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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: daters
cipher variations:
ebufst fcvgtu gdwhuv hexivw ifyjwx
jgzkxy khalyz libmza mjcnab nkdobc
olepcd pmfqde qngref rohsfg spitgh
tqjuhi urkvij vslwjk wtmxkl xunylm
yvozmn zwpano axqbop byrcpq czsdqr

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: daters
Cipher: wzgvih

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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: daters

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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: daters
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: daters
Cipher: qngref

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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: daters
Cipher: 411144512434

Extended Methods:
Method #1

Plaintext: daters
method variations:

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

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Method #3

Plaintext: daters
method variations:
aqyfot qyfota yfotaq
fotaqy otaqyf taqyfo

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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: daters

all 720 cipher variations:
daters datesr datres datrse datsre datser daetrs daetsr daerts daerst daesrt
daestr darets darest dartes dartse darste darset dasert dasetr dasret dasrte
dastre daster dtaers dtaesr dtares dtarse dtasre dtaser dtears dteasr dteras
dtersa dtesra dtesar dtreas dtresa dtraes dtrase dtrsae dtrsea dtsera dtsear
dtsrea dtsrae dtsare dtsaer detars detasr detras detrsa detsra detsar deatrs
deatsr dearts dearst deasrt deastr derats derast dertas dertsa dersta dersat
desart desatr desrat desrta destra destar drteas drtesa drtaes drtase drtsae
drtsea dretas dretsa dreats dreast dresat dresta draets draest drates dratse
draste draset drseat drseta drsaet drsate drstae drstea dstera dstear dstrea
dstrae dstare dstaer dsetra dsetar dserta dserat dseart dseatr dsreta dsreat
dsrtea dsrtae dsrate dsraet dsaert dsaetr dsaret dsarte dsatre dsater adters
adtesr adtres adtrse adtsre adtser adetrs adetsr aderts aderst adesrt adestr
adrets adrest adrtes adrtse adrste adrset adsert adsetr adsret adsrte adstre
adster atders atdesr atdres atdrse atdsre atdser atedrs atedsr aterds atersd
atesrd atesdr atreds atresd atrdes atrdse atrsde atrsed atserd atsedr atsred
atsrde atsdre atsder aetdrs aetdsr aetrds aetrsd aetsrd aetsdr aedtrs aedtsr
aedrts aedrst aedsrt aedstr aerdts aerdst aertds aertsd aerstd aersdt aesdrt
aesdtr aesrdt aesrtd aestrd aestdr arteds artesd artdes artdse artsde artsed
aretds aretsd aredts aredst aresdt arestd ardets ardest ardtes ardtse ardste
ardset arsedt arsetd arsdet arsdte arstde arsted asterd astedr astred astrde
astdre astder asetrd asetdr asertd aserdt asedrt asedtr asretd asredt asrted
asrtde asrdte asrdet asdert asdetr asdret asdrte asdtre asdter taders tadesr
tadres tadrse tadsre tadser taedrs taedsr taerds taersd taesrd taesdr tareds
taresd tardes tardse tarsde tarsed taserd tasedr tasred tasrde tasdre tasder
tdaers tdaesr tdares tdarse tdasre tdaser tdears tdeasr tderas tdersa tdesra
tdesar tdreas tdresa tdraes tdrase tdrsae tdrsea tdsera tdsear tdsrea tdsrae
tdsare tdsaer tedars tedasr tedras tedrsa tedsra tedsar teadrs teadsr teards
tearsd teasrd teasdr terads terasd terdas terdsa tersda tersad tesard tesadr
tesrad tesrda tesdra tesdar trdeas trdesa trdaes trdase trdsae trdsea tredas
tredsa treads treasd tresad tresda traeds traesd trades tradse trasde trased
trsead trseda trsaed trsade trsdae trsdea tsdera tsdear tsdrea tsdrae tsdare
tsdaer tsedra tsedar tserda tserad tseard tseadr tsreda tsread tsrdea tsrdae
tsrade tsraed tsaerd tsaedr tsared tsarde tsadre tsader eatdrs eatdsr eatrds
eatrsd eatsrd eatsdr eadtrs eadtsr eadrts eadrst eadsrt eadstr eardts eardst
eartds eartsd earstd earsdt easdrt easdtr easrdt easrtd eastrd eastdr etadrs
etadsr etards etarsd etasrd etasdr etdars etdasr etdras etdrsa etdsra etdsar
etrdas etrdsa etrads etrasd etrsad etrsda etsdra etsdar etsrda etsrad etsard
etsadr edtars edtasr edtras edtrsa edtsra edtsar edatrs edatsr edarts edarst
edasrt edastr edrats edrast edrtas edrtsa edrsta edrsat edsart edsatr edsrat
edsrta edstra edstar ertdas ertdsa ertads ertasd ertsad ertsda erdtas erdtsa
erdats erdast erdsat erdsta eradts eradst eratds eratsd erastd erasdt ersdat
ersdta ersadt ersatd erstad erstda estdra estdar estrda estrad estard estadr
esdtra esdtar esdrta esdrat esdart esdatr esrdta esrdat esrtda esrtad esratd
esradt esadrt esadtr esardt esartd esatrd esatdr rateds ratesd ratdes ratdse
ratsde ratsed raetds raetsd raedts raedst raesdt raestd radets radest radtes
radtse radste radset rasedt rasetd rasdet rasdte rastde rasted rtaeds rtaesd
rtades rtadse rtasde rtased rteads rteasd rtedas rtedsa rtesda rtesad rtdeas
rtdesa rtdaes rtdase rtdsae rtdsea rtseda rtsead rtsdea rtsdae rtsade rtsaed
retads retasd retdas retdsa retsda retsad reatds reatsd readts readst reasdt
reastd redats redast redtas redtsa redsta redsat resadt resatd resdat resdta
restda restad rdteas rdtesa rdtaes rdtase rdtsae rdtsea rdetas rdetsa rdeats
rdeast rdesat rdesta rdaets rdaest rdates rdatse rdaste rdaset rdseat rdseta
rdsaet rdsate rdstae rdstea rsteda rstead rstdea rstdae rstade rstaed rsetda
rsetad rsedta rsedat rseadt rseatd rsdeta rsdeat rsdtea rsdtae rsdate rsdaet
rsaedt rsaetd rsadet rsadte rsatde rsated saterd satedr satred satrde satdre
satder saetrd saetdr saertd saerdt saedrt saedtr saretd saredt sarted sartde
sardte sardet sadert sadetr sadret sadrte sadtre sadter staerd staedr stared
starde stadre stader steard steadr sterad sterda stedra stedar stread streda
straed strade strdae strdea stdera stdear stdrea stdrae stdare stdaer setard
setadr setrad setrda setdra setdar seatrd seatdr seartd seardt seadrt seadtr
seratd seradt sertad sertda serdta serdat sedart sedatr sedrat sedrta sedtra
sedtar srtead srteda srtaed srtade srtdae srtdea sretad sretda sreatd sreadt
sredat sredta sraetd sraedt srated sratde sradte sradet srdeat srdeta srdaet
srdate srdtae srdtea sdtera sdtear sdtrea sdtrae sdtare sdtaer sdetra sdetar
sderta sderat sdeart sdeatr sdreta sdreat sdrtea sdrtae sdrate sdraet sdaert
sdaetr sdaret sdarte sdatre sdater

Read more ...[1] , [2] , [3]

History of cryptography
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