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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: syndra
cipher variations:
tzoesb uapftc vbqgud wcrhve xdsiwf
yetjxg zfukyh agvlzi bhwmaj cixnbk
djyocl ekzpdm flaqen gmbrfo hncsgp
iodthq jpeuir kqfvjs lrgwkt mshxlu
ntiymv oujznw pvkaox qwlbpy rxmcqz

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: syndra
Cipher: hbmwiz

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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: syndra

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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: syndra
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: syndra
Cipher: flaqen

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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: syndra
Cipher: 344533412411

Extended Methods:
Method #1

Plaintext: syndra
method variations:

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

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Method #3

Plaintext: syndra
method variations:
tpsfdl psfdlt sfdltp
fdltps dltpsf ltpsfd

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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: syndra

all 720 cipher variations:
syndra syndar synrda synrad synard synadr sydnra sydnar sydrna sydran sydarn
sydanr syrdna syrdan syrnda syrnad syrand syradn syadrn syadnr syardn syarnd
syanrd syandr snydra snydar snyrda snyrad snyard snyadr sndyra sndyar sndrya
sndray sndary sndayr snrdya snrday snryda snryad snrayd snrady snadry snadyr
snardy snaryd snayrd snaydr sdnyra sdnyar sdnrya sdnray sdnary sdnayr sdynra
sdynar sdyrna sdyran sdyarn sdyanr sdryna sdryan sdrnya sdrnay sdrany sdrayn
sdayrn sdaynr sdaryn sdarny sdanry sdanyr srndya srnday srnyda srnyad srnayd
srnady srdnya srdnay srdyna srdyan srdayn srdany srydna srydan srynda srynad
sryand sryadn sradyn sradny sraydn sraynd sranyd srandy sandry sandyr sanrdy
sanryd sanyrd sanydr sadnry sadnyr sadrny sadryn sadyrn sadynr sardny sardyn
sarndy sarnyd sarynd sarydn saydrn saydnr sayrdn sayrnd saynrd sayndr ysndra
ysndar ysnrda ysnrad ysnard ysnadr ysdnra ysdnar ysdrna ysdran ysdarn ysdanr
ysrdna ysrdan ysrnda ysrnad ysrand ysradn ysadrn ysadnr ysardn ysarnd ysanrd
ysandr ynsdra ynsdar ynsrda ynsrad ynsard ynsadr yndsra yndsar yndrsa yndras
yndars yndasr ynrdsa ynrdas ynrsda ynrsad ynrasd ynrads ynadrs ynadsr ynards
ynarsd ynasrd ynasdr ydnsra ydnsar ydnrsa ydnras ydnars ydnasr ydsnra ydsnar
ydsrna ydsran ydsarn ydsanr ydrsna ydrsan ydrnsa ydrnas ydrans ydrasn ydasrn
ydasnr ydarsn ydarns ydanrs ydansr yrndsa yrndas yrnsda yrnsad yrnasd yrnads
yrdnsa yrdnas yrdsna yrdsan yrdasn yrdans yrsdna yrsdan yrsnda yrsnad yrsand
yrsadn yradsn yradns yrasdn yrasnd yransd yrands yandrs yandsr yanrds yanrsd
yansrd yansdr yadnrs yadnsr yadrns yadrsn yadsrn yadsnr yardns yardsn yarnds
yarnsd yarsnd yarsdn yasdrn yasdnr yasrdn yasrnd yasnrd yasndr nysdra nysdar
nysrda nysrad nysard nysadr nydsra nydsar nydrsa nydras nydars nydasr nyrdsa
nyrdas nyrsda nyrsad nyrasd nyrads nyadrs nyadsr nyards nyarsd nyasrd nyasdr
nsydra nsydar nsyrda nsyrad nsyard nsyadr nsdyra nsdyar nsdrya nsdray nsdary
nsdayr nsrdya nsrday nsryda nsryad nsrayd nsrady nsadry nsadyr nsardy nsaryd
nsayrd nsaydr ndsyra ndsyar ndsrya ndsray ndsary ndsayr ndysra ndysar ndyrsa
ndyras ndyars ndyasr ndrysa ndryas ndrsya ndrsay ndrasy ndrays ndayrs ndaysr
ndarys ndarsy ndasry ndasyr nrsdya nrsday nrsyda nrsyad nrsayd nrsady nrdsya
nrdsay nrdysa nrdyas nrdays nrdasy nrydsa nrydas nrysda nrysad nryasd nryads
nradys nradsy nrayds nraysd nrasyd nrasdy nasdry nasdyr nasrdy nasryd nasyrd
nasydr nadsry nadsyr nadrsy nadrys nadyrs nadysr nardsy nardys narsdy narsyd
narysd naryds naydrs naydsr nayrds nayrsd naysrd naysdr dynsra dynsar dynrsa
dynras dynars dynasr dysnra dysnar dysrna dysran dysarn dysanr dyrsna dyrsan
dyrnsa dyrnas dyrans dyrasn dyasrn dyasnr dyarsn dyarns dyanrs dyansr dnysra
dnysar dnyrsa dnyras dnyars dnyasr dnsyra dnsyar dnsrya dnsray dnsary dnsayr
dnrsya dnrsay dnrysa dnryas dnrays dnrasy dnasry dnasyr dnarsy dnarys dnayrs
dnaysr dsnyra dsnyar dsnrya dsnray dsnary dsnayr dsynra dsynar dsyrna dsyran
dsyarn dsyanr dsryna dsryan dsrnya dsrnay dsrany dsrayn dsayrn dsaynr dsaryn
dsarny dsanry dsanyr drnsya drnsay drnysa drnyas drnays drnasy drsnya drsnay
drsyna drsyan drsayn drsany drysna drysan drynsa drynas dryans dryasn drasyn
drasny draysn drayns dranys dransy dansry dansyr danrsy danrys danyrs danysr
dasnry dasnyr dasrny dasryn dasyrn dasynr darsny darsyn darnsy darnys daryns
darysn daysrn daysnr dayrsn dayrns daynrs daynsr ryndsa ryndas rynsda rynsad
rynasd rynads rydnsa rydnas rydsna rydsan rydasn rydans rysdna rysdan rysnda
rysnad rysand rysadn ryadsn ryadns ryasdn ryasnd ryansd ryands rnydsa rnydas
rnysda rnysad rnyasd rnyads rndysa rndyas rndsya rndsay rndasy rndays rnsdya
rnsday rnsyda rnsyad rnsayd rnsady rnadsy rnadys rnasdy rnasyd rnaysd rnayds
rdnysa rdnyas rdnsya rdnsay rdnasy rdnays rdynsa rdynas rdysna rdysan rdyasn
rdyans rdsyna rdsyan rdsnya rdsnay rdsany rdsayn rdaysn rdayns rdasyn rdasny
rdansy rdanys rsndya rsnday rsnyda rsnyad rsnayd rsnady rsdnya rsdnay rsdyna
rsdyan rsdayn rsdany rsydna rsydan rsynda rsynad rsyand rsyadn rsadyn rsadny
rsaydn rsaynd rsanyd rsandy randsy randys ransdy ransyd ranysd ranyds radnsy
radnys radsny radsyn radysn radyns rasdny rasdyn rasndy rasnyd rasynd rasydn
raydsn raydns raysdn raysnd raynsd raynds ayndrs ayndsr aynrds aynrsd aynsrd
aynsdr aydnrs aydnsr aydrns aydrsn aydsrn aydsnr ayrdns ayrdsn ayrnds ayrnsd
ayrsnd ayrsdn aysdrn aysdnr aysrdn aysrnd aysnrd aysndr anydrs anydsr anyrds
anyrsd anysrd anysdr andyrs andysr andrys andrsy andsry andsyr anrdys anrdsy
anryds anrysd anrsyd anrsdy ansdry ansdyr ansrdy ansryd ansyrd ansydr adnyrs
adnysr adnrys adnrsy adnsry adnsyr adynrs adynsr adyrns adyrsn adysrn adysnr
adryns adrysn adrnys adrnsy adrsny adrsyn adsyrn adsynr adsryn adsrny adsnry
adsnyr arndys arndsy arnyds arnysd arnsyd arnsdy ardnys ardnsy ardyns ardysn
ardsyn ardsny arydns arydsn arynds arynsd arysnd arysdn arsdyn arsdny arsydn
arsynd arsnyd arsndy asndry asndyr asnrdy asnryd asnyrd asnydr asdnry asdnyr
asdrny asdryn asdyrn asdynr asrdny asrdyn asrndy asrnyd asrynd asrydn asydrn
asydnr asyrdn asyrnd asynrd asyndr

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History of cryptography
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