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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: malvin
cipher variations:
nbmwjo ocnxkp pdoylq qepzmr rfqans
sgrbot thscpu uitdqv vjuerw wkvfsx
xlwgty ymxhuz znyiva aozjwb bpakxc
cqblyd drcmze esdnaf fteobg gufpch
hvgqdi iwhrej jxisfk kyjtgl lzkuhm

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: malvin
Cipher: nzoerm

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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: malvin

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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: malvin
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: malvin
Cipher: znyiva

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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: malvin
Cipher: 231113154233

Extended Methods:
Method #1

Plaintext: malvin
method variations:

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

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Method #3

Plaintext: malvin
method variations:
cacumh acumhc cumhca
umhcac mhcacu hcacum

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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: malvin

all 720 cipher variations:
malvin malvni malivn malinv malniv malnvi mavlin mavlni maviln mavinl mavnil
mavnli maivln maivnl mailvn mailnv mainlv mainvl manvil manvli manivl manilv
manliv manlvi mlavin mlavni mlaivn mlainv mlaniv mlanvi mlvain mlvani mlvian
mlvina mlvnia mlvnai mlivan mlivna mliavn mlianv mlinav mlinva mlnvia mlnvai
mlniva mlniav mlnaiv mlnavi mvlain mvlani mvlian mvlina mvlnia mvlnai mvalin
mvalni mvailn mvainl mvanil mvanli mvialn mvianl mvilan mvilna mvinla mvinal
mvnail mvnali mvnial mvnila mvnlia mvnlai milvan milvna milavn milanv milnav
milnva mivlan mivlna mivaln mivanl mivnal mivnla miavln miavnl mialvn mialnv
mianlv mianvl minval minvla minavl minalv minlav minlva mnlvia mnlvai mnliva
mnliav mnlaiv mnlavi mnvlia mnvlai mnvila mnvial mnvail mnvali mnivla mnival
mnilva mnilav mnialv mniavl mnavil mnavli mnaivl mnailv mnaliv mnalvi amlvin
amlvni amlivn amlinv amlniv amlnvi amvlin amvlni amviln amvinl amvnil amvnli
amivln amivnl amilvn amilnv aminlv aminvl amnvil amnvli amnivl amnilv amnliv
amnlvi almvin almvni almivn alminv almniv almnvi alvmin alvmni alvimn alvinm
alvnim alvnmi alivmn alivnm alimvn alimnv alinmv alinvm alnvim alnvmi alnivm
alnimv alnmiv alnmvi avlmin avlmni avlimn avlinm avlnim avlnmi avmlin avmlni
avmiln avminl avmnil avmnli avimln avimnl avilmn avilnm avinlm avinml avnmil
avnmli avniml avnilm avnlim avnlmi ailvmn ailvnm ailmvn ailmnv ailnmv ailnvm
aivlmn aivlnm aivmln aivmnl aivnml aivnlm aimvln aimvnl aimlvn aimlnv aimnlv
aimnvl ainvml ainvlm ainmvl ainmlv ainlmv ainlvm anlvim anlvmi anlivm anlimv
anlmiv anlmvi anvlim anvlmi anvilm anviml anvmil anvmli anivlm anivml anilvm
anilmv animlv animvl anmvil anmvli anmivl anmilv anmliv anmlvi lamvin lamvni
lamivn laminv lamniv lamnvi lavmin lavmni lavimn lavinm lavnim lavnmi laivmn
laivnm laimvn laimnv lainmv lainvm lanvim lanvmi lanivm lanimv lanmiv lanmvi
lmavin lmavni lmaivn lmainv lmaniv lmanvi lmvain lmvani lmvian lmvina lmvnia
lmvnai lmivan lmivna lmiavn lmianv lminav lminva lmnvia lmnvai lmniva lmniav
lmnaiv lmnavi lvmain lvmani lvmian lvmina lvmnia lvmnai lvamin lvamni lvaimn
lvainm lvanim lvanmi lviamn lvianm lviman lvimna lvinma lvinam lvnaim lvnami
lvniam lvnima lvnmia lvnmai limvan limvna limavn limanv limnav limnva livman
livmna livamn livanm livnam livnma liavmn liavnm liamvn liamnv lianmv lianvm
linvam linvma linavm linamv linmav linmva lnmvia lnmvai lnmiva lnmiav lnmaiv
lnmavi lnvmia lnvmai lnvima lnviam lnvaim lnvami lnivma lnivam lnimva lnimav
lniamv lniavm lnavim lnavmi lnaivm lnaimv lnamiv lnamvi valmin valmni valimn
valinm valnim valnmi vamlin vamlni vamiln vaminl vamnil vamnli vaimln vaimnl
vailmn vailnm vainlm vainml vanmil vanmli vaniml vanilm vanlim vanlmi vlamin
vlamni vlaimn vlainm vlanim vlanmi vlmain vlmani vlmian vlmina vlmnia vlmnai
vliman vlimna vliamn vlianm vlinam vlinma vlnmia vlnmai vlnima vlniam vlnaim
vlnami vmlain vmlani vmlian vmlina vmlnia vmlnai vmalin vmalni vmailn vmainl
vmanil vmanli vmialn vmianl vmilan vmilna vminla vminal vmnail vmnali vmnial
vmnila vmnlia vmnlai vilman vilmna vilamn vilanm vilnam vilnma vimlan vimlna
vimaln vimanl vimnal vimnla viamln viamnl vialmn vialnm vianlm vianml vinmal
vinmla vinaml vinalm vinlam vinlma vnlmia vnlmai vnlima vnliam vnlaim vnlami
vnmlia vnmlai vnmila vnmial vnmail vnmali vnimla vnimal vnilma vnilam vnialm
vniaml vnamil vnamli vnaiml vnailm vnalim vnalmi ialvmn ialvnm ialmvn ialmnv
ialnmv ialnvm iavlmn iavlnm iavmln iavmnl iavnml iavnlm iamvln iamvnl iamlvn
iamlnv iamnlv iamnvl ianvml ianvlm ianmvl ianmlv ianlmv ianlvm ilavmn ilavnm
ilamvn ilamnv ilanmv ilanvm ilvamn ilvanm ilvman ilvmna ilvnma ilvnam ilmvan
ilmvna ilmavn ilmanv ilmnav ilmnva ilnvma ilnvam ilnmva ilnmav ilnamv ilnavm
ivlamn ivlanm ivlman ivlmna ivlnma ivlnam ivalmn ivalnm ivamln ivamnl ivanml
ivanlm ivmaln ivmanl ivmlan ivmlna ivmnla ivmnal ivnaml ivnalm ivnmal ivnmla
ivnlma ivnlam imlvan imlvna imlavn imlanv imlnav imlnva imvlan imvlna imvaln
imvanl imvnal imvnla imavln imavnl imalvn imalnv imanlv imanvl imnval imnvla
imnavl imnalv imnlav imnlva inlvma inlvam inlmva inlmav inlamv inlavm invlma
invlam invmla invmal invaml invalm inmvla inmval inmlva inmlav inmalv inmavl
inavml inavlm inamvl inamlv inalmv inalvm nalvim nalvmi nalivm nalimv nalmiv
nalmvi navlim navlmi navilm naviml navmil navmli naivlm naivml nailvm nailmv
naimlv naimvl namvil namvli namivl namilv namliv namlvi nlavim nlavmi nlaivm
nlaimv nlamiv nlamvi nlvaim nlvami nlviam nlvima nlvmia nlvmai nlivam nlivma
nliavm nliamv nlimav nlimva nlmvia nlmvai nlmiva nlmiav nlmaiv nlmavi nvlaim
nvlami nvliam nvlima nvlmia nvlmai nvalim nvalmi nvailm nvaiml nvamil nvamli
nvialm nviaml nvilam nvilma nvimla nvimal nvmail nvmali nvmial nvmila nvmlia
nvmlai nilvam nilvma nilavm nilamv nilmav nilmva nivlam nivlma nivalm nivaml
nivmal nivmla niavlm niavml nialvm nialmv niamlv niamvl nimval nimvla nimavl
nimalv nimlav nimlva nmlvia nmlvai nmliva nmliav nmlaiv nmlavi nmvlia nmvlai
nmvila nmvial nmvail nmvali nmivla nmival nmilva nmilav nmialv nmiavl nmavil
nmavli nmaivl nmailv nmaliv nmalvi

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

History of cryptography
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