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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: medria
cipher variations:
nfesjb ogftkc phguld qihvme rjiwnf
skjxog tlkyph umlzqi vnmarj wonbsk
xpoctl yqpdum zrqevn asrfwo btsgxp
cuthyq dvuizr ewvjas fxwkbt gyxlcu
hzymdv iaznew jbaofx kcbpgy ldcqhz

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: medria
Cipher: nvwirz

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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: medria

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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: medria
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: medria
Cipher: zrqevn

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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: medria
Cipher: 235141244211

Extended Methods:
Method #1

Plaintext: medria
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
m e d r i a 
2 5 4 2 4 1 
3 1 1 4 2 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: medria
Cipher: widcqb

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Method #3

Plaintext: medria
method variations:
xqftbf qftbfx ftbfxq
tbfxqf bfxqft fxqftb

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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: medria

all 720 cipher variations:
medria medrai medira mediar medair medari merdia merdai merida meriad meraid
meradi meirda meirad meidra meidar meiadr meiard mearid meardi meaird meaidr
meadir meadri mderia mderai mdeira mdeiar mdeair mdeari mdreia mdreai mdriea
mdriae mdraie mdraei mdirea mdirae mdiera mdiear mdiaer mdiare mdarie mdarei
mdaire mdaier mdaeir mdaeri mrdeia mrdeai mrdiea mrdiae mrdaie mrdaei mredia
mredai mreida mreiad mreaid mreadi mrieda mriead mridea mridae mriade mriaed
mraeid mraedi mraied mraide mradie mradei midrea midrae midera midear midaer
midare mirdea mirdae mireda miread miraed mirade mierda mierad miedra miedar
mieadr mieard miared miarde miaerd miaedr miader miadre madrie madrei madire
madier madeir maderi mardie mardei maride maried mareid maredi mairde maired
maidre maider maiedr maierd maerid maerdi maeird maeidr maedir maedri emdria
emdrai emdira emdiar emdair emdari emrdia emrdai emrida emriad emraid emradi
emirda emirad emidra emidar emiadr emiard emarid emardi emaird emaidr emadir
emadri edmria edmrai edmira edmiar edmair edmari edrmia edrmai edrima edriam
edraim edrami edirma ediram edimra edimar ediamr ediarm edarim edarmi edairm
edaimr edamir edamri erdmia erdmai erdima erdiam erdaim erdami ermdia ermdai
ermida ermiad ermaid ermadi erimda erimad eridma eridam eriadm eriamd eramid
eramdi eraimd eraidm eradim eradmi eidrma eidram eidmra eidmar eidamr eidarm
eirdma eirdam eirmda eirmad eiramd eiradm eimrda eimrad eimdra eimdar eimadr
eimard eiarmd eiardm eiamrd eiamdr eiadmr eiadrm eadrim eadrmi eadirm eadimr
eadmir eadmri eardim eardmi earidm earimd earmid earmdi eairdm eairmd eaidrm
eaidmr eaimdr eaimrd eamrid eamrdi eamird eamidr eamdir eamdri demria demrai
demira demiar demair demari dermia dermai derima deriam deraim derami deirma
deiram deimra deimar deiamr deiarm dearim dearmi deairm deaimr deamir deamri
dmeria dmerai dmeira dmeiar dmeair dmeari dmreia dmreai dmriea dmriae dmraie
dmraei dmirea dmirae dmiera dmiear dmiaer dmiare dmarie dmarei dmaire dmaier
dmaeir dmaeri drmeia drmeai drmiea drmiae drmaie drmaei dremia dremai dreima
dreiam dreaim dreami driema drieam drimea drimae driame driaem draeim draemi
draiem draime dramie dramei dimrea dimrae dimera dimear dimaer dimare dirmea
dirmae direma diream diraem dirame dierma dieram diemra diemar dieamr diearm
diarem diarme diaerm diaemr diamer diamre damrie damrei damire damier dameir
dameri darmie darmei darime dariem dareim daremi dairme dairem daimre daimer
daiemr daierm daerim daermi daeirm daeimr daemir daemri redmia redmai redima
rediam redaim redami remdia remdai remida remiad remaid remadi reimda reimad
reidma reidam reiadm reiamd reamid reamdi reaimd reaidm readim readmi rdemia
rdemai rdeima rdeiam rdeaim rdeami rdmeia rdmeai rdmiea rdmiae rdmaie rdmaei
rdimea rdimae rdiema rdieam rdiaem rdiame rdamie rdamei rdaime rdaiem rdaeim
rdaemi rmdeia rmdeai rmdiea rmdiae rmdaie rmdaei rmedia rmedai rmeida rmeiad
rmeaid rmeadi rmieda rmiead rmidea rmidae rmiade rmiaed rmaeid rmaedi rmaied
rmaide rmadie rmadei ridmea ridmae ridema rideam ridaem ridame rimdea rimdae
rimeda rimead rimaed rimade riemda riemad riedma riedam rieadm rieamd riamed
riamde riaemd riaedm riadem riadme radmie radmei radime radiem radeim rademi
ramdie ramdei ramide ramied rameid ramedi raimde raimed raidme raidem raiedm
raiemd raemid raemdi raeimd raeidm raedim raedmi iedrma iedram iedmra iedmar
iedamr iedarm ierdma ierdam iermda iermad ieramd ieradm iemrda iemrad iemdra
iemdar iemadr iemard iearmd ieardm ieamrd ieamdr ieadmr ieadrm iderma ideram
idemra idemar ideamr idearm idrema idream idrmea idrmae idrame idraem idmrea
idmrae idmera idmear idmaer idmare idarme idarem idamre idamer idaemr idaerm
irdema irdeam irdmea irdmae irdame irdaem iredma iredam iremda iremad ireamd
ireadm irmeda irmead irmdea irmdae irmade irmaed iraemd iraedm iramed iramde
iradme iradem imdrea imdrae imdera imdear imdaer imdare imrdea imrdae imreda
imread imraed imrade imerda imerad imedra imedar imeadr imeard imared imarde
imaerd imaedr imader imadre iadrme iadrem iadmre iadmer iademr iaderm iardme
iardem iarmde iarmed iaremd iaredm iamrde iamred iamdre iamder iamedr iamerd
iaermd iaerdm iaemrd iaemdr iaedmr iaedrm aedrim aedrmi aedirm aedimr aedmir
aedmri aerdim aerdmi aeridm aerimd aermid aermdi aeirdm aeirmd aeidrm aeidmr
aeimdr aeimrd aemrid aemrdi aemird aemidr aemdir aemdri aderim adermi adeirm
adeimr ademir ademri adreim adremi adriem adrime adrmie adrmei adirem adirme
adierm adiemr adimer adimre admrie admrei admire admier admeir admeri ardeim
ardemi ardiem ardime ardmie ardmei aredim aredmi areidm areimd aremid aremdi
ariedm ariemd aridem aridme arimde arimed armeid armedi armied armide armdie
armdei aidrem aidrme aiderm aidemr aidmer aidmre airdem airdme airedm airemd
airmed airmde aierdm aiermd aiedrm aiedmr aiemdr aiemrd aimred aimrde aimerd
aimedr aimder aimdre amdrie amdrei amdire amdier amdeir amderi amrdie amrdei
amride amried amreid amredi amirde amired amidre amider amiedr amierd amerid
amerdi ameird ameidr amedir amedri

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History of cryptography
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