Providing Confidentiality with Encryption

Question 1

What are the two elements that make up the encryption method?

Answer 1

1) Algorithm

2) Key

Question 2

What does the encryption key do?

Answer 2

it is a number that provides variability for the encryption

Question 3

what is a pseudo-random number and what is it used for?

Answer 3

a number that appears to be random but is created by deterministic algorithm. It provides a nonce (number used once) for the starting value known as the Initialization Vector for a crypto algorithm used to create encryption keys

Question 4

What logical operation compares two inputs and if only one of those inputs is 1 it will output a 1 (TRUE), or if they are the same it will output binary 0 (FALSE)

Answer 4

XOR
(X = exclusive, meaning that the two input values must be either exclusively 1, or exclusively 0 for the output to be a 1)

Question 5

In encryption, confusion means what?

Answer 5

is a measure of how different the ciphertext is from the plain text

Question 6

in encryption, small changes in the plaintext result in large changes in ciphertext is known as what?

Answer 6

diffusion

Question 7

regarding algorithms, what to security experts discourage? Why?

Answer 7

secret algorithms that nobody else can access

without subjecting them to review, flaws can remain hidden

Question 8

an algorithm is said to have high resilience if…

Answer 8

if the algorithm remains difficult to crack even if part of it is leaked

Question 9

Why would a stream cipher be better suited to encrypting an audio stream over the network?

Answer 9

because it is continuous in fashion, and not a fixed size. You just can’t deal with it in blocks one at a time.

Question 10

Stream ciphers should never re-use what?

Answer 10

the encryption key

Question 11

What is the simplest of block cipher modes and describe its basic operation.
Why is it deprecated?

Answer 11

ECB - Electronic Codebook.
It divides the data into blocks and encrypts each block with the same key
Because it uses the same key to encrypt each block it is unsafe which is why it is deprecated

Question 12

which block cipher mode starts with IV on the first block then combines each subsequent block with the previous block using a XOR operation?

Answer 12

Cipher Block Chaining mode (CBC)

Question 13

Which block cipher mode converts the blocks to a stream cipher?

Answer 13

Counter Mode (CTM/CTR)

Question 14

Which block cipher mode also assures integrity using hashing and is widely used due to its efficiency to quickly encrypt and decrypt?

Answer 14

GCM - Galois/Counter Mode

Question 15

Symetric encryption is AKA?

Answer 15

secret-key or session-key

Question 16

What type of key does RADIUS use to encrypt communication between the RADIUS server and the RADIUS client (e.g. VPN concentrator)?

Answer 16

Symmetric key

Question 17

Why is asymettric encryption mostly only used for key exchange and not for the raw data itself?

Answer 17

Because it’s very resource intensive

Question 18

Certificates are used in xxx encryption. They include the xxx keys along with details on the xxx and on the xxx xxxx. If an owner wants to share a key they share a copy of the xxx

Answer 18

Certificates are used in ASYMMETRIC encryption. They include the PUBLIC keys along with details on the OWNER and on the CERTIFICATE AUTHORITY. If an owner wants to share a key they share a copy of the CERTIFICATE

Question 19

Which asymmetric encryption algorithm is widely used to protect data transmitted over the internet?
What is the key size?

Answer 19

RSA.

The key size is 2048bits

Question 20

In ephemeral key generation,, the Perfect Forward Secrecy feature indicates keys have been generated using a _____ _____ What is the goal?

Answer 20

it generates public keys using a non-deterministic algorithm. The goal is to prevent the use of the same keys being generated which could compromise data encrypted in the past

Question 21

Which cryptographic key generation technique is often used with small wireless devices

Answer 21

ECC - Elliptic Curve Cryptography

Question 22

Which version of Diffie-Hellman uses ECC to generate ephemeral keys?

Answer 22

ECDHE - Elliptic Curve Diffie-Hellman Ephemeral

Question 23

What can be used to indicate the use of steganography?

Answer 23

File hashing. If hashes of files are taken regularly, they can be compared with previous hashes to see if any files have been modified.

Question 24

what is the pseudo-random number used for the initialization vector also known as?

Answer 24

a nonce (which is a number used once)

Question 25

Which supports perfect forward secrecy for ephemeral keys, Diffie-Hellman or RSA?

Answer 25

Diffie-Hellman

Question 26

Which encryption algorithm was

a) the first public-key cryptography system
b) key generated based on the factoring of two large prime numbers that make it very hard to guess in order to obtain the private key.

Answer 26

RSA

Question 27

Which algorithm allows Diffie-Hellman key exchange to use digital signature for authentication?

Answer 27

DSA

Question 28

What is considered the successor to DSA and why is it suitable for low power devices?

Answer 28

ECDSA (Elliptic Curve DSA)
Suitable for low power devices (like mobile or IoT devices) because Elliptic Curve Cryptography is faster because it uses shorter key lengths while keeping the same level of security