Chapter 17 - Security

Question 1

Public Key

Answer 1

Type of Cryptography where different keys are use, one for encryption and one for decryption

Question 2

Private Key

Answer 2

• A private key is an unpublished key which has never been transmitted anywhere
• It has a matching public key
• It decrypts data its matching public key has encrypted

Question 3

Plain text

Answer 3

Original data before encryption

Question 4

Cipher Text

Answer 4

The result of encryption is transmitted to the recipient.

Question 5

Encryption

Answer 5

Encryption alters the data to something unreadable by anybody for whom the data is not intended to

Question 6

Symmetric key encryption

Answer 6

A single key is used for both encryption and decryption

Question 7

Asymmetric key encryption

Answer 7

One key is used to encrypt the message, and the matching key is used to decrypt the message

Question 8

Purpose of Asymmetric cryptography

Answer 8

• To provide better security by using two different keys, private and public
• One key is used to encrypt the message and the other is used to decrypt the message

Question 9

How is asymmetric key cryptography used

Answer 9

• Uses matching pair of keys
• A public key is available for everyone, receivers public key is used to encrypt the data before being sent.
• A private key is only known to the owner of the keys, receiver’s private key is used for decrypting the message received.

Question 10

Benefits of asymmetric key cryptography

Answer 10

• more secure as one key is private
• allows method authentication
• detects tampering
• allows non-repudiation

Question 11

Drawbacks of symmetric key encryption

Answer 11

• Key has to be exchanged securely
• once compromised key can be used to decrypt both sent and received messages
• cannot ensure non-reputation

Question 12

Differences between Symmetric and Asymmetric cryptography

Answer 12

• Symmetric cryptography uses a single key whereas asymmetric cryptography uses a pair of keys
• Symmetric key is shared whereas only the public key is shared in asymmetric cryptography. So the risk of compromise is higher in symmetric encryption so asymmetric is more secure
• Symmetric cryptography is a simple process that can be carried out quickly but asymmetric is much more complex, so slower.
• length of key of symmetric is shorter

Question 13

Sending a private message

Answer 13

• Public key sent to sender
• Sender encrypts data with the public key and sends the cipher text
• Receiver decrypts data with the private key.

Question 14

Reasons for using key cryptography

Answer 14

• To ensure the message is authentic
• To ensure only the intended receiver can understand the message
• To ensure the message has not been altered during transmission
• Non-repudiation, neither the sender nor receiver can deny that transmission has occurred

Question 15

Purpose of Quantum Cryptography

Answer 15

• To produce a virtually unbreakable encryption system using the laws of quantum mechanics
• Eavesdropping can be detected as properties of photons change
• To protect the security of data over fiber optic cables to enable using longer keys.

Question 16

Benefits of Quantum Cryptography

Answer 16

• Longer keys can be used
• Eavesdropping can be detected
• Virtually unbreakable
• Provides security based on laws of physics rather than mathematical algorithms so more secure

Question 17

Drawbacks of Quantum Cryptography

Answer 17

• Limited range
• Polarized light may change during transmission
• High cost of purchasing required
• Lacks vital features such as digital signature.