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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: ansprd
cipher variations:
botqse cpurtf dqvsug erwtvh fsxuwi
gtyvxj huzwyk ivaxzl jwbyam kxczbn
lydaco mzebdp nafceq obgdfr pchegs
qdifht rejgiu sfkhjv tglikw uhmjlx
vinkmy wjolnz xkpmoa ylqnpb zmroqc

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: ansprd
Cipher: zmhkiw

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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: ansprd

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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: ansprd
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: ansprd
Cipher: nafceq

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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: ansprd
Cipher: 113334532441

Extended Methods:
Method #1

Plaintext: ansprd
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
a n s p r d 
1 3 3 5 2 4 
1 3 4 3 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: ansprd
Cipher: lxrlod

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Method #3

Plaintext: ansprd
method variations:
lnyhta nyhtal yhtaln
htalny talnyh alnyht

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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: ansprd

all 720 cipher variations:
ansprd anspdr ansrpd ansrdp ansdrp ansdpr anpsrd anpsdr anprsd anprds anpdrs
anpdsr anrpsd anrpds anrspd anrsdp anrdsp anrdps andprs andpsr andrps andrsp
andsrp andspr asnprd asnpdr asnrpd asnrdp asndrp asndpr aspnrd aspndr asprnd
asprdn aspdrn aspdnr asrpnd asrpdn asrnpd asrndp asrdnp asrdpn asdprn asdpnr
asdrpn asdrnp asdnrp asdnpr apsnrd apsndr apsrnd apsrdn apsdrn apsdnr apnsrd
apnsdr apnrsd apnrds apndrs apndsr aprnsd aprnds aprsnd aprsdn aprdsn aprdns
apdnrs apdnsr apdrns apdrsn apdsrn apdsnr arspnd arspdn arsnpd arsndp arsdnp
arsdpn arpsnd arpsdn arpnsd arpnds arpdns arpdsn arnpsd arnpds arnspd arnsdp
arndsp arndps ardpns ardpsn ardnps ardnsp ardsnp ardspn adsprn adspnr adsrpn
adsrnp adsnrp adsnpr adpsrn adpsnr adprsn adprns adpnrs adpnsr adrpsn adrpns
adrspn adrsnp adrnsp adrnps adnprs adnpsr adnrps adnrsp adnsrp adnspr nasprd
naspdr nasrpd nasrdp nasdrp nasdpr napsrd napsdr naprsd naprds napdrs napdsr
narpsd narpds narspd narsdp nardsp nardps nadprs nadpsr nadrps nadrsp nadsrp
nadspr nsaprd nsapdr nsarpd nsardp nsadrp nsadpr nspard nspadr nsprad nsprda
nspdra nspdar nsrpad nsrpda nsrapd nsradp nsrdap nsrdpa nsdpra nsdpar nsdrpa
nsdrap nsdarp nsdapr npsard npsadr npsrad npsrda npsdra npsdar npasrd npasdr
nparsd npards npadrs npadsr nprasd nprads nprsad nprsda nprdsa nprdas npdars
npdasr npdras npdrsa npdsra npdsar nrspad nrspda nrsapd nrsadp nrsdap nrsdpa
nrpsad nrpsda nrpasd nrpads nrpdas nrpdsa nrapsd nrapds nraspd nrasdp nradsp
nradps nrdpas nrdpsa nrdaps nrdasp nrdsap nrdspa ndspra ndspar ndsrpa ndsrap
ndsarp ndsapr ndpsra ndpsar ndprsa ndpras ndpars ndpasr ndrpsa ndrpas ndrspa
ndrsap ndrasp ndraps ndaprs ndapsr ndarps ndarsp ndasrp ndaspr snaprd snapdr
snarpd snardp snadrp snadpr snpard snpadr snprad snprda snpdra snpdar snrpad
snrpda snrapd snradp snrdap snrdpa sndpra sndpar sndrpa sndrap sndarp sndapr
sanprd sanpdr sanrpd sanrdp sandrp sandpr sapnrd sapndr saprnd saprdn sapdrn
sapdnr sarpnd sarpdn sarnpd sarndp sardnp sardpn sadprn sadpnr sadrpn sadrnp
sadnrp sadnpr spanrd spandr sparnd spardn spadrn spadnr spnard spnadr spnrad
spnrda spndra spndar sprnad sprnda sprand spradn sprdan sprdna spdnra spdnar
spdrna spdran spdarn spdanr srapnd srapdn sranpd srandp sradnp sradpn srpand
srpadn srpnad srpnda srpdna srpdan srnpad srnpda srnapd srnadp srndap srndpa
srdpna srdpan srdnpa srdnap srdanp srdapn sdaprn sdapnr sdarpn sdarnp sdanrp
sdanpr sdparn sdpanr sdpran sdprna sdpnra sdpnar sdrpan sdrpna sdrapn sdranp
sdrnap sdrnpa sdnpra sdnpar sdnrpa sdnrap sdnarp sdnapr pnsard pnsadr pnsrad
pnsrda pnsdra pnsdar pnasrd pnasdr pnarsd pnards pnadrs pnadsr pnrasd pnrads
pnrsad pnrsda pnrdsa pnrdas pndars pndasr pndras pndrsa pndsra pndsar psnard
psnadr psnrad psnrda psndra psndar psanrd psandr psarnd psardn psadrn psadnr
psrand psradn psrnad psrnda psrdna psrdan psdarn psdanr psdran psdrna psdnra
psdnar pasnrd pasndr pasrnd pasrdn pasdrn pasdnr pansrd pansdr panrsd panrds
pandrs pandsr parnsd parnds parsnd parsdn pardsn pardns padnrs padnsr padrns
padrsn padsrn padsnr prsand prsadn prsnad prsnda prsdna prsdan prasnd prasdn
pransd prands pradns pradsn prnasd prnads prnsad prnsda prndsa prndas prdans
prdasn prdnas prdnsa prdsna prdsan pdsarn pdsanr pdsran pdsrna pdsnra pdsnar
pdasrn pdasnr pdarsn pdarns pdanrs pdansr pdrasn pdrans pdrsan pdrsna pdrnsa
pdrnas pdnars pdnasr pdnras pdnrsa pdnsra pdnsar rnspad rnspda rnsapd rnsadp
rnsdap rnsdpa rnpsad rnpsda rnpasd rnpads rnpdas rnpdsa rnapsd rnapds rnaspd
rnasdp rnadsp rnadps rndpas rndpsa rndaps rndasp rndsap rndspa rsnpad rsnpda
rsnapd rsnadp rsndap rsndpa rspnad rspnda rspand rspadn rspdan rspdna rsapnd
rsapdn rsanpd rsandp rsadnp rsadpn rsdpan rsdpna rsdapn rsdanp rsdnap rsdnpa
rpsnad rpsnda rpsand rpsadn rpsdan rpsdna rpnsad rpnsda rpnasd rpnads rpndas
rpndsa rpansd rpands rpasnd rpasdn rpadsn rpadns rpdnas rpdnsa rpdans rpdasn
rpdsan rpdsna raspnd raspdn rasnpd rasndp rasdnp rasdpn rapsnd rapsdn rapnsd
rapnds rapdns rapdsn ranpsd ranpds ranspd ransdp randsp randps radpns radpsn
radnps radnsp radsnp radspn rdspan rdspna rdsapn rdsanp rdsnap rdsnpa rdpsan
rdpsna rdpasn rdpans rdpnas rdpnsa rdapsn rdapns rdaspn rdasnp rdansp rdanps
rdnpas rdnpsa rdnaps rdnasp rdnsap rdnspa dnspra dnspar dnsrpa dnsrap dnsarp
dnsapr dnpsra dnpsar dnprsa dnpras dnpars dnpasr dnrpsa dnrpas dnrspa dnrsap
dnrasp dnraps dnaprs dnapsr dnarps dnarsp dnasrp dnaspr dsnpra dsnpar dsnrpa
dsnrap dsnarp dsnapr dspnra dspnar dsprna dspran dsparn dspanr dsrpna dsrpan
dsrnpa dsrnap dsranp dsrapn dsaprn dsapnr dsarpn dsarnp dsanrp dsanpr dpsnra
dpsnar dpsrna dpsran dpsarn dpsanr dpnsra dpnsar dpnrsa dpnras dpnars dpnasr
dprnsa dprnas dprsna dprsan dprasn dprans dpanrs dpansr dparns dparsn dpasrn
dpasnr drspna drspan drsnpa drsnap drsanp drsapn drpsna drpsan drpnsa drpnas
drpans drpasn drnpsa drnpas drnspa drnsap drnasp drnaps drapns drapsn dranps
dransp drasnp draspn dasprn daspnr dasrpn dasrnp dasnrp dasnpr dapsrn dapsnr
daprsn daprns dapnrs dapnsr darpsn darpns darspn darsnp darnsp darnps danprs
danpsr danrps danrsp dansrp danspr

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History of cryptography
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