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algin


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: umbra
cipher variations:
vncsb wodtc xpeud yqfve zrgwf
ashxg btiyh cujzi dvkaj ewlbk
fxmcl gyndm hzoen iapfo jbqgp
kcrhq ldsir metjs nfukt ogvlu
phwmv qixnw rjyox skzpy tlaqz

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: umbra
Cipher: fnyiz

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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: umbra
Cipher: BAABB ABABB AAAAB BAAAA AAAAA

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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: umbra
cipher variations:
vncsbjleabxjgiblhiqbzfkybndmgbpzqwbdxseb
rvumbftwubtrycbhpakbwodtckmfbcykhjcmijrc
aglzcoenhcqarxceytfcswvncguxvcuszdciqblc
xpeudlngcdzlikdnjksdbhmadpfoidrbsydfzugd
txwodhvywdvtaedjrcmdyqfvemohdeamjleoklte
cinbeqgpjesctzegavheuyxpeiwzxewubfeksdne
zrgwfnpiefbnkmfplmufdjocfrhqkftduafhbwif
vzyqfjxayfxvcgflteofashxgoqjfgcolngqmnvg
ekpdgsirlguevbgicxjgwazrgkybzgywdhgmufpg
btiyhprkghdpmohrnowhflqehtjsmhvfwchjdykh
xbashlzcahzxeihnvgqhcujziqslhieqnpisopxi
gmrfiuktniwgxdikezliycbtimadbiayfjiowhri
dvkajrtmijfroqjtpqyjhnsgjvluojxhyejlfamj
zdcujnbecjbzgkjpxisjewlbksunjkgsprkuqrzk
iothkwmvpkyizfkmgbnkaedvkocfdkcahlkqyjtk
fxmcltvoklhtqslvrsaljpuilxnwqlzjaglnhcol
bfewlpdgeldbimlrzkulgyndmuwplmiurtmwstbm
kqvjmyoxrmakbhmoidpmcgfxmqehfmecjnmsalvm
hzoenvxqmnjvsunxtucnlrwknzpysnblcinpjeqn
dhgynrfignfdkontbmwniapfowyrnokwtvoyuvdo
msxloaqztocmdjoqkfroeihzosgjhogelpoucnxo
jbqgpxzsoplxuwpzvwepntympbraupdnekprlgsp
fjiapthkiphfmqpvdoypkcrhqyatpqmyvxqawxfq
ouznqcsbvqeoflqsmhtqgkjbquiljqignrqwepzq
ldsirzbuqrnzwyrbxygrpvaordtcwrfpgmrtniur
hlkcrvjmkrjhosrxfqarmetjsacvrsoaxzscyzhs
qwbpseudxsgqhnsuojvsimldswknlskiptsygrbs
nfuktbdwstpbyatdzaitrxcqtfveythriotvpkwt
jnmetxlomtljqutzhsctogvlucextuqczbueabju
sydrugwfzuisjpuwqlxukonfuympnumkrvuaitdu
phwmvdfyuvrdacvfbckvtzesvhxgavjtkqvxrmyv
lpogvznqovnlswvbjuevqixnwegzvwsebdwgcdlw
uaftwiyhbwkulrwysnzwmqphwaorpwomtxwckvfw
rjyoxfhawxtfcexhdemxvbguxjzicxlvmsxztoax
nrqixbpsqxpnuyxdlwgxskzpygibxyugdfyiefny
wchvykajdymwntyaupbyosrjycqtryqovzyemxhy
tlaqzhjcyzvhegzjfgozxdiwzlbkeznxouzbvqcz
ptskzdruszrpwazfnyizumbraikdzawifhakghpa
yejxamclfaoypvacwrdaqutlaesvtasqxbagozja

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: umbra
Cipher: hzoen

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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: umbra
Cipher: 5423212411

Extended Methods:
Method #1

Plaintext: umbra
method variations:
zrgwfewmblkbrgqpgwmv

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
u m b r a 
5 2 2 2 1 
4 3 1 4 1 
They are then read out in rows:
5222143141
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: umbra
Cipher: kgqcd

Read more ...
Method #3

Plaintext: umbra
method variations:
ihfdv hfdvi fdvih
dvihf vihfd

Read more ...[RUS] , [EN]

 

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: umbra

all 120 cipher variations:
umbra umbar umrba umrab umarb umabr ubmra ubmar ubrma ubram ubarm
ubamr urbma urbam urmba urmab uramb urabm uabrm uabmr uarbm uarmb
uamrb uambr mubra mubar murba murab muarb muabr mbura mbuar mbrua
mbrau mbaru mbaur mrbua mrbau mruba mruab mraub mrabu mabru mabur
marbu marub maurb maubr bmura bmuar bmrua bmrau bmaru bmaur bumra
bumar burma buram buarm buamr bruma bruam brmua brmau bramu braum
baurm baumr barum barmu bamru bamur rmbua rmbau rmuba rmuab rmaub
rmabu rbmua rbmau rbuma rbuam rbaum rbamu rubma rubam rumba rumab
ruamb ruabm rabum rabmu raubm raumb ramub rambu ambru ambur amrbu
amrub amurb amubr abmru abmur abrmu abrum aburm abumr arbmu arbum
armbu armub arumb arubm aubrm aubmr aurbm aurmb aumrb aumbr

Read more ...[1] , [2] , [3]

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