Quiz #4

Question 1

What is a one way hash

Answer 1

A function (usually mathematical) that takes a variable-length string,a message, and compresses and transforms it into a fixed-length value referred to as a hash value.

Question 2

What is a message digest.

Answer 2

A hash value

Question 3

What does a one hash value provides

Answer 3

A fingerprint to identify a specific message

Question 4

What is the goal of a one way hash

Answer 4

To ensure that message has not be altered during transmission.

Question 5

Hashing function

Answer 5

Usually an algorithm that is not secret - publicly known.

Question 6

How hashing function Runs

Answer 6

In one direction, not the other direction. The receiver does not attempt to reverse the process at the other end, but instead runs the samehashing function one way and compares the two results.

Question 7

Difference between one way hashing and one way function used on public key cryptography.

Answer 7

In public key cryptography, the security is provided because it is very hard, without knowing the key, to perform the one-way function backwards on a message and come up with readable plaintext. However, one-way hash functionsare never used in reverse; they create a hash value and call it a day.

Question 8

How to make a one way hashing value visible to a specific person only

Answer 8

Since hashing one-way function takes place without the use of any keys.anyone who receives the message can run the hash value and verify the message’s integrity.
However, if a sender only wants a specific person to be able to view the hash value sent with the message, the value would be encrypted with a key. This is referred to as the message authentication code (MAC).

Question 9

What is Message Authentication Code (MAC)

Answer 9

A one-way hash value that is encrypted with a symmetric key.

A MAC is a key dependent one-way hash function

Question 10

One-Way Function Used in Public Key Cryptography

Answer 10

Provide confidentiality and authentication, only private key can reverse the one-way function to result in plaintext.

Function encrypts in one Direction and then decrypts in the reverse direction.

Question 11

One-Way Hashing Function

Answer 11

Provides integrity of a message, not confidentiality or authentication

It is never performed in reverse

The results of a one-way hash is a hashing value.

It is used in hashing to create a fingerprint for a message.

Question 12

what is a digital signature

Answer 12

A digital signature is an encrypted hash value of a message.

Question 13

Hashing function and digital signature of hash value

Answer 13

Hashing ensures the integrity of the message

Digital signature of hash value provides authentication and nonrepudiation

Question 14

What the act of signing means

Answer 14

The act of signing just means that the hash value of a message was encrypted with a private key.

Question 15

Choices within cryptography

Answer 15

• A message can be encrypted, which provides confidentiality.
• A message can be hashed, which provides integrity
• A message can be digitally signed, which provides authentication and integrity.
• A message can be encrypted and digitally signed, which provides confidentiality, authentication, and integrity.

Question 16

What can digital signature standard DSS provides

Answer 16

Who sent what messages and when,

Question 17

SHA and DSA

Answer 17

Secure Hash Algorithm - creates a 160-bit output which is then inputted into the DSA. It’s used to ensure the integrity of the message.

Digital Signature Algorithm - used to digitally sign the message.

Question 18

Most widely used digital signature algorithms

Answer 18

RSA and DSA

Question 19

Collision free or repetitive free

Answer 19

When a hashing algorithm ensures that it does not create the same value for two or more messages.

Question 20

characteristics for Good cryptographic hash functions

Answer 20

• The hash should be computed on the entire message.
• The hash should be a one-way function so that messages are not disclosed by their
signatures.
• It should be impossible, given a message and its hash value, to compute another
message with the same hash value.
• It should be resistant to birthday attacks, meaning an attacker should not be able
to find two messages with the same hash value.

Question 21

MD4

Answer 21

MD4 is a one-way hash function designed by Ron Rivest. It produces 128-bit hash, or message digest, values. It is used for high-speed computation in software implementations and is optimized for microprocessors.

Question 22

how many bits MD4 and SHA produce

Answer 22

MD4 produces 128 bits hash value or message digest

SHA produces 160 bits hash value or message digest

Question 23

Birthday attack

Answer 23

Attack against one way has hash function

Question 24

One time Pad

Answer 24

A perfect encryption scheme because it is unbreakable and each pad is used exactly once

A one-time pad uses a truly nonrepeating set of random bits that are combined bitwise XOR with the message to produce ciphertext

The random key is the same size as the message and is only used once

Question 25

How key distribution is done today

Answer 25

by a protocol through automated means and not manually

Question 26

Keys exchange protocol

Answer 26

KDC, RSA, Diffie-Hellman

Question 27

Key Management Principles

Answer 27

Keys should not be in cleartext outside the cryptography device

Backup copies should be available and easily accessible when required

Question 28

multiparty control for emergency key recovery.

Answer 28

This means that if a key needs to be recovered, more than one person is required to be involved with this process.

Question 29

Link encryption

Answer 29

encrypts all the data along a specific communication path like a satellite link, T3 line, or telephone circuit.

This provides extra protection against packet sniffers and eavesdroppers

Question 30

end-to-end encryption

Answer 30

the headers, addresses,routing, and trailer information are not encrypted; therefore, attackers can learn more
about a captured packet and where it is headed.

Question 31

Encryption can happen at the highest levels of the OSI model or the lowest levels.

Answer 31

If the encryption happens at the lower layers, then it is link encryption and at the higher levels, it is considered end-to-end encryption.

Question 32

Link versus End-to-End Encryption

Answer 32

End-to-end encryption happens at higher
layers and does not encrypt headers and trailers.

Link-layer encryption happens at lower layers and encrypts headers and trailers of the packet

Question 33

A hop

Answer 33

A hop is a computer that helps a packet get to its destination.

Question 34

Privacy-Enhanced Mail (PEM)

Answer 34

Is an Internet standard to provide secure e-mail over the Internet. The protocols within PEM provide authentication, message integrity, encryption,
and key management

Question 35

specific components that can be used in PEM

Answer 35

• Messages encrypted with DES in CBC mode.
• Authentication provided by MD2 or MD5.
• Public key management provided using RSA.
• X.509 standard used for certification structure and format.

Question 36

Pretty Good Privacy

Answer 36

PGP is a complete working system that uses cryptographic protection to pro-tect e-mail and files.