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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: seroon
cipher variations:
tfsppo ugtqqp vhurrq wivssr xjwtts
ykxuut zlyvvu amzwwv bnaxxw cobyyx
dpczzy eqdaaz frebba gsfccb htgddc
iuheed jviffe kwjggf lxkhhg myliih
nzmjji oankkj pbollk qcpmml rdqnnm

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: seroon
Cipher: hvillm

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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: seroon

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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: seroon
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: seroon
Cipher: frebba

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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: seroon
Cipher: 345124434333

Extended Methods:
Method #1

Plaintext: seroon
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
s e r o o n 
3 5 2 4 4 3 
4 1 4 3 3 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: seroon
Cipher: xrodon

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Method #3

Plaintext: seroon
method variations:
yftsnn ftsnny tsnnyf
snnyft nnyfts nyftsn

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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: seroon

all 720 cipher variations:
seroon serono seroon serono sernoo sernoo seoron seorno seoorn seoonr seonor
seonro seoorn seoonr seoron seorno seonro seonor senoor senoro senoor senoro
senroo senroo sreoon sreono sreoon sreono srenoo srenoo sroeon sroeno srooen
sroone sronoe sroneo srooen sroone sroeon sroeno sroneo sronoe srnooe srnoeo
srnooe srnoeo srneoo srneoo soreon soreno soroen sorone sornoe sorneo soeron
soerno soeorn soeonr soenor soenro sooern sooenr sooren soorne soonre sooner
soneor sonero sonoer sonore sonroe sonreo soroen sorone soreon soreno sorneo
sornoe sooren soorne sooern sooenr sooner soonre soeorn soeonr soeron soerno
soenro soenor sonoer sonore soneor sonero sonreo sonroe snrooe snroeo snrooe
snroeo snreoo snreoo snoroe snoreo snoore snooer snoeor snoero snoore snooer
snoroe snoreo snoero snoeor sneoor sneoro sneoor sneoro sneroo sneroo esroon
esrono esroon esrono esrnoo esrnoo esoron esorno esoorn esoonr esonor esonro
esoorn esoonr esoron esorno esonro esonor esnoor esnoro esnoor esnoro esnroo
esnroo ersoon ersono ersoon ersono ersnoo ersnoo eroson erosno eroosn eroons
eronos eronso eroosn eroons eroson erosno eronso eronos ernoos ernoso ernoos
ernoso ernsoo ernsoo eorson eorsno eorosn eorons eornos eornso eosron eosrno
eosorn eosonr eosnor eosnro eoosrn eoosnr eoorsn eoorns eoonrs eoonsr eonsor
eonsro eonosr eonors eonros eonrso eorosn eorons eorson eorsno eornso eornos
eoorsn eoorns eoosrn eoosnr eoonsr eoonrs eosorn eosonr eosron eosrno eosnro
eosnor eonosr eonors eonsor eonsro eonrso eonros enroos enroso enroos enroso
enrsoo enrsoo enoros enorso enoors enoosr enosor enosro enoors enoosr enoros
enorso enosro enosor ensoor ensoro ensoor ensoro ensroo ensroo resoon resono
resoon resono resnoo resnoo reoson reosno reoosn reoons reonos reonso reoosn
reoons reoson reosno reonso reonos renoos renoso renoos renoso rensoo rensoo
rseoon rseono rseoon rseono rsenoo rsenoo rsoeon rsoeno rsooen rsoone rsonoe
rsoneo rsooen rsoone rsoeon rsoeno rsoneo rsonoe rsnooe rsnoeo rsnooe rsnoeo
rsneoo rsneoo roseon roseno rosoen rosone rosnoe rosneo roeson roesno roeosn
roeons roenos roenso rooesn rooens roosen roosne roonse roones roneos roneso
ronoes ronose ronsoe ronseo rosoen rosone roseon roseno rosneo rosnoe roosen
roosne rooesn rooens roones roonse roeosn roeons roeson roesno roenso roenos
ronoes ronose roneos roneso ronseo ronsoe rnsooe rnsoeo rnsooe rnsoeo rnseoo
rnseoo rnosoe rnoseo rnoose rnooes rnoeos rnoeso rnoose rnooes rnosoe rnoseo
rnoeso rnoeos rneoos rneoso rneoos rneoso rnesoo rnesoo oerson oersno oerosn
oerons oernos oernso oesron oesrno oesorn oesonr oesnor oesnro oeosrn oeosnr
oeorsn oeorns oeonrs oeonsr oensor oensro oenosr oenors oenros oenrso oreson
oresno oreosn oreons orenos orenso orseon orseno orsoen orsone orsnoe orsneo
orosen orosne oroesn oroens orones oronse ornsoe ornseo ornose ornoes orneos
orneso osreon osreno osroen osrone osrnoe osrneo oseron oserno oseorn oseonr
osenor osenro osoern osoenr osoren osorne osonre osoner osneor osnero osnoer
osnore osnroe osnreo oorsen oorsne ooresn oorens oornes oornse oosren oosrne
oosern oosenr oosner oosnre ooesrn ooesnr ooersn ooerns ooenrs ooensr oonser
oonsre oonesr ooners oonres oonrse onrsoe onrseo onrose onroes onreos onreso
onsroe onsreo onsore onsoer onseor onsero onosre onoser onorse onores onoers
onoesr onesor onesro oneosr oneors oneros onerso oerosn oerons oerson oersno
oernso oernos oeorsn oeorns oeosrn oeosnr oeonsr oeonrs oesorn oesonr oesron
oesrno oesnro oesnor oenosr oenors oensor oensro oenrso oenros oreosn oreons
oreson oresno orenso orenos oroesn oroens orosen orosne oronse orones orsoen
orsone orseon orseno orsneo orsnoe ornose ornoes ornsoe ornseo orneso orneos
ooresn oorens oorsen oorsne oornse oornes ooersn ooerns ooesrn ooesnr ooensr
ooenrs oosern oosenr oosren oosrne oosnre oosner oonesr ooners oonser oonsre
oonrse oonres osroen osrone osreon osreno osrneo osrnoe osoren osorne osoern
osoenr osoner osonre oseorn oseonr oseron oserno osenro osenor osnoer osnore
osneor osnero osnreo osnroe onrose onroes onrsoe onrseo onreso onreos onorse
onores onosre onoser onoesr onoers onsore onsoer onsroe onsreo onsero onseor
oneosr oneors onesor onesro onerso oneros neroos neroso neroos neroso nersoo
nersoo neoros neorso neoors neoosr neosor neosro neoors neoosr neoros neorso
neosro neosor nesoor nesoro nesoor nesoro nesroo nesroo nreoos nreoso nreoos
nreoso nresoo nresoo nroeos nroeso nrooes nroose nrosoe nroseo nrooes nroose
nroeos nroeso nroseo nrosoe nrsooe nrsoeo nrsooe nrsoeo nrseoo nrseoo noreos
noreso noroes norose norsoe norseo noeros noerso noeors noeosr noesor noesro
nooers nooesr noores noorse noosre nooser noseor nosero nosoer nosore nosroe
nosreo noroes norose noreos noreso norseo norsoe noores noorse nooers nooesr
nooser noosre noeors noeosr noeros noerso noesro noesor nosoer nosore noseor
nosero nosreo nosroe nsrooe nsroeo nsrooe nsroeo nsreoo nsreoo nsoroe nsoreo
nsoore nsooer nsoeor nsoero nsoore nsooer nsoroe nsoreo nsoero nsoeor nseoor
nseoro nseoor nseoro nseroo nseroo

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History of cryptography
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