No matching activity found.
|Independent Verification of IPsec Functionality in FreeBSD|
|<personname><firstname>David</firstname><surname>Honig</surname></personname><affiliation> <_:address-1/> </affiliation>|
|FreeBSD is a registered trademark of the FreeBSD Foundation.|
|Motif, OSF/1, and UNIX are registered trademarks and IT DialTone and The Open Group are trademarks of The Open Group in the United States and other countries.|
|Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this document, and the FreeBSD Project was aware of the trademark claim, the designations have been followed by the <quote>™</quote> or the <quote>®</quote> symbol.|
|$FreeBSD: head/en_US.ISO8859-1/articles/ipsec-must/article.xml 52227 2018-09-06 01:30:47Z ebrandi $|
|You installed IPsec and it seems to be working. How do you know? I describe a method for experimentally verifying that IPsec is working.|
|First, lets assume you have <link linkend="ipsec-install"> installed <emphasis>IPsec</emphasis></link>. How do you know it is <link linkend="caveat">working</link>? Sure, your connection will not work if it is misconfigured, and it will work when you finally get it right. <citerefentry><refentrytitle>netstat</refentrytitle><manvolnum>1</manvolnum></citerefentry> will list it. But can you independently confirm it?|
|First, some crypto-relevant info theory:|
|Encrypted data is uniformly distributed, i.e., has maximal entropy per symbol;|
|Raw, uncompressed data is typically redundant, i.e., has sub-maximal entropy.|
|Suppose you could measure the entropy of the data to- and from- your network interface. Then you could see the difference between unencrypted data and encrypted data. This would be true even if some of the data in <quote>encrypted mode</quote> was not encrypted---as the outermost IP header must be if the packet is to be routable.|
|Ueli Maurer's <quote>Universal Statistical Test for Random Bit Generators</quote>(<link xlink:href="https://web.archive.org/web/20011115002319/http://www.geocities.com/SiliconValley/Code/4704/universal.pdf"> <acronym>MUST</acronym></link>) quickly measures the entropy of a sample. It uses a compression-like algorithm. <link linkend="code">The code is given below</link> for a variant which measures successive (~quarter megabyte) chunks of a file.|
|We also need a way to capture the raw network data. A program called <citerefentry><refentrytitle>tcpdump</refentrytitle><manvolnum>1</manvolnum></citerefentry> lets you do this, if you have enabled the <emphasis>Berkeley Packet Filter</emphasis> interface in your <link linkend="kernel">kernel's config file</link>.|
No matching activity found.