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CISSP > Cryptography > Flashcards

Cryptography Flashcards

1
Q

What are the 4 fundamental goals of cryptography?

A
  1. Confidentiality
  2. Integrity
  3. Authentication
  4. Non repudiation
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2
Q

What is a message called before and after it is encrypted?

A

Plaintext & cyphertext

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3
Q

What is the Kerchoff principle?

A

States that a system should be secure even though everything is known.

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4
Q

What is FIPS140-2?

A

Federal Information Processing Standard. It is the definition for hardware and software requirements for crypto.

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5
Q

Logical AND

A

Both items need to be true.

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6
Q

Logical OR

A

v

At least one is true

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7
Q

Logical NOT

A

~

Inverse

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8
Q

Exclusive OR (XOR)

A

+

Only one needs to be true

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9
Q

Modulo

A

%

Remainder

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10
Q

One way function is…

A

The basis of public crypto systems.

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11
Q

What is a nonce?

A

Random number that acts as a placeholder for a variable in a formula.

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12
Q

What is the concept of zero knowledge proof?

A

Ability for a third party to prove knowledge of a password without divulging the password.

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13
Q

Split knowledge can also be called…

A

Separation of duties.

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14
Q

What is M of N control?

A 
M = minimum number of people needed to divulge.
N = Total population of key holders
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15
Q

What is a transposition cipher vs substitution cipher?

A

rearranging letters vs substituting them

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16
Q

What is a polyalphabetic cipher?

A

The use of multiple alphabets to encrypt the data.

17
Q

What is frequency analysis vs period analysis?

A

Studying the frequency of characters to break an encryption mechanism.

18
Q

What must be performed to ensure the integrity of a one time pad?

A
  1. The one time pad must be truly random.
  2. Pad must be kept secret and used once.
  3. Key must be as long as the message.
19
Q

What is a major obstacle of one time pads?

A

They are not scalable.

20
Q

What is a running key cipher?

A

Cipher is from a known string of characters ie a book.

21
Q

What is a block cipher vs a stream cipher?

A

Block operates on a groups of characters at the same time vs stream does one at a time.

22
Q

What is confusion and what is diffusion?

A

Confusion - Complication of relationship between plaintext and ciphertext
Diffusion - One change causes additional downstream changes.

23
Q

What is a symmetric key system and what are its weaknesses

A

Key is shared amongst others.
Weaknesses: key distribution, scalability, no non-repudiation, new keys needed frequently.

Keys needed (n*(n-1))/2

24
Q

What is an asymmetric key system and what are its strengths/ weaknesses?

A

Public/ private key system
Strengths: group changes are less impactful, provided non-repudiation

Weaknesses: slower
Keys needed: n*2

25
Q

What is DES?

A

Uses a 64bit block. (56 bit key and 8bit checksum)

26
Q

What are the 5 modes of DES?

A

Electronic Code Book (ECB) - Most basic 64 bit block based. Used for small stuff.

Cipher Block Chaining (CBC) - Each block is encrypted with previous block data.

Cipher Feedback (CFB) - Encrypts each block as memory fills.

Output Feedback Mode (OFB) - Like CEB but data is not encrypted with previous block.

Counter Mode (CTR) - like others but seed is from a basic counter.

27
Q

What is triple DES?

A

Expansion of DES where text is encrypted 3 times. Keys are either 168 or 112 bits.

28
Q

What are the characteristics of Blowfish?

A

Operates on 64bit blocks and keys can range from 32-448 bits.

29
Q

What are the characteristics of Skipjack?

A

Operates on 64bit blocks and operates on an 80 bit key and supports key escrow.

30
Q

What are the characteristics of AES/ Rijndael?

A

Operates on 128 bit blocks with following key strengths:
128bit - 10 rounds of encryption
192bit - 12 rounds of encryption
256bit - 14 rounds of encryption.

31
Q

What is Diffie-Helman?

A

Method of exchanging keys without both parties meeting.

32
Q 
What mistake did the Soviets make during the 1940's using a one time cipher?
A. Key values not random
B. Key values not long enough
C. Key values used multiple times
D. Key values were disclosed
A

A. Key values not random

33
Q

What is the minimum number of keys in a symmetric system?

A

One

34
Q 
What DES operating mode can be used for large messages:
A. Cipher Block Chaining (CBC)
B. Electronic Codebook (ECB)
C. Cipher Feedback (CFB)
D. Output Feedback (OFB)
A

D. Output Feedback (OFB)

35
Q 
Many crypto systems rely on the difficulty of factoring the product of large prime numbers.  What characteristic is this?
A. Diffusion
B. Confusion
C. One way function
D. Kerchoff
A

C. One way function

36
Q 
What AES function uses pre & post whitening techniques?
A. Rijendael
B. Twofish
C. Blowfish
D. Skipjack
A

B. Two fish

CISSP (9 decks)

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