Introduction to Cryptography C3A

Question 1

Secure Systems

Answer 1

1. Security Policy
2. Security Environment
3. Security Mechanisms
4. Monitoring and auditing procedures

Question 2

What is Encryption?

Answer 2

Encryption is a mechanism that can be incorporated into security protocols
- The conversion into a form is called a ciphertext, which is not meant not to be read easily

Question 3

What is Decryption?

Answer 3

The process of converting encrypted data back into its original form

Question 4

Cryptographic Techniques

Answer 4

-Encryption
-Algorithm
-Key
= The algorithm is used to transform plaintext into a ciphertext

Question 5

Classes of algorithms:

Answer 5

Reversible, symmetric (Conventional)
Reversible, asymmetric (Public key)
One-Way (Hash)

Question 6

Properties of Algorithms

Answer 6

Reversible: can transform ciphertext back to plaintext
Symmetric: uses one key for both encryption and decryption
Asymmetric: uses different keys for encryption / decryption

Question 7

What is Symmetric Key

Answer 7

Also called private or secret key cryptography
- The same key is used to encrypt and decrypt data

Question 8

Asymmetric, Reversibile

Answer 8

Uses a key pair
- Either key can be used to encrypt a message - the other is then used to decrypt it (public and private key)
- One key is published and another is kept secret

Question 9

Symmetric vs Asymmetric Key

Answer 9

SYMMETRIC
- both share same key
- typically faster x100
ASYMMETRIC
- Two separate key: public and private key
- Typically slower

Question 10

One-Way (Hash)

Answer 10

• Create a message digest or “fingerprint”.
• Plaintext message can not be deduced from its hash
• Used for passwords by OS

Question 11

Brute Force Attack

Answer 11

• Trying out all possible values of a password to get through.

Question 12

Passwords Cracking

Answer 12

Using “password recovery” tool.