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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: sheafy
cipher variations:
tifbgz ujgcha vkhdib wliejc xmjfkd
ynkgle zolhmf apming bqnjoh crokpi
dsplqj etqmrk furnsl gvsotm hwtpun
ixuqvo jyvrwp kzwsxq laxtyr mbyuzs
nczvat odawbu pebxcv qfcydw rgdzex

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: sheafy
Cipher: hsvzub

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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: sheafy

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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: sheafy
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: sheafy
Cipher: furnsl

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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: sheafy
Cipher: 343251111245

Extended Methods:
Method #1

Plaintext: sheafy
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
s h e a f y 
3 3 5 1 1 4 
4 2 1 1 2 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: sheafy
Cipher: neqiaw

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Method #3

Plaintext: sheafy
method variations:
owaarp waarpo aarpow
arpowa rpowaa powaar

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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: sheafy

all 720 cipher variations:
sheafy sheayf shefay shefya sheyfa sheyaf shaefy shaeyf shafey shafye shayfe
shayef shfaey shfaye shfeay shfeya shfyea shfyae shyafe shyaef shyfae shyfea
shyefa shyeaf sehafy sehayf sehfay sehfya sehyfa sehyaf seahfy seahyf seafhy
seafyh seayfh seayhf sefahy sefayh sefhay sefhya sefyha sefyah seyafh seyahf
seyfah seyfha seyhfa seyhaf saehfy saehyf saefhy saefyh saeyfh saeyhf sahefy
saheyf sahfey sahfye sahyfe sahyef safhey safhye safehy safeyh safyeh safyhe
sayhfe sayhef sayfhe sayfeh sayefh sayehf sfeahy sfeayh sfehay sfehya sfeyha
sfeyah sfaehy sfaeyh sfahey sfahye sfayhe sfayeh sfhaey sfhaye sfheay sfheya
sfhyea sfhyae sfyahe sfyaeh sfyhae sfyhea sfyeha sfyeah syeafh syeahf syefah
syefha syehfa syehaf syaefh syaehf syafeh syafhe syahfe syahef syfaeh syfahe
syfeah syfeha syfhea syfhae syhafe syhaef syhfae syhfea syhefa syheaf hseafy
hseayf hsefay hsefya hseyfa hseyaf hsaefy hsaeyf hsafey hsafye hsayfe hsayef
hsfaey hsfaye hsfeay hsfeya hsfyea hsfyae hsyafe hsyaef hsyfae hsyfea hsyefa
hsyeaf hesafy hesayf hesfay hesfya hesyfa hesyaf heasfy heasyf heafsy heafys
heayfs heaysf hefasy hefays hefsay hefsya hefysa hefyas heyafs heyasf heyfas
heyfsa heysfa heysaf haesfy haesyf haefsy haefys haeyfs haeysf hasefy haseyf
hasfey hasfye hasyfe hasyef hafsey hafsye hafesy hafeys hafyes hafyse haysfe
haysef hayfse hayfes hayefs hayesf hfeasy hfeays hfesay hfesya hfeysa hfeyas
hfaesy hfaeys hfasey hfasye hfayse hfayes hfsaey hfsaye hfseay hfseya hfsyea
hfsyae hfyase hfyaes hfysae hfysea hfyesa hfyeas hyeafs hyeasf hyefas hyefsa
hyesfa hyesaf hyaefs hyaesf hyafes hyafse hyasfe hyasef hyfaes hyfase hyfeas
hyfesa hyfsea hyfsae hysafe hysaef hysfae hysfea hysefa hyseaf ehsafy ehsayf
ehsfay ehsfya ehsyfa ehsyaf ehasfy ehasyf ehafsy ehafys ehayfs ehaysf ehfasy
ehfays ehfsay ehfsya ehfysa ehfyas ehyafs ehyasf ehyfas ehyfsa ehysfa ehysaf
eshafy eshayf eshfay eshfya eshyfa eshyaf esahfy esahyf esafhy esafyh esayfh
esayhf esfahy esfayh esfhay esfhya esfyha esfyah esyafh esyahf esyfah esyfha
esyhfa esyhaf eashfy eashyf easfhy easfyh easyfh easyhf eahsfy eahsyf eahfsy
eahfys eahyfs eahysf eafhsy eafhys eafshy eafsyh eafysh eafyhs eayhfs eayhsf
eayfhs eayfsh eaysfh eayshf efsahy efsayh efshay efshya efsyha efsyah efashy
efasyh efahsy efahys efayhs efaysh efhasy efhays efhsay efhsya efhysa efhyas
efyahs efyash efyhas efyhsa efysha efysah eysafh eysahf eysfah eysfha eyshfa
eyshaf eyasfh eyashf eyafsh eyafhs eyahfs eyahsf eyfash eyfahs eyfsah eyfsha
eyfhsa eyfhas eyhafs eyhasf eyhfas eyhfsa eyhsfa eyhsaf ahesfy ahesyf ahefsy
ahefys aheyfs aheysf ahsefy ahseyf ahsfey ahsfye ahsyfe ahsyef ahfsey ahfsye
ahfesy ahfeys ahfyes ahfyse ahysfe ahysef ahyfse ahyfes ahyefs ahyesf aehsfy
aehsyf aehfsy aehfys aehyfs aehysf aeshfy aeshyf aesfhy aesfyh aesyfh aesyhf
aefshy aefsyh aefhsy aefhys aefyhs aefysh aeysfh aeyshf aeyfsh aeyfhs aeyhfs
aeyhsf asehfy asehyf asefhy asefyh aseyfh aseyhf ashefy asheyf ashfey ashfye
ashyfe ashyef asfhey asfhye asfehy asfeyh asfyeh asfyhe asyhfe asyhef asyfhe
asyfeh asyefh asyehf afeshy afesyh afehsy afehys afeyhs afeysh afsehy afseyh
afshey afshye afsyhe afsyeh afhsey afhsye afhesy afheys afhyes afhyse afyshe
afyseh afyhse afyhes afyehs afyesh ayesfh ayeshf ayefsh ayefhs ayehfs ayehsf
aysefh aysehf aysfeh aysfhe ayshfe ayshef ayfseh ayfshe ayfesh ayfehs ayfhes
ayfhse ayhsfe ayhsef ayhfse ayhfes ayhefs ayhesf fheasy fheays fhesay fhesya
fheysa fheyas fhaesy fhaeys fhasey fhasye fhayse fhayes fhsaey fhsaye fhseay
fhseya fhsyea fhsyae fhyase fhyaes fhysae fhysea fhyesa fhyeas fehasy fehays
fehsay fehsya fehysa fehyas feahsy feahys feashy feasyh feaysh feayhs fesahy
fesayh feshay feshya fesyha fesyah feyash feyahs feysah feysha feyhsa feyhas
faehsy faehys faeshy faesyh faeysh faeyhs fahesy faheys fahsey fahsye fahyse
fahyes fashey fashye fasehy faseyh fasyeh fasyhe fayhse fayhes fayshe fayseh
fayesh fayehs fseahy fseayh fsehay fsehya fseyha fseyah fsaehy fsaeyh fsahey
fsahye fsayhe fsayeh fshaey fshaye fsheay fsheya fshyea fshyae fsyahe fsyaeh
fsyhae fsyhea fsyeha fsyeah fyeash fyeahs fyesah fyesha fyehsa fyehas fyaesh
fyaehs fyaseh fyashe fyahse fyahes fysaeh fysahe fyseah fyseha fyshea fyshae
fyhase fyhaes fyhsae fyhsea fyhesa fyheas yheafs yheasf yhefas yhefsa yhesfa
yhesaf yhaefs yhaesf yhafes yhafse yhasfe yhasef yhfaes yhfase yhfeas yhfesa
yhfsea yhfsae yhsafe yhsaef yhsfae yhsfea yhsefa yhseaf yehafs yehasf yehfas
yehfsa yehsfa yehsaf yeahfs yeahsf yeafhs yeafsh yeasfh yeashf yefahs yefash
yefhas yefhsa yefsha yefsah yesafh yesahf yesfah yesfha yeshfa yeshaf yaehfs
yaehsf yaefhs yaefsh yaesfh yaeshf yahefs yahesf yahfes yahfse yahsfe yahsef
yafhes yafhse yafehs yafesh yafseh yafshe yashfe yashef yasfhe yasfeh yasefh
yasehf yfeahs yfeash yfehas yfehsa yfesha yfesah yfaehs yfaesh yfahes yfahse
yfashe yfaseh yfhaes yfhase yfheas yfhesa yfhsea yfhsae yfsahe yfsaeh yfshae
yfshea yfseha yfseah yseafh yseahf ysefah ysefha ysehfa ysehaf ysaefh ysaehf
ysafeh ysafhe ysahfe ysahef ysfaeh ysfahe ysfeah ysfeha ysfhea ysfhae yshafe
yshaef yshfae yshfea yshefa ysheaf

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History of cryptography
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