PRINCIPLES OF CRYPTOGRAPHY
Prdxciles of Cryptograpky
of auset
4’Aehericatio( NAthetlication refers to -the praocess of vercifying thecanidextrty
be vsod to
~ yptograzpkie tecniqyes, suck as. diqitel siguaturtes,
Lasecute aMMerr
athexticte -the idetify of fausere ore device ik
*Not-tepudiatiox iAdkieved -kerougk rontoatrerkie -teckniques tike digte kert. and
sendere
prevets deyig actione by exabling serderc and reeceiverc to prve mecsaae
feceiverc .
2-lypes of Cryetograply attacks?
’) Brate -force etacks:
*4 brazte foree attack involvec possible owbinalions to erak a pass worcd ore
Htryivg all
" H relies on compxtational powett
"Tine- coxcunarg and recourte-itexcive
·EKectiveness depexds n key lexgth avd compexty
"OHen witigcied by acowt bckouts orc rate tiniting
Cpkerctext-oly attacks:
*A ephectext only attaek avalys es entYpted data witkot acee< to plaiKtet o kes
goal is to derive the plaictext
*ttackets eplait paterAs and frequengy analysts
" Offen elies on statistical mettod
"Efective against weak eneryptick algorcitkm.
)ckosen plaitext attacks:
"Attackert seledts plairtexts to enetgpt akd analyses cipkerctexts
Weakyesses
.Aims to discover ereryptin ky ort
"Exploits predietable reskips bet plaitext avd ciphet text
"Exkances crgpiavalyss y coxtcotting input data.
" Vsefd against sywmetcic and asymwetct enctyptiox systzru
Jchosen eipkerctert attacks:
plaivetxt
"AttacKerc depts ciphetctet witk ckosn
Exploits decpion otace weakveses
"Aiws to HOVer seeret Keys
. sshanes securit aualysis of crypioqapkic systeme.
kon plaistext attacks:
. yptanaly sis metthod using both plaitext and its eNeTYpted text.
.telps find key ore Weakye in exetypticn agotitkms
"Requikces access to ateast pare of plaitext
.EHeiye agaist weakert Ketyptiox Metkods.
fey axd
algcttkw atak:
"Focvses en discoverdg yetio/Aenypicx key
qets weakyes(es in arypticx algordthne ttelf
.gor ettack plotts poorc key naMagmekt ercweak key geveretior
rk attack aalyees algorci tkuw's streuclure fott vulnerabitities
B-What is Kerckkof% Principle?
eretlo's Priveiple is a-fodanetel quidetine in ctyploqcaky propeced by -the
cetry ayriograplet Auqute Kerckles
STedec -tkat a eyptograpkic yctem shodd remin secue even if everytking abot the
$ctew ,except -the key, is public kyowledge
e picile kighliglts -the iuportacee et ey secay of -the sargpion algocátks itet
Ahentages:
"Prowotes algorzilou -tanpareng aNd pudic sezetiy
"Excoages robust eroptogapkiz decig -tkseugh open tecting
"Reduces reliavee on chscuciby, incrensixq long-terc sstemseccy:
"Allows for. easlere recovery it key is cowptomised
biReqaiter
sadvartages:
ligky serute ky wanagenent practices
"Vnerable it Keys ae pootcly prcolectd
" Ivaeased omplexity in decigning robst Key distibtetioy Systems
4- What is CryptologY?
7e Ctryptoloqy is -the study of serure cooniertiou teekaiques
" t inolves two main arceas.
Sue codes
crqyptvalysis > breakisg codes
"lH exsuta data cotidentiadlitys ixtegrir avd atteiaation.
5-What is Cryptograpky?
Croptograply is tte practice of sanrdig ifocmatiok ttcougk eodig
" Htraeforms data ikto uwteadable forauats, called encyptiok,to preoteet
acthotdzed eess. from
" tuvoves two Key process
0 Kerypliox :Sabling data
) beyptiox: festorcing data to ite oeiginal forwa.
6-What is ryptaualycis?
Ciyrtanalyis is-the study of brenativg ot axtalyzivg aryplogaghic yeee
*t ains -to uncovetc weakyss in encryption alyorzit s
ves teduiqes to decrpt secucity witkout kucwivg the k
7- Wkat is exCryptiou aud decryptioK?
EKeryption DecrypioK
The preocess of coverctivg plai-text ixto -Tie praoeecs of coxvercting diphereet back, into
LaKTaNdable ciphert ext reodable plain-text
Requites aM orYptiot adgerittou anda "Reqáres couIteet dectyption Key -torestoe
key -to pereforam -the trosforcvuaticn . the orcigikal datz
S-what is plaintext ad Cipkerctet?
Plaik Text CipkercTet
"Readable,nenerypfed data-tat ayone can EKeYpted verion of plaittexti appativ
wKdercstand. nteAdable characters
Vneabe to uazttorized access it vot Protezts sensitive ieforcmatiok -frow wMantkoriss
SeCured
9-Symonetde Ciphere Vs tsyumetic Cipkerc?
Symmetrcic Cipkerc Asznametric ipher
"Same key is used fot< bott eNetypti on and Diferevt Keys arte vsed; one -forr enetoptio
derypio (Pblic ke)and otker forc derypticn (praiväte key)
"Less seuzity if Key is shared "More sece, przivte ker remains secret
Needs seue "Public key can be opexly skarted
·Best, forc arge data eKetYptior : Used fore seue key exchange and small
|data.
o- StregmCiphet Vs Block Cipker.
Stneam Cipkerr Block Cipkere
Ererypts dota cne bit oe byte ata ttme. |" Exetypts data ifixed-se blocks (G4, 128 bits)
Gevaally fasterc due to lowerc overchead Stowert de to block ptocecing akd predding
-Siupler aNd requires lecs wemor | Morce cowplex aud reequitres Wore memory
Erctots otfect cnlythe curtst bit/byte. "Eaotrs aftet te ettireLock beikg proesed
0y4eK usec swallerc key sizes FTypically raqires larqerc key sizec fore
securcty .
I(|-Types -kere
o Sywometele Cipkerc !
()’MStream
aivy Cihe ae 2types of suweltcie Gipkere
"Er"Bestagptsted fotc situatioKs wkere dita awes in streams ot Mesds to be enypted in raal tine.
data oNe bit ot byte at a time
"R4(Ri vest Cipker ):0we widely used, but now coKs0dered inseeure
Salsa 20 avd dhacka 20: Modetch streamCipkers kyown for speed ad Secuaty
Block
*
Cipketts
Exetyrt data in fixal- size blocks, ypicaly CA ott 128 bits
Dta that doesut fitthe block size wst be padded.
NAMples:
"DES (Data Saypiou stzydard): 64-bit Block. eipkAt witk a 5b-bit Key, Mow latrgey chscléte
due to weak Key lengt
*3DES(Taple DES)A more secue vercsion of DES, eKcTYpting data -turaee tiwes wrtk
dierert keys
"AESAdvanced Exeryption standatd): 128- bit block eipkec wittk key leugths of 128, 192 orc
256 bits; aaAtthy thetardard for KCIYptic
"Blowiski64-bits bleck eipkere designed as an atetcnative to DES witk variable Key length.
"Twofish?SuecessoK to Blowfisk, <es 128-bit blocks witk Key lengtks up to 256 bits
12-Tpes of Asymmeie pkerr?
)RSA (Rivest-shamir AAlenan)
" tis widely vsed
"Basal ou -te difiedty of factorcix larege prinne no
6)ECC (Elliptic Ccve Oryptoqzply)
" Vses the wathematics ef el tiptic cuNes
"Prcovides Saelevel of secuity as RSA
)DSA (oigital siqatae-goriftun)
"
ftraiwariy 2veed for creating digital sigact
Alews
Si
pacties to sharea Cemon Key EnSIes arthenticity 17-Pi
) Disie- tellwan
riwarily veed jor Keytoedange
"& Atows 2
"H's
patiee <hare a comMoM Key
"An cneYpicu algorcithm used ik varieuseyptoqraphic systz ms.
. frovides botth eneryphen and diqita Sgnatures
I3- What is 4dditive Cipkt ?
siwplect forc of eKeryption
Also krown as the skitt Cipketc otc Caesate Cpke ,is oKe of the
is a type of subeliHution cipkerc where cach leterc i tke plaintoxt is skitted bya
"+
Jixed Ko of positieks down o ptke alpkabet
4-What is fixe Cipker?
subelitetion cipkert, whick ts a morce CoMplex Varciatio of the
’A ype ot mOMoalpkabetic
CaeSatt Cipker
"H ubies botk nattipliation and additicK ix its exrypliok -forcnla morce
additick, przyidikg
*1ke cipketrc yses 2 Keys: ore forr vatiplicatiok akd one forc
seity tanthe Caesatt ipke
Adatag:
"More Secute
bisadiatage:
Vdverable to FreaueCe Analysis
"Siwple to lwplenert
15- Verm Cipkert ?
Symoetrac enerptiok netkod based cx XOR epercatiok
"Ore-tine se key ersures pergfet secaáty (oMe tine pad)
"Key wust be -the saMe length asthe plaintext.
Advatages: bisatartage:
SMoe seae Vidverable
" Sinple to inplevt
I5- Playdair Cipkerr ?
’ke plazygaitc cipkec is a malsnmetrde excyiox tecdodqve.
eNerpts digtaphs instead of single lettes, naking it wote secue tan simple
substittion cipkerS
"sere.
bisadvatagei
"Vidnerable
"Siuple to iupleeyt
I7-Pigpx Cipkerc ?
’H is asuple substitetio cipkere-that uses a uique syubol system to represest letets
"W's also Kuown as Masonic Ciphert orc Treewason's cipker dve to its associatiou wtk
wasoic rituals
bisadvartagesi
Sece Kot complex " Not Secue:
" Siwple b inplewet
18-5-box desigu Prineiçles?
->NoK--Good-livUxieatdforouity ty:Aekiere
:letradve KOK- lineatt <ubstHctions to tesist liveatc
Ltforeopt distrzibutions fore all inputs
ttacks
pencelet'ox Efiiekey : Cptiuize fere coupitatioua eticieny in botk s/w oud o
oaity
plety ad Robuetvesc: Meittaix a sinple desigu -that anu be easily analyzd for
ive Mappixg Sack iput naps sdavely to ofp; tererrsible substtetiok "
*Balanced ofp: SKsMae wnifom rabability fotz all ofp values
Yo
N
M DS
19- LYsre?
’" fsr stavds for Linear Fealback Suitt
Registerc
qouerates pseudo- randomseqyeNce -forc ettyptogtapky
" Used iK Key stem
geeratiok ert cyption
"Nof suitble forc ligi-ceaity ayrtoqraplic appliaiicxs -
ypes:
1-Fibonacd LFSR
- Feed back from sevetal poits ix -the ragisterc 4-Coxter-based LFSR
"Siuple desigk ,etficiet ix kfw
"Sivple eay to inpleuert " Suitable for steam eipkers
" Etficiett in haacdware systems
"Balaneer speed wttk setdity
"Lecs seure " InTAses rentonwES.
2- aalois LFSR
"Faster Hkax Fiboacei LFSR.
. Morce etiient in Ww systeus
5.faal lel LFSR
"strovqerc aqainst iwaqr attacks
. Linited seasity forc kiqh-larel evcryptiox "lmproves speed in LFESR
"Boosts pereformane ix
citceuits and system kigh-speed
3"Nou-linear LFSR
.Less vuhetable to liner atlacks
.More secute forr kigk-leve eneyption
"tedle laiqes data set.
.ttadr to plediet -kan tikeas LESRS
tuereased desiqn cowplexyakd implenmettälion.
PatHerms:
-tap
"LFSR gaterates pseudo-taxdom <oquente bacel en fecdback
Ued ix crptogtaçly, cONaicatics, ert or deteetiok, witk tepaating attens.
becigk:
20- A5/1?
’ tis a stteam cipkert for GSM obile
" Uilizes comwMicafioMS
b4-bits Kezs-fott eNTyYPting date and voice
*Coutbives 3 likear -fecdback skitt Reqisters for o/p
Abrastiags:
Fastpesciig spel bisadvataqesi
" Nat sere.
" Low
recMIE VSage " Lack ofwpdates
"Easy -to iuplmert
- Depekdeng on
outdated teckndoqy
21- DES ?
sdatqe:
" Simple avd etficiert
litial Pematcion { Pot of coufusiou
"Fast.
bisadetage: Rod 1 eKrypion
"Not secIe Ditfwiok
Linited Key sze
Rond 46 eneryption
final Permtaticn
