Cryptography

Question 1

Cryptography

Answer 1

The primary objective is to provide many fundamental security properties we covered earlier: confidentiality, integrity, non-repudiation, and authentication.

Question 2

Confidentiality in Cryptography

Answer 2

The fundamental security service provided by cryptography. It helps keep information from an unauthorised person, often referred to as privacy or secrecy. One way of achieving confidentiality is by using mathematical algorithms for data encryption.

Question 3

Integrity

Answer 3

The data may get modified by an unauthorised entity intentionally or accidentally. Provides a means for detecting whether data has been manipulated by an unauthorised user.

Question 4

Authentication

Answer 4

Confirms to the receiver that the data has been sent only by an identified and verified sender.

Two variants; message and entity authentication.

Question 5

What is message authentication?

Answer 5

Identifies the originator of the message without any regard to the system that has sent the message

Question 6

What is entity authentication?

Answer 6

Assurance that data has been received from a specific entity, say a particular website.

Question 7

Protecting Passwords

Answer 7

Very important to prevent unauthorised access. Common technique is hashing.

Hashing is the transformation of string or characters into a value that represents the original string; hashing the same string outputs the same hash value.

Question 8

Hashing vs Encryption

Answer 8

Hashing and encryption are two terms that are often confused or used incorrectly. The key difference is that hashing is a one way function (it is not possible to decrypt and obtain original value), where encryption is a two way function.

Encryption should only be used where it is necessary to obtain the original password as the ability to decrypt is a serious security risk.

Question 9

Salting a Password

Answer 9

Protect against hackers cracking a password hash by using a salt - randomly generated string that is added to each password. Unique for every user so an attacker has to crack hashes one at a time using the salt.

Makes cracking large amounts of data harder as time grows in proportion to number of hashes.