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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: drabik
cipher variations:
esbcjl ftcdkm gudeln hvefmo iwfgnp
jxghoq kyhipr lzijqs majkrt nbklsu
oclmtv pdmnuw qenovx rfopwy sgpqxz
thqrya uirszb vjstac wktubd xluvce
ymvwdf znwxeg aoxyfh bpyzgi cqzahj

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: drabik
Cipher: wizyrp

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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: drabik

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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: drabik
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: drabik
Cipher: qenovx

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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: drabik
Cipher: 412411214252

Extended Methods:
Method #1

Plaintext: drabik
method variations:

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

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Method #3

Plaintext: drabik
method variations:
fdfqwr dfqwrf fqwrfd
qwrfdf wrfdfq rfdfqw

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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: drabik

all 720 cipher variations:
drabik drabki draibk draikb drakib drakbi drbaik drbaki drbiak drbika drbkia
drbkai dribak dribka driabk driakb drikab drikba drkbia drkbai drkiba drkiab
drkaib drkabi darbik darbki daribk darikb darkib darkbi dabrik dabrki dabirk
dabikr dabkir dabkri daibrk daibkr dairbk dairkb daikrb daikbr dakbir dakbri
dakibr dakirb dakrib dakrbi dbarik dbarki dbairk dbaikr dbakir dbakri dbraik
dbraki dbriak dbrika dbrkia dbrkai dbirak dbirka dbiark dbiakr dbikar dbikra
dbkria dbkrai dbkira dbkiar dbkair dbkari diabrk diabkr diarbk diarkb diakrb
diakbr dibark dibakr dibrak dibrka dibkra dibkar dirbak dirbka dirabk dirakb
dirkab dirkba dikbra dikbar dikrba dikrab dikarb dikabr dkabir dkabri dkaibr
dkairb dkarib dkarbi dkbair dkbari dkbiar dkbira dkbria dkbrai dkibar dkibra
dkiabr dkiarb dkirab dkirba dkrbia dkrbai dkriba dkriab dkraib dkrabi rdabik
rdabki rdaibk rdaikb rdakib rdakbi rdbaik rdbaki rdbiak rdbika rdbkia rdbkai
rdibak rdibka rdiabk rdiakb rdikab rdikba rdkbia rdkbai rdkiba rdkiab rdkaib
rdkabi radbik radbki radibk radikb radkib radkbi rabdik rabdki rabidk rabikd
rabkid rabkdi raibdk raibkd raidbk raidkb raikdb raikbd rakbid rakbdi rakibd
rakidb rakdib rakdbi rbadik rbadki rbaidk rbaikd rbakid rbakdi rbdaik rbdaki
rbdiak rbdika rbdkia rbdkai rbidak rbidka rbiadk rbiakd rbikad rbikda rbkdia
rbkdai rbkida rbkiad rbkaid rbkadi riabdk riabkd riadbk riadkb riakdb riakbd
ribadk ribakd ribdak ribdka ribkda ribkad ridbak ridbka ridabk ridakb ridkab
ridkba rikbda rikbad rikdba rikdab rikadb rikabd rkabid rkabdi rkaibd rkaidb
rkadib rkadbi rkbaid rkbadi rkbiad rkbida rkbdia rkbdai rkibad rkibda rkiabd
rkiadb rkidab rkidba rkdbia rkdbai rkdiba rkdiab rkdaib rkdabi ardbik ardbki
ardibk ardikb ardkib ardkbi arbdik arbdki arbidk arbikd arbkid arbkdi aribdk
aribkd aridbk aridkb arikdb arikbd arkbid arkbdi arkibd arkidb arkdib arkdbi
adrbik adrbki adribk adrikb adrkib adrkbi adbrik adbrki adbirk adbikr adbkir
adbkri adibrk adibkr adirbk adirkb adikrb adikbr adkbir adkbri adkibr adkirb
adkrib adkrbi abdrik abdrki abdirk abdikr abdkir abdkri abrdik abrdki abridk
abrikd abrkid abrkdi abirdk abirkd abidrk abidkr abikdr abikrd abkrid abkrdi
abkird abkidr abkdir abkdri aidbrk aidbkr aidrbk aidrkb aidkrb aidkbr aibdrk
aibdkr aibrdk aibrkd aibkrd aibkdr airbdk airbkd airdbk airdkb airkdb airkbd
aikbrd aikbdr aikrbd aikrdb aikdrb aikdbr akdbir akdbri akdibr akdirb akdrib
akdrbi akbdir akbdri akbidr akbird akbrid akbrdi akibdr akibrd akidbr akidrb
akirdb akirbd akrbid akrbdi akribd akridb akrdib akrdbi bradik bradki braidk
braikd brakid brakdi brdaik brdaki brdiak brdika brdkia brdkai bridak bridka
briadk briakd brikad brikda brkdia brkdai brkida brkiad brkaid brkadi bardik
bardki baridk barikd barkid barkdi badrik badrki badirk badikr badkir badkri
baidrk baidkr bairdk bairkd baikrd baikdr bakdir bakdri bakidr bakird bakrid
bakrdi bdarik bdarki bdairk bdaikr bdakir bdakri bdraik bdraki bdriak bdrika
bdrkia bdrkai bdirak bdirka bdiark bdiakr bdikar bdikra bdkria bdkrai bdkira
bdkiar bdkair bdkari biadrk biadkr biardk biarkd biakrd biakdr bidark bidakr
bidrak bidrka bidkra bidkar birdak birdka biradk birakd birkad birkda bikdra
bikdar bikrda bikrad bikard bikadr bkadir bkadri bkaidr bkaird bkarid bkardi
bkdair bkdari bkdiar bkdira bkdria bkdrai bkidar bkidra bkiadr bkiard bkirad
bkirda bkrdia bkrdai bkrida bkriad bkraid bkradi irabdk irabkd iradbk iradkb
irakdb irakbd irbadk irbakd irbdak irbdka irbkda irbkad irdbak irdbka irdabk
irdakb irdkab irdkba irkbda irkbad irkdba irkdab irkadb irkabd iarbdk iarbkd
iardbk iardkb iarkdb iarkbd iabrdk iabrkd iabdrk iabdkr iabkdr iabkrd iadbrk
iadbkr iadrbk iadrkb iadkrb iadkbr iakbdr iakbrd iakdbr iakdrb iakrdb iakrbd
ibardk ibarkd ibadrk ibadkr ibakdr ibakrd ibradk ibrakd ibrdak ibrdka ibrkda
ibrkad ibdrak ibdrka ibdark ibdakr ibdkar ibdkra ibkrda ibkrad ibkdra ibkdar
ibkadr ibkard idabrk idabkr idarbk idarkb idakrb idakbr idbark idbakr idbrak
idbrka idbkra idbkar idrbak idrbka idrabk idrakb idrkab idrkba idkbra idkbar
idkrba idkrab idkarb idkabr ikabdr ikabrd ikadbr ikadrb ikardb ikarbd ikbadr
ikbard ikbdar ikbdra ikbrda ikbrad ikdbar ikdbra ikdabr ikdarb ikdrab ikdrba
ikrbda ikrbad ikrdba ikrdab ikradb ikrabd krabid krabdi kraibd kraidb kradib
kradbi krbaid krbadi krbiad krbida krbdia krbdai kribad kribda kriabd kriadb
kridab kridba krdbia krdbai krdiba krdiab krdaib krdabi karbid karbdi karibd
karidb kardib kardbi kabrid kabrdi kabird kabidr kabdir kabdri kaibrd kaibdr
kairbd kairdb kaidrb kaidbr kadbir kadbri kadibr kadirb kadrib kadrbi kbarid
kbardi kbaird kbaidr kbadir kbadri kbraid kbradi kbriad kbrida kbrdia kbrdai
kbirad kbirda kbiard kbiadr kbidar kbidra kbdria kbdrai kbdira kbdiar kbdair
kbdari kiabrd kiabdr kiarbd kiardb kiadrb kiadbr kibard kibadr kibrad kibrda
kibdra kibdar kirbad kirbda kirabd kiradb kirdab kirdba kidbra kidbar kidrba
kidrab kidarb kidabr kdabir kdabri kdaibr kdairb kdarib kdarbi kdbair kdbari
kdbiar kdbira kdbria kdbrai kdibar kdibra kdiabr kdiarb kdirab kdirba kdrbia
kdrbai kdriba kdriab kdraib kdrabi

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History of cryptography
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