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Information Security > Chapter 4 and 5: Public Key Cryptography/ Hash functions > Flashcards

Chapter 4 and 5: Public Key Cryptography/ Hash functions Flashcards

1
Q

There are two keys describe the public key and private key to the sender and recipient

A

sender uses recipients public key to encrypt

Recipient uses private key to decrypt

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2
Q

Public key cryptography is based on….

A

trap door one way function, one way meaning it is easy to compute in one direction but hard in the other direction

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3
Q

what is a digital signature

A

sign by encrypting with your private key, any one can verify the signature by decrypting with public key.but ONLY YOU could have signed it.

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4
Q

the general knapsack is …

A

NP-complete

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5
Q

general knapsack is ..

A

hard to solve

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6
Q

super increasing knapsack

A

is easy to solve, each weight greater than the sum of all previous weights

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7
Q

what are the weakness of knapsack

A

Trap door, one way, lattice reduction

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8
Q

Trapdoor with knapsack is

A

convert SIK into general knapsack using modular arithmetic

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9
Q

one way knapsack is

A

general knapsack easy to encrypt, hard to solve.

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10
Q

knapsack is secure or insecure

A

insecure

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11
Q

RSA

A

2 large prime numbers, N=pq is the modulus.

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12
Q

RSA public key is

A

(N,e)

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13
Q

RSA private key is

A

d

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14
Q

what breaks the RSA

A

factoring the modulus breaks the RSA

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15
Q

what is Diffie Hellman (g^a and g^b)

A

Not used for encrypting or signing

it is based on discrete log problem

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16
Q

in diffie hellman what can trudy find to get k

A

trudy can find a or by then she gets the key k , if trudy can solve discrete log problem she can find a or b

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17
Q

what must you be aware of in MIM

A

Man in the middle, attack on diffie hellman

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18
Q

digital signature provides what

A

provides integrity and on repudiation

19
Q

No non-repudiation with ..

A

Symmetric keys

20
Q

what does the certificate contain

A

it contains the name of the user and users public key and other info. it is signed by the issuer a CA certificate authority

21
Q

the signature on a certificate is verified using what

A

CA’s public key.

22
Q

what is PKI

A

Public key infrastructure: the stuff needed to securely use public key crypto

23
Q

what are the three PKI trust models

A

Monopoly model, oligarchy model, anarchy model

24
Q

what are the plus’s in symmetric key

A

sped, no public key infrastructure (PKI) needed

25
Q

what are the plus’s in public key

A

signatures (non-repudiation)

no shared secret (but, private keys…)

26
Q

what are the 5 things a crypto hash function must have?

A 
Compression- output length is small
efficiencry- easy to compute for any x
one-way
wak collision resistance
strong collision resistance
27
Q

what are the popular crypto hashes

A

MD5 and SHA-1

28
Q

what is MD5

A

128 bit output
MD5 collisions are easy to find
invented by Rivest

29
Q

what is SHA-1

A

160 but output

a U.S government standard inner workings similar to MD5

30
Q

what is HMAC

A

a hashed MAC

31
Q

where are hash’s used

A 
authentication
message integrity
message fingerprint
data corruption detection
digital signature efficiency
32
Q

Spam reduction work for the sender is

A

2 to the N hashes

33
Q

spam reduction work for the recipient is

A

always 1 hash

34
Q

spam reduction chose n that is

A

work acceptable for normal email user

work is too high for spammers

35
Q

where do we use random numbers

A

generate keys
symmetric keys
RSA: prime numbers
Diffie Hellman: secret values

36
Q

what is entropy

A

is a measure of randomness

37
Q

where are random numbers being used to gnerate keys

A

Symmetric keys
RSA: prime numbers
Diffie Hellman: Secret values

38
Q

cards that are shuffled what factor

A

52! > 2^225 possible shuffles

39
Q

Randomness two features

A

can get quality random bits by such methods

BUT quantity of bits is very limited

40
Q

what is watermark’s two features

A

visibility and robustness

41
Q

describe visibility in water mark

A

Invisible- watermark is not obvious

visible such as TOP SECRET

42
Q

what are the two features in robustness

A

robust and fragile

43
Q

describe robust

A

robust is readable even if attacked example add robust invisible mark to digital music, if pirated music appears on internet can trace back to original soure of leak

44
Q

describe fragile

A

fragile is damaged if attacked example add fragile invisible mark to audio file, if watermark is unreadable, recipient knows that audio has been tampered integrity

Information Security (5 decks)

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