Encryption and Hashing

Question 1

Symmetric Encryption

Answer 1

Encryption that uses the same key to both encrypt and decrypt.
USES - Encrypted Harddrives

Question 2

Asymmetric Encryption

Answer 2

Encryption where different keys encrypt and decrypt the data

USES - Online transactions

Question 3

Client-Server Communication

Answer 3

The client generates a session key and uses the public key to encrypt it -> The server decrypts the session key with the private key -> Client-Server now communicate using symmetric encryption with the session key

Question 4

Private Key

Answer 4

The private key consists of 2 very large prime numbers

Question 5

Public Key

Answer 5

The public key is the product of the 2 prime numbers making the private
key. As no efficient non-quantum integer factorisation algorithm exists, it is practically impossible to
crack the private key by brute force.

Question 6

Hashing

Answer 6

Using an algorithm to map data of any size to a fixed size. Unlike encryption, hashing cannot be undone, it is therefore a lossy
process.
Uses:
• Rapid data access in a hash table
• Error checking and corruption detection - such as downloads
• Password verification - the plaintext password would not have to be stored
A good hash algorithm:*
• Same message = Same hash
• Quick to compute
• Impossible to generate a message from the hash
• A small change = a big hash change
• Impossible to find 2 messages with the same hash