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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: paresi
cipher variations:
qbsftj rctguk sduhvl teviwm ufwjxn
vgxkyo whylzp xizmaq yjanbr zkbocs
alcpdt bmdqeu cnerfv dofsgw epgthx
fqhuiy grivjz hsjwka itkxlb julymc
kvmznd lwnaoe mxobpf nypcqg ozqdrh

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: paresi
Cipher: kzivhr

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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: paresi

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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: paresi
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: paresi
Cipher: cnerfv

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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: paresi
Cipher: 531124513442

Extended Methods:
Method #1

Plaintext: paresi
method variations:

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

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Method #3

Plaintext: paresi
method variations:
cfyltw fyltwc yltwcf
ltwcfy twcfyl wcfylt

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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: paresi

all 720 cipher variations:
paresi pareis parsei parsie parise paries paersi paeris paesri paesir paeisr
paeirs paseri paseir pasrei pasrie pasire pasier paiesr paiers paiser paisre
pairse paires praesi praeis prasei prasie praise praies preasi preais presai
presia preisa preias prseai prseia prsaei prsaie prsiae prsiea priesa prieas
prisea prisae priase priaes perasi perais persai persia perisa perias pearsi
pearis peasri peasir peaisr peairs pesari pesair pesrai pesria pesira pesiar
peiasr peiars peisar peisra peirsa peiras psreai psreia psraei psraie psriae
psriea pserai pseria pseari pseair pseiar pseira psaeri psaeir psarei psarie
psaire psaier psiear psiera psiaer psiare psirae psirea piresa pireas pirsea
pirsae pirase piraes piersa pieras piesra piesar pieasr piears pisera pisear
pisrea pisrae pisare pisaer piaesr piaers piaser piasre piarse piares apresi
apreis aprsei aprsie aprise apries apersi aperis apesri apesir apeisr apeirs
apseri apseir apsrei apsrie apsire apsier apiesr apiers apiser apisre apirse
apires arpesi arpeis arpsei arpsie arpise arpies arepsi arepis arespi aresip
areisp areips arsepi arseip arspei arspie arsipe arsiep ariesp arieps arisep
arispe aripse aripes aerpsi aerpis aerspi aersip aerisp aerips aeprsi aepris
aepsri aepsir aepisr aepirs aespri aespir aesrpi aesrip aesirp aesipr aeipsr
aeiprs aeispr aeisrp aeirsp aeirps asrepi asreip asrpei asrpie asripe asriep
aserpi aserip asepri asepir aseipr aseirp asperi aspeir asprei asprie aspire
aspier asiepr asierp asiper asipre asirpe asirep airesp aireps airsep airspe
airpse airpes aiersp aierps aiesrp aiespr aiepsr aieprs aiserp aisepr aisrep
aisrpe aispre aisper aipesr aipers aipser aipsre aiprse aipres rapesi rapeis
rapsei rapsie rapise rapies raepsi raepis raespi raesip raeisp raeips rasepi
raseip raspei raspie rasipe rasiep raiesp raieps raisep raispe raipse raipes
rpaesi rpaeis rpasei rpasie rpaise rpaies rpeasi rpeais rpesai rpesia rpeisa
rpeias rpseai rpseia rpsaei rpsaie rpsiae rpsiea rpiesa rpieas rpisea rpisae
rpiase rpiaes repasi repais repsai repsia repisa repias reapsi reapis reaspi
reasip reaisp reaips resapi resaip respai respia resipa resiap reiasp reiaps
reisap reispa reipsa reipas rspeai rspeia rspaei rspaie rspiae rspiea rsepai
rsepia rseapi rseaip rseiap rseipa rsaepi rsaeip rsapei rsapie rsaipe rsaiep
rsieap rsiepa rsiaep rsiape rsipae rsipea ripesa ripeas ripsea ripsae ripase
ripaes riepsa riepas riespa riesap rieasp rieaps risepa riseap rispea rispae
risape risaep riaesp riaeps riasep riaspe riapse riapes earpsi earpis earspi
earsip earisp earips eaprsi eapris eapsri eapsir eapisr eapirs easpri easpir
easrpi easrip easirp easipr eaipsr eaiprs eaispr eaisrp eairsp eairps erapsi
erapis eraspi erasip eraisp eraips erpasi erpais erpsai erpsia erpisa erpias
erspai erspia ersapi ersaip ersiap ersipa eripsa eripas erispa erisap eriasp
eriaps eprasi eprais eprsai eprsia eprisa eprias eparsi eparis epasri epasir
epaisr epairs epsari epsair epsrai epsria epsira epsiar epiasr epiars episar
episra epirsa epiras esrpai esrpia esrapi esraip esriap esripa esprai espria
espari espair espiar espira esapri esapir esarpi esarip esairp esaipr esipar
esipra esiapr esiarp esirap esirpa eirpsa eirpas eirspa eirsap eirasp eiraps
eiprsa eipras eipsra eipsar eipasr eipars eispra eispar eisrpa eisrap eisarp
eisapr eiapsr eiaprs eiaspr eiasrp eiarsp eiarps sarepi sareip sarpei sarpie
saripe sariep saerpi saerip saepri saepir saeipr saeirp saperi sapeir saprei
saprie sapire sapier saiepr saierp saiper saipre sairpe sairep sraepi sraeip
srapei srapie sraipe sraiep sreapi sreaip srepai srepia sreipa sreiap srpeai
srpeia srpaei srpaie srpiae srpiea sriepa srieap sripea sripae sriape sriaep
serapi seraip serpai serpia seripa seriap searpi searip seapri seapir seaipr
seairp separi sepair seprai sepria sepira sepiar seiapr seiarp seipar seipra
seirpa seirap spreai spreia spraei spraie spriae spriea sperai speria speari
speair speiar speira spaeri spaeir sparei sparie spaire spaier spiear spiera
spiaer spiare spirae spirea sirepa sireap sirpea sirpae sirape siraep sierpa
sierap siepra siepar sieapr siearp sipera sipear siprea siprae sipare sipaer
siaepr siaerp siaper siapre siarpe siarep iaresp iareps iarsep iarspe iarpse
iarpes iaersp iaerps iaesrp iaespr iaepsr iaeprs iaserp iasepr iasrep iasrpe
iaspre iasper iapesr iapers iapser iapsre iaprse iapres iraesp iraeps irasep
iraspe irapse irapes ireasp ireaps iresap irespa irepsa irepas irseap irsepa
irsaep irsape irspae irspea irpesa irpeas irpsea irpsae irpase irpaes ierasp
ieraps iersap ierspa ierpsa ierpas iearsp iearps ieasrp ieaspr ieapsr ieaprs
iesarp iesapr iesrap iesrpa iespra iespar iepasr iepars iepsar iepsra ieprsa
iepras isreap isrepa israep isrape isrpae isrpea iserap iserpa isearp iseapr
isepar isepra isaerp isaepr isarep isarpe isapre isaper ispear ispera ispaer
ispare isprae isprea ipresa ipreas iprsea iprsae iprase ipraes ipersa iperas
ipesra ipesar ipeasr ipears ipsera ipsear ipsrea ipsrae ipsare ipsaer ipaesr
ipaers ipaser ipasre iparse ipares

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History of cryptography
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