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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: bugeye
cipher variations:
cvhfzf dwigag exjhbh fykici gzljdj
hamkek ibnlfl jcomgm kdpnhn leqoio
mfrpjp ngsqkq ohtrlr piusms qjvtnt
rkwuou slxvpv tmywqw unzxrx voaysy
wpbztz xqcaua yrdbvb zsecwc atfdxd

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: bugeye
Cipher: yftvbv

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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: bugeye

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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: bugeye
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: bugeye
Cipher: ohtrlr

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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: bugeye
Cipher: 215422514551

Extended Methods:
Method #1

Plaintext: bugeye
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
b u g e y e 
2 5 2 5 4 5 
1 4 2 1 5 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: bugeye
Cipher: wwyqbe

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Method #3

Plaintext: bugeye
method variations:
viwqzf iwqzfv wqzfvi
qzfviw zfviwq fviwqz

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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: bugeye

all 720 cipher variations:
bugeye bugeey bugyee bugyee bugeye bugeey buegye buegey bueyge bueyeg bueeyg
bueegy buyege buyeeg buygee buygee buyege buyeeg bueeyg bueegy bueyeg bueyge
buegye buegey bgueye bgueey bguyee bguyee bgueye bgueey bgeuye bgeuey bgeyue
bgeyeu bgeeyu bgeeuy bgyeue bgyeeu bgyuee bgyuee bgyeue bgyeeu bgeeyu bgeeuy
bgeyeu bgeyue bgeuye bgeuey beguye beguey begyue begyeu begeyu begeuy beugye
beugey beuyge beuyeg beueyg beuegy beyuge beyueg beygue beygeu beyegu beyeug
beeuyg beeugy beeyug beeygu beegyu beeguy bygeue bygeeu byguee byguee bygeue
bygeeu byegue byegeu byeuge byeueg byeeug byeegu byuege byueeg byugee byugee
byuege byueeg byeeug byeegu byeueg byeuge byegue byegeu begeyu begeuy begyeu
begyue beguye beguey beegyu beeguy beeygu beeyug beeuyg beeugy beyegu beyeug
beygeu beygue beyuge beyueg beueyg beuegy beuyeg beuyge beugye beugey ubgeye
ubgeey ubgyee ubgyee ubgeye ubgeey ubegye ubegey ubeyge ubeyeg ubeeyg ubeegy
ubyege ubyeeg ubygee ubygee ubyege ubyeeg ubeeyg ubeegy ubeyeg ubeyge ubegye
ubegey ugbeye ugbeey ugbyee ugbyee ugbeye ugbeey ugebye ugebey ugeybe ugeyeb
ugeeyb ugeeby ugyebe ugyeeb ugybee ugybee ugyebe ugyeeb ugeeyb ugeeby ugeyeb
ugeybe ugebye ugebey uegbye uegbey uegybe uegyeb uegeyb uegeby uebgye uebgey
uebyge uebyeg uebeyg uebegy ueybge ueybeg ueygbe ueygeb ueyegb ueyebg ueebyg
ueebgy ueeybg ueeygb ueegyb ueegby uygebe uygeeb uygbee uygbee uygebe uygeeb
uyegbe uyegeb uyebge uyebeg uyeebg uyeegb uybege uybeeg uybgee uybgee uybege
uybeeg uyeebg uyeegb uyebeg uyebge uyegbe uyegeb uegeyb uegeby uegyeb uegybe
uegbye uegbey ueegyb ueegby ueeygb ueeybg ueebyg ueebgy ueyegb ueyebg ueygeb
ueygbe ueybge ueybeg uebeyg uebegy uebyeg uebyge uebgye uebgey gubeye gubeey
gubyee gubyee gubeye gubeey guebye guebey gueybe gueyeb gueeyb gueeby guyebe
guyeeb guybee guybee guyebe guyeeb gueeyb gueeby gueyeb gueybe guebye guebey
gbueye gbueey gbuyee gbuyee gbueye gbueey gbeuye gbeuey gbeyue gbeyeu gbeeyu
gbeeuy gbyeue gbyeeu gbyuee gbyuee gbyeue gbyeeu gbeeyu gbeeuy gbeyeu gbeyue
gbeuye gbeuey gebuye gebuey gebyue gebyeu gebeyu gebeuy geubye geubey geuybe
geuyeb geueyb geueby geyube geyueb geybue geybeu geyebu geyeub geeuyb geeuby
geeyub geeybu geebyu geebuy gybeue gybeeu gybuee gybuee gybeue gybeeu gyebue
gyebeu gyeube gyeueb gyeeub gyeebu gyuebe gyueeb gyubee gyubee gyuebe gyueeb
gyeeub gyeebu gyeueb gyeube gyebue gyebeu gebeyu gebeuy gebyeu gebyue gebuye
gebuey geebyu geebuy geeybu geeyub geeuyb geeuby geyebu geyeub geybeu geybue
geyube geyueb geueyb geueby geuyeb geuybe geubye geubey eugbye eugbey eugybe
eugyeb eugeyb eugeby eubgye eubgey eubyge eubyeg eubeyg eubegy euybge euybeg
euygbe euygeb euyegb euyebg euebyg euebgy eueybg eueygb euegyb euegby egubye
egubey eguybe eguyeb egueyb egueby egbuye egbuey egbyue egbyeu egbeyu egbeuy
egybue egybeu egyube egyueb egyeub egyebu egebyu egebuy egeybu egeyub egeuyb
egeuby ebguye ebguey ebgyue ebgyeu ebgeyu ebgeuy ebugye ebugey ebuyge ebuyeg
ebueyg ebuegy ebyuge ebyueg ebygue ebygeu ebyegu ebyeug ebeuyg ebeugy ebeyug
ebeygu ebegyu ebeguy eygbue eygbeu eygube eygueb eygeub eygebu eybgue eybgeu
eybuge eybueg eybeug eybegu eyubge eyubeg eyugbe eyugeb eyuegb eyuebg eyebug
eyebgu eyeubg eyeugb eyegub eyegbu eegbyu eegbuy eegybu eegyub eeguyb eeguby
eebgyu eebguy eebygu eebyug eebuyg eebugy eeybgu eeybug eeygbu eeygub eeyugb
eeyubg eeubyg eeubgy eeuybg eeuygb eeugyb eeugby yugebe yugeeb yugbee yugbee
yugebe yugeeb yuegbe yuegeb yuebge yuebeg yueebg yueegb yubege yubeeg yubgee
yubgee yubege yubeeg yueebg yueegb yuebeg yuebge yuegbe yuegeb yguebe ygueeb
ygubee ygubee yguebe ygueeb ygeube ygeueb ygebue ygebeu ygeebu ygeeub ygbeue
ygbeeu ygbuee ygbuee ygbeue ygbeeu ygeebu ygeeub ygebeu ygebue ygeube ygeueb
yegube yegueb yegbue yegbeu yegebu yegeub yeugbe yeugeb yeubge yeubeg yeuebg
yeuegb yebuge yebueg yebgue yebgeu yebegu yebeug yeeubg yeeugb yeebug yeebgu
yeegbu yeegub ybgeue ybgeeu ybguee ybguee ybgeue ybgeeu ybegue ybegeu ybeuge
ybeueg ybeeug ybeegu ybuege ybueeg ybugee ybugee ybuege ybueeg ybeeug ybeegu
ybeueg ybeuge ybegue ybegeu yegebu yegeub yegbeu yegbue yegube yegueb yeegbu
yeegub yeebgu yeebug yeeubg yeeugb yebegu yebeug yebgeu yebgue yebuge yebueg
yeuebg yeuegb yeubeg yeubge yeugbe yeugeb eugeyb eugeby eugyeb eugybe eugbye
eugbey euegyb euegby eueygb eueybg euebyg euebgy euyegb euyebg euygeb euygbe
euybge euybeg eubeyg eubegy eubyeg eubyge eubgye eubgey egueyb egueby eguyeb
eguybe egubye egubey egeuyb egeuby egeyub egeybu egebyu egebuy egyeub egyebu
egyueb egyube egybue egybeu egbeyu egbeuy egbyeu egbyue egbuye egbuey eeguyb
eeguby eegyub eegybu eegbyu eegbuy eeugyb eeugby eeuygb eeuybg eeubyg eeubgy
eeyugb eeyubg eeygub eeygbu eeybgu eeybug eebuyg eebugy eebyug eebygu eebgyu
eebguy eygeub eygebu eygueb eygube eygbue eygbeu eyegub eyegbu eyeugb eyeubg
eyebug eyebgu eyuegb eyuebg eyugeb eyugbe eyubge eyubeg eybeug eybegu eybueg
eybuge eybgue eybgeu ebgeyu ebgeuy ebgyeu ebgyue ebguye ebguey ebegyu ebeguy
ebeygu ebeyug ebeuyg ebeugy ebyegu ebyeug ebygeu ebygue ebyuge ebyueg ebueyg
ebuegy ebuyeg ebuyge ebugye ebugey

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History of cryptography
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