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HCISSP ISC2 > Most used MDC & MAC > Flashcards

Flashcards in Most used MDC & MAC Deck (20)
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1
Q

What does MD5 stands for?

A

MD5 stands for message digest 5

2
Q

What does SHA stands for?

A

SHA stands for Secure hash algorithm.

3
Q

When MD5 must not be considered to be used?

A

MD5 must not be considered to be used if collision resistance is required.

4
Q

How do MD5 and SHA-1 compare related to speed?

A

MD5 is 25% faster than SHA1

5
Q

How do MD5 and SHA1 compare related to simplicity?

A

Both are simple in all aspects

6
Q

How do MD5 and SHA1 compare regarding to security?

A

SHA1 offers better security agains brute force and birthday attacks

7
Q

What are the commonly used modification detection codes (MDCs)?

A

MD5 and SHA1

8
Q

Which are the commonly used message authentication codes (MACs)?

A

DES-CBC-MAC (Data encryption standard in cipher block chaining mode) and HMAC (Hashed message authentication code)

9
Q

How does CBC-MAC (cipher block chaining message authentication code) work?

A

A CBC-MAC is computed by encrypting a message in CBC mode and taking the last ciphertext block or a part of it as the MAC. This MAC do not need to be signed any further as it has already been produced using a shared secret K.

10
Q

What does CBC-MAC stands for?

A

cipher block chaining message authentication code

11
Q

what does DES-CBC-MAC stands for?

A

Data encryption standard in cipher block chaining mode

12
Q

What does HMAC stands for?

A

Hashed message authentication code

13
Q

Can CBC-MAC be used to check non-repudiation?

A

No since it is not possible to say exactly who has created a MAC (sender and receiver have the key k).

14
Q

With which kind of cipher can CBC-MAC be used?

A

This scheme works with any block cipher.

15
Q

How is the security of CBC-MAC against birthday attacks?

A

Good as an attacker does not know k the birthday attack is much more dificult to launch (if not impossible) allowing shorter MACs.

16
Q

How can CBC-MAC security be strengthened?

A

both parts should agree upon a second key k’ different from k and performin a triple encryption on the LAST block: MAC = E(K;D(K’;E(K;Cn-1))) doubling the key space while adding only little computing effort.

17
Q

Why are symmetric blocks ciphers not used to create modification detection codes(MDCs)?

A

relatively small block size of 64 bits offers insufficient security against birthday attacks and they require more computing than cryptographic hash function so they are more slow.

18
Q

Why construct message authentication codes (MACs) from modification detection codes (MDCs)?

A

Cryptographic hash function generally executes faster than symmetric block cphers and there are no export restrictions to cryptographic hash functions.

19
Q

What is the basic idea of constructing message authentication codes (MACs) from modification detection codes (MDCs)?

A

To “mix” a secret key k with the input and compute an modification detection code (MDC).

20
Q

How is the construction of HMAC?

A

HMAC construction is H(K || p 1 || H(K || p 2 || m)) where p1 and p2 are padding patterns to fill up the key to one input block of the cryptographic hash function.

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