Final-Knowledge-Points-Spring11.doc

8/14/2019 Final-Knowledge-Points-Spring11.doc

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Knowledge Points of ITIS 6200/8200

Spring Semester of 2011

Chapter 1:

1. The asi!s of modern !r"pto s"stems.

2. #h" in the modern !r"pto s"stems we want to ma$e the en!r"ption/de!r"ption

algorithms p%li!&

'. (ame at least two ad)antages and two disad)antages of s"mmetri! en!r"ption

algorithms* and pro)ide e+amples to e+plain them.

,. (ame at least two ad)antages and two disad)antages of as"mmetri! en!r"ption

algorithms* and pro)ide e+amples to e+plain them.

-. #h" do we sa" a p%li!/pri)ate $e" en!r"ption algorithm sho%ld e ro%st against

!hosen plainte+t atta!$s&

6. #hat is a onetime pad& #h" is it safe e)en %nder r%tefor!e atta!$s&

. #hat is a transposition !ipher& #hat is a s%stit%tion !ipher& o% sho%ld e ale to

pro)ide an e+ample of ea!h $ind of !iphers.

Chapter 2:

1. #hat are the e+pe!ted properties of a good hash f%n!tion&

2. #h" do we !all an as"mmetri! en!r"ption algorithm a trapdoor onewa" f%n!tion&

'. e)isit page 1 of the slides* and lin$ the f%n!tionalities of the hash f%n!tions to the

proto!ols s%!h as it !ommitment* fair !oin flip* et!3 that we introd%!e later.

,. 4ow to %se the hash )al%es of the files to )erif" the integrit" of the file s"stem& #h" do

we need a $e"ed hash f%n!tion to sol)e this prolem&

-. 5nderstand the forward sear!h atta!$. If we des!rie a s!enario* "o% sho%ld e ale tofig%re o%t whether or not it is )%lnerale to forward sear!h atta!$* and how the atta!$ is

!ond%!ted.

6. #h" is it )er" diffi!%lt for an ea)esdropper to fig%re o%t the sele!ted en!r"ption in the

er$le7s p%le proto!ol&


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. 5nderstand the repla" atta!$. If we des!rie a s!enario* "o% sho%ld e ale to fig%re o%t

the repla" atta!$. (ote that some similar atta!$ happens when we introd%!e the

a%thenti!ation/$e" management proto!ols in Chapter '.

8. #hen we are doing d%al as"mmetri! en!r"ption* wh" sho%ld we alwa"s sign with o%r

pri)ate $e" first* then en!r"pt with the other part"7s p%li! $e"&

Chapter ':

1. #h" sho%ld we disting%ish the %sage of short term $e"s session $e"s3 and long term

$e"s inter!hange $e"s3&

2. 5nderstand maninthemiddle atta!$. If we des!rie a s!enario* "o% sho%ld e ale to

fig%re o%t how the maninthemiddle atta!$ will e !ond%!ted.

'. #h" !an an interlo!$ proto!ol defend against maninthemiddle atta!$& #hat is a good

interlo!$ proto!ol and what is a ad interlo!$ proto!ol&

,. 4ow sho%ld a s"stem store the %ser names and !orresponding passwords& #h" is it not

safe eno%gh to store the hash res%lts of the passwords& #hat is a slat& The differen!e

etween a p%li! salt and a pri)ate salt. #h" !an a salt ma$e the di!tionar" atta!$

impra!ti!al& #h" do we sa" that the salt impro)e the safet" of the o)erall s"stem %t not

for a spe!ifi! %ser&

-. 5nderstand the one$e" per time login thro%gh a hash !hain.

6. 5nderstand the fi)e a%thenti!ation and $e" e+!hange proto!ols that we introd%!e in the

!lass. 5nderstand their )%lnerailities and the potential atta!$s. o% do not need to

rememer the proto!ols. #e ma" des!rie some proto!ols similar to these proto!ols and

)%lnerale to similar atta!$s and "o% sho%ld e ale to fig%re the atta!$s o%t.

. 5nderstand the !on!ept of se!ret splitting and se!ret sharing.

Chapter ,:

1. 4ow to %se a hash f%n!tion to timestamp a file&

2. #h" !an the lin$ing proto!ol defend against the !oll%sion atta!$ etween the signer and

the end %sers& #hat is a good !haining me!hanism&


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'. 4ow !an we !onstr%!t a hash tree so that we need to p%lish onl" one res%lt and we !an

timestamp a large n%mer of files& 4ow !an we determine the !orresponding )al%es in

the hash tree that sho%ld e pro)ided to ea!h %ser&

,. 5nderstand the it !ommitment proto!ols. #h" are some !ommitment proto!ols

)%lnerale to forward sear!h atta!$s&

-. 4ow to %se a it !ommitment proto!ol to a!hie)e fair !oin flip&

6. The %sage of !omm%tati)e en!r"ption f%n!tion.

. 4ow !an m%ltiple parties generate an en!r"ption $e" 9ointl" so that the final res%lt is o%t

of the !ontrol of an" !oll%si)e gro%ps as long as there is one honest part"& #hen we

generalie this approa!h* how !an m%ltiple parties 9ointl" do &

8. 4ow !an m%ltiple parties sh%ffle a de!$ of !ards 9ointl" so that no parties !an !oll%de to

!ontrol the !ard dealing pro!ed%re&

. The %sage of !omm%tati)e en!r"ption algorithms.

Chapter -:

1. #hat is a general pro!ed%re of ;ero $nowledge proof& #h" sho%ld we ma$e s%re that

the sol%tion to the new prolem !annot e easil" mapped a!$ to the sol%tion of the

original prolem& #hat are the


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>?S and S@

1. In >?S* whi!h !omponent !ontri%tes the most to the safet"& 4ow large is the lo!$

sie& 4ow long is the $e"&2. #hat is the !omplementation propert" of >?S& @nd wh" does this propert" effe!ti)el"

impa!t the safet" of the algorithm&'. #h" !annot do%le >?S ma$e the effe!ti)e $e" length to e 112 its& #hat is the meet

in the middle atta!$& #h" !an triple >?S ma$e the effe!ti)e $e" length 112 its&,. >ifferent modes of >?S. Spe!ifi!all"* "o% sho%ld %nderstand the str%!t%re of ?CA mode

and CAC mode. #hat se!%rit" prolems ma" e !a%sed " the ?CA mode& In the CAC

mode* if we pro)ide one of the en!r"ption/de!r"ption !hain str%!t%res* "o% sho%ld e aleto draw the other one.

-. #hat are the ad)antages of an initial )e!tor& #h" !an we transmit the IB in plainte+t&

6. o% sho%ld e ale to identif" how the errors in transmission will impa!t the de!r"ptionres%lts. The selfhealing propert" of >?S.

. o% sho%ld e ale to !ond%!t mod%lar !al!%lation %sing the e

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Final-Knowledge-Points-Spring11.doc