtiyi srtyii srtyii siryit
siryti siriyt sirity sirtiy sirtyi siyrit siyrti siyirt siyitr siytir siytri
siiyrt siiytr siiryt siirty siitry siityr sityir sityri sitiyr sitiry sitriy
sitryi siriyt sirity siryit siryti sirtyi sirtiy siiryt siirty siiyrt siiytr
siityr siitry siyirt siyitr siyrit siyrti siytri siytir sitiyr sitiry sityir
sityri sitryi sitriy striiy striyi striiy striyi stryii stryii stiriy stiryi
stiiry stiiyr stiyir stiyri stiiry stiiyr stiriy stiryi stiyri stiyir styiir
styiri styiir styiri styrii styrii

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History of cryptography
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