N5 security precautions: Encryption and Firewalls

2. Encryption
Encryption is the conversion of data into a form that cannot be easily
understood by unauthorised people
Decryption is the inverse of encryption - reversing the steps of encryption in
order to get the original message

3. Encryption
Encryption allows us to protect data an message from anyone we do not want
to see it.
The encrypted data is known as cyphertext

4. Symmetric Encryption
 Same key is used to encrypt and decrypt
 Sender and receiver both know the key

5. Symmetric Encryption
Advantages
Faster and easier to implement that asymmetric encryption
Disadvantages
Sender and receiver need to know the key, but how do they share that
securely?
If they have a secure way of sending the key, why would they need to use
encryption…?

6. Asymmetric Encryption
 A pair of keys is used to encrypt the data
 Private key and public key
 Anyone can encrypt a message using a public key
 Only the holder of the private key can decrypt the message
 Asymmetric encryption is also known as public-key encryption

7. Asymmetric Encryption
Example
1.Aaron(the recipient) generates a pair of keys, one public and one private
2.He sends the public key to Alison (the sender)
3.Alison encrypts the message using the public key and sends it to Aaron
4.Aaron decrypts the message using the private key

8. Asymmetric Encryption
Advantages
No need for private key exchange
Increased security – only person with private key can decrypt
Can be used for Digital Signatures
Disadvantages
Slow – takes time to encrypt and decrypt
Could be cracked using brute force – try all possible keys
(although RSA Security claim that using a 2048 bit key would not be
crackable until around 2030).

9. Security Protocols
Security protocols ensure data is protected when sent across a network
Hyper Text Transfer Protocol Secure
The secure version of HTTP
Data sent between browser and the website is encrypted
Used with banks, shops, webmail etc. to encrypt credit card and other
transaction and personal details

10. Firewall
 Prevents unauthorised access to a private network
 Can be hardware and/or software
 All messages entering or leaving network pass through firewall which
checks to see if the meet allowed criteria

11. Firewall