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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: auntly
cipher variations:
bvoumz cwpvna dxqwob eyrxpc fzsyqd
gatzre hbuasf icvbtg jdwcuh kexdvi
lfyewj mgzfxk nhagyl oibhzm pjcian
qkdjbo rlekcp smfldq tngmer uohnfs
vpiogt wqjphu xrkqiv yslrjw ztmskx

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: auntly
Cipher: zfmgob

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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: auntly

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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: auntly
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: auntly
Cipher: nhagyl

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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: auntly
Cipher: 115433441345

Extended Methods:
Method #1

Plaintext: auntly
method variations:

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

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Method #3

Plaintext: auntly
method variations:
vosdse osdsev sdsevo
dsevos sevosd evosds

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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: auntly

all 720 cipher variations:
auntly auntyl aunlty aunlyt aunylt aunytl autnly autnyl autlny autlyn autyln
autynl aultny aultyn aulnty aulnyt aulynt aulytn auytln auytnl auyltn auylnt
auynlt auyntl anutly anutyl anulty anulyt anuylt anuytl antuly antuyl antluy
antlyu antylu antyul anltuy anltyu anluty anluyt anlyut anlytu anytlu anytul
anyltu anylut anyult anyutl atnuly atnuyl atnluy atnlyu atnylu atnyul atunly
atunyl atulny atulyn atuyln atuynl atluny atluyn atlnuy atlnyu atlynu atlyun
atyuln atyunl atylun atylnu atynlu atynul alntuy alntyu alnuty alnuyt alnyut
alnytu altnuy altnyu altuny altuyn altyun altynu alutny alutyn alunty alunyt
aluynt aluytn alytun alytnu alyutn alyunt alynut alyntu ayntlu ayntul aynltu
aynlut aynult aynutl aytnlu aytnul aytlnu aytlun aytuln aytunl ayltnu ayltun
aylntu aylnut aylunt aylutn ayutln ayutnl ayultn ayulnt ayunlt ayuntl uantly
uantyl uanlty uanlyt uanylt uanytl uatnly uatnyl uatlny uatlyn uatyln uatynl
ualtny ualtyn ualnty ualnyt ualynt ualytn uaytln uaytnl uayltn uaylnt uaynlt
uayntl unatly unatyl unalty unalyt unaylt unaytl untaly untayl untlay untlya
untyla untyal unltay unltya unlaty unlayt unlyat unlyta unytla unytal unylta
unylat unyalt unyatl utnaly utnayl utnlay utnlya utnyla utnyal utanly utanyl
utalny utalyn utayln utaynl utlany utlayn utlnay utlnya utlyna utlyan utyaln
utyanl utylan utylna utynla utynal ulntay ulntya ulnaty ulnayt ulnyat ulnyta
ultnay ultnya ultany ultayn ultyan ultyna ulatny ulatyn ulanty ulanyt ulaynt
ulaytn ulytan ulytna ulyatn ulyant ulynat ulynta uyntla uyntal uynlta uynlat
uynalt uynatl uytnla uytnal uytlna uytlan uytaln uytanl uyltna uyltan uylnta
uylnat uylant uylatn uyatln uyatnl uyaltn uyalnt uyanlt uyantl nuatly nuatyl
nualty nualyt nuaylt nuaytl nutaly nutayl nutlay nutlya nutyla nutyal nultay
nultya nulaty nulayt nulyat nulyta nuytla nuytal nuylta nuylat nuyalt nuyatl
nautly nautyl naulty naulyt nauylt nauytl natuly natuyl natluy natlyu natylu
natyul naltuy naltyu naluty naluyt nalyut nalytu naytlu naytul nayltu naylut
nayult nayutl ntauly ntauyl ntaluy ntalyu ntaylu ntayul ntualy ntuayl ntulay
ntulya ntuyla ntuyal ntluay ntluya ntlauy ntlayu ntlyau ntlyua ntyula ntyual
ntylua ntylau ntyalu ntyaul nlatuy nlatyu nlauty nlauyt nlayut nlaytu nltauy
nltayu nltuay nltuya nltyua nltyau nlutay nlutya nluaty nluayt nluyat nluyta
nlytua nlytau nlyuta nlyuat nlyaut nlyatu nyatlu nyatul nyaltu nyalut nyault
nyautl nytalu nytaul nytlau nytlua nytula nytual nyltau nyltua nylatu nylaut
nyluat nyluta nyutla nyutal nyulta nyulat nyualt nyuatl tunaly tunayl tunlay
tunlya tunyla tunyal tuanly tuanyl tualny tualyn tuayln tuaynl tulany tulayn
tulnay tulnya tulyna tulyan tuyaln tuyanl tuylan tuylna tuynla tuynal tnualy
tnuayl tnulay tnulya tnuyla tnuyal tnauly tnauyl tnaluy tnalyu tnaylu tnayul
tnlauy tnlayu tnluay tnluya tnlyua tnlyau tnyalu tnyaul tnylau tnylua tnyula
tnyual tanuly tanuyl tanluy tanlyu tanylu tanyul taunly taunyl taulny taulyn
tauyln tauynl taluny taluyn talnuy talnyu talynu talyun tayuln tayunl taylun
taylnu taynlu taynul tlnauy tlnayu tlnuay tlnuya tlnyua tlnyau tlanuy tlanyu
tlauny tlauyn tlayun tlaynu tluany tluayn tlunay tlunya tluyna tluyan tlyaun
tlyanu tlyuan tlyuna tlynua tlynau tynalu tynaul tynlau tynlua tynula tynual
tyanlu tyanul tyalnu tyalun tyauln tyaunl tylanu tylaun tylnau tylnua tyluna
tyluan tyualn tyuanl tyulan tyulna tyunla tyunal luntay luntya lunaty lunayt
lunyat lunyta lutnay lutnya lutany lutayn lutyan lutyna luatny luatyn luanty
luanyt luaynt luaytn luytan luytna luyatn luyant luynat luynta lnutay lnutya
lnuaty lnuayt lnuyat lnuyta lntuay lntuya lntauy lntayu lntyau lntyua lnatuy
lnatyu lnauty lnauyt lnayut lnaytu lnytau lnytua lnyatu lnyaut lnyuat lnyuta
ltnuay ltnuya ltnauy ltnayu ltnyau ltnyua ltunay ltunya ltuany ltuayn ltuyan
ltuyna ltauny ltauyn ltanuy ltanyu ltaynu ltayun ltyuan ltyuna ltyaun ltyanu
ltynau ltynua lantuy lantyu lanuty lanuyt lanyut lanytu latnuy latnyu latuny
latuyn latyun latynu lautny lautyn launty launyt lauynt lauytn laytun laytnu
layutn layunt laynut layntu lyntau lyntua lynatu lynaut lynuat lynuta lytnau
lytnua lytanu lytaun lytuan lytuna lyatnu lyatun lyantu lyanut lyaunt lyautn
lyutan lyutna lyuatn lyuant lyunat lyunta yuntla yuntal yunlta yunlat yunalt
yunatl yutnla yutnal yutlna yutlan yutaln yutanl yultna yultan yulnta yulnat
yulant yulatn yuatln yuatnl yualtn yualnt yuanlt yuantl ynutla ynutal ynulta
ynulat ynualt ynuatl yntula yntual yntlua yntlau yntalu yntaul ynltua ynltau
ynluta ynluat ynlaut ynlatu ynatlu ynatul ynaltu ynalut ynault ynautl ytnula
ytnual ytnlua ytnlau ytnalu ytnaul ytunla ytunal ytulna ytulan ytualn ytuanl
ytluna ytluan ytlnua ytlnau ytlanu ytlaun ytauln ytaunl ytalun ytalnu ytanlu
ytanul ylntua ylntau ylnuta ylnuat ylnaut ylnatu yltnua yltnau yltuna yltuan
yltaun yltanu ylutna ylutan ylunta ylunat yluant yluatn ylatun ylatnu ylautn
ylaunt ylanut ylantu yantlu yantul yanltu yanlut yanult yanutl yatnlu yatnul
yatlnu yatlun yatuln yatunl yaltnu yaltun yalntu yalnut yalunt yalutn yautln
yautnl yaultn yaulnt yaunlt yauntl

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History of cryptography
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