A firewall restricts access to and from the Internet as a means of preventing hacker attacks and other security breaches. This is accomplished by using packet filters and proxy services. Packet filters control which data is allowed into your system from the Internet. Only authorized data can enter. Proxy servers combine a dedicated computer with special software that carefully examines all traffic passing to and from the Internet.
Encryption involves making data unintelligible to all but the sender and intended recipient.
Most computer encryption uses a two key cipher. These two keys are related to each other by a complex and unique mathematical formula. When one of these keys is used to encode a message from the sender, the other key can be used to decode it on the receiving end.