Linux Security HOWTO : Password Security and Encryption : Linux IPSEC Implementations
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6.3. Linux IPSEC Implementations

Along with CIPE, and other forms of data encryption, there are also several other implementations of IPSEC for Linux. IPSEC is an effort by the IETF to create cryptographically-secure communications at the IP network level, and to provide authentication, integrity, access control, and confidentiality. Information on IPSEC and Internet draft can be found at http://www.ietf.org/html.charters/ipsec-charter.html. You can also find links to other protocols involving key management, and an IPSEC mailing list and archives.

The x-kernel Linux implementation, which is being developed at the University of Arizona, uses an object-based framework for implementing network protocols called x-kernel, and can be found at http://www.cs.arizona.edu/xkernel/hpcc-blue/linux.html. Most simply, the x-kernel is a method of passing messages at the kernel level, which makes for an easier implementation.

Another freely-available IPSEC implementation is the Linux FreeS/WAN IPSEC. Their web page states,

"These services allow you to build secure tunnels through untrusted networks. Everything passing through the untrusted net is encrypted by the IPSEC gateway machine and decrypted by the gateway at the other end. The result is Virtual Private Network or VPN. This is a network which is effectively private even though it includes machines at several different sites connected by the insecure Internet."

It's available for download from http://www.xs4all.nl/~freeswan/, and has just reached 1.0 at the time of this writing.

As with other forms of cryptography, it is not distributed with the kernel by default due to export restrictions.


Linux Security HOWTO : Password Security and Encryption : Linux IPSEC Implementations
Previous: SSL, S-HTTP and S/MIME
Next: ssh (Secure Shell) and stelnet