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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: queant
cipher variations:
rvfbou swgcpv txhdqw uyierx vzjfsy
wakgtz xblhua ycmivb zdnjwc aeokxd
bfplye cgqmzf dhrnag eisobh fjtpci
gkuqdj hlvrek imwsfl jnxtgm koyuhn
lpzvio mqawjp nrbxkq oscylr ptdzms

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: queant
Cipher: jfvzmg

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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: queant

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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: queant
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: queant
Cipher: dhrnag

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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: queant
Cipher: 145451113344

Extended Methods:
Method #1

Plaintext: queant
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
q u e a n t 
1 5 5 1 3 4 
4 4 1 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: queant
Cipher: vestas

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Method #3

Plaintext: queant
method variations:
yyalsd yalsdy alsdyy
lsdyya sdyyal dyyals

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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: queant

all 720 cipher variations:
queant queatn quenat quenta quetna quetan quaent quaetn quanet quante quatne
quaten qunaet qunate quneat quneta quntea quntae qutane qutaen qutnae qutnea
qutena qutean qeuant qeuatn qeunat qeunta qeutna qeutan qeaunt qeautn qeanut
qeantu qeatnu qeatun qenaut qenatu qenuat qenuta qentua qentau qetanu qetaun
qetnau qetnua qetuna qetuan qaeunt qaeutn qaenut qaentu qaetnu qaetun qauent
qauetn qaunet qaunte qautne qauten qanuet qanute qaneut qanetu qanteu qantue
qatune qatuen qatnue qatneu qatenu qateun qneaut qneatu qneuat qneuta qnetua
qnetau qnaeut qnaetu qnauet qnaute qnatue qnateu qnuaet qnuate qnueat qnueta
qnutea qnutae qntaue qntaeu qntuae qntuea qnteua qnteau qteanu qteaun qtenau
qtenua qteuna qteuan qtaenu qtaeun qtaneu qtanue qtaune qtauen qtnaeu qtnaue
qtneau qtneua qtnuea qtnuae qtuane qtuaen qtunae qtunea qtuena qtuean uqeant
uqeatn uqenat uqenta uqetna uqetan uqaent uqaetn uqanet uqante uqatne uqaten
uqnaet uqnate uqneat uqneta uqntea uqntae uqtane uqtaen uqtnae uqtnea uqtena
uqtean ueqant ueqatn ueqnat ueqnta ueqtna ueqtan ueaqnt ueaqtn ueanqt ueantq
ueatnq ueatqn uenaqt uenatq uenqat uenqta uentqa uentaq uetanq uetaqn uetnaq
uetnqa uetqna uetqan uaeqnt uaeqtn uaenqt uaentq uaetnq uaetqn uaqent uaqetn
uaqnet uaqnte uaqtne uaqten uanqet uanqte uaneqt uanetq uanteq uantqe uatqne
uatqen uatnqe uatneq uatenq uateqn uneaqt uneatq uneqat uneqta unetqa unetaq
unaeqt unaetq unaqet unaqte unatqe unateq unqaet unqate unqeat unqeta unqtea
unqtae untaqe untaeq untqae untqea unteqa unteaq uteanq uteaqn utenaq utenqa
uteqna uteqan utaenq utaeqn utaneq utanqe utaqne utaqen utnaeq utnaqe utneaq
utneqa utnqea utnqae utqane utqaen utqnae utqnea utqena utqean euqant euqatn
euqnat euqnta euqtna euqtan euaqnt euaqtn euanqt euantq euatnq euatqn eunaqt
eunatq eunqat eunqta euntqa euntaq eutanq eutaqn eutnaq eutnqa eutqna eutqan
equant equatn equnat equnta equtna equtan eqaunt eqautn eqanut eqantu eqatnu
eqatun eqnaut eqnatu eqnuat eqnuta eqntua eqntau eqtanu eqtaun eqtnau eqtnua
eqtuna eqtuan eaqunt eaqutn eaqnut eaqntu eaqtnu eaqtun eauqnt eauqtn eaunqt
eauntq eautnq eautqn eanuqt eanutq eanqut eanqtu eantqu eantuq eatunq eatuqn
eatnuq eatnqu eatqnu eatqun enqaut enqatu enquat enquta enqtua enqtau enaqut
enaqtu enauqt enautq enatuq enatqu enuaqt enuatq enuqat enuqta enutqa enutaq
entauq entaqu entuaq entuqa entqua entqau etqanu etqaun etqnau etqnua etquna
etquan etaqnu etaqun etanqu etanuq etaunq etauqn etnaqu etnauq etnqau etnqua
etnuqa etnuaq etuanq etuaqn etunaq etunqa etuqna etuqan aueqnt aueqtn auenqt
auentq auetnq auetqn auqent auqetn auqnet auqnte auqtne auqten aunqet aunqte
auneqt aunetq aunteq auntqe autqne autqen autnqe autneq autenq auteqn aeuqnt
aeuqtn aeunqt aeuntq aeutnq aeutqn aequnt aequtn aeqnut aeqntu aeqtnu aeqtun
aenqut aenqtu aenuqt aenutq aentuq aentqu aetqnu aetqun aetnqu aetnuq aetunq
aetuqn aqeunt aqeutn aqenut aqentu aqetnu aqetun aquent aquetn aqunet aqunte
aqutne aquten aqnuet aqnute aqneut aqnetu aqnteu aqntue aqtune aqtuen aqtnue
aqtneu aqtenu aqteun anequt aneqtu aneuqt aneutq anetuq anetqu anqeut anqetu
anquet anqute anqtue anqteu anuqet anuqte anueqt anuetq anuteq anutqe antque
antqeu antuqe antueq anteuq antequ ateqnu atequn atenqu atenuq ateunq ateuqn
atqenu atqeun atqneu atqnue atqune atquen atnqeu atnque atnequ atneuq atnueq
atnuqe atuqne atuqen atunqe atuneq atuenq atueqn nueaqt nueatq nueqat nueqta
nuetqa nuetaq nuaeqt nuaetq nuaqet nuaqte nuatqe nuateq nuqaet nuqate nuqeat
nuqeta nuqtea nuqtae nutaqe nutaeq nutqae nutqea nuteqa nuteaq neuaqt neuatq
neuqat neuqta neutqa neutaq neauqt neautq neaqut neaqtu neatqu neatuq neqaut
neqatu nequat nequta neqtua neqtau netaqu netauq netqau netqua netuqa netuaq
naeuqt naeutq naequt naeqtu naetqu naetuq naueqt nauetq nauqet nauqte nautqe
nauteq naquet naqute naqeut naqetu naqteu naqtue natuqe natueq natque natqeu
natequ nateuq nqeaut nqeatu nqeuat nqeuta nqetua nqetau nqaeut nqaetu nqauet
nqaute nqatue nqateu nquaet nquate nqueat nqueta nqutea nqutae nqtaue nqtaeu
nqtuae nqtuea nqteua nqteau nteaqu nteauq nteqau ntequa nteuqa nteuaq ntaequ
ntaeuq ntaqeu ntaque ntauqe ntaueq ntqaeu ntqaue ntqeau ntqeua ntquea ntquae
ntuaqe ntuaeq ntuqae ntuqea ntueqa ntueaq tueanq tueaqn tuenaq tuenqa tueqna
tueqan tuaenq tuaeqn tuaneq tuanqe tuaqne tuaqen tunaeq tunaqe tuneaq tuneqa
tunqea tunqae tuqane tuqaen tuqnae tuqnea tuqena tuqean teuanq teuaqn teunaq
teunqa teuqna teuqan teaunq teauqn teanuq teanqu teaqnu teaqun tenauq tenaqu
tenuaq tenuqa tenqua tenqau teqanu teqaun teqnau teqnua tequna tequan taeunq
taeuqn taenuq taenqu taeqnu taequn tauenq taueqn tauneq taunqe tauqne tauqen
tanueq tanuqe taneuq tanequ tanqeu tanque taqune taquen taqnue taqneu taqenu
taqeun tneauq tneaqu tneuaq tneuqa tnequa tneqau tnaeuq tnaequ tnaueq tnauqe
tnaque tnaqeu tnuaeq tnuaqe tnueaq tnueqa tnuqea tnuqae tnqaue tnqaeu tnquae
tnquea tnqeua tnqeau tqeanu tqeaun tqenau tqenua tqeuna tqeuan tqaenu tqaeun
tqaneu tqanue tqaune tqauen tqnaeu tqnaue tqneau tqneua tqnuea tqnuae tquane
tquaen tqunae tqunea tquena tquean

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History of cryptography
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