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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: pagens
cipher variations:
qbhfot rcigpu sdjhqv tekirw ufljsx
vgmkty whnluz xiomva yjpnwb zkqoxc
alrpyd bmsqze cntraf dousbg epvtch
fqwudi grxvej hsywfk itzxgl juayhm
kvbzin lwcajo mxdbkp nyeclq ozfdmr

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: pagens
Cipher: kztvmh

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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: pagens

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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: pagens
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: pagens
Cipher: cntraf

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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: pagens
Cipher: 531122513334

Extended Methods:
Method #1

Plaintext: pagens
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
p a g e n s 
5 1 2 5 3 3 
3 1 2 1 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: pagens
Cipher: ewncbs

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Method #3

Plaintext: pagens
method variations:
cfwlny fwlnyc wlnycf
lnycfw nycfwl ycfwln

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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: pagens

all 720 cipher variations:
pagens pagesn pagnes pagnse pagsne pagsen paegns paegsn paengs paensg paesng
paesgn panegs panesg panges pangse pansge panseg paseng pasegn pasneg pasnge
pasgne pasgen pgaens pgaesn pganes pganse pgasne pgasen pgeans pgeasn pgenas
pgensa pgesna pgesan pgneas pgnesa pgnaes pgnase pgnsae pgnsea pgsena pgsean
pgsnea pgsnae pgsane pgsaen pegans pegasn pegnas pegnsa pegsna pegsan peagns
peagsn peangs peansg peasng peasgn penags penasg pengas pengsa pensga pensag
pesang pesagn pesnag pesnga pesgna pesgan pngeas pngesa pngaes pngase pngsae
pngsea pnegas pnegsa pneags pneasg pnesag pnesga pnaegs pnaesg pnages pnagse
pnasge pnaseg pnseag pnsega pnsaeg pnsage pnsgae pnsgea psgena psgean psgnea
psgnae psgane psgaen psegna psegan psenga psenag pseang pseagn psnega psneag
psngea psngae psnage psnaeg psaeng psaegn psaneg psange psagne psagen apgens
apgesn apgnes apgnse apgsne apgsen apegns apegsn apengs apensg apesng apesgn
apnegs apnesg apnges apngse apnsge apnseg apseng apsegn apsneg apsnge apsgne
apsgen agpens agpesn agpnes agpnse agpsne agpsen agepns agepsn agenps agensp
agesnp agespn agneps agnesp agnpes agnpse agnspe agnsep agsenp agsepn agsnep
agsnpe agspne agspen aegpns aegpsn aegnps aegnsp aegsnp aegspn aepgns aepgsn
aepngs aepnsg aepsng aepsgn aenpgs aenpsg aengps aengsp aensgp aenspg aespng
aespgn aesnpg aesngp aesgnp aesgpn angeps angesp angpes angpse angspe angsep
anegps anegsp anepgs anepsg anespg anesgp anpegs anpesg anpges anpgse anpsge
anpseg ansepg ansegp anspeg anspge ansgpe ansgep asgenp asgepn asgnep asgnpe
asgpne asgpen asegnp asegpn asengp asenpg asepng asepgn asnegp asnepg asngep
asngpe asnpge asnpeg aspeng aspegn aspneg aspnge aspgne aspgen gapens gapesn
gapnes gapnse gapsne gapsen gaepns gaepsn gaenps gaensp gaesnp gaespn ganeps
ganesp ganpes ganpse ganspe gansep gasenp gasepn gasnep gasnpe gaspne gaspen
gpaens gpaesn gpanes gpanse gpasne gpasen gpeans gpeasn gpenas gpensa gpesna
gpesan gpneas gpnesa gpnaes gpnase gpnsae gpnsea gpsena gpsean gpsnea gpsnae
gpsane gpsaen gepans gepasn gepnas gepnsa gepsna gepsan geapns geapsn geanps
geansp geasnp geaspn genaps genasp genpas genpsa genspa gensap gesanp gesapn
gesnap gesnpa gespna gespan gnpeas gnpesa gnpaes gnpase gnpsae gnpsea gnepas
gnepsa gneaps gneasp gnesap gnespa gnaeps gnaesp gnapes gnapse gnaspe gnasep
gnseap gnsepa gnsaep gnsape gnspae gnspea gspena gspean gspnea gspnae gspane
gspaen gsepna gsepan gsenpa gsenap gseanp gseapn gsnepa gsneap gsnpea gsnpae
gsnape gsnaep gsaenp gsaepn gsanep gsanpe gsapne gsapen eagpns eagpsn eagnps
eagnsp eagsnp eagspn eapgns eapgsn eapngs eapnsg eapsng eapsgn eanpgs eanpsg
eangps eangsp eansgp eanspg easpng easpgn easnpg easngp easgnp easgpn egapns
egapsn eganps egansp egasnp egaspn egpans egpasn egpnas egpnsa egpsna egpsan
egnpas egnpsa egnaps egnasp egnsap egnspa egspna egspan egsnpa egsnap egsanp
egsapn epgans epgasn epgnas epgnsa epgsna epgsan epagns epagsn epangs epansg
epasng epasgn epnags epnasg epngas epngsa epnsga epnsag epsang epsagn epsnag
epsnga epsgna epsgan engpas engpsa engaps engasp engsap engspa enpgas enpgsa
enpags enpasg enpsag enpsga enapgs enapsg enagps enagsp enasgp enaspg enspag
enspga ensapg ensagp ensgap ensgpa esgpna esgpan esgnpa esgnap esganp esgapn
espgna espgan espnga espnag espang espagn esnpga esnpag esngpa esngap esnagp
esnapg esapng esapgn esanpg esangp esagnp esagpn nageps nagesp nagpes nagpse
nagspe nagsep naegps naegsp naepgs naepsg naespg naesgp napegs napesg napges
napgse napsge napseg nasepg nasegp naspeg naspge nasgpe nasgep ngaeps ngaesp
ngapes ngapse ngaspe ngasep ngeaps ngeasp ngepas ngepsa ngespa ngesap ngpeas
ngpesa ngpaes ngpase ngpsae ngpsea ngsepa ngseap ngspea ngspae ngsape ngsaep
negaps negasp negpas negpsa negspa negsap neagps neagsp neapgs neapsg neaspg
neasgp nepags nepasg nepgas nepgsa nepsga nepsag nesapg nesagp nespag nespga
nesgpa nesgap npgeas npgesa npgaes npgase npgsae npgsea npegas npegsa npeags
npeasg npesag npesga npaegs npaesg npages npagse npasge npaseg npseag npsega
npsaeg npsage npsgae npsgea nsgepa nsgeap nsgpea nsgpae nsgape nsgaep nsegpa
nsegap nsepga nsepag nseapg nseagp nspega nspeag nspgea nspgae nspage nspaeg
nsaepg nsaegp nsapeg nsapge nsagpe nsagep sagenp sagepn sagnep sagnpe sagpne
sagpen saegnp saegpn saengp saenpg saepng saepgn sanegp sanepg sangep sangpe
sanpge sanpeg sapeng sapegn sapneg sapnge sapgne sapgen sgaenp sgaepn sganep
sganpe sgapne sgapen sgeanp sgeapn sgenap sgenpa sgepna sgepan sgneap sgnepa
sgnaep sgnape sgnpae sgnpea sgpena sgpean sgpnea sgpnae sgpane sgpaen seganp
segapn segnap segnpa segpna segpan seagnp seagpn seangp seanpg seapng seapgn
senagp senapg sengap sengpa senpga senpag sepang sepagn sepnag sepnga sepgna
sepgan sngeap sngepa sngaep sngape sngpae sngpea snegap snegpa sneagp sneapg
snepag snepga snaegp snaepg snagep snagpe snapge snapeg snpeag snpega snpaeg
snpage snpgae snpgea spgena spgean spgnea spgnae spgane spgaen spegna spegan
spenga spenag speang speagn spnega spneag spngea spngae spnage spnaeg spaeng
spaegn spaneg spange spagne spagen

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History of cryptography
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