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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: kumasi
cipher variations:
lvnbtj mwocuk nxpdvl oyqewm pzrfxn
qasgyo rbthzp scuiaq tdvjbr uewkcs
vfxldt wgymeu xhznfv yiaogw zjbphx
akcqiy bldrjz cmeska dnftlb eogumc
fphvnd gqiwoe hrjxpf iskyqg jtlzrh

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: kumasi
Cipher: pfnzhr

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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: kumasi

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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: kumasi
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: kumasi
Cipher: xhznfv

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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: kumasi
Cipher: 525423113442

Extended Methods:
Method #1

Plaintext: kumasi
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
k u m a s i 
5 5 2 1 3 4 
2 4 3 1 4 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: kumasi
Cipher: zbsrci

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Method #3

Plaintext: kumasi
method variations:
wicltw icltww cltwwi
ltwwic twwicl wwiclt

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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: kumasi

all 720 cipher variations:
kumasi kumais kumsai kumsia kumisa kumias kuamsi kuamis kuasmi kuasim kuaism
kuaims kusami kusaim kusmai kusmia kusima kusiam kuiasm kuiams kuisam kuisma
kuimsa kuimas kmuasi kmuais kmusai kmusia kmuisa kmuias kmausi kmauis kmasui
kmasiu kmaisu kmaius kmsaui kmsaiu kmsuai kmsuia kmsiua kmsiau kmiasu kmiaus
kmisau kmisua kmiusa kmiuas kamusi kamuis kamsui kamsiu kamisu kamius kaumsi
kaumis kausmi kausim kauism kauims kasumi kasuim kasmui kasmiu kasimu kasium
kaiusm kaiums kaisum kaismu kaimsu kaimus ksmaui ksmaiu ksmuai ksmuia ksmiua
ksmiau ksamui ksamiu ksaumi ksauim ksaium ksaimu ksuami ksuaim ksumai ksumia
ksuima ksuiam ksiaum ksiamu ksiuam ksiuma ksimua ksimau kimasu kimaus kimsau
kimsua kimusa kimuas kiamsu kiamus kiasmu kiasum kiausm kiaums kisamu kisaum
kismau kismua kisuma kisuam kiuasm kiuams kiusam kiusma kiumsa kiumas ukmasi
ukmais ukmsai ukmsia ukmisa ukmias ukamsi ukamis ukasmi ukasim ukaism ukaims
uksami uksaim uksmai uksmia uksima uksiam ukiasm ukiams ukisam ukisma ukimsa
ukimas umkasi umkais umksai umksia umkisa umkias umaksi umakis umaski umasik
umaisk umaiks umsaki umsaik umskai umskia umsika umsiak umiask umiaks umisak
umiska umiksa umikas uamksi uamkis uamski uamsik uamisk uamiks uakmsi uakmis
uaksmi uaksim uakism uakims uaskmi uaskim uasmki uasmik uasimk uasikm uaiksm
uaikms uaiskm uaismk uaimsk uaimks usmaki usmaik usmkai usmkia usmika usmiak
usamki usamik usakmi usakim usaikm usaimk uskami uskaim uskmai uskmia uskima
uskiam usiakm usiamk usikam usikma usimka usimak uimask uimaks uimsak uimska
uimksa uimkas uiamsk uiamks uiasmk uiaskm uiaksm uiakms uisamk uisakm uismak
uismka uiskma uiskam uikasm uikams uiksam uiksma uikmsa uikmas mukasi mukais
muksai muksia mukisa mukias muaksi muakis muaski muasik muaisk muaiks musaki
musaik muskai muskia musika musiak muiask muiaks muisak muiska muiksa muikas
mkuasi mkuais mkusai mkusia mkuisa mkuias mkausi mkauis mkasui mkasiu mkaisu
mkaius mksaui mksaiu mksuai mksuia mksiua mksiau mkiasu mkiaus mkisau mkisua
mkiusa mkiuas makusi makuis maksui maksiu makisu makius mauksi maukis mauski
mausik mauisk mauiks masuki masuik maskui maskiu masiku masiuk maiusk maiuks
maisuk maisku maiksu maikus mskaui mskaiu mskuai mskuia mskiua mskiau msakui
msakiu msauki msauik msaiuk msaiku msuaki msuaik msukai msukia msuika msuiak
msiauk msiaku msiuak msiuka msikua msikau mikasu mikaus miksau miksua mikusa
mikuas miaksu miakus miasku miasuk miausk miauks misaku misauk miskau miskua
misuka misuak miuask miuaks miusak miuska miuksa miukas aumksi aumkis aumski
aumsik aumisk aumiks aukmsi aukmis auksmi auksim aukism aukims auskmi auskim
ausmki ausmik ausimk ausikm auiksm auikms auiskm auismk auimsk auimks amuksi
amukis amuski amusik amuisk amuiks amkusi amkuis amksui amksiu amkisu amkius
amskui amskiu amsuki amsuik amsiuk amsiku amiksu amikus amisku amisuk amiusk
amiuks akmusi akmuis akmsui akmsiu akmisu akmius akumsi akumis akusmi akusim
akuism akuims aksumi aksuim aksmui aksmiu aksimu aksium akiusm akiums akisum
akismu akimsu akimus asmkui asmkiu asmuki asmuik asmiuk asmiku askmui askmiu
askumi askuim askium askimu asukmi asukim asumki asumik asuimk asuikm asikum
asikmu asiukm asiumk asimuk asimku aimksu aimkus aimsku aimsuk aimusk aimuks
aikmsu aikmus aiksmu aiksum aikusm aikums aiskmu aiskum aismku aismuk aisumk
aisukm aiuksm aiukms aiuskm aiusmk aiumsk aiumks sumaki sumaik sumkai sumkia
sumika sumiak suamki suamik suakmi suakim suaikm suaimk sukami sukaim sukmai
sukmia sukima sukiam suiakm suiamk suikam suikma suimka suimak smuaki smuaik
smukai smukia smuika smuiak smauki smauik smakui smakiu smaiku smaiuk smkaui
smkaiu smkuai smkuia smkiua smkiau smiaku smiauk smikau smikua smiuka smiuak
samuki samuik samkui samkiu samiku samiuk saumki saumik saukmi saukim sauikm
sauimk sakumi sakuim sakmui sakmiu sakimu sakium saiukm saiumk saikum saikmu
saimku saimuk skmaui skmaiu skmuai skmuia skmiua skmiau skamui skamiu skaumi
skauim skaium skaimu skuami skuaim skumai skumia skuima skuiam skiaum skiamu
skiuam skiuma skimua skimau simaku simauk simkau simkua simuka simuak siamku
siamuk siakmu siakum siaukm siaumk sikamu sikaum sikmau sikmua sikuma sikuam
siuakm siuamk siukam siukma siumka siumak iumask iumaks iumsak iumska iumksa
iumkas iuamsk iuamks iuasmk iuaskm iuaksm iuakms iusamk iusakm iusmak iusmka
iuskma iuskam iukasm iukams iuksam iuksma iukmsa iukmas imuask imuaks imusak
imuska imuksa imukas imausk imauks imasuk imasku imaksu imakus imsauk imsaku
imsuak imsuka imskua imskau imkasu imkaus imksau imksua imkusa imkuas iamusk
iamuks iamsuk iamsku iamksu iamkus iaumsk iaumks iausmk iauskm iauksm iaukms
iasumk iasukm iasmuk iasmku iaskmu iaskum iakusm iakums iaksum iaksmu iakmsu
iakmus ismauk ismaku ismuak ismuka ismkua ismkau isamuk isamku isaumk isaukm
isakum isakmu isuamk isuakm isumak isumka isukma isukam iskaum iskamu iskuam
iskuma iskmua iskmau ikmasu ikmaus ikmsau ikmsua ikmusa ikmuas ikamsu ikamus
ikasmu ikasum ikausm ikaums iksamu iksaum iksmau iksmua iksuma iksuam ikuasm
ikuams ikusam ikusma ikumsa ikumas

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History of cryptography
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