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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: anteed
cipher variations:
bouffe cpvggf dqwhhg erxiih fsyjji
gtzkkj huallk ivbmml jwcnnm kxdoon
lyeppo mzfqqp nagrrq obhssr pcitts
qdjuut rekvvu sflwwv tgmxxw uhnyyx
viozzy wjpaaz xkqbba ylrccb zmsddc

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: anteed
Cipher: zmgvvw

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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: anteed

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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: anteed
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: anteed
Cipher: nagrrq

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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: anteed
Cipher: 113344515141

Extended Methods:
Method #1

Plaintext: anteed
method variations:

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

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Method #3

Plaintext: anteed
method variations:
lsyvqa syvqal yvqals
vqalsy qalsyv alsyvq

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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: anteed

all 720 cipher variations:
anteed antede anteed antede antdee antdee aneted anetde aneetd aneedt anedet
anedte aneetd aneedt aneted anetde anedte anedet andeet andete andeet andete
andtee andtee atneed atnede atneed atnede atndee atndee atened atende ateend
ateedn ateden atedne ateend ateedn atened atende atedne ateden atdeen atdene
atdeen atdene atdnee atdnee aetned aetnde aetend aetedn aetden aetdne aented
aentde aenetd aenedt aendet aendte aeentd aeendt aeetnd aeetdn aeedtn aeednt
aednet aednte aedent aedetn aedten aedtne aetend aetedn aetned aetnde aetdne
aetden aeetnd aeetdn aeentd aeendt aeednt aeedtn aenetd aenedt aented aentde
aendte aendet aedent aedetn aednet aednte aedtne aedten adteen adtene adteen
adtene adtnee adtnee adeten adetne adeetn adeent adenet adente adeetn adeent
adeten adetne adente adenet adneet adnete adneet adnete adntee adntee nateed
natede nateed natede natdee natdee naeted naetde naeetd naeedt naedet naedte
naeetd naeedt naeted naetde naedte naedet nadeet nadete nadeet nadete nadtee
nadtee ntaeed ntaede ntaeed ntaede ntadee ntadee nteaed nteade nteead nteeda
ntedea ntedae nteead nteeda nteaed nteade ntedae ntedea ntdeea ntdeae ntdeea
ntdeae ntdaee ntdaee netaed netade netead neteda netdea netdae neated neatde
neaetd neaedt neadet neadte neeatd neeadt neetad neetda needta needat nedaet
nedate nedeat nedeta nedtea nedtae netead neteda netaed netade netdae netdea
neetad neetda neeatd neeadt needat needta neaetd neaedt neated neatde neadte
neadet nedeat nedeta nedaet nedate nedtae nedtea ndteea ndteae ndteea ndteae
ndtaee ndtaee ndetea ndetae ndeeta ndeeat ndeaet ndeate ndeeta ndeeat ndetea
ndetae ndeate ndeaet ndaeet ndaete ndaeet ndaete ndatee ndatee tnaeed tnaede
tnaeed tnaede tnadee tnadee tneaed tneade tneead tneeda tnedea tnedae tneead
tneeda tneaed tneade tnedae tnedea tndeea tndeae tndeea tndeae tndaee tndaee
taneed tanede taneed tanede tandee tandee taened taende taeend taeedn taeden
taedne taeend taeedn taened taende taedne taeden tadeen tadene tadeen tadene
tadnee tadnee teaned teande teaend teaedn teaden teadne tenaed tenade tenead
teneda tendea tendae teenad teenda teeand teeadn teedan teedna tednea tednae
tedena tedean tedaen tedane teaend teaedn teaned teande teadne teaden teeand
teeadn teenad teenda teedna teedan tenead teneda tenaed tenade tendae tendea
tedena tedean tednea tednae tedane tedaen tdaeen tdaene tdaeen tdaene tdanee
tdanee tdeaen tdeane tdeean tdeena tdenea tdenae tdeean tdeena tdeaen tdeane
tdenae tdenea tdneea tdneae tdneea tdneae tdnaee tdnaee entaed entade entead
enteda entdea entdae enated enatde enaetd enaedt enadet enadte eneatd eneadt
enetad enetda enedta enedat endaet endate endeat endeta endtea endtae etnaed
etnade etnead etneda etndea etndae etaned etande etaend etaedn etaden etadne
eteand eteadn etenad etenda etedna etedan etdaen etdane etdean etdena etdnea
etdnae eatned eatnde eatend eatedn eatden eatdne eanted eantde eanetd eanedt
eandet eandte eaentd eaendt eaetnd eaetdn eaedtn eaednt eadnet eadnte eadent
eadetn eadten eadtne eetand eetadn eetnad eetnda eetdna eetdan eeatnd eeatdn
eeantd eeandt eeadnt eeadtn eenatd eenadt eentad eentda eendta eendat eedant
eedatn eednat eednta eedtna eedtan edtaen edtane edtean edtena edtnea edtnae
edaten edatne edaetn edaent edanet edante edeatn edeant edetan edetna edenta
edenat ednaet ednate edneat edneta edntea edntae entead enteda entaed entade
entdae entdea enetad enetda eneatd eneadt enedat enedta enaetd enaedt enated
enatde enadte enadet endeat endeta endaet endate endtae endtea etnead etneda
etnaed etnade etndae etndea etenad etenda eteand eteadn etedan etedna etaend
etaedn etaned etande etadne etaden etdean etdena etdaen etdane etdnae etdnea
eetnad eetnda eetand eetadn eetdan eetdna eentad eentda eenatd eenadt eendat
eendta eeantd eeandt eeatnd eeatdn eeadtn eeadnt eednat eednta eedant eedatn
eedtan eedtna eatend eatedn eatned eatnde eatdne eatden eaetnd eaetdn eaentd
eaendt eaednt eaedtn eanetd eanedt eanted eantde eandte eandet eadent eadetn
eadnet eadnte eadtne eadten edtean edtena edtaen edtane edtnae edtnea edetan
edetna edeatn edeant edenat edenta edaetn edaent edaten edatne edante edanet
edneat edneta ednaet ednate edntae edntea dnteea dnteae dnteea dnteae dntaee
dntaee dnetea dnetae dneeta dneeat dneaet dneate dneeta dneeat dnetea dnetae
dneate dneaet dnaeet dnaete dnaeet dnaete dnatee dnatee dtneea dtneae dtneea
dtneae dtnaee dtnaee dtenea dtenae dteena dteean dteaen dteane dteena dteean
dtenea dtenae dteane dteaen dtaeen dtaene dtaeen dtaene dtanee dtanee detnea
detnae detena detean detaen detane dentea dentae deneta deneat denaet denate
deenta deenat deetna deetan deeatn deeant deanet deante deaent deaetn deaten
deatne detena detean detnea detnae detane detaen deetna deetan deenta deenat
deeant deeatn deneta deneat dentea dentae denate denaet deaent deaetn deanet
deante deatne deaten dateen datene dateen datene datnee datnee daeten daetne
daeetn daeent daenet daente daeetn daeent daeten daetne daente daenet daneet
danete daneet danete dantee dantee

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History of cryptography
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