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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: cyamus
cipher variations:
dzbnvt eacowu fbdpxv gceqyw hdfrzx
iegsay jfhtbz kgiuca lhjvdb mikwec
njlxfd okmyge plnzhf qmoaig rnpbjh
soqcki tprdlj uqsemk vrtfnl wsugom
xtvhpn yuwiqo zvxjrp awyksq bxzltr

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: cyamus
Cipher: xbznfh

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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: cyamus

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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: cyamus
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: cyamus
Cipher: plnzhf

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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: cyamus
Cipher: 314511235434

Extended Methods:
Method #1

Plaintext: cyamus
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
c y a m u s 
3 4 1 2 5 3 
1 5 1 3 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: cyamus
Cipher: sfpvlt

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Method #3

Plaintext: cyamus
method variations:
qefxoo efxooq fxooqe
xooqef ooqefx oqefxo

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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: cyamus

all 720 cipher variations:
cyamus cyamsu cyaums cyausm cyasum cyasmu cymaus cymasu cymuas cymusa cymsua
cymsau cyumas cyumsa cyuams cyuasm cyusam cyusma cysmua cysmau cysuma cysuam
cysaum cysamu caymus caymsu cayums cayusm caysum caysmu camyus camysu camuys
camusy camsuy camsyu caumys caumsy cauyms cauysm causym causmy casmuy casmyu
casumy casuym casyum casymu cmayus cmaysu cmauys cmausy cmasuy cmasyu cmyaus
cmyasu cmyuas cmyusa cmysua cmysau cmuyas cmuysa cmuays cmuasy cmusay cmusya
cmsyua cmsyau cmsuya cmsuay cmsauy cmsayu cuamys cuamsy cuayms cuaysm cuasym
cuasmy cumays cumasy cumyas cumysa cumsya cumsay cuymas cuymsa cuyams cuyasm
cuysam cuysma cusmya cusmay cusyma cusyam cusaym cusamy csamuy csamyu csaumy
csauym csayum csaymu csmauy csmayu csmuay csmuya csmyua csmyau csumay csumya
csuamy csuaym csuyam csuyma csymua csymau csyuma csyuam csyaum csyamu ycamus
ycamsu ycaums ycausm ycasum ycasmu ycmaus ycmasu ycmuas ycmusa ycmsua ycmsau
ycumas ycumsa ycuams ycuasm ycusam ycusma ycsmua ycsmau ycsuma ycsuam ycsaum
ycsamu yacmus yacmsu yacums yacusm yacsum yacsmu yamcus yamcsu yamucs yamusc
yamsuc yamscu yaumcs yaumsc yaucms yaucsm yauscm yausmc yasmuc yasmcu yasumc
yasucm yascum yascmu ymacus ymacsu ymaucs ymausc ymasuc ymascu ymcaus ymcasu
ymcuas ymcusa ymcsua ymcsau ymucas ymucsa ymuacs ymuasc ymusac ymusca ymscua
ymscau ymsuca ymsuac ymsauc ymsacu yuamcs yuamsc yuacms yuacsm yuascm yuasmc
yumacs yumasc yumcas yumcsa yumsca yumsac yucmas yucmsa yucams yucasm yucsam
yucsma yusmca yusmac yuscma yuscam yusacm yusamc ysamuc ysamcu ysaumc ysaucm
ysacum ysacmu ysmauc ysmacu ysmuac ysmuca ysmcua ysmcau ysumac ysumca ysuamc
ysuacm ysucam ysucma yscmua yscmau yscuma yscuam yscaum yscamu aycmus aycmsu
aycums aycusm aycsum aycsmu aymcus aymcsu aymucs aymusc aymsuc aymscu ayumcs
ayumsc ayucms ayucsm ayuscm ayusmc aysmuc aysmcu aysumc aysucm ayscum ayscmu
acymus acymsu acyums acyusm acysum acysmu acmyus acmysu acmuys acmusy acmsuy
acmsyu acumys acumsy acuyms acuysm acusym acusmy acsmuy acsmyu acsumy acsuym
acsyum acsymu amcyus amcysu amcuys amcusy amcsuy amcsyu amycus amycsu amyucs
amyusc amysuc amyscu amuycs amuysc amucys amucsy amuscy amusyc amsyuc amsycu
amsuyc amsucy amscuy amscyu aucmys aucmsy aucyms aucysm aucsym aucsmy aumcys
aumcsy aumycs aumysc aumsyc aumscy auymcs auymsc auycms auycsm auyscm auysmc
ausmyc ausmcy ausymc ausycm auscym auscmy ascmuy ascmyu ascumy ascuym ascyum
ascymu asmcuy asmcyu asmucy asmuyc asmyuc asmycu asumcy asumyc asucmy asucym
asuycm asuymc asymuc asymcu asyumc asyucm asycum asycmu myacus myacsu myaucs
myausc myasuc myascu mycaus mycasu mycuas mycusa mycsua mycsau myucas myucsa
myuacs myuasc myusac myusca myscua myscau mysuca mysuac mysauc mysacu maycus
maycsu mayucs mayusc maysuc mayscu macyus macysu macuys macusy macsuy macsyu
maucys maucsy mauycs mauysc mausyc mauscy mascuy mascyu masucy masuyc masyuc
masycu mcayus mcaysu mcauys mcausy mcasuy mcasyu mcyaus mcyasu mcyuas mcyusa
mcysua mcysau mcuyas mcuysa mcuays mcuasy mcusay mcusya mcsyua mcsyau mcsuya
mcsuay mcsauy mcsayu muacys muacsy muaycs muaysc muasyc muascy mucays mucasy
mucyas mucysa mucsya mucsay muycas muycsa muyacs muyasc muysac muysca muscya
muscay musyca musyac musayc musacy msacuy msacyu msaucy msauyc msayuc msaycu
mscauy mscayu mscuay mscuya mscyua mscyau msucay msucya msuacy msuayc msuyac
msuyca msycua msycau msyuca msyuac msyauc msyacu uyamcs uyamsc uyacms uyacsm
uyascm uyasmc uymacs uymasc uymcas uymcsa uymsca uymsac uycmas uycmsa uycams
uycasm uycsam uycsma uysmca uysmac uyscma uyscam uysacm uysamc uaymcs uaymsc
uaycms uaycsm uayscm uaysmc uamycs uamysc uamcys uamcsy uamscy uamsyc uacmys
uacmsy uacyms uacysm uacsym uacsmy uasmcy uasmyc uascmy uascym uasycm uasymc
umaycs umaysc umacys umacsy umascy umasyc umyacs umyasc umycas umycsa umysca
umysac umcyas umcysa umcays umcasy umcsay umcsya umsyca umsyac umscya umscay
umsacy umsayc ucamys ucamsy ucayms ucaysm ucasym ucasmy ucmays ucmasy ucmyas
ucmysa ucmsya ucmsay ucymas ucymsa ucyams ucyasm ucysam ucysma ucsmya ucsmay
ucsyma ucsyam ucsaym ucsamy usamcy usamyc usacmy usacym usaycm usaymc usmacy
usmayc usmcay usmcya usmyca usmyac uscmay uscmya uscamy uscaym uscyam uscyma
usymca usymac usycma usycam usyacm usyamc syamuc syamcu syaumc syaucm syacum
syacmu symauc symacu symuac symuca symcua symcau syumac syumca syuamc syuacm
syucam syucma sycmua sycmau sycuma sycuam sycaum sycamu saymuc saymcu sayumc
sayucm saycum saycmu samyuc samycu samuyc samucy samcuy samcyu saumyc saumcy
sauymc sauycm saucym saucmy sacmuy sacmyu sacumy sacuym sacyum sacymu smayuc
smaycu smauyc smaucy smacuy smacyu smyauc smyacu smyuac smyuca smycua smycau
smuyac smuyca smuayc smuacy smucay smucya smcyua smcyau smcuya smcuay smcauy
smcayu suamyc suamcy suaymc suaycm suacym suacmy sumayc sumacy sumyac sumyca
sumcya sumcay suymac suymca suyamc suyacm suycam suycma sucmya sucmay sucyma
sucyam sucaym sucamy scamuy scamyu scaumy scauym scayum scaymu scmauy scmayu
scmuay scmuya scmyua scmyau scumay scumya scuamy scuaym scuyam scuyma scymua
scymau scyuma scyuam scyaum scyamu

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History of cryptography
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