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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: stuyck
cipher variations:
tuvzdl uvwaem vwxbfn wxycgo xyzdhp
yzaeiq zabfjr abcgks bcdhlt cdeimu
defjnv efgkow fghlpx ghimqy hijnrz
ijkosa jklptb klmquc lmnrvd mnoswe
noptxf opquyg pqrvzh qrswai rstxbj

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: stuyck
Cipher: hgfbxp

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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: stuyck

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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: stuyck
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: stuyck
Cipher: fghlpx

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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: stuyck
Cipher: 344454453152

Extended Methods:
Method #1

Plaintext: stuyck
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
s t u y c k 
3 4 5 4 3 5 
4 4 4 5 1 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: stuyck
Cipher: suxtyf

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Method #3

Plaintext: stuyck
method variations:
tytpvm ytpvmt tpvmty
pvmtyt vmtytp mtytpv

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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: stuyck

all 720 cipher variations:
stuyck stuykc stucyk stucky stukcy stukyc styuck styukc stycuk stycku stykcu
stykuc stcyuk stcyku stcuyk stcuky stckuy stckyu stkycu stkyuc stkcyu stkcuy
stkucy stkuyc sutyck sutykc sutcyk sutcky sutkcy sutkyc suytck suytkc suyctk
suyckt suykct suyktc sucytk sucykt suctyk suctky suckty suckyt sukyct sukytc
sukcyt sukcty suktcy suktyc syutck syutkc syuctk syuckt syukct syuktc sytuck
sytukc sytcuk sytcku sytkcu sytkuc syctuk syctku sycutk sycukt syckut sycktu
syktcu syktuc sykctu sykcut sykuct sykutc scuytk scuykt scutyk scutky scukty
scukyt scyutk scyukt scytuk scytku scyktu scykut sctyuk sctyku sctuyk sctuky
sctkuy sctkyu sckytu sckyut scktyu scktuy sckuty sckuyt skuyct skuytc skucyt
skucty skutcy skutyc skyuct skyutc skycut skyctu skytcu skytuc skcyut skcytu
skcuyt skcuty skctuy skctyu sktycu sktyuc sktcyu sktcuy sktucy sktuyc tsuyck
tsuykc tsucyk tsucky tsukcy tsukyc tsyuck tsyukc tsycuk tsycku tsykcu tsykuc
tscyuk tscyku tscuyk tscuky tsckuy tsckyu tskycu tskyuc tskcyu tskcuy tskucy
tskuyc tusyck tusykc tuscyk tuscky tuskcy tuskyc tuysck tuyskc tuycsk tuycks
tuykcs tuyksc tucysk tucyks tucsyk tucsky tucksy tuckys tukycs tukysc tukcys
tukcsy tukscy tuksyc tyusck tyuskc tyucsk tyucks tyukcs tyuksc tysuck tysukc
tyscuk tyscku tyskcu tyskuc tycsuk tycsku tycusk tycuks tyckus tycksu tykscu
tyksuc tykcsu tykcus tykucs tykusc tcuysk tcuyks tcusyk tcusky tcuksy tcukys
tcyusk tcyuks tcysuk tcysku tcyksu tcykus tcsyuk tcsyku tcsuyk tcsuky tcskuy
tcskyu tckysu tckyus tcksyu tcksuy tckusy tckuys tkuycs tkuysc tkucys tkucsy
tkuscy tkusyc tkyucs tkyusc tkycus tkycsu tkyscu tkysuc tkcyus tkcysu tkcuys
tkcusy tkcsuy tkcsyu tksycu tksyuc tkscyu tkscuy tksucy tksuyc utsyck utsykc
utscyk utscky utskcy utskyc utysck utyskc utycsk utycks utykcs utyksc utcysk
utcyks utcsyk utcsky utcksy utckys utkycs utkysc utkcys utkcsy utkscy utksyc
ustyck ustykc ustcyk ustcky ustkcy ustkyc usytck usytkc usyctk usyckt usykct
usyktc uscytk uscykt usctyk usctky usckty usckyt uskyct uskytc uskcyt uskcty
usktcy usktyc uystck uystkc uysctk uysckt uyskct uysktc uytsck uytskc uytcsk
uytcks uytkcs uytksc uyctsk uyctks uycstk uycskt uyckst uyckts uyktcs uyktsc
uykcts uykcst uyksct uykstc ucsytk ucsykt ucstyk ucstky ucskty ucskyt ucystk
ucyskt ucytsk ucytks ucykts ucykst uctysk uctyks uctsyk uctsky uctksy uctkys
uckyts uckyst ucktys ucktsy ucksty ucksyt uksyct uksytc ukscyt ukscty ukstcy
ukstyc ukysct ukystc ukycst ukycts ukytcs ukytsc ukcyst ukcyts ukcsyt ukcsty
ukctsy ukctys uktycs uktysc uktcys uktcsy uktscy uktsyc ytusck ytuskc ytucsk
ytucks ytukcs ytuksc ytsuck ytsukc ytscuk ytscku ytskcu ytskuc ytcsuk ytcsku
ytcusk ytcuks ytckus ytcksu ytkscu ytksuc ytkcsu ytkcus ytkucs ytkusc yutsck
yutskc yutcsk yutcks yutkcs yutksc yustck yustkc yusctk yusckt yuskct yusktc
yucstk yucskt yuctsk yuctks yuckts yuckst yuksct yukstc yukcst yukcts yuktcs
yuktsc ysutck ysutkc ysuctk ysuckt ysukct ysuktc ystuck ystukc ystcuk ystcku
ystkcu ystkuc ysctuk ysctku yscutk yscukt ysckut yscktu ysktcu ysktuc yskctu
yskcut yskuct yskutc ycustk ycuskt ycutsk ycutks ycukts ycukst ycsutk ycsukt
ycstuk ycstku ycsktu ycskut yctsuk yctsku yctusk yctuks yctkus yctksu yckstu
ycksut ycktsu ycktus yckuts yckust ykusct ykustc ykucst ykucts ykutcs ykutsc
yksuct yksutc ykscut yksctu ykstcu ykstuc ykcsut ykcstu ykcust ykcuts ykctus
ykctsu yktscu yktsuc yktcsu yktcus yktucs yktusc ctuysk ctuyks ctusyk ctusky
ctuksy ctukys ctyusk ctyuks ctysuk ctysku ctyksu ctykus ctsyuk ctsyku ctsuyk
ctsuky ctskuy ctskyu ctkysu ctkyus ctksyu ctksuy ctkusy ctkuys cutysk cutyks
cutsyk cutsky cutksy cutkys cuytsk cuytks cuystk cuyskt cuykst cuykts cusytk
cusykt custyk custky cuskty cuskyt cukyst cukyts cuksyt cuksty cuktsy cuktys
cyutsk cyutks cyustk cyuskt cyukst cyukts cytusk cytuks cytsuk cytsku cytksu
cytkus cystuk cystku cysutk cysukt cyskut cysktu cyktsu cyktus cykstu cyksut
cykust cykuts csuytk csuykt csutyk csutky csukty csukyt csyutk csyukt csytuk
csytku csyktu csykut cstyuk cstyku cstuyk cstuky cstkuy cstkyu cskytu cskyut
csktyu csktuy cskuty cskuyt ckuyst ckuyts ckusyt ckusty ckutsy ckutys ckyust
ckyuts ckysut ckystu ckytsu ckytus cksyut cksytu cksuyt cksuty ckstuy ckstyu
cktysu cktyus cktsyu cktsuy cktusy cktuys ktuycs ktuysc ktucys ktucsy ktuscy
ktusyc ktyucs ktyusc ktycus ktycsu ktyscu ktysuc ktcyus ktcysu ktcuys ktcusy
ktcsuy ktcsyu ktsycu ktsyuc ktscyu ktscuy ktsucy ktsuyc kutycs kutysc kutcys
kutcsy kutscy kutsyc kuytcs kuytsc kuycts kuycst kuysct kuystc kucyts kucyst
kuctys kuctsy kucsty kucsyt kusyct kusytc kuscyt kuscty kustcy kustyc kyutcs
kyutsc kyucts kyucst kyusct kyustc kytucs kytusc kytcus kytcsu kytscu kytsuc
kyctus kyctsu kycuts kycust kycsut kycstu kystcu kystuc kysctu kyscut kysuct
kysutc kcuyts kcuyst kcutys kcutsy kcusty kcusyt kcyuts kcyust kcytus kcytsu
kcystu kcysut kctyus kctysu kctuys kctusy kctsuy kctsyu kcsytu kcsyut kcstyu
kcstuy kcsuty kcsuyt ksuyct ksuytc ksucyt ksucty ksutcy ksutyc ksyuct ksyutc
ksycut ksyctu ksytcu ksytuc kscyut kscytu kscuyt kscuty ksctuy ksctyu kstycu
kstyuc kstcyu kstcuy kstucy kstuyc

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History of cryptography
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