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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: brcutp
cipher variations:
csdvuq dtewvr eufxws fvgyxt gwhzyu
hxiazv iyjbaw jzkcbx kaldcy lbmedz
mcnfea ndogfb oephgc pfqihd qgrjie
rhskjf sitlkg tjumlh ukvnmi vlwonj
wmxpok xnyqpl yozrqm zpasrn aqbtso

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: brcutp
Cipher: yixfgk

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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: brcutp

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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: brcutp
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: brcutp
Cipher: oephgc

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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: brcutp
Cipher: 212431544453

Extended Methods:
Method #1

Plaintext: brcutp
method variations:

Method #2
Bifid cipher
The message is converted to its coordinates in the usual manner, but they are written vertically beneath:
b r c u t p 
2 2 3 5 4 5 
1 4 1 4 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: brcutp
Cipher: gxyqqo

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Method #3

Plaintext: brcutp
method variations:
fovtyh ovtyhf vtyhfo
tyhfov yhfovt hfovty

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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: brcutp

all 720 cipher variations:
brcutp brcupt brctup brctpu brcptu brcput bructp brucpt brutcp brutpc bruptc
brupct brtucp brtupc brtcup brtcpu brtpcu brtpuc brputc brpuct brptuc brptcu
brpctu brpcut bcrutp bcrupt bcrtup bcrtpu bcrptu bcrput bcurtp bcurpt bcutrp
bcutpr bcuptr bcuprt bcturp bctupr bctrup bctrpu bctpru bctpur bcputr bcpurt
bcptur bcptru bcprtu bcprut bucrtp bucrpt buctrp buctpr bucptr bucprt burctp
burcpt burtcp burtpc burptc burpct butrcp butrpc butcrp butcpr butpcr butprc
buprtc buprct buptrc buptcr bupctr bupcrt btcurp btcupr btcrup btcrpu btcpru
btcpur btucrp btucpr bturcp bturpc btuprc btupcr btrucp btrupc btrcup btrcpu
btrpcu btrpuc btpurc btpucr btpruc btprcu btpcru btpcur bpcutr bpcurt bpctur
bpctru bpcrtu bpcrut bpuctr bpucrt bputcr bputrc bpurtc bpurct bptucr bpturc
bptcur bptcru bptrcu bptruc bprutc bpruct bprtuc bprtcu bprctu bprcut rbcutp
rbcupt rbctup rbctpu rbcptu rbcput rbuctp rbucpt rbutcp rbutpc rbuptc rbupct
rbtucp rbtupc rbtcup rbtcpu rbtpcu rbtpuc rbputc rbpuct rbptuc rbptcu rbpctu
rbpcut rcbutp rcbupt rcbtup rcbtpu rcbptu rcbput rcubtp rcubpt rcutbp rcutpb
rcuptb rcupbt rctubp rctupb rctbup rctbpu rctpbu rctpub rcputb rcpubt rcptub
rcptbu rcpbtu rcpbut rucbtp rucbpt ructbp ructpb rucptb rucpbt rubctp rubcpt
rubtcp rubtpc rubptc rubpct rutbcp rutbpc rutcbp rutcpb rutpcb rutpbc rupbtc
rupbct ruptbc ruptcb rupctb rupcbt rtcubp rtcupb rtcbup rtcbpu rtcpbu rtcpub
rtucbp rtucpb rtubcp rtubpc rtupbc rtupcb rtbucp rtbupc rtbcup rtbcpu rtbpcu
rtbpuc rtpubc rtpucb rtpbuc rtpbcu rtpcbu rtpcub rpcutb rpcubt rpctub rpctbu
rpcbtu rpcbut rpuctb rpucbt rputcb rputbc rpubtc rpubct rptucb rptubc rptcub
rptcbu rptbcu rptbuc rpbutc rpbuct rpbtuc rpbtcu rpbctu rpbcut crbutp crbupt
crbtup crbtpu crbptu crbput crubtp crubpt crutbp crutpb cruptb crupbt crtubp
crtupb crtbup crtbpu crtpbu crtpub crputb crpubt crptub crptbu crpbtu crpbut
cbrutp cbrupt cbrtup cbrtpu cbrptu cbrput cburtp cburpt cbutrp cbutpr cbuptr
cbuprt cbturp cbtupr cbtrup cbtrpu cbtpru cbtpur cbputr cbpurt cbptur cbptru
cbprtu cbprut cubrtp cubrpt cubtrp cubtpr cubptr cubprt curbtp curbpt curtbp
curtpb curptb curpbt cutrbp cutrpb cutbrp cutbpr cutpbr cutprb cuprtb cuprbt
cuptrb cuptbr cupbtr cupbrt ctburp ctbupr ctbrup ctbrpu ctbpru ctbpur ctubrp
ctubpr cturbp cturpb ctuprb ctupbr ctrubp ctrupb ctrbup ctrbpu ctrpbu ctrpub
ctpurb ctpubr ctprub ctprbu ctpbru ctpbur cpbutr cpburt cpbtur cpbtru cpbrtu
cpbrut cpubtr cpubrt cputbr cputrb cpurtb cpurbt cptubr cpturb cptbur cptbru
cptrbu cptrub cprutb cprubt cprtub cprtbu cprbtu cprbut urcbtp urcbpt urctbp
urctpb urcptb urcpbt urbctp urbcpt urbtcp urbtpc urbptc urbpct urtbcp urtbpc
urtcbp urtcpb urtpcb urtpbc urpbtc urpbct urptbc urptcb urpctb urpcbt ucrbtp
ucrbpt ucrtbp ucrtpb ucrptb ucrpbt ucbrtp ucbrpt ucbtrp ucbtpr ucbptr ucbprt
uctbrp uctbpr uctrbp uctrpb uctprb uctpbr ucpbtr ucpbrt ucptbr ucptrb ucprtb
ucprbt ubcrtp ubcrpt ubctrp ubctpr ubcptr ubcprt ubrctp ubrcpt ubrtcp ubrtpc
ubrptc ubrpct ubtrcp ubtrpc ubtcrp ubtcpr ubtpcr ubtprc ubprtc ubprct ubptrc
ubptcr ubpctr ubpcrt utcbrp utcbpr utcrbp utcrpb utcprb utcpbr utbcrp utbcpr
utbrcp utbrpc utbprc utbpcr utrbcp utrbpc utrcbp utrcpb utrpcb utrpbc utpbrc
utpbcr utprbc utprcb utpcrb utpcbr upcbtr upcbrt upctbr upctrb upcrtb upcrbt
upbctr upbcrt upbtcr upbtrc upbrtc upbrct uptbcr uptbrc uptcbr uptcrb uptrcb
uptrbc uprbtc uprbct uprtbc uprtcb uprctb uprcbt trcubp trcupb trcbup trcbpu
trcpbu trcpub trucbp trucpb trubcp trubpc trupbc trupcb trbucp trbupc trbcup
trbcpu trbpcu trbpuc trpubc trpucb trpbuc trpbcu trpcbu trpcub tcrubp tcrupb
tcrbup tcrbpu tcrpbu tcrpub tcurbp tcurpb tcubrp tcubpr tcupbr tcuprb tcburp
tcbupr tcbrup tcbrpu tcbpru tcbpur tcpubr tcpurb tcpbur tcpbru tcprbu tcprub
tucrbp tucrpb tucbrp tucbpr tucpbr tucprb turcbp turcpb turbcp turbpc turpbc
turpcb tubrcp tubrpc tubcrp tubcpr tubpcr tubprc tuprbc tuprcb tupbrc tupbcr
tupcbr tupcrb tbcurp tbcupr tbcrup tbcrpu tbcpru tbcpur tbucrp tbucpr tburcp
tburpc tbuprc tbupcr tbrucp tbrupc tbrcup tbrcpu tbrpcu tbrpuc tbpurc tbpucr
tbpruc tbprcu tbpcru tbpcur tpcubr tpcurb tpcbur tpcbru tpcrbu tpcrub tpucbr
tpucrb tpubcr tpubrc tpurbc tpurcb tpbucr tpburc tpbcur tpbcru tpbrcu tpbruc
tprubc tprucb tprbuc tprbcu tprcbu tprcub prcutb prcubt prctub prctbu prcbtu
prcbut pructb prucbt prutcb prutbc prubtc prubct prtucb prtubc prtcub prtcbu
prtbcu prtbuc prbutc prbuct prbtuc prbtcu prbctu prbcut pcrutb pcrubt pcrtub
pcrtbu pcrbtu pcrbut pcurtb pcurbt pcutrb pcutbr pcubtr pcubrt pcturb pctubr
pctrub pctrbu pctbru pctbur pcbutr pcburt pcbtur pcbtru pcbrtu pcbrut pucrtb
pucrbt puctrb puctbr pucbtr pucbrt purctb purcbt purtcb purtbc purbtc purbct
putrcb putrbc putcrb putcbr putbcr putbrc pubrtc pubrct pubtrc pubtcr pubctr
pubcrt ptcurb ptcubr ptcrub ptcrbu ptcbru ptcbur ptucrb ptucbr pturcb pturbc
ptubrc ptubcr ptrucb ptrubc ptrcub ptrcbu ptrbcu ptrbuc ptburc ptbucr ptbruc
ptbrcu ptbcru ptbcur pbcutr pbcurt pbctur pbctru pbcrtu pbcrut pbuctr pbucrt
pbutcr pbutrc pburtc pburct pbtucr pbturc pbtcur pbtcru pbtrcu pbtruc pbrutc
pbruct pbrtuc pbrtcu pbrctu pbrcut

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History of cryptography
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