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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: uhlman
cipher variations:
vimnbo wjnocp xkopdq ylpqer zmqrfs
anrsgt bosthu cptuiv dquvjw ervwkx
fswxly gtxymz huyzna ivzaob jwabpc
kxbcqd lycdre mzdesf naeftg obfguh
pcghvi qdhiwj reijxk sfjkyl tgklzm

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: uhlman
Cipher: fsonzm

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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: uhlman

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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: uhlman
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: uhlman
Cipher: huyzna

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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: uhlman
Cipher: 543213231133

Extended Methods:
Method #1

Plaintext: uhlman
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
u h l m a n 
5 3 1 2 1 3 
4 2 3 3 1 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: uhlman
Cipher: pflinl

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Method #3

Plaintext: uhlman
method variations:
obhclx bhclxo hclxob
clxobh lxobhc xobhcl

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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: uhlman

all 720 cipher variations:
uhlman uhlmna uhlamn uhlanm uhlnam uhlnma uhmlan uhmlna uhmaln uhmanl uhmnal
uhmnla uhamln uhamnl uhalmn uhalnm uhanlm uhanml uhnmal uhnmla uhnaml uhnalm
uhnlam uhnlma ulhman ulhmna ulhamn ulhanm ulhnam ulhnma ulmhan ulmhna ulmahn
ulmanh ulmnah ulmnha ulamhn ulamnh ulahmn ulahnm ulanhm ulanmh ulnmah ulnmha
ulnamh ulnahm ulnham ulnhma umlhan umlhna umlahn umlanh umlnah umlnha umhlan
umhlna umhaln umhanl umhnal umhnla umahln umahnl umalhn umalnh umanlh umanhl
umnhal umnhla umnahl umnalh umnlah umnlha ualmhn ualmnh ualhmn ualhnm ualnhm
ualnmh uamlhn uamlnh uamhln uamhnl uamnhl uamnlh uahmln uahmnl uahlmn uahlnm
uahnlm uahnml uanmhl uanmlh uanhml uanhlm uanlhm uanlmh unlmah unlmha unlamh
unlahm unlham unlhma unmlah unmlha unmalh unmahl unmhal unmhla unamlh unamhl
unalmh unalhm unahlm unahml unhmal unhmla unhaml unhalm unhlam unhlma hulman
hulmna hulamn hulanm hulnam hulnma humlan humlna humaln humanl humnal humnla
huamln huamnl hualmn hualnm huanlm huanml hunmal hunmla hunaml hunalm hunlam
hunlma hluman hlumna hluamn hluanm hlunam hlunma hlmuan hlmuna hlmaun hlmanu
hlmnau hlmnua hlamun hlamnu hlaumn hlaunm hlanum hlanmu hlnmau hlnmua hlnamu
hlnaum hlnuam hlnuma hmluan hmluna hmlaun hmlanu hmlnau hmlnua hmulan hmulna
hmualn hmuanl hmunal hmunla hmauln hmaunl hmalun hmalnu hmanlu hmanul hmnual
hmnula hmnaul hmnalu hmnlau hmnlua halmun halmnu halumn halunm halnum halnmu
hamlun hamlnu hamuln hamunl hamnul hamnlu haumln haumnl haulmn haulnm haunlm
haunml hanmul hanmlu hanuml hanulm hanlum hanlmu hnlmau hnlmua hnlamu hnlaum
hnluam hnluma hnmlau hnmlua hnmalu hnmaul hnmual hnmula hnamlu hnamul hnalmu
hnalum hnaulm hnauml hnumal hnumla hnuaml hnualm hnulam hnulma lhuman lhumna
lhuamn lhuanm lhunam lhunma lhmuan lhmuna lhmaun lhmanu lhmnau lhmnua lhamun
lhamnu lhaumn lhaunm lhanum lhanmu lhnmau lhnmua lhnamu lhnaum lhnuam lhnuma
luhman luhmna luhamn luhanm luhnam luhnma lumhan lumhna lumahn lumanh lumnah
lumnha luamhn luamnh luahmn luahnm luanhm luanmh lunmah lunmha lunamh lunahm
lunham lunhma lmuhan lmuhna lmuahn lmuanh lmunah lmunha lmhuan lmhuna lmhaun
lmhanu lmhnau lmhnua lmahun lmahnu lmauhn lmaunh lmanuh lmanhu lmnhau lmnhua
lmnahu lmnauh lmnuah lmnuha laumhn laumnh lauhmn lauhnm launhm launmh lamuhn
lamunh lamhun lamhnu lamnhu lamnuh lahmun lahmnu lahumn lahunm lahnum lahnmu
lanmhu lanmuh lanhmu lanhum lanuhm lanumh lnumah lnumha lnuamh lnuahm lnuham
lnuhma lnmuah lnmuha lnmauh lnmahu lnmhau lnmhua lnamuh lnamhu lnaumh lnauhm
lnahum lnahmu lnhmau lnhmua lnhamu lnhaum lnhuam lnhuma mhluan mhluna mhlaun
mhlanu mhlnau mhlnua mhulan mhulna mhualn mhuanl mhunal mhunla mhauln mhaunl
mhalun mhalnu mhanlu mhanul mhnual mhnula mhnaul mhnalu mhnlau mhnlua mlhuan
mlhuna mlhaun mlhanu mlhnau mlhnua mluhan mluhna mluahn mluanh mlunah mlunha
mlauhn mlaunh mlahun mlahnu mlanhu mlanuh mlnuah mlnuha mlnauh mlnahu mlnhau
mlnhua mulhan mulhna mulahn mulanh mulnah mulnha muhlan muhlna muhaln muhanl
muhnal muhnla muahln muahnl mualhn mualnh muanlh muanhl munhal munhla munahl
munalh munlah munlha maluhn malunh malhun malhnu malnhu malnuh maulhn maulnh
mauhln mauhnl maunhl maunlh mahuln mahunl mahlun mahlnu mahnlu mahnul manuhl
manulh manhul manhlu manlhu manluh mnluah mnluha mnlauh mnlahu mnlhau mnlhua
mnulah mnulha mnualh mnuahl mnuhal mnuhla mnaulh mnauhl mnaluh mnalhu mnahlu
mnahul mnhual mnhula mnhaul mnhalu mnhlau mnhlua ahlmun ahlmnu ahlumn ahlunm
ahlnum ahlnmu ahmlun ahmlnu ahmuln ahmunl ahmnul ahmnlu ahumln ahumnl ahulmn
ahulnm ahunlm ahunml ahnmul ahnmlu ahnuml ahnulm ahnlum ahnlmu alhmun alhmnu
alhumn alhunm alhnum alhnmu almhun almhnu almuhn almunh almnuh almnhu alumhn
alumnh aluhmn aluhnm alunhm alunmh alnmuh alnmhu alnumh alnuhm alnhum alnhmu
amlhun amlhnu amluhn amlunh amlnuh amlnhu amhlun amhlnu amhuln amhunl amhnul
amhnlu amuhln amuhnl amulhn amulnh amunlh amunhl amnhul amnhlu amnuhl amnulh
amnluh amnlhu aulmhn aulmnh aulhmn aulhnm aulnhm aulnmh aumlhn aumlnh aumhln
aumhnl aumnhl aumnlh auhmln auhmnl auhlmn auhlnm auhnlm auhnml aunmhl aunmlh
aunhml aunhlm aunlhm aunlmh anlmuh anlmhu anlumh anluhm anlhum anlhmu anmluh
anmlhu anmulh anmuhl anmhul anmhlu anumlh anumhl anulmh anulhm anuhlm anuhml
anhmul anhmlu anhuml anhulm anhlum anhlmu nhlmau nhlmua nhlamu nhlaum nhluam
nhluma nhmlau nhmlua nhmalu nhmaul nhmual nhmula nhamlu nhamul nhalmu nhalum
nhaulm nhauml nhumal nhumla nhuaml nhualm nhulam nhulma nlhmau nlhmua nlhamu
nlhaum nlhuam nlhuma nlmhau nlmhua nlmahu nlmauh nlmuah nlmuha nlamhu nlamuh
nlahmu nlahum nlauhm nlaumh nlumah nlumha nluamh nluahm nluham nluhma nmlhau
nmlhua nmlahu nmlauh nmluah nmluha nmhlau nmhlua nmhalu nmhaul nmhual nmhula
nmahlu nmahul nmalhu nmaluh nmaulh nmauhl nmuhal nmuhla nmuahl nmualh nmulah
nmulha nalmhu nalmuh nalhmu nalhum naluhm nalumh namlhu namluh namhlu namhul
namuhl namulh nahmlu nahmul nahlmu nahlum nahulm nahuml naumhl naumlh nauhml
nauhlm naulhm naulmh nulmah nulmha nulamh nulahm nulham nulhma numlah numlha
numalh numahl numhal numhla nuamlh nuamhl nualmh nualhm nuahlm nuahml nuhmal
nuhmla nuhaml nuhalm nuhlam nuhlma

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History of cryptography
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