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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: zandow
cipher variations:
aboepx bcpfqy cdqgrz derhsa efsitb
fgtjuc ghukvd hivlwe ijwmxf jkxnyg
klyozh lmzpai mnaqbj nobrck opcsdl
pqdtem qreufn rsfvgo stgwhp tuhxiq
uviyjr vwjzks wxkalt xylbmu yzmcnv

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: zandow
Cipher: azmwld

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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: zandow

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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: zandow
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: zandow
Cipher: mnaqbj

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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: zandow
Cipher: 551133414325

Extended Methods:
Method #1

Plaintext: zandow
method variations:

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

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Method #3

Plaintext: zandow
method variations:
elsqhz lsqhze sqhzel
qhzels hzelsq zelsqh

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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: zandow

all 720 cipher variations:
zandow zandwo zanodw zanowd zanwod zanwdo zadnow zadnwo zadonw zadown zadwon
zadwno zaodnw zaodwn zaondw zaonwd zaownd zaowdn zawdon zawdno zawodn zawond
zawnod zawndo znadow znadwo znaodw znaowd znawod znawdo zndaow zndawo zndoaw
zndowa zndwoa zndwao znodaw znodwa znoadw znoawd znowad znowda znwdoa znwdao
znwoda znwoad znwaod znwado zdnaow zdnawo zdnoaw zdnowa zdnwoa zdnwao zdanow
zdanwo zdaonw zdaown zdawon zdawno zdoanw zdoawn zdonaw zdonwa zdowna zdowan
zdwaon zdwano zdwoan zdwona zdwnoa zdwnao zondaw zondwa zonadw zonawd zonwad
zonwda zodnaw zodnwa zodanw zodawn zodwan zodwna zoadnw zoadwn zoandw zoanwd
zoawnd zoawdn zowdan zowdna zowadn zowand zownad zownda zwndoa zwndao zwnoda
zwnoad zwnaod zwnado zwdnoa zwdnao zwdona zwdoan zwdaon zwdano zwodna zwodan
zwonda zwonad zwoand zwoadn zwadon zwadno zwaodn zwaond zwanod zwando azndow
azndwo aznodw aznowd aznwod aznwdo azdnow azdnwo azdonw azdown azdwon azdwno
azodnw azodwn azondw azonwd azownd azowdn azwdon azwdno azwodn azwond azwnod
azwndo anzdow anzdwo anzodw anzowd anzwod anzwdo andzow andzwo andozw andowz
andwoz andwzo anodzw anodwz anozdw anozwd anowzd anowdz anwdoz anwdzo anwodz
anwozd anwzod anwzdo adnzow adnzwo adnozw adnowz adnwoz adnwzo adznow adznwo
adzonw adzown adzwon adzwno adoznw adozwn adonzw adonwz adownz adowzn adwzon
adwzno adwozn adwonz adwnoz adwnzo aondzw aondwz aonzdw aonzwd aonwzd aonwdz
aodnzw aodnwz aodznw aodzwn aodwzn aodwnz aozdnw aozdwn aozndw aoznwd aozwnd
aozwdn aowdzn aowdnz aowzdn aowznd aownzd aowndz awndoz awndzo awnodz awnozd
awnzod awnzdo awdnoz awdnzo awdonz awdozn awdzon awdzno awodnz awodzn awondz
awonzd awoznd awozdn awzdon awzdno awzodn awzond awznod awzndo nazdow nazdwo
nazodw nazowd nazwod nazwdo nadzow nadzwo nadozw nadowz nadwoz nadwzo naodzw
naodwz naozdw naozwd naowzd naowdz nawdoz nawdzo nawodz nawozd nawzod nawzdo
nzadow nzadwo nzaodw nzaowd nzawod nzawdo nzdaow nzdawo nzdoaw nzdowa nzdwoa
nzdwao nzodaw nzodwa nzoadw nzoawd nzowad nzowda nzwdoa nzwdao nzwoda nzwoad
nzwaod nzwado ndzaow ndzawo ndzoaw ndzowa ndzwoa ndzwao ndazow ndazwo ndaozw
ndaowz ndawoz ndawzo ndoazw ndoawz ndozaw ndozwa ndowza ndowaz ndwaoz ndwazo
ndwoaz ndwoza ndwzoa ndwzao nozdaw nozdwa nozadw nozawd nozwad nozwda nodzaw
nodzwa nodazw nodawz nodwaz nodwza noadzw noadwz noazdw noazwd noawzd noawdz
nowdaz nowdza nowadz nowazd nowzad nowzda nwzdoa nwzdao nwzoda nwzoad nwzaod
nwzado nwdzoa nwdzao nwdoza nwdoaz nwdaoz nwdazo nwodza nwodaz nwozda nwozad
nwoazd nwoadz nwadoz nwadzo nwaodz nwaozd nwazod nwazdo danzow danzwo danozw
danowz danwoz danwzo daznow daznwo dazonw dazown dazwon dazwno daoznw daozwn
daonzw daonwz daownz daowzn dawzon dawzno dawozn dawonz dawnoz dawnzo dnazow
dnazwo dnaozw dnaowz dnawoz dnawzo dnzaow dnzawo dnzoaw dnzowa dnzwoa dnzwao
dnozaw dnozwa dnoazw dnoawz dnowaz dnowza dnwzoa dnwzao dnwoza dnwoaz dnwaoz
dnwazo dznaow dznawo dznoaw dznowa dznwoa dznwao dzanow dzanwo dzaonw dzaown
dzawon dzawno dzoanw dzoawn dzonaw dzonwa dzowna dzowan dzwaon dzwano dzwoan
dzwona dzwnoa dzwnao donzaw donzwa donazw donawz donwaz donwza doznaw doznwa
dozanw dozawn dozwan dozwna doaznw doazwn doanzw doanwz doawnz doawzn dowzan
dowzna dowazn dowanz downaz downza dwnzoa dwnzao dwnoza dwnoaz dwnaoz dwnazo
dwznoa dwznao dwzona dwzoan dwzaon dwzano dwozna dwozan dwonza dwonaz dwoanz
dwoazn dwazon dwazno dwaozn dwaonz dwanoz dwanzo oandzw oandwz oanzdw oanzwd
oanwzd oanwdz oadnzw oadnwz oadznw oadzwn oadwzn oadwnz oazdnw oazdwn oazndw
oaznwd oazwnd oazwdn oawdzn oawdnz oawzdn oawznd oawnzd oawndz onadzw onadwz
onazdw onazwd onawzd onawdz ondazw ondawz ondzaw ondzwa ondwza ondwaz onzdaw
onzdwa onzadw onzawd onzwad onzwda onwdza onwdaz onwzda onwzad onwazd onwadz
odnazw odnawz odnzaw odnzwa odnwza odnwaz odanzw odanwz odaznw odazwn odawzn
odawnz odzanw odzawn odznaw odznwa odzwna odzwan odwazn odwanz odwzan odwzna
odwnza odwnaz ozndaw ozndwa oznadw oznawd oznwad oznwda ozdnaw ozdnwa ozdanw
ozdawn ozdwan ozdwna ozadnw ozadwn ozandw ozanwd ozawnd ozawdn ozwdan ozwdna
ozwadn ozwand ozwnad ozwnda owndza owndaz ownzda ownzad ownazd ownadz owdnza
owdnaz owdzna owdzan owdazn owdanz owzdna owzdan owznda owznad owzand owzadn
owadzn owadnz owazdn owaznd owanzd owandz wandoz wandzo wanodz wanozd wanzod
wanzdo wadnoz wadnzo wadonz wadozn wadzon wadzno waodnz waodzn waondz waonzd
waoznd waozdn wazdon wazdno wazodn wazond waznod wazndo wnadoz wnadzo wnaodz
wnaozd wnazod wnazdo wndaoz wndazo wndoaz wndoza wndzoa wndzao wnodaz wnodza
wnoadz wnoazd wnozad wnozda wnzdoa wnzdao wnzoda wnzoad wnzaod wnzado wdnaoz
wdnazo wdnoaz wdnoza wdnzoa wdnzao wdanoz wdanzo wdaonz wdaozn wdazon wdazno
wdoanz wdoazn wdonaz wdonza wdozna wdozan wdzaon wdzano wdzoan wdzona wdznoa
wdznao wondaz wondza wonadz wonazd wonzad wonzda wodnaz wodnza wodanz wodazn
wodzan wodzna woadnz woadzn woandz woanzd woaznd woazdn wozdan wozdna wozadn
wozand woznad woznda wzndoa wzndao wznoda wznoad wznaod wznado wzdnoa wzdnao
wzdona wzdoan wzdaon wzdano wzodna wzodan wzonda wzonad wzoand wzoadn wzadon
wzadno wzaodn wzaond wzanod wzando

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History of cryptography
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