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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: csgate
cipher variations:
dthbuf euicvg fvjdwh gwkexi hxlfyj
iymgzk jznhal kaoibm lbpjcn mcqkdo
ndrlep oesmfq pftngr qguohs rhvpit
siwqju tjxrkv ukyslw vlztmx wmauny
xnbvoz yocwpa zpdxqb aqeyrc brfzsd

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: csgate
Cipher: xhtzgv

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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: csgate

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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: csgate
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: csgate
Cipher: pftngr

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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: csgate
Cipher: 313422114451

Extended Methods:
Method #1

Plaintext: csgate
method variations:

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

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Method #3

Plaintext: csgate
method variations:
libqyl ibqyll bqylli
qyllib yllibq llibqy

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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: csgate

all 720 cipher variations:
csgate csgaet csgtae csgtea csgeta csgeat csagte csaget csatge csateg csaetg
csaegt cstage cstaeg cstgae cstgea cstega csteag cseatg cseagt csetag csetga
csegta csegat cgsate cgsaet cgstae cgstea cgseta cgseat cgaste cgaset cgatse
cgates cgaets cgaest cgtase cgtaes cgtsae cgtsea cgtesa cgteas cgeats cgeast
cgetas cgetsa cgesta cgesat cagste cagset cagtse cagtes cagets cagest casgte
casget castge casteg casetg casegt catsge catseg catgse catges categs catesg
caestg caesgt caetsg caetgs caegts caegst ctgase ctgaes ctgsae ctgsea ctgesa
ctgeas ctagse ctages ctasge ctaseg ctaesg ctaegs ctsage ctsaeg ctsgae ctsgea
ctsega ctseag cteasg cteags ctesag ctesga ctegsa ctegas cegats cegast cegtas
cegtsa cegsta cegsat ceagts ceagst ceatgs ceatsg ceastg ceasgt cetags cetasg
cetgas cetgsa cetsga cetsag cesatg cesagt cestag cestga cesgta cesgat scgate
scgaet scgtae scgtea scgeta scgeat scagte scaget scatge scateg scaetg scaegt
sctage sctaeg sctgae sctgea sctega scteag sceatg sceagt scetag scetga scegta
scegat sgcate sgcaet sgctae sgctea sgceta sgceat sgacte sgacet sgatce sgatec
sgaetc sgaect sgtace sgtaec sgtcae sgtcea sgteca sgteac sgeatc sgeact sgetac
sgetca sgecta sgecat sagcte sagcet sagtce sagtec sagetc sagect sacgte sacget
sactge sacteg sacetg sacegt satcge satceg satgce satgec sategc satecg saectg
saecgt saetcg saetgc saegtc saegct stgace stgaec stgcae stgcea stgeca stgeac
stagce stagec stacge staceg staecg staegc stcage stcaeg stcgae stcgea stcega
stceag steacg steagc stecag stecga stegca stegac segatc segact segtac segtca
segcta segcat seagtc seagct seatgc seatcg seactg seacgt setagc setacg setgac
setgca setcga setcag secatg secagt sectag sectga secgta secgat gscate gscaet
gsctae gsctea gsceta gsceat gsacte gsacet gsatce gsatec gsaetc gsaect gstace
gstaec gstcae gstcea gsteca gsteac gseatc gseact gsetac gsetca gsecta gsecat
gcsate gcsaet gcstae gcstea gcseta gcseat gcaste gcaset gcatse gcates gcaets
gcaest gctase gctaes gctsae gctsea gctesa gcteas gceats gceast gcetas gcetsa
gcesta gcesat gacste gacset gactse gactes gacets gacest gascte gascet gastce
gastec gasetc gasect gatsce gatsec gatcse gatces gatecs gatesc gaestc gaesct
gaetsc gaetcs gaects gaecst gtcase gtcaes gtcsae gtcsea gtcesa gtceas gtacse
gtaces gtasce gtasec gtaesc gtaecs gtsace gtsaec gtscae gtscea gtseca gtseac
gteasc gteacs gtesac gtesca gtecsa gtecas gecats gecast gectas gectsa gecsta
gecsat geacts geacst geatcs geatsc geastc geasct getacs getasc getcas getcsa
getsca getsac gesatc gesact gestac gestca gescta gescat asgcte asgcet asgtce
asgtec asgetc asgect ascgte ascget asctge ascteg ascetg ascegt astcge astceg
astgce astgec astegc astecg asectg asecgt asetcg asetgc asegtc asegct agscte
agscet agstce agstec agsetc agsect agcste agcset agctse agctes agcets agcest
agtcse agtces agtsce agtsec agtesc agtecs agects agecst agetcs agetsc agestc
agesct acgste acgset acgtse acgtes acgets acgest acsgte acsget acstge acsteg
acsetg acsegt actsge actseg actgse actges actegs actesg acestg acesgt acetsg
acetgs acegts acegst atgcse atgces atgsce atgsec atgesc atgecs atcgse atcges
atcsge atcseg atcesg atcegs atscge atsceg atsgce atsgec atsegc atsecg atecsg
atecgs atescg atesgc ategsc ategcs aegcts aegcst aegtcs aegtsc aegstc aegsct
aecgts aecgst aectgs aectsg aecstg aecsgt aetcgs aetcsg aetgcs aetgsc aetsgc
aetscg aesctg aescgt aestcg aestgc aesgtc aesgct tsgace tsgaec tsgcae tsgcea
tsgeca tsgeac tsagce tsagec tsacge tsaceg tsaecg tsaegc tscage tscaeg tscgae
tscgea tscega tsceag tseacg tseagc tsecag tsecga tsegca tsegac tgsace tgsaec
tgscae tgscea tgseca tgseac tgasce tgasec tgacse tgaces tgaecs tgaesc tgcase
tgcaes tgcsae tgcsea tgcesa tgceas tgeacs tgeasc tgecas tgecsa tgesca tgesac
tagsce tagsec tagcse tagces tagecs tagesc tasgce tasgec tascge tasceg tasecg
tasegc tacsge tacseg tacgse tacges tacegs tacesg taescg taesgc taecsg taecgs
taegcs taegsc tcgase tcgaes tcgsae tcgsea tcgesa tcgeas tcagse tcages tcasge
tcaseg tcaesg tcaegs tcsage tcsaeg tcsgae tcsgea tcsega tcseag tceasg tceags
tcesag tcesga tcegsa tcegas tegacs tegasc tegcas tegcsa tegsca tegsac teagcs
teagsc teacgs teacsg teascg teasgc tecags tecasg tecgas tecgsa tecsga tecsag
tesacg tesagc tescag tescga tesgca tesgac esgatc esgact esgtac esgtca esgcta
esgcat esagtc esagct esatgc esatcg esactg esacgt estagc estacg estgac estgca
estcga estcag escatg escagt esctag esctga escgta escgat egsatc egsact egstac
egstca egscta egscat egastc egasct egatsc egatcs egacts egacst egtasc egtacs
egtsac egtsca egtcsa egtcas egcats egcast egctas egctsa egcsta egcsat eagstc
eagsct eagtsc eagtcs eagcts eagcst easgtc easgct eastgc eastcg easctg eascgt
eatsgc eatscg eatgsc eatgcs eatcgs eatcsg eacstg eacsgt eactsg eactgs eacgts
eacgst etgasc etgacs etgsac etgsca etgcsa etgcas etagsc etagcs etasgc etascg
etacsg etacgs etsagc etsacg etsgac etsgca etscga etscag etcasg etcags etcsag
etcsga etcgsa etcgas ecgats ecgast ecgtas ecgtsa ecgsta ecgsat ecagts ecagst
ecatgs ecatsg ecastg ecasgt ectags ectasg ectgas ectgsa ectsga ectsag ecsatg
ecsagt ecstag ecstga ecsgta ecsgat

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History of cryptography
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