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fernleaf


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: lidos
cipher variations:
mjept nkfqu olgrv pmhsw qnitx
rojuy spkvz tqlwa urmxb vsnyc
wtozd xupae yvqbf zwrcg axsdh
bytei czufj davgk ebwhl fcxim
gdyjn hezko ifalp jgbmq khcnr

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: lidos
Cipher: orwlh

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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: lidos
Cipher: ABABA ABAAA AAABB ABBAB BAAAB

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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: lidos
cipher variations:
mjeptizkrdepqtnafwvxwvcxhslizrkrudlghafv
cxghfynmjpudslzqtynjnkfqujalsefqruobgxwy
xwdyitmjaslsvemhibgwdyhigzonkqvetmaruzok
olgrvkbmtfgrsvpchyxzyxezjunkbtmtwfnijchx
ezijhapolrwfunbsvaplpmhswlcnughstwqdizya
zyfakvolcunuxgojkdiyfajkibqpmsxgvoctwbqm
qnitxmdovhituxrejazbazgblwpmdvovyhpklejz
gbkljcrqntyhwpduxcrnrojuynepwijuvysfkbac
bahcmxqnewpwziqlmfkahclmkdsrouzixqevydso
spkvzofqxjkvwztglcbdcbidnyrofxqxajrmnglb
idmnletspvajyrfwzetptqlwapgryklwxauhmdce
dcjeozspgyrybksnohmcjenomfutqwbkzsgxafuq
urmxbqhszlmxybvinedfedkfpatqhzszcltopind
kfopngvurxclathybgvrvsnycritamnyzcwjofeg
felgqburiatadmupqjoelgpqohwvsydmbuizchws
wtozdsjubnozadxkpgfhgfmhrcvsjbubenvqrkpf
mhqrpixwtzencvjadixtxupaetkvcopabeylqhgi
hgnisdwtkcvcfowrslqgnirsqjyxuafodwkbejyu
yvqbfulwdpqbcfzmrihjihojtexuldwdgpxstmrh
ojstrkzyvbgpexlcfkzvzwrcgvmxeqrcdgansjik
jipkufyvmexehqytunsipktuslazwchqfymdglaw
axsdhwnyfrsdehbotkjlkjqlvgzwnfyfirzuvotj
qluvtmbaxdirgznehmbxbyteixozgsteficpulkm
lkrmwhaxogzgjsavwpukrmvwuncbyejshaofincy
czufjypahtufgjdqvmlnmlsnxibyphahktbwxqvl
snwxvodczfktibpgjodzdavgkzqbiuvghkerwnmo
nmtoyjczqibilucxyrwmtoxywpedaglujcqhkpea
ebwhlarcjvwhilfsxonponupzkdarjcjmvdyzsxn
upyzxqfebhmvkdrilqfbfcximbsdkwxijmgtypoq
povqalebskdknwezatyovqzayrgfcinwlesjmrgc
gdyjnctelxyjknhuzqprqpwrbmfctleloxfabuzp
wrabzshgdjoxmftknshdhezkodufmyzkloivarqs
rqxscngdumfmpygbcvaqxsbcatihekpyngulotie
ifalpevgnzalmpjwbsrtsrytdohevngnqzhcdwbr
ytcdbujiflqzohvmpujfjgbmqfwhoabmnqkxctsu
tszuepifwohoraidexcszudecvkjgmrapiwnqvkg
khcnrgxipbcnorlydutvutavfqjgxpipsbjefydt
avefdwlkhnsbqjxorwlhlidoshyjqcdopsmzevuw
vubwgrkhyqjqtckfgzeubwfgexmliotcrkypsxmi

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: lidos
Cipher: yvqbf

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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: lidos
Cipher: 1342414334

Extended Methods:
Method #1

Plaintext: lidos
method variations:
qoitxvtoycaytdhfdyin

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
l i d o s 
1 4 4 4 3 
3 2 1 3 4 
They are then read out in rows:
1444332134
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: lidos
Cipher: qtnbs

Read more ...
Method #3

Plaintext: lidos
method variations:
srqnd rqnds qndsr
ndsrq dsrqn

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: lidos

all 120 cipher variations:
lidos lidso liods liosd lisod lisdo ldios ldiso ldois ldosi ldsoi
ldsio lodis lodsi loids loisd losid losdi lsdoi lsdio lsodi lsoid
lsiod lsido ildos ildso ilods ilosd ilsod ilsdo idlos idlso idols
idosl idsol idslo iodls iodsl iolds iolsd iosld iosdl isdol isdlo
isodl isold islod isldo dilos dilso diols diosl disol dislo dlios
dliso dlois dlosi dlsoi dlsio dolis dolsi doils doisl dosil dosli
dsloi dslio dsoli dsoil dsiol dsilo oidls oidsl oilds oilsd oisld
oisdl odils odisl odlis odlsi odsli odsil oldis oldsi olids olisd
olsid olsdi osdli osdil osldi oslid osild osidl sidol sidlo siodl
siold silod sildo sdiol sdilo sdoil sdoli sdloi sdlio sodil sodli
soidl soild solid soldi sldoi sldio slodi sloid sliod slido

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

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