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CISSP > PKI and Cryptographic Applications > Flashcards

PKI and Cryptographic Applications Flashcards

1
Q

What are the THREE most common Public-Key Cryptosystems?

A

RSA, EL GAMAL and Elliptic Curve

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2
Q

In a Public-Key system how many keys does a user have ?

A

Two

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3
Q

What are the names of these TWO keys

A

Public Key - Known to everyone

Private Key - ONLY known and for the USER.

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4
Q

What does RSA stand for ?

A

Rivset, Shamir,Adleman ( These are the founders)

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5
Q

What are some facts about RSA

A
  1. Developed in 1977
  2. Worldwide standard
  3. Uses large PRIME NUMBERS to create key pairs
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6
Q

What letters represent what in the RSA formula?

A

C = Cipher text

P = Plain Text

e= Public Key

d = Private Key

n = p+q

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7
Q

Out of all the expressions/letters in the RSA formula which one is the largest number?

A

‘n’ as n = p+q

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8
Q

Why is Mark Hellman Knapsack different to RSA ?

A

Uses FACTORING SETS(Super increasing sets) instead of LARGE PRIME NUMBERS

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9
Q

What year was Mark Hellman Knapsack broken?

A

1984

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10
Q

What is Key length BEST PRACTICE ?

A
  1. Understand the encryption algorithm and Key length
  2. Time lines of the data ( eg. will it be sensitive for only a month then use a smaller key etc)
    • MORE IMPORTANT THE DATA , STRONGER the KEY to use
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11
Q

If the Key length for RSA and DSA is 1024 , what is the key length for Elliptic Curve ?

A

160 bit

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12
Q

What are some facts about EL GAMAL ?

A
  1. Extension of Diffie Hellman ( Symmetric Key exchange algorithm
  2. Provides encryption/ decryption of messages (NOT JUST KEY)
  3. Developed by Dr.T.EL GAMAL
  4. Doubles the length of ANY message it encrypts
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13
Q

What are some facts about Elliptic Curve ?

A
  1. Developed by Mathematicians Neal Kobilitz and Victor Miller
  2. Proposed in 1985
  3. Harder to solve than PRIME FACTORISATION (Used by RSA)
  4. Only a small key is needed
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14
Q

What does a hash function do ?

A

Creates a UNIQUE MESSAGE DIGEST

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15
Q

What TWO things can the Message digest be used for ?

A
  1. Non-Repudiation

2. Digital Signature

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16
Q

What is the bit size of Message digests?

A

128 bits or LARGER

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17
Q

What functions do single digit message digests provide ?

A
  1. Parity

2. Low level/Single digit checksum

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18
Q

RSA requirements for HASH FUNCTIONS

A
  1. INPUT can be ANY length.
  2. OUTPUT has a FIXED length
  3. HASH FUNCTION relatively easy to COMPUTE for any input.
  4. HASH FUNCTION are ONE-WAY.
  5. COLLISION FREE ( No two messages produce the SAME hash value)
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19
Q

What does HAVAL stand for ?

A

Hash of Variable Length

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20
Q

What are some facts about HAVAL?

A
  1. Modification of MD5
  2. Uses 1024bit blocks
  3. Hash values 128,160,192,224,256
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21
Q

What hash function is a modification of MD5 ?

A

HAVAL

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22
Q

What are the FIVE hash values for HAVAL ?

A

128,160,192,224,256

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23
Q

What size block does HAVAL use ?

A

1024 bit

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24
Q

What does SHA stand for

A

Secure Hashing Algorithm

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25
Q

How many versions of SHA is there ?

A

3 ( SHA-1,SHA-2,SHA-3)

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26
Q

Out of all THREE SHA’s what one is considered SECURE?

A

SHA-2

27
Q

Who developed SHA-1 ?

A

NIST

28
Q

Where is SHA-1 specified as a SECURE HASH STANDARD?

A

FIPS-180

29
Q

What length size message can SHA-1 handle ?

A

Any size

30
Q

What is the message digest size for SHA-1?

A

160bit

Message length needs to be a multiple of 512, IF not then SHA will parse the message until it is a multiple of 512

31
Q

What are the FOUR variants of SHA-2?

A
  1. SHA-256
  2. SHA-224
  3. SHA-512
  4. SHA-384
32
Q

What TWO of the variants are truncated versions of SHA ?

A

SHA-224 & SHA-384

33
Q

What is the message digest size for all FOUR of the SHA-2 variants?

A

SHA-256 = 256 MD

SHA-224 = 224 MD

SHA-512 = 512 MD

SHA-384 = 384 MD

34
Q

What is the BLOCK SIZE for all FOUR of the SHA-2 variants?

A

SHA-256 = 512 bit block

SHA-224 = 1024 bit block

SHA-512 = 1024 bit block

SHA-384 = 1024 bit block

35
Q

What algorithm is confirmed as the SHA-3 standard ?

A

KEECAK

36
Q

Is SHA-3 in use ?

A

no, it is still in DRAFT phase.

37
Q

What does MD2 stand for ?

A

Message Digest 2

38
Q

Who developed MD2,MD4 & MD5 ?

A

Ronald Rivset ( One of the RSA founders)

39
Q

When was MD2 developed ?

A

1989

40
Q

What is the MD2 message digest size ?

A

128 bit ( Original message + CHECKSUM)

41
Q

What function does MD2 NOT have ?

A

One way function

42
Q

What size bit processor does MD2 support?

A

8 bit

43
Q

Is MD2 still in use ?

A

NO

44
Q

MD2 Facts ?

A
  • Developed by Ronald Rivset in 1989 ( One of the RSA founder)
  • Provide a SECURE hash function for 8 bit processors
    • Pads the message so that the length is a multiple of 16 bytes.
  • Computes a 16 byte CHECKSUM and ADDS it to the END of the message
  • 128bit Message digest ( Original message and the added CHECKSUM) ** If CHECKSUM computed after MESSAGE DIGEST – COLLISIONS may OCCUR ( Nathanlie Rogier, Pascal Chavad)
  • NO One-Way function !!!

** !! ** THIS IS NO LONGER USED ** !! **

45
Q

What does MD4 stand for ?

A

Message Digest 4

46
Q

What size bit processor does MD4 support?

A

32

47
Q

Has the security increased in MD4 compared to MD2

A

YES

48
Q

What size does a message length need to be for MD4 ?

A

Message length needs to be 64 bits less than multiple of 512 ( If not then it will pad until it reaches that)

49
Q

EXAMPLE ; No answer required

A

EXAMPLE: 16 bit message

16 bit Message - - > Padded with 432 additional bits to make it 448 bits

16 + 432 = 448 512 - 448 = 64 ** 64 bits SMALLER than 512 **

50
Q

What is the MD4 message digest size ?

A

128bit

51
Q

What size block does MD4 process ?

A

512 bit block

52
Q

Is MD4 still in use ?

A

NO

53
Q

What does MD5 stand for ?

A

Message Digest 5

54
Q

What is the MD5 message digest size ?

A

128bit

55
Q

What size block does MD5 process ?

A

512bit

56
Q

What size does a message length need to be for MD5 ?

A

Message length needs to be 64 bits less than multiple of 512 ( If not then it will pad until it reaches that)

57
Q

Why was extra security added to MD5 ?

A

to REDUCE the speed of MESSAGE DIGEST production.

58
Q

Are MD2,MD4,MD5 recommended and in use ?

A

MD2, MD4, MD5 - NO LONGER ACCEPTED OR RECOMMENDED

59
Q

HASH Algorithms and Message Digest sizes ?

A

Hashing Variable Length - HAVAL ( MD5 variant )

128, 160, 192, 224, 256

Hashing Message Authentication Code ( HMAC )

Variable

Message Digest 2 ( MD2 )

128

Message Digest 4 ( MD4 )

128

Message Digest 5 ( MD5 )

128

Secure Hashing Algorithm (SHA/SHA-1)

160

SHA - 224

224

SHA - 256

256

SHA - 384

384

SHA - 512

512

60
Q

What is used to implement digital signatures?

A

HASHING

61
Q

TWO goals for DIGITAL SIGNATURES?

A

Non Repudiation ( Assure the receiver that the message truly came from claimed sender.)

Integrity (Assure the receiver that the message WAS NOT altered while in transit between sender & receiver)

62
Q

What does digital signatures require ?

A
  1. PUBLIC KEY cryptosystem (Asymmetric)

2. HASHING function.

63
Q

EXAMPLE ; No answer required

A

Example: Alice wants to digitally sign a message sing a hashing algorithm

  1. Alice generates a MESSAGE DIGEST of the message using a HASHING ALGORITHM ( SHA-1, SHA-256, SHA-512 etc)
  2. Alice ENCRYPTS only the MESSAGE DIGEST using her PRIVATE KEY (This is the DIGITAL SIGNATURE).
  3. Alice attaches the signed MESSAGE DIGEST to the PLAIN-TEXT message
  4. Alice sends the appended message to Bob
64
Q

EXAMPLE ; No answer required

A

Example: Bob receives the DIGITALLY SIGNED message and does the following:

  1. Bob DECRYPTS the DIGITAL SIGNATURE, using Alice’s PUBLIC KEY.
  2. Bob uses the same HASH FUNCTION to create the MESSAGE DIGEST (MD) of the full PLAIN-TEXT message.
  3. Bob compares the DECRYPTED MESSAGE DIGEST (MD) received from Alice with the MESSAGE DIGEST(MD) he computed himself.

Outcomes:

IF THEY MATCH = Assured the message was sent by Alice

IF THEY DO NOT MATCH = Message not sent by Alice or modified in transit.

CISSP (1 decks)

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