  This paper is focused on privacy issues related to the prefix part of IPv6
addresses. Long-lived prefixes may introduce additional tracking opportunities
for communication partners and third parties. We outline a number of prefix
alteration schemes that may be deployed to maintain the unlinkability of users'
activities. While none of the schemes will solve all privacy problems on the
Internet on their own, we argue that the development of practical prefix
alteration techniques constitutes a worthwile avenue to pursue: They would
allow Internet Service Providers to increase the attainable privacy level well
above the status quo in today's IPv4 networks.
