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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: angsts
cipher variations:
bohtut cpiuvu dqjvwv erkwxw fslxyx
gtmyzy hunzaz ivoaba jwpbcb kxqcdc
lyrded mzsefe natfgf obughg pcvhih
qdwiji rexjkj sfyklk tgzlml uhamnm
vibnon wjcopo xkdpqp yleqrq zmfrsr

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: angsts
Cipher: zmthgh

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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: angsts

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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: angsts
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: angsts
Cipher: natfgf

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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: angsts
Cipher: 113322344434

Extended Methods:
Method #1

Plaintext: angsts
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
a n g s t s 
1 3 2 3 4 3 
1 3 2 4 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: angsts
Cipher: lmolrt

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Method #3

Plaintext: angsts
method variations:
lhmtod hmtodl mtodlh
todlhm odlhmt dlhmto

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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: angsts

all 720 cipher variations:
angsts angsst angtss angtss angsts angsst ansgts ansgst anstgs anstsg ansstg
anssgt antsgs antssg antgss antgss antsgs antssg ansstg anssgt anstsg anstgs
ansgts ansgst agnsts agnsst agntss agntss agnsts agnsst agsnts agsnst agstns
agstsn agsstn agssnt agtsns agtssn agtnss agtnss agtsns agtssn agsstn agssnt
agstsn agstns agsnts agsnst asgnts asgnst asgtns asgtsn asgstn asgsnt asngts
asngst asntgs asntsg asnstg asnsgt astngs astnsg astgns astgsn astsgn astsng
assntg assngt asstng asstgn assgtn assgnt atgsns atgssn atgnss atgnss atgsns
atgssn atsgns atsgsn atsngs atsnsg atssng atssgn atnsgs atnssg atngss atngss
atnsgs atnssg atssng atssgn atsnsg atsngs atsgns atsgsn asgstn asgsnt asgtsn
asgtns asgnts asgnst assgtn assgnt asstgn asstng assntg assngt astsgn astsng
astgsn astgns astngs astnsg asnstg asnsgt asntsg asntgs asngts asngst nagsts
nagsst nagtss nagtss nagsts nagsst nasgts nasgst nastgs nastsg nasstg nassgt
natsgs natssg natgss natgss natsgs natssg nasstg nassgt nastsg nastgs nasgts
nasgst ngasts ngasst ngatss ngatss ngasts ngasst ngsats ngsast ngstas ngstsa
ngssta ngssat ngtsas ngtssa ngtass ngtass ngtsas ngtssa ngssta ngssat ngstsa
ngstas ngsats ngsast nsgats nsgast nsgtas nsgtsa nsgsta nsgsat nsagts nsagst
nsatgs nsatsg nsastg nsasgt nstags nstasg nstgas nstgsa nstsga nstsag nssatg
nssagt nsstag nsstga nssgta nssgat ntgsas ntgssa ntgass ntgass ntgsas ntgssa
ntsgas ntsgsa ntsags ntsasg ntssag ntssga ntasgs ntassg ntagss ntagss ntasgs
ntassg ntssag ntssga ntsasg ntsags ntsgas ntsgsa nsgsta nsgsat nsgtsa nsgtas
nsgats nsgast nssgta nssgat nsstga nsstag nssatg nssagt nstsga nstsag nstgsa
nstgas nstags nstasg nsastg nsasgt nsatsg nsatgs nsagts nsagst gnasts gnasst
gnatss gnatss gnasts gnasst gnsats gnsast gnstas gnstsa gnssta gnssat gntsas
gntssa gntass gntass gntsas gntssa gnssta gnssat gnstsa gnstas gnsats gnsast
gansts gansst gantss gantss gansts gansst gasnts gasnst gastns gastsn gasstn
gassnt gatsns gatssn gatnss gatnss gatsns gatssn gasstn gassnt gastsn gastns
gasnts gasnst gsants gsanst gsatns gsatsn gsastn gsasnt gsnats gsnast gsntas
gsntsa gsnsta gsnsat gstnas gstnsa gstans gstasn gstsan gstsna gssnta gssnat
gsstna gsstan gssatn gssant gtasns gtassn gtanss gtanss gtasns gtassn gtsans
gtsasn gtsnas gtsnsa gtssna gtssan gtnsas gtnssa gtnass gtnass gtnsas gtnssa
gtssna gtssan gtsnsa gtsnas gtsans gtsasn gsastn gsasnt gsatsn gsatns gsants
gsanst gssatn gssant gsstan gsstna gssnta gssnat gstsan gstsna gstasn gstans
gstnas gstnsa gsnsta gsnsat gsntsa gsntas gsnats gsnast sngats sngast sngtas
sngtsa sngsta sngsat snagts snagst snatgs snatsg snastg snasgt sntags sntasg
sntgas sntgsa sntsga sntsag snsatg snsagt snstag snstga snsgta snsgat sgnats
sgnast sgntas sgntsa sgnsta sgnsat sgants sganst sgatns sgatsn sgastn sgasnt
sgtans sgtasn sgtnas sgtnsa sgtsna sgtsan sgsatn sgsant sgstan sgstna sgsnta
sgsnat sagnts sagnst sagtns sagtsn sagstn sagsnt sangts sangst santgs santsg
sanstg sansgt satngs satnsg satgns satgsn satsgn satsng sasntg sasngt sastng
sastgn sasgtn sasgnt stgans stgasn stgnas stgnsa stgsna stgsan stagns stagsn
stangs stansg stasng stasgn stnags stnasg stngas stngsa stnsga stnsag stsang
stsagn stsnag stsnga stsgna stsgan ssgatn ssgant ssgtan ssgtna ssgnta ssgnat
ssagtn ssagnt ssatgn ssatng ssantg ssangt sstagn sstang sstgan sstgna sstnga
sstnag ssnatg ssnagt ssntag ssntga ssngta ssngat tngsas tngssa tngass tngass
tngsas tngssa tnsgas tnsgsa tnsags tnsasg tnssag tnssga tnasgs tnassg tnagss
tnagss tnasgs tnassg tnssag tnssga tnsasg tnsags tnsgas tnsgsa tgnsas tgnssa
tgnass tgnass tgnsas tgnssa tgsnas tgsnsa tgsans tgsasn tgssan tgssna tgasns
tgassn tganss tganss tgasns tgassn tgssan tgssna tgsasn tgsans tgsnas tgsnsa
tsgnas tsgnsa tsgans tsgasn tsgsan tsgsna tsngas tsngsa tsnags tsnasg tsnsag
tsnsga tsangs tsansg tsagns tsagsn tsasgn tsasng tssnag tssnga tssang tssagn
tssgan tssgna tagsns tagssn tagnss tagnss tagsns tagssn tasgns tasgsn tasngs
tasnsg tassng tassgn tansgs tanssg tangss tangss tansgs tanssg tassng tassgn
tasnsg tasngs tasgns tasgsn tsgsan tsgsna tsgasn tsgans tsgnas tsgnsa tssgan
tssgna tssagn tssang tssnag tssnga tsasgn tsasng tsagsn tsagns tsangs tsansg
tsnsag tsnsga tsnasg tsnags tsngas tsngsa sngsta sngsat sngtsa sngtas sngats
sngast snsgta snsgat snstga snstag snsatg snsagt sntsga sntsag sntgsa sntgas
sntags sntasg snastg snasgt snatsg snatgs snagts snagst sgnsta sgnsat sgntsa
sgntas sgnats sgnast sgsnta sgsnat sgstna sgstan sgsatn sgsant sgtsna sgtsan
sgtnsa sgtnas sgtans sgtasn sgastn sgasnt sgatsn sgatns sgants sganst ssgnta
ssgnat ssgtna ssgtan ssgatn ssgant ssngta ssngat ssntga ssntag ssnatg ssnagt
sstnga sstnag sstgna sstgan sstagn sstang ssantg ssangt ssatng ssatgn ssagtn
ssagnt stgsna stgsan stgnsa stgnas stgans stgasn stsgna stsgan stsnga stsnag
stsang stsagn stnsga stnsag stngsa stngas stnags stnasg stasng stasgn stansg
stangs stagns stagsn sagstn sagsnt sagtsn sagtns sagnts sagnst sasgtn sasgnt
sastgn sastng sasntg sasngt satsgn satsng satgsn satgns satngs satnsg sanstg
sansgt santsg santgs sangts sangst

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History of cryptography
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