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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: jihyun
cipher variations:
kjizvo lkjawp mlkbxq nmlcyr onmdzs
poneat qpofbu rqpgcv srqhdw tsriex
utsjfy vutkgz wvulha xwvmib yxwnjc
zyxokd azyple bazqmf cbarng dcbsoh
edctpi feduqj gfevrk hgfwsl ihgxtm

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: jihyun
Cipher: qrsbfm

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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: jihyun

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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: jihyun
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: jihyun
Cipher: wvulha

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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: jihyun
Cipher: 424232455433

Extended Methods:
Method #1

Plaintext: jihyun
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
j i h y u n 
4 4 3 4 5 3 
2 2 2 5 4 3 
They are then read out in rows:
Then divided up into pairs again, and the pairs turned back into letters using the square:
Plain: jihyun
Cipher: tspgwo

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Method #3

Plaintext: jihyun
method variations:
rmrzos mrzosr rzosrm
zosrmr osrmrz srmrzo

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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: jihyun

all 720 cipher variations:
jihyun jihynu jihuyn jihuny jihnuy jihnyu jiyhun jiyhnu jiyuhn jiyunh jiynuh
jiynhu jiuyhn jiuynh jiuhyn jiuhny jiunhy jiunyh jinyuh jinyhu jinuyh jinuhy
jinhuy jinhyu jhiyun jhiynu jhiuyn jhiuny jhinuy jhinyu jhyiun jhyinu jhyuin
jhyuni jhynui jhyniu jhuyin jhuyni jhuiyn jhuiny jhuniy jhunyi jhnyui jhnyiu
jhnuyi jhnuiy jhniuy jhniyu jyhiun jyhinu jyhuin jyhuni jyhnui jyhniu jyihun
jyihnu jyiuhn jyiunh jyinuh jyinhu jyuihn jyuinh jyuhin jyuhni jyunhi jyunih
jyniuh jynihu jynuih jynuhi jynhui jynhiu juhyin juhyni juhiyn juhiny juhniy
juhnyi juyhin juyhni juyihn juyinh juynih juynhi juiyhn juiynh juihyn juihny
juinhy juinyh junyih junyhi juniyh junihy junhiy junhyi jnhyui jnhyiu jnhuyi
jnhuiy jnhiuy jnhiyu jnyhui jnyhiu jnyuhi jnyuih jnyiuh jnyihu jnuyhi jnuyih
jnuhyi jnuhiy jnuihy jnuiyh jniyuh jniyhu jniuyh jniuhy jnihuy jnihyu ijhyun
ijhynu ijhuyn ijhuny ijhnuy ijhnyu ijyhun ijyhnu ijyuhn ijyunh ijynuh ijynhu
ijuyhn ijuynh ijuhyn ijuhny ijunhy ijunyh ijnyuh ijnyhu ijnuyh ijnuhy ijnhuy
ijnhyu ihjyun ihjynu ihjuyn ihjuny ihjnuy ihjnyu ihyjun ihyjnu ihyujn ihyunj
ihynuj ihynju ihuyjn ihuynj ihujyn ihujny ihunjy ihunyj ihnyuj ihnyju ihnuyj
ihnujy ihnjuy ihnjyu iyhjun iyhjnu iyhujn iyhunj iyhnuj iyhnju iyjhun iyjhnu
iyjuhn iyjunh iyjnuh iyjnhu iyujhn iyujnh iyuhjn iyuhnj iyunhj iyunjh iynjuh
iynjhu iynujh iynuhj iynhuj iynhju iuhyjn iuhynj iuhjyn iuhjny iuhnjy iuhnyj
iuyhjn iuyhnj iuyjhn iuyjnh iuynjh iuynhj iujyhn iujynh iujhyn iujhny iujnhy
iujnyh iunyjh iunyhj iunjyh iunjhy iunhjy iunhyj inhyuj inhyju inhuyj inhujy
inhjuy inhjyu inyhuj inyhju inyuhj inyujh inyjuh inyjhu inuyhj inuyjh inuhyj
inuhjy inujhy inujyh injyuh injyhu injuyh injuhy injhuy injhyu hijyun hijynu
hijuyn hijuny hijnuy hijnyu hiyjun hiyjnu hiyujn hiyunj hiynuj hiynju hiuyjn
hiuynj hiujyn hiujny hiunjy hiunyj hinyuj hinyju hinuyj hinujy hinjuy hinjyu
hjiyun hjiynu hjiuyn hjiuny hjinuy hjinyu hjyiun hjyinu hjyuin hjyuni hjynui
hjyniu hjuyin hjuyni hjuiyn hjuiny hjuniy hjunyi hjnyui hjnyiu hjnuyi hjnuiy
hjniuy hjniyu hyjiun hyjinu hyjuin hyjuni hyjnui hyjniu hyijun hyijnu hyiujn
hyiunj hyinuj hyinju hyuijn hyuinj hyujin hyujni hyunji hyunij hyniuj hyniju
hynuij hynuji hynjui hynjiu hujyin hujyni hujiyn hujiny hujniy hujnyi huyjin
huyjni huyijn huyinj huynij huynji huiyjn huiynj huijyn huijny huinjy huinyj
hunyij hunyji huniyj hunijy hunjiy hunjyi hnjyui hnjyiu hnjuyi hnjuiy hnjiuy
hnjiyu hnyjui hnyjiu hnyuji hnyuij hnyiuj hnyiju hnuyji hnuyij hnujyi hnujiy
hnuijy hnuiyj hniyuj hniyju hniuyj hniujy hnijuy hnijyu yihjun yihjnu yihujn
yihunj yihnuj yihnju yijhun yijhnu yijuhn yijunh yijnuh yijnhu yiujhn yiujnh
yiuhjn yiuhnj yiunhj yiunjh yinjuh yinjhu yinujh yinuhj yinhuj yinhju yhijun
yhijnu yhiujn yhiunj yhinuj yhinju yhjiun yhjinu yhjuin yhjuni yhjnui yhjniu
yhujin yhujni yhuijn yhuinj yhunij yhunji yhnjui yhnjiu yhnuji yhnuij yhniuj
yhniju yjhiun yjhinu yjhuin yjhuni yjhnui yjhniu yjihun yjihnu yjiuhn yjiunh
yjinuh yjinhu yjuihn yjuinh yjuhin yjuhni yjunhi yjunih yjniuh yjnihu yjnuih
yjnuhi yjnhui yjnhiu yuhjin yuhjni yuhijn yuhinj yuhnij yuhnji yujhin yujhni
yujihn yujinh yujnih yujnhi yuijhn yuijnh yuihjn yuihnj yuinhj yuinjh yunjih
yunjhi yunijh yunihj yunhij yunhji ynhjui ynhjiu ynhuji ynhuij ynhiuj ynhiju
ynjhui ynjhiu ynjuhi ynjuih ynjiuh ynjihu ynujhi ynujih ynuhji ynuhij ynuihj
ynuijh ynijuh ynijhu yniujh yniuhj ynihuj ynihju uihyjn uihynj uihjyn uihjny
uihnjy uihnyj uiyhjn uiyhnj uiyjhn uiyjnh uiynjh uiynhj uijyhn uijynh uijhyn
uijhny uijnhy uijnyh uinyjh uinyhj uinjyh uinjhy uinhjy uinhyj uhiyjn uhiynj
uhijyn uhijny uhinjy uhinyj uhyijn uhyinj uhyjin uhyjni uhynji uhynij uhjyin
uhjyni uhjiyn uhjiny uhjniy uhjnyi uhnyji uhnyij uhnjyi uhnjiy uhnijy uhniyj
uyhijn uyhinj uyhjin uyhjni uyhnji uyhnij uyihjn uyihnj uyijhn uyijnh uyinjh
uyinhj uyjihn uyjinh uyjhin uyjhni uyjnhi uyjnih uynijh uynihj uynjih uynjhi
uynhji uynhij ujhyin ujhyni ujhiyn ujhiny ujhniy ujhnyi ujyhin ujyhni ujyihn
ujyinh ujynih ujynhi ujiyhn ujiynh ujihyn ujihny ujinhy ujinyh ujnyih ujnyhi
ujniyh ujnihy ujnhiy ujnhyi unhyji unhyij unhjyi unhjiy unhijy unhiyj unyhji
unyhij unyjhi unyjih unyijh unyihj unjyhi unjyih unjhyi unjhiy unjihy unjiyh
uniyjh uniyhj unijyh unijhy unihjy unihyj nihyuj nihyju nihuyj nihujy nihjuy
nihjyu niyhuj niyhju niyuhj niyujh niyjuh niyjhu niuyhj niuyjh niuhyj niuhjy
niujhy niujyh nijyuh nijyhu nijuyh nijuhy nijhuy nijhyu nhiyuj nhiyju nhiuyj
nhiujy nhijuy nhijyu nhyiuj nhyiju nhyuij nhyuji nhyjui nhyjiu nhuyij nhuyji
nhuiyj nhuijy nhujiy nhujyi nhjyui nhjyiu nhjuyi nhjuiy nhjiuy nhjiyu nyhiuj
nyhiju nyhuij nyhuji nyhjui nyhjiu nyihuj nyihju nyiuhj nyiujh nyijuh nyijhu
nyuihj nyuijh nyuhij nyuhji nyujhi nyujih nyjiuh nyjihu nyjuih nyjuhi nyjhui
nyjhiu nuhyij nuhyji nuhiyj nuhijy nuhjiy nuhjyi nuyhij nuyhji nuyihj nuyijh
nuyjih nuyjhi nuiyhj nuiyjh nuihyj nuihjy nuijhy nuijyh nujyih nujyhi nujiyh
nujihy nujhiy nujhyi njhyui njhyiu njhuyi njhuiy njhiuy njhiyu njyhui njyhiu
njyuhi njyuih njyiuh njyihu njuyhi njuyih njuhyi njuhiy njuihy njuiyh njiyuh
njiyhu njiuyh njiuhy njihuy njihyu

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History of cryptography
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