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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: myoung
cipher variations:
nzpvoh oaqwpi pbrxqj qcsyrk rdtzsl
seuatm tfvbun ugwcvo vhxdwp wiyexq
xjzfyr ykagzs zlbhat amcibu bndjcv
coekdw dpflex eqgmfy frhngz gsioha
htjpib iukqjc jvlrkd kwmsle lxntmf

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: myoung
Cipher: nblfmt

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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: myoung

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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: myoung
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: myoung
Cipher: zlbhat

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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: myoung
Cipher: 234543543322

Extended Methods:
Method #1

Plaintext: myoung
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
m y o u n g 
2 4 4 5 3 2 
3 5 3 4 3 2 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: myoung
Cipher: ryhxsh

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Method #3

Plaintext: myoung
method variations:
suxohg uxohgs xohgsu
ohgsux hgsuxo gsuxoh

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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: myoung

all 720 cipher variations:
myoung myougn myonug myongu myognu myogun myuong myuogn myunog myungo myugno
myugon mynuog mynugo mynoug mynogu myngou mynguo myguno myguon mygnuo mygnou
mygonu mygoun moyung moyugn moynug moyngu moygnu moygun mouyng mouygn mounyg
moungy mougny mougyn monuyg monugy monyug monygu mongyu monguy moguny moguyn
mognuy mognyu mogynu mogyun muoyng muoygn muonyg muongy muogny muogyn muyong
muyogn muynog muyngo muygno muygon munyog munygo munoyg munogy mungoy mungyo
mugyno mugyon mugnyo mugnoy mugony mugoyn mnouyg mnougy mnoyug mnoygu mnogyu
mnoguy mnuoyg mnuogy mnuyog mnuygo mnugyo mnugoy mnyuog mnyugo mnyoug mnyogu
mnygou mnyguo mnguyo mnguoy mngyuo mngyou mngoyu mngouy mgouny mgouyn mgonuy
mgonyu mgoynu mgoyun mguony mguoyn mgunoy mgunyo mguyno mguyon mgnuoy mgnuyo
mgnouy mgnoyu mgnyou mgnyuo mgyuno mgyuon mgynuo mgynou mgyonu mgyoun ymoung
ymougn ymonug ymongu ymognu ymogun ymuong ymuogn ymunog ymungo ymugno ymugon
ymnuog ymnugo ymnoug ymnogu ymngou ymnguo ymguno ymguon ymgnuo ymgnou ymgonu
ymgoun yomung yomugn yomnug yomngu yomgnu yomgun youmng youmgn younmg youngm
yougnm yougmn yonumg yonugm yonmug yonmgu yongmu yongum yogunm yogumn yognum
yognmu yogmnu yogmun yuomng yuomgn yuonmg yuongm yuognm yuogmn yumong yumogn
yumnog yumngo yumgno yumgon yunmog yunmgo yunomg yunogm yungom yungmo yugmno
yugmon yugnmo yugnom yugonm yugomn ynoumg ynougm ynomug ynomgu ynogmu ynogum
ynuomg ynuogm ynumog ynumgo ynugmo ynugom ynmuog ynmugo ynmoug ynmogu ynmgou
ynmguo yngumo ynguom yngmuo yngmou yngomu yngoum ygounm ygoumn ygonum ygonmu
ygomnu ygomun yguonm yguomn ygunom ygunmo ygumno ygumon ygnuom ygnumo ygnoum
ygnomu ygnmou ygnmuo ygmuno ygmuon ygmnuo ygmnou ygmonu ygmoun oymung oymugn
oymnug oymngu oymgnu oymgun oyumng oyumgn oyunmg oyungm oyugnm oyugmn oynumg
oynugm oynmug oynmgu oyngmu oyngum oygunm oygumn oygnum oygnmu oygmnu oygmun
omyung omyugn omynug omyngu omygnu omygun omuyng omuygn omunyg omungy omugny
omugyn omnuyg omnugy omnyug omnygu omngyu omnguy omguny omguyn omgnuy omgnyu
omgynu omgyun oumyng oumygn oumnyg oumngy oumgny oumgyn ouymng ouymgn ouynmg
ouyngm ouygnm ouygmn ounymg ounygm ounmyg ounmgy oungmy oungym ougynm ougymn
ougnym ougnmy ougmny ougmyn onmuyg onmugy onmyug onmygu onmgyu onmguy onumyg
onumgy onuymg onuygm onugym onugmy onyumg onyugm onymug onymgu onygmu onygum
onguym ongumy ongyum ongymu ongmyu ongmuy ogmuny ogmuyn ogmnuy ogmnyu ogmynu
ogmyun ogumny ogumyn ogunmy ogunym oguynm oguymn ognumy ognuym ognmuy ognmyu
ognymu ognyum ogyunm ogyumn ogynum ogynmu ogymnu ogymun uyomng uyomgn uyonmg
uyongm uyognm uyogmn uymong uymogn uymnog uymngo uymgno uymgon uynmog uynmgo
uynomg uynogm uyngom uyngmo uygmno uygmon uygnmo uygnom uygonm uygomn uoymng
uoymgn uoynmg uoyngm uoygnm uoygmn uomyng uomygn uomnyg uomngy uomgny uomgyn
uonmyg uonmgy uonymg uonygm uongym uongmy uogmny uogmyn uognmy uognym uogynm
uogymn umoyng umoygn umonyg umongy umogny umogyn umyong umyogn umynog umyngo
umygno umygon umnyog umnygo umnoyg umnogy umngoy umngyo umgyno umgyon umgnyo
umgnoy umgony umgoyn unomyg unomgy unoymg unoygm unogym unogmy unmoyg unmogy
unmyog unmygo unmgyo unmgoy unymog unymgo unyomg unyogm unygom unygmo ungmyo
ungmoy ungymo ungyom ungoym ungomy ugomny ugomyn ugonmy ugonym ugoynm ugoymn
ugmony ugmoyn ugmnoy ugmnyo ugmyno ugmyon ugnmoy ugnmyo ugnomy ugnoym ugnyom
ugnymo ugymno ugymon ugynmo ugynom ugyonm ugyomn nyoumg nyougm nyomug nyomgu
nyogmu nyogum nyuomg nyuogm nyumog nyumgo nyugmo nyugom nymuog nymugo nymoug
nymogu nymgou nymguo nygumo nyguom nygmuo nygmou nygomu nygoum noyumg noyugm
noymug noymgu noygmu noygum nouymg nouygm noumyg noumgy nougmy nougym nomuyg
nomugy nomyug nomygu nomgyu nomguy nogumy noguym nogmuy nogmyu nogymu nogyum
nuoymg nuoygm nuomyg nuomgy nuogmy nuogym nuyomg nuyogm nuymog nuymgo nuygmo
nuygom numyog numygo numoyg numogy numgoy numgyo nugymo nugyom nugmyo nugmoy
nugomy nugoym nmouyg nmougy nmoyug nmoygu nmogyu nmoguy nmuoyg nmuogy nmuyog
nmuygo nmugyo nmugoy nmyuog nmyugo nmyoug nmyogu nmygou nmyguo nmguyo nmguoy
nmgyuo nmgyou nmgoyu nmgouy ngoumy ngouym ngomuy ngomyu ngoymu ngoyum nguomy
nguoym ngumoy ngumyo nguymo nguyom ngmuoy ngmuyo ngmouy ngmoyu ngmyou ngmyuo
ngyumo ngyuom ngymuo ngymou ngyomu ngyoum gyounm gyoumn gyonum gyonmu gyomnu
gyomun gyuonm gyuomn gyunom gyunmo gyumno gyumon gynuom gynumo gynoum gynomu
gynmou gynmuo gymuno gymuon gymnuo gymnou gymonu gymoun goyunm goyumn goynum
goynmu goymnu goymun gouynm gouymn gounym gounmy goumny goumyn gonuym gonumy
gonyum gonymu gonmyu gonmuy gomuny gomuyn gomnuy gomnyu gomynu gomyun guoynm
guoymn guonym guonmy guomny guomyn guyonm guyomn guynom guynmo guymno guymon
gunyom gunymo gunoym gunomy gunmoy gunmyo gumyno gumyon gumnyo gumnoy gumony
gumoyn gnouym gnoumy gnoyum gnoymu gnomyu gnomuy gnuoym gnuomy gnuyom gnuymo
gnumyo gnumoy gnyuom gnyumo gnyoum gnyomu gnymou gnymuo gnmuyo gnmuoy gnmyuo
gnmyou gnmoyu gnmouy gmouny gmouyn gmonuy gmonyu gmoynu gmoyun gmuony gmuoyn
gmunoy gmunyo gmuyno gmuyon gmnuoy gmnuyo gmnouy gmnoyu gmnyou gmnyuo gmyuno
gmyuon gmynuo gmynou gmyonu gmyoun

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History of cryptography
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