What is IPSec? How does it relate to VPNs and firewalls?
IPSec is an evolving standard for secure private communications over the Internet. Normal IPv4 packets consist of headers and payload, both of which contain information of value to an attacker. The header contains source and destination IP addresses, which are required for routing but may be spoofed or altered in what are known as “man-in-the-middle” attacks; the payload consists of information which may be confidential to a particular organization. IPSec provides mechanisms to protect both header and payload data. The IPSec Authentication Header (AH) digitally signs the outbound packet, both data payload and headers, with a hash value appended to the packet, verifying the identity of the source and destination machines and the integrity of the payload. The IPSec Encapsulating Security Payload (ESP) guarantees the integrity and confidentiality of the data in the original message by combining a secure hash and encryption of either the original payload by itself, or the headers and paylo
