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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: podite
cipher variations:
qpejuf rqfkvg srglwh tshmxi utinyj
vujozk wvkpal xwlqbm yxmrcn zynsdo
azotep bapufq cbqvgr dcrwhs edsxit
fetyju gfuzkv hgvalw ihwbmx jixcny
kjydoz lkzepa mlafqb nmbgrc onchsd

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: podite
Cipher: klwrgv

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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: podite

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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: podite
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: podite
Cipher: cbqvgr

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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: podite
Cipher: 534341424451

Extended Methods:
Method #1

Plaintext: podite
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
p o d i t e 
5 4 4 4 4 5 
3 3 1 2 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: podite
Cipher: utynfd

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Method #3

Plaintext: podite
method variations:
ssqryv sqryvs qryvss
ryvssq yvssqr vssqry

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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: podite

all 720 cipher variations:
podite podiet podtie podtei podeti podeit poidte poidet poitde poited poietd
poiedt potide potied potdie potdei potedi poteid poeitd poeidt poetid poetdi
poedti poedit pdoite pdoiet pdotie pdotei pdoeti pdoeit pdiote pdioet pditoe
pditeo pdieto pdieot pdtioe pdtieo pdtoie pdtoei pdteoi pdteio pdeito pdeiot
pdetio pdetoi pdeoti pdeoit pidote pidoet pidtoe pidteo pideto pideot piodte
piodet piotde pioted pioetd pioedt pitode pitoed pitdoe pitdeo pitedo piteod
pieotd pieodt pietod pietdo piedto piedot ptdioe ptdieo ptdoie ptdoei ptdeoi
ptdeio ptidoe ptideo ptiode ptioed ptieod ptiedo ptoide ptoied ptodie ptodei
ptoedi ptoeid pteiod pteido pteoid pteodi ptedoi ptedio pedito pediot pedtio
pedtoi pedoti pedoit peidto peidot peitdo peitod peiotd peiodt petido petiod
petdio petdoi petodi petoid peoitd peoidt peotid peotdi peodti peodit opdite
opdiet opdtie opdtei opdeti opdeit opidte opidet opitde opited opietd opiedt
optide optied optdie optdei optedi opteid opeitd opeidt opetid opetdi opedti
opedit odpite odpiet odptie odptei odpeti odpeit odipte odipet oditpe oditep
odietp odiept odtipe odtiep odtpie odtpei odtepi odteip odeitp odeipt odetip
odetpi odepti odepit oidpte oidpet oidtpe oidtep oidetp oidept oipdte oipdet
oiptde oipted oipetd oipedt oitpde oitped oitdpe oitdep oitedp oitepd oieptd
oiepdt oietpd oietdp oiedtp oiedpt otdipe otdiep otdpie otdpei otdepi otdeip
otidpe otidep otipde otiped otiepd otiedp otpide otpied otpdie otpdei otpedi
otpeid oteipd oteidp otepid otepdi otedpi otedip oeditp oedipt oedtip oedtpi
oedpti oedpit oeidtp oeidpt oeitdp oeitpd oeiptd oeipdt oetidp oetipd oetdip
oetdpi oetpdi oetpid oepitd oepidt oeptid oeptdi oepdti oepdit dopite dopiet
doptie doptei dopeti dopeit doipte doipet doitpe doitep doietp doiept dotipe
dotiep dotpie dotpei dotepi doteip doeitp doeipt doetip doetpi doepti doepit
dpoite dpoiet dpotie dpotei dpoeti dpoeit dpiote dpioet dpitoe dpiteo dpieto
dpieot dptioe dptieo dptoie dptoei dpteoi dpteio dpeito dpeiot dpetio dpetoi
dpeoti dpeoit dipote dipoet diptoe dipteo dipeto dipeot diopte diopet diotpe
diotep dioetp dioept ditope ditoep ditpoe ditpeo ditepo diteop dieotp dieopt
dietop dietpo diepto diepot dtpioe dtpieo dtpoie dtpoei dtpeoi dtpeio dtipoe
dtipeo dtiope dtioep dtieop dtiepo dtoipe dtoiep dtopie dtopei dtoepi dtoeip
dteiop dteipo dteoip dteopi dtepoi dtepio depito depiot deptio deptoi depoti
depoit deipto deipot deitpo deitop deiotp deiopt detipo detiop detpio detpoi
detopi detoip deoitp deoipt deotip deotpi deopti deopit iodpte iodpet iodtpe
iodtep iodetp iodept iopdte iopdet ioptde iopted iopetd iopedt iotpde iotped
iotdpe iotdep iotedp iotepd ioeptd ioepdt ioetpd ioetdp ioedtp ioedpt idopte
idopet idotpe idotep idoetp idoept idpote idpoet idptoe idpteo idpeto idpeot
idtpoe idtpeo idtope idtoep idteop idtepo idepto idepot idetpo idetop ideotp
ideopt ipdote ipdoet ipdtoe ipdteo ipdeto ipdeot ipodte ipodet ipotde ipoted
ipoetd ipoedt iptode iptoed iptdoe iptdeo iptedo ipteod ipeotd ipeodt ipetod
ipetdo ipedto ipedot itdpoe itdpeo itdope itdoep itdeop itdepo itpdoe itpdeo
itpode itpoed itpeod itpedo itopde itoped itodpe itodep itoedp itoepd itepod
itepdo iteopd iteodp itedop itedpo iedpto iedpot iedtpo iedtop iedotp iedopt
iepdto iepdot ieptdo ieptod iepotd iepodt ietpdo ietpod ietdpo ietdop ietodp
ietopd ieoptd ieopdt ieotpd ieotdp ieodtp ieodpt todipe todiep todpie todpei
todepi todeip toidpe toidep toipde toiped toiepd toiedp topide topied topdie
topdei topedi topeid toeipd toeidp toepid toepdi toedpi toedip tdoipe tdoiep
tdopie tdopei tdoepi tdoeip tdiope tdioep tdipoe tdipeo tdiepo tdieop tdpioe
tdpieo tdpoie tdpoei tdpeoi tdpeio tdeipo tdeiop tdepio tdepoi tdeopi tdeoip
tidope tidoep tidpoe tidpeo tidepo tideop tiodpe tiodep tiopde tioped tioepd
tioedp tipode tipoed tipdoe tipdeo tipedo tipeod tieopd tieodp tiepod tiepdo
tiedpo tiedop tpdioe tpdieo tpdoie tpdoei tpdeoi tpdeio tpidoe tpideo tpiode
tpioed tpieod tpiedo tpoide tpoied tpodie tpodei tpoedi tpoeid tpeiod tpeido
tpeoid tpeodi tpedoi tpedio tedipo tediop tedpio tedpoi tedopi tedoip teidpo
teidop teipdo teipod teiopd teiodp tepido tepiod tepdio tepdoi tepodi tepoid
teoipd teoidp teopid teopdi teodpi teodip eoditp eodipt eodtip eodtpi eodpti
eodpit eoidtp eoidpt eoitdp eoitpd eoiptd eoipdt eotidp eotipd eotdip eotdpi
eotpdi eotpid eopitd eopidt eoptid eoptdi eopdti eopdit edoitp edoipt edotip
edotpi edopti edopit ediotp ediopt editop editpo edipto edipot edtiop edtipo
edtoip edtopi edtpoi edtpio edpito edpiot edptio edptoi edpoti edpoit eidotp
eidopt eidtop eidtpo eidpto eidpot eiodtp eiodpt eiotdp eiotpd eioptd eiopdt
eitodp eitopd eitdop eitdpo eitpdo eitpod eipotd eipodt eiptod eiptdo eipdto
eipdot etdiop etdipo etdoip etdopi etdpoi etdpio etidop etidpo etiodp etiopd
etipod etipdo etoidp etoipd etodip etodpi etopdi etopid etpiod etpido etpoid
etpodi etpdoi etpdio epdito epdiot epdtio epdtoi epdoti epdoit epidto epidot
epitdo epitod epiotd epiodt eptido eptiod eptdio eptdoi eptodi eptoid epoitd
epoidt epotid epotdi epodti epodit

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History of cryptography
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