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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: aglint
cipher variations:
bhmjou cinkpv djolqw ekpmrx flqnsy
gmrotz hnspua iotqvb jpurwc kqvsxd
lrwtye msxuzf ntyvag ouzwbh pvaxci
qwbydj rxczek sydafl tzebgm uafchn
vbgdio wchejp xdifkq yejglr zfkhms

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: aglint
Cipher: ztormg

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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: aglint

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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: aglint
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: aglint
Cipher: ntyvag

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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: aglint
Cipher: 112213423344

Extended Methods:
Method #1

Plaintext: aglint
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
a g l i n t 
1 2 1 4 3 4 
1 2 3 2 3 4 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: aglint
Cipher: fqsfhs

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Method #3

Plaintext: aglint
method variations:
fbsmsd bsmsdf smsdfb
msdfbs sdfbsm dfbsms

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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: aglint

all 720 cipher variations:
aglint aglitn aglnit aglnti agltni agltin agilnt agiltn aginlt agintl agitnl
agitln agnilt agnitl agnlit agnlti agntli agntil agtinl agtiln agtnil agtnli
agtlni agtlin algint algitn algnit algnti algtni algtin alignt aligtn alingt
alintg alitng alitgn alnigt alnitg alngit alngti alntgi alntig alting altign
altnig altngi altgni altgin ailgnt ailgtn ailngt ailntg ailtng ailtgn aiglnt
aigltn aignlt aigntl aigtnl aigtln ainglt aingtl ainlgt ainltg aintlg aintgl
aitgnl aitgln aitngl aitnlg aitlng aitlgn anligt anlitg anlgit anlgti anltgi
anltig anilgt aniltg aniglt anigtl anitgl anitlg angilt angitl anglit anglti
angtli angtil antigl antilg antgil antgli antlgi antlig atling atlign atlnig
atlngi atlgni atlgin atilng atilgn atinlg atingl atignl atigln atnilg atnigl
atnlig atnlgi atngli atngil atginl atgiln atgnil atgnli atglni atglin galint
galitn galnit galnti galtni galtin gailnt gailtn gainlt gaintl gaitnl gaitln
ganilt ganitl ganlit ganlti gantli gantil gatinl gatiln gatnil gatnli gatlni
gatlin glaint glaitn glanit glanti glatni glatin gliant gliatn glinat glinta
glitna glitan glniat glnita glnait glnati glntai glntia gltina gltian gltnia
gltnai gltani gltain gilant gilatn gilnat gilnta giltna giltan gialnt gialtn
gianlt giantl giatnl giatln ginalt ginatl ginlat ginlta gintla gintal gitanl
gitaln gitnal gitnla gitlna gitlan gnliat gnlita gnlait gnlati gnltai gnltia
gnilat gnilta gnialt gniatl gnital gnitla gnailt gnaitl gnalit gnalti gnatli
gnatil gntial gntila gntail gntali gntlai gntlia gtlina gtlian gtlnia gtlnai
gtlani gtlain gtilna gtilan gtinla gtinal gtianl gtialn gtnila gtnial gtnlia
gtnlai gtnali gtnail gtainl gtailn gtanil gtanli gtalni gtalin lgaint lgaitn
lganit lganti lgatni lgatin lgiant lgiatn lginat lginta lgitna lgitan lgniat
lgnita lgnait lgnati lgntai lgntia lgtina lgtian lgtnia lgtnai lgtani lgtain
lagint lagitn lagnit lagnti lagtni lagtin laignt laigtn laingt laintg laitng
laitgn lanigt lanitg langit langti lantgi lantig lating latign latnig latngi
latgni latgin liagnt liagtn liangt liantg liatng liatgn ligant ligatn lignat
lignta ligtna ligtan lingat lingta linagt linatg lintag lintga litgna litgan
litnga litnag litang litagn lnaigt lnaitg lnagit lnagti lnatgi lnatig lniagt
lniatg lnigat lnigta lnitga lnitag lngiat lngita lngait lngati lngtai lngtia
lntiga lntiag lntgia lntgai lntagi lntaig ltaing ltaign ltanig ltangi ltagni
ltagin ltiang ltiagn ltinag ltinga ltigna ltigan ltniag ltniga ltnaig ltnagi
ltngai ltngia ltgina ltgian ltgnia ltgnai ltgani ltgain iglant iglatn iglnat
iglnta igltna igltan igalnt igaltn iganlt igantl igatnl igatln ignalt ignatl
ignlat ignlta igntla igntal igtanl igtaln igtnal igtnla igtlna igtlan ilgant
ilgatn ilgnat ilgnta ilgtna ilgtan ilagnt ilagtn ilangt ilantg ilatng ilatgn
ilnagt ilnatg ilngat ilngta ilntga ilntag iltang iltagn iltnag iltnga iltgna
iltgan ialgnt ialgtn ialngt ialntg ialtng ialtgn iaglnt iagltn iagnlt iagntl
iagtnl iagtln ianglt iangtl ianlgt ianltg iantlg iantgl iatgnl iatgln iatngl
iatnlg iatlng iatlgn inlagt inlatg inlgat inlgta inltga inltag inalgt inaltg
inaglt inagtl inatgl inatlg ingalt ingatl inglat inglta ingtla ingtal intagl
intalg intgal intgla intlga intlag itlang itlagn itlnag itlnga itlgna itlgan
italng italgn itanlg itangl itagnl itagln itnalg itnagl itnlag itnlga itngla
itngal itganl itgaln itgnal itgnla itglna itglan ngliat nglita nglait nglati
ngltai ngltia ngilat ngilta ngialt ngiatl ngital ngitla ngailt ngaitl ngalit
ngalti ngatli ngatil ngtial ngtila ngtail ngtali ngtlai ngtlia nlgiat nlgita
nlgait nlgati nlgtai nlgtia nligat nligta nliagt nliatg nlitag nlitga nlaigt
nlaitg nlagit nlagti nlatgi nlatig nltiag nltiga nltaig nltagi nltgai nltgia
nilgat nilgta nilagt nilatg niltag niltga niglat niglta nigalt nigatl nigtal
nigtla niaglt niagtl nialgt nialtg niatlg niatgl nitgal nitgla nitagl nitalg
nitlag nitlga naligt nalitg nalgit nalgti naltgi naltig nailgt nailtg naiglt
naigtl naitgl naitlg nagilt nagitl naglit naglti nagtli nagtil natigl natilg
natgil natgli natlgi natlig ntliag ntliga ntlaig ntlagi ntlgai ntlgia ntilag
ntilga ntialg ntiagl ntigal ntigla ntailg ntaigl ntalig ntalgi ntagli ntagil
ntgial ntgila ntgail ntgali ntglai ntglia tglina tglian tglnia tglnai tglani
tglain tgilna tgilan tginla tginal tgianl tgialn tgnila tgnial tgnlia tgnlai
tgnali tgnail tgainl tgailn tganil tganli tgalni tgalin tlgina tlgian tlgnia
tlgnai tlgani tlgain tligna tligan tlinga tlinag tliang tliagn tlniga tlniag
tlngia tlngai tlnagi tlnaig tlaing tlaign tlanig tlangi tlagni tlagin tilgna
tilgan tilnga tilnag tilang tilagn tiglna tiglan tignla tignal tiganl tigaln
tingla tingal tinlga tinlag tinalg tinagl tiagnl tiagln tiangl tianlg tialng
tialgn tnliga tnliag tnlgia tnlgai tnlagi tnlaig tnilga tnilag tnigla tnigal
tniagl tnialg tngila tngial tnglia tnglai tngali tngail tnaigl tnailg tnagil
tnagli tnalgi tnalig taling talign talnig talngi talgni talgin tailng tailgn
tainlg taingl taignl taigln tanilg tanigl tanlig tanlgi tangli tangil taginl
tagiln tagnil tagnli taglni taglin

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History of cryptography
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