IPv6 Privacy Extensions: How Your Phone Hides Its Real Name

Introduction: The Permanent Identifier Flaw

In standard IPv6 setup (SLAAC), your device uses its physical MAC address to generate the second half of its IP address (this is called EUI-64). This means that out of the 32 numbers in your IPv6 address, the last 16 numbers will be the exact same everywhere you go. A website could easily track you from your house to a coffee shop. To stop this, we invented Privacy Extensions.

The Randomization Fix

When Privacy Extensions are enabled (which they are by default in Windows, iOS, and Android), your device doesn't use its real MAC address. Instead, it generates a random, complex string for the second half of the IPv6 address. Furthermore, it changes this random string every 24 hours.

Conclusion

Privacy Extensions ensure that the massive size of the IPv6 namespace isn't used to build persistent, unblockable tracking cookies. Verify your IPv6 privacy settings here.