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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: umbles
cipher variations:
vncmft wodngu xpeohv yqfpiw zrgqjx
ashrky btislz cujtma dvkunb ewlvoc
fxmwpd gynxqe hzoyrf iapzsg jbqath
kcrbui ldscvj metdwk nfuexl ogvfym
phwgzn qixhao rjyibp skzjcq tlakdr

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: umbles
Cipher: fnyovh

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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: umbles

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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: umbles
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: umbles
Cipher: hzoyrf

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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: umbles
Cipher: 542321135134

Extended Methods:
Method #1

Plaintext: umbles
method variations:

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

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Method #3

Plaintext: umbles
method variations:
ihaxly haxlyi axlyih
xlyiha lyihax yihaxl

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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: umbles

all 720 cipher variations:
umbles umblse umbels umbesl umbsel umbsle umlbes umlbse umlebs umlesb umlseb
umlsbe umelbs umelsb umebls umebsl umesbl umeslb umsleb umslbe umselb umsebl
umsbel umsble ubmles ubmlse ubmels ubmesl ubmsel ubmsle ublmes ublmse ublems
ublesm ublsem ublsme ubelms ubelsm ubemls ubemsl ubesml ubeslm ubslem ubslme
ubselm ubseml ubsmel ubsmle ulbmes ulbmse ulbems ulbesm ulbsem ulbsme ulmbes
ulmbse ulmebs ulmesb ulmseb ulmsbe ulembs ulemsb ulebms ulebsm ulesbm ulesmb
ulsmeb ulsmbe ulsemb ulsebm ulsbem ulsbme ueblms ueblsm uebmls uebmsl uebsml
uebslm uelbms uelbsm uelmbs uelmsb uelsmb uelsbm uemlbs uemlsb uembls uembsl
uemsbl uemslb ueslmb ueslbm uesmlb uesmbl uesbml uesblm usblem usblme usbelm
usbeml usbmel usbmle uslbem uslbme uslebm uslemb uslmeb uslmbe uselbm uselmb
useblm usebml usembl usemlb usmleb usmlbe usmelb usmebl usmbel usmble mubles
mublse mubels mubesl mubsel mubsle mulbes mulbse mulebs mulesb mulseb mulsbe
muelbs muelsb muebls muebsl muesbl mueslb musleb muslbe muselb musebl musbel
musble mbules mbulse mbuels mbuesl mbusel mbusle mblues mbluse mbleus mblesu
mblseu mblsue mbelus mbelsu mbeuls mbeusl mbesul mbeslu mbsleu mbslue mbselu
mbseul mbsuel mbsule mlbues mlbuse mlbeus mlbesu mlbseu mlbsue mlubes mlubse
mluebs mluesb mluseb mlusbe mleubs mleusb mlebus mlebsu mlesbu mlesub mlsueb
mlsube mlseub mlsebu mlsbeu mlsbue meblus meblsu mebuls mebusl mebsul mebslu
melbus melbsu melubs melusb melsub melsbu meulbs meulsb meubls meubsl meusbl
meuslb meslub meslbu mesulb mesubl mesbul mesblu msbleu msblue msbelu msbeul
msbuel msbule mslbeu mslbue mslebu msleub mslueb mslube mselbu mselub mseblu
msebul mseubl mseulb msuleb msulbe msuelb msuebl msubel msuble bmules bmulse
bmuels bmuesl bmusel bmusle bmlues bmluse bmleus bmlesu bmlseu bmlsue bmelus
bmelsu bmeuls bmeusl bmesul bmeslu bmsleu bmslue bmselu bmseul bmsuel bmsule
bumles bumlse bumels bumesl bumsel bumsle bulmes bulmse bulems bulesm bulsem
bulsme buelms buelsm buemls buemsl buesml bueslm buslem buslme buselm buseml
busmel busmle blumes blumse bluems bluesm blusem blusme blmues blmuse blmeus
blmesu blmseu blmsue blemus blemsu bleums bleusm blesum blesmu blsmeu blsmue
blsemu blseum blsuem blsume beulms beulsm beumls beumsl beusml beuslm belums
belusm belmus belmsu belsmu belsum bemlus bemlsu bemuls bemusl bemsul bemslu
beslmu beslum besmlu besmul besuml besulm bsulem bsulme bsuelm bsueml bsumel
bsumle bsluem bslume bsleum bslemu bslmeu bslmue bselum bselmu bseulm bseuml
bsemul bsemlu bsmleu bsmlue bsmelu bsmeul bsmuel bsmule lmbues lmbuse lmbeus
lmbesu lmbseu lmbsue lmubes lmubse lmuebs lmuesb lmuseb lmusbe lmeubs lmeusb
lmebus lmebsu lmesbu lmesub lmsueb lmsube lmseub lmsebu lmsbeu lmsbue lbmues
lbmuse lbmeus lbmesu lbmseu lbmsue lbumes lbumse lbuems lbuesm lbusem lbusme
lbeums lbeusm lbemus lbemsu lbesmu lbesum lbsuem lbsume lbseum lbsemu lbsmeu
lbsmue lubmes lubmse lubems lubesm lubsem lubsme lumbes lumbse lumebs lumesb
lumseb lumsbe luembs luemsb luebms luebsm luesbm luesmb lusmeb lusmbe lusemb
lusebm lusbem lusbme lebums lebusm lebmus lebmsu lebsmu lebsum leubms leubsm
leumbs leumsb leusmb leusbm lemubs lemusb lembus lembsu lemsbu lemsub lesumb
lesubm lesmub lesmbu lesbmu lesbum lsbuem lsbume lsbeum lsbemu lsbmeu lsbmue
lsubem lsubme lsuebm lsuemb lsumeb lsumbe lseubm lseumb lsebum lsebmu lsembu
lsemub lsmueb lsmube lsmeub lsmebu lsmbeu lsmbue emblus emblsu embuls embusl
embsul embslu emlbus emlbsu emlubs emlusb emlsub emlsbu emulbs emulsb emubls
emubsl emusbl emuslb emslub emslbu emsulb emsubl emsbul emsblu ebmlus ebmlsu
ebmuls ebmusl ebmsul ebmslu eblmus eblmsu eblums eblusm eblsum eblsmu ebulms
ebulsm ebumls ebumsl ebusml ebuslm ebslum ebslmu ebsulm ebsuml ebsmul ebsmlu
elbmus elbmsu elbums elbusm elbsum elbsmu elmbus elmbsu elmubs elmusb elmsub
elmsbu elumbs elumsb elubms elubsm elusbm elusmb elsmub elsmbu elsumb elsubm
elsbum elsbmu eublms eublsm eubmls eubmsl eubsml eubslm eulbms eulbsm eulmbs
eulmsb eulsmb eulsbm eumlbs eumlsb eumbls eumbsl eumsbl eumslb euslmb euslbm
eusmlb eusmbl eusbml eusblm esblum esblmu esbulm esbuml esbmul esbmlu eslbum
eslbmu eslubm eslumb eslmub eslmbu esulbm esulmb esublm esubml esumbl esumlb
esmlub esmlbu esmulb esmubl esmbul esmblu smbleu smblue smbelu smbeul smbuel
smbule smlbeu smlbue smlebu smleub smlueb smlube smelbu smelub smeblu smebul
smeubl smeulb smuleb smulbe smuelb smuebl smubel smuble sbmleu sbmlue sbmelu
sbmeul sbmuel sbmule sblmeu sblmue sblemu sbleum sbluem sblume sbelmu sbelum
sbemlu sbemul sbeuml sbeulm sbulem sbulme sbuelm sbueml sbumel sbumle slbmeu
slbmue slbemu slbeum slbuem slbume slmbeu slmbue slmebu slmeub slmueb slmube
slembu slemub slebmu slebum sleubm sleumb slumeb slumbe sluemb sluebm slubem
slubme seblmu seblum sebmlu sebmul sebuml sebulm selbmu selbum selmbu selmub
selumb selubm semlbu semlub semblu sembul semubl semulb seulmb seulbm seumlb
seumbl seubml seublm sublem sublme subelm subeml submel submle sulbem sulbme
sulebm sulemb sulmeb sulmbe suelbm suelmb sueblm suebml suembl suemlb sumleb
sumlbe sumelb sumebl sumbel sumble

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History of cryptography
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