Security at the Internet Layer

43 I nternet Protocol, version 6, was conceived with two main goals: increase address space and improve security, relative to IPv4. 1 The community achieved the first goal by increasing the IP address length from 32 bits to 128 bits. To meet the second goal, the Internet Engineering Task Force chartered the IP Security Working Group to design a security architecture and corresponding protocols that would provide cryptographically based security for IPv6 As work progressed, however, the IP community realized that the security architecture proposed for IPv6 could also be used for IPv4. Consequently, they extended this charter to retrofitting the security protocols , or IPsec protocols, into IPv4 implementations. 2 Many IPv4 software vendors have announced they will support the IPsec protocols in future releases. This retrofitting is an important part of the working group's charter because IPv6 deployment is turning out to be slow. As the sidebar " Should Security Be at the Internet Layer? " describes, some vendors are using other security technologies and protocols to retrofit security at some higher layer in the TCP/IP protocol stack. In this article, I overview the proposed security architecture and the two main protocols—the IP Security Protocol and the Internet Key Management Protocol—describe the risks they address, and touch on some implementation requirements. IPsec's major advantage is that it can provide security services transparently to both applications and users. Also, the application programs using IPsec need not be modified in any way. This is particularly important when securing application programs that are not available in source code, which is common today. This transparency sets IPsec apart from security protocols that operate above the Internet layer. At present, IPsec is likely to be used in conjunction with and complemented by other security technologies, mechanisms, and protocols. Examples include firewalls and strong authentication mechanisms for access control , and higher layer security protocols for end-to-end communication security. 3,4 In the near future, however, as virtual private networking and corporate intranets and extranets mature, IPsec is likely to be deployed on a larger scale. During the past decade, reports of network-based attacks and exploitations of bugs and design limitations have grown dramatically. 5 More recently, the use and proliferation of downloadable, executable content, such as that provided by Java applets and ActiveX controls, have opened new possibilities to attack networked computer systems and Internet sites. A 1996 survey (http:// www.trouble.org/survey) of approximately 2,200 …