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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: dubito
cipher variations:
evcjup fwdkvq gxelwr hyfmxs izgnyt
jahozu kbipav lcjqbw mdkrcx nelsdy
ofmtez pgnufa qhovgb ripwhc sjqxid
tkryje ulszkf vmtalg wnubmh xovcni
ypwdoj zqxepk aryfql bszgrm ctahsn

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: dubito
Cipher: wfyrgl

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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: dubito

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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: dubito
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: dubito
Cipher: qhovgb

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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: dubito
Cipher: 415421424443

Extended Methods:
Method #1

Plaintext: dubito
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
d u b i t o 
4 5 2 4 4 4 
1 4 1 2 4 3 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: dubito
Cipher: yrtqfo

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Method #3

Plaintext: dubito
method variations:
viqrts iqrtsv qrtsvi
rtsviq tsviqr sviqrt

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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: dubito

all 720 cipher variations:
dubito dubiot dubtio dubtoi duboti duboit duibto duibot duitbo duitob duiotb
duiobt dutibo dutiob dutbio dutboi dutobi dutoib duoitb duoibt duotib duotbi
duobti duobit dbuito dbuiot dbutio dbutoi dbuoti dbuoit dbiuto dbiuot dbituo
dbitou dbiotu dbiout dbtiuo dbtiou dbtuio dbtuoi dbtoui dbtoiu dboitu dboiut
dbotiu dbotui dbouti dbouit dibuto dibuot dibtuo dibtou dibotu dibout diubto
diubot diutbo diutob diuotb diuobt ditubo dituob ditbuo ditbou ditobu ditoub
dioutb dioubt diotub diotbu diobtu diobut dtbiuo dtbiou dtbuio dtbuoi dtboui
dtboiu dtibuo dtibou dtiubo dtiuob dtioub dtiobu dtuibo dtuiob dtubio dtuboi
dtuobi dtuoib dtoiub dtoibu dtouib dtoubi dtobui dtobiu dobitu dobiut dobtiu
dobtui dobuti dobuit doibtu doibut doitbu doitub doiutb doiubt dotibu dotiub
dotbiu dotbui dotubi dotuib douitb douibt doutib doutbi doubti doubit udbito
udbiot udbtio udbtoi udboti udboit udibto udibot uditbo uditob udiotb udiobt
udtibo udtiob udtbio udtboi udtobi udtoib udoitb udoibt udotib udotbi udobti
udobit ubdito ubdiot ubdtio ubdtoi ubdoti ubdoit ubidto ubidot ubitdo ubitod
ubiotd ubiodt ubtido ubtiod ubtdio ubtdoi ubtodi ubtoid uboitd uboidt ubotid
ubotdi ubodti ubodit uibdto uibdot uibtdo uibtod uibotd uibodt uidbto uidbot
uidtbo uidtob uidotb uidobt uitdbo uitdob uitbdo uitbod uitobd uitodb uiodtb
uiodbt uiotdb uiotbd uiobtd uiobdt utbido utbiod utbdio utbdoi utbodi utboid
utibdo utibod utidbo utidob utiodb utiobd utdibo utdiob utdbio utdboi utdobi
utdoib utoidb utoibd utodib utodbi utobdi utobid uobitd uobidt uobtid uobtdi
uobdti uobdit uoibtd uoibdt uoitbd uoitdb uoidtb uoidbt uotibd uotidb uotbid
uotbdi uotdbi uotdib uoditb uodibt uodtib uodtbi uodbti uodbit budito budiot
budtio budtoi budoti budoit buidto buidot buitdo buitod buiotd buiodt butido
butiod butdio butdoi butodi butoid buoitd buoidt buotid buotdi buodti buodit
bduito bduiot bdutio bdutoi bduoti bduoit bdiuto bdiuot bdituo bditou bdiotu
bdiout bdtiuo bdtiou bdtuio bdtuoi bdtoui bdtoiu bdoitu bdoiut bdotiu bdotui
bdouti bdouit biduto biduot bidtuo bidtou bidotu bidout biudto biudot biutdo
biutod biuotd biuodt bitudo bituod bitduo bitdou bitodu bitoud bioutd bioudt
biotud biotdu biodtu biodut btdiuo btdiou btduio btduoi btdoui btdoiu btiduo
btidou btiudo btiuod btioud btiodu btuido btuiod btudio btudoi btuodi btuoid
btoiud btoidu btouid btoudi btodui btodiu boditu bodiut bodtiu bodtui boduti
boduit boidtu boidut boitdu boitud boiutd boiudt botidu botiud botdiu botdui
botudi botuid bouitd bouidt boutid boutdi boudti boudit iubdto iubdot iubtdo
iubtod iubotd iubodt iudbto iudbot iudtbo iudtob iudotb iudobt iutdbo iutdob
iutbdo iutbod iutobd iutodb iuodtb iuodbt iuotdb iuotbd iuobtd iuobdt ibudto
ibudot ibutdo ibutod ibuotd ibuodt ibduto ibduot ibdtuo ibdtou ibdotu ibdout
ibtduo ibtdou ibtudo ibtuod ibtoud ibtodu ibodtu ibodut ibotdu ibotud iboutd
iboudt idbuto idbuot idbtuo idbtou idbotu idbout idubto idubot idutbo idutob
iduotb iduobt idtubo idtuob idtbuo idtbou idtobu idtoub idoutb idoubt idotub
idotbu idobtu idobut itbduo itbdou itbudo itbuod itboud itbodu itdbuo itdbou
itdubo itduob itdoub itdobu itudbo itudob itubdo itubod ituobd ituodb itodub
itodbu itoudb itoubd itobud itobdu iobdtu iobdut iobtdu iobtud iobutd iobudt
iodbtu iodbut iodtbu iodtub iodutb iodubt iotdbu iotdub iotbdu iotbud iotubd
iotudb ioudtb ioudbt ioutdb ioutbd ioubtd ioubdt tubido tubiod tubdio tubdoi
tubodi tuboid tuibdo tuibod tuidbo tuidob tuiodb tuiobd tudibo tudiob tudbio
tudboi tudobi tudoib tuoidb tuoibd tuodib tuodbi tuobdi tuobid tbuido tbuiod
tbudio tbudoi tbuodi tbuoid tbiudo tbiuod tbiduo tbidou tbiodu tbioud tbdiuo
tbdiou tbduio tbduoi tbdoui tbdoiu tboidu tboiud tbodiu tbodui tboudi tbouid
tibudo tibuod tibduo tibdou tibodu tiboud tiubdo tiubod tiudbo tiudob tiuodb
tiuobd tidubo tiduob tidbuo tidbou tidobu tidoub tioudb tioubd tiodub tiodbu
tiobdu tiobud tdbiuo tdbiou tdbuio tdbuoi tdboui tdboiu tdibuo tdibou tdiubo
tdiuob tdioub tdiobu tduibo tduiob tdubio tduboi tduobi tduoib tdoiub tdoibu
tdouib tdoubi tdobui tdobiu tobidu tobiud tobdiu tobdui tobudi tobuid toibdu
toibud toidbu toidub toiudb toiubd todibu todiub todbiu todbui todubi toduib
touidb touibd toudib toudbi toubdi toubid oubitd oubidt oubtid oubtdi oubdti
oubdit ouibtd ouibdt ouitbd ouitdb ouidtb ouidbt outibd outidb outbid outbdi
outdbi outdib ouditb oudibt oudtib oudtbi oudbti oudbit obuitd obuidt obutid
obutdi obudti obudit obiutd obiudt obitud obitdu obidtu obidut obtiud obtidu
obtuid obtudi obtdui obtdiu obditu obdiut obdtiu obdtui obduti obduit oibutd
oibudt oibtud oibtdu oibdtu oibdut oiubtd oiubdt oiutbd oiutdb oiudtb oiudbt
oitubd oitudb oitbud oitbdu oitdbu oitdub oidutb oidubt oidtub oidtbu oidbtu
oidbut otbiud otbidu otbuid otbudi otbdui otbdiu otibud otibdu otiubd otiudb
otidub otidbu otuibd otuidb otubid otubdi otudbi otudib otdiub otdibu otduib
otdubi otdbui otdbiu odbitu odbiut odbtiu odbtui odbuti odbuit odibtu odibut
oditbu oditub odiutb odiubt odtibu odtiub odtbiu odtbui odtubi odtuib oduitb
oduibt odutib odutbi odubti odubit

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History of cryptography
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