[ipv6hackers] Generation of Interface-IDs in Windows 7

Fernando Gont fgont at si6networks.com
Thu Nov 10 05:24:58 CET 2011


As you probably know, Windows 7 generates autoconfigured addresses with
a different algorithm than that specified in RFC 4862.

In other words, it does not embed the MAC address in the Interface ID,
because of the privacy implications of doing that.

Supposedly (i.e., as once told by some MS guy), the interface ID was
generated as a result of hashing the network prefix together with other
(secret?) data, such that the Interface ID remains constant for a given
network, but changes as the host moves from one network to another.

However, I see that the same interface ID is generate when multiple
prefixes are advertised by a SLAAC router.

Has anyone figured out the algorithm that Windows 7 uses for generating
the Interface IDs?


Best regards,
Fernando Gont
SI6 Networks
e-mail: fgont at si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492

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