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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: roding
cipher variations:
spejoh tqfkpi urglqj vshmrk wtinsl
xujotm yvkpun zwlqvo axmrwp bynsxq
czotyr dapuzs ebqvat fcrwbu gdsxcv
hetydw ifuzex jgvafy khwbgz lixcha
mjydib nkzejc olafkd pmbgle qnchmf

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: roding
Cipher: ilwrmt

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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: roding

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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: roding
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: roding
Cipher: ebqvat

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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: roding
Cipher: 244341423322

Extended Methods:
Method #1

Plaintext: roding
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
r o d i n g 
2 4 4 4 3 2 
4 3 1 2 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: roding
Cipher: rthofh

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Method #3

Plaintext: roding
method variations:
tsqmhg sqmhgt qmhgts
mhgtsq hgtsqm gtsqmh

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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: roding

all 720 cipher variations:
roding rodign rodnig rodngi rodgni rodgin roidng roidgn roindg roingd roignd
roigdn ronidg ronigd rondig rondgi rongdi rongid rogind rogidn rognid rogndi
rogdni rogdin rdoing rdoign rdonig rdongi rdogni rdogin rdiong rdiogn rdinog
rdingo rdigno rdigon rdniog rdnigo rdnoig rdnogi rdngoi rdngio rdgino rdgion
rdgnio rdgnoi rdgoni rdgoin ridong ridogn ridnog ridngo ridgno ridgon riodng
riodgn riondg riongd riognd riogdn rinodg rinogd rindog rindgo ringdo ringod
rigond rigodn rignod rigndo rigdno rigdon rndiog rndigo rndoig rndogi rndgoi
rndgio rnidog rnidgo rniodg rniogd rnigod rnigdo rnoidg rnoigd rnodig rnodgi
rnogdi rnogid rngiod rngido rngoid rngodi rngdoi rngdio rgdino rgdion rgdnio
rgdnoi rgdoni rgdoin rgidno rgidon rgindo rginod rgiond rgiodn rgnido rgniod
rgndio rgndoi rgnodi rgnoid rgoind rgoidn rgonid rgondi rgodni rgodin ording
ordign ordnig ordngi ordgni ordgin oridng oridgn orindg oringd orignd origdn
ornidg ornigd orndig orndgi orngdi orngid orgind orgidn orgnid orgndi orgdni
orgdin odring odrign odrnig odrngi odrgni odrgin odirng odirgn odinrg odingr
odignr odigrn odnirg odnigr odnrig odnrgi odngri odngir odginr odgirn odgnir
odgnri odgrni odgrin oidrng oidrgn oidnrg oidngr oidgnr oidgrn oirdng oirdgn
oirndg oirngd oirgnd oirgdn oinrdg oinrgd oindrg oindgr oingdr oingrd oigrnd
oigrdn oignrd oigndr oigdnr oigdrn ondirg ondigr ondrig ondrgi ondgri ondgir
onidrg onidgr onirdg onirgd onigrd onigdr onridg onrigd onrdig onrdgi onrgdi
onrgid ongird ongidr ongrid ongrdi ongdri ongdir ogdinr ogdirn ogdnir ogdnri
ogdrni ogdrin ogidnr ogidrn ogindr oginrd ogirnd ogirdn ognidr ognird ogndir
ogndri ognrdi ognrid ogrind ogridn ogrnid ogrndi ogrdni ogrdin doring dorign
dornig dorngi dorgni dorgin doirng doirgn doinrg doingr doignr doigrn donirg
donigr donrig donrgi dongri dongir doginr dogirn dognir dognri dogrni dogrin
droing droign dronig drongi drogni drogin driong driogn drinog dringo drigno
drigon drniog drnigo drnoig drnogi drngoi drngio drgino drgion drgnio drgnoi
drgoni drgoin dirong dirogn dirnog dirngo dirgno dirgon diorng diorgn dionrg
diongr diognr diogrn dinorg dinogr dinrog dinrgo dingro dingor digonr digorn
dignor dignro digrno digron dnriog dnrigo dnroig dnrogi dnrgoi dnrgio dnirog
dnirgo dniorg dniogr dnigor dnigro dnoirg dnoigr dnorig dnorgi dnogri dnogir
dngior dngiro dngoir dngori dngroi dngrio dgrino dgrion dgrnio dgrnoi dgroni
dgroin dgirno dgiron dginro dginor dgionr dgiorn dgniro dgnior dgnrio dgnroi
dgnori dgnoir dgoinr dgoirn dgonir dgonri dgorni dgorin iodrng iodrgn iodnrg
iodngr iodgnr iodgrn iordng iordgn iorndg iorngd iorgnd iorgdn ionrdg ionrgd
iondrg iondgr iongdr iongrd iogrnd iogrdn iognrd iogndr iogdnr iogdrn idorng
idorgn idonrg idongr idognr idogrn idrong idrogn idrnog idrngo idrgno idrgon
idnrog idnrgo idnorg idnogr idngor idngro idgrno idgron idgnro idgnor idgonr
idgorn irdong irdogn irdnog irdngo irdgno irdgon irodng irodgn irondg irongd
irognd irogdn irnodg irnogd irndog irndgo irngdo irngod irgond irgodn irgnod
irgndo irgdno irgdon indrog indrgo indorg indogr indgor indgro inrdog inrdgo
inrodg inrogd inrgod inrgdo inordg inorgd inodrg inodgr inogdr inogrd ingrod
ingrdo ingord ingodr ingdor ingdro igdrno igdron igdnro igdnor igdonr igdorn
igrdno igrdon igrndo igrnod igrond igrodn ignrdo ignrod igndro igndor ignodr
ignord igornd igordn igonrd igondr igodnr igodrn nodirg nodigr nodrig nodrgi
nodgri nodgir noidrg noidgr noirdg noirgd noigrd noigdr noridg norigd nordig
nordgi norgdi norgid nogird nogidr nogrid nogrdi nogdri nogdir ndoirg ndoigr
ndorig ndorgi ndogri ndogir ndiorg ndiogr ndirog ndirgo ndigro ndigor ndriog
ndrigo ndroig ndrogi ndrgoi ndrgio ndgiro ndgior ndgrio ndgroi ndgori ndgoir
nidorg nidogr nidrog nidrgo nidgro nidgor niodrg niodgr niordg niorgd niogrd
niogdr nirodg nirogd nirdog nirdgo nirgdo nirgod nigord nigodr nigrod nigrdo
nigdro nigdor nrdiog nrdigo nrdoig nrdogi nrdgoi nrdgio nridog nridgo nriodg
nriogd nrigod nrigdo nroidg nroigd nrodig nrodgi nrogdi nrogid nrgiod nrgido
nrgoid nrgodi nrgdoi nrgdio ngdiro ngdior ngdrio ngdroi ngdori ngdoir ngidro
ngidor ngirdo ngirod ngiord ngiodr ngrido ngriod ngrdio ngrdoi ngrodi ngroid
ngoird ngoidr ngorid ngordi ngodri ngodir godinr godirn godnir godnri godrni
godrin goidnr goidrn goindr goinrd goirnd goirdn gonidr gonird gondir gondri
gonrdi gonrid gorind goridn gornid gorndi gordni gordin gdoinr gdoirn gdonir
gdonri gdorni gdorin gdionr gdiorn gdinor gdinro gdirno gdiron gdnior gdniro
gdnoir gdnori gdnroi gdnrio gdrino gdrion gdrnio gdrnoi gdroni gdroin gidonr
gidorn gidnor gidnro gidrno gidron giodnr giodrn giondr gionrd giornd giordn
ginodr ginord gindor gindro ginrdo ginrod girond girodn girnod girndo girdno
girdon gndior gndiro gndoir gndori gndroi gndrio gnidor gnidro gniodr gniord
gnirod gnirdo gnoidr gnoird gnodir gnodri gnordi gnorid gnriod gnrido gnroid
gnrodi gnrdoi gnrdio grdino grdion grdnio grdnoi grdoni grdoin gridno gridon
grindo grinod griond griodn grnido grniod grndio grndoi grnodi grnoid groind
groidn gronid grondi grodni grodin

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History of cryptography
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