...and usually these 64 bits are made from the MAC address of the interface linked to this IPv6 address (padded if 48 bits).
I think what you're looking for is RFC 4941, Privacy Extensions for Stateless Address Autoconfiguration in IPv6:
This document describes an extension to IPv6 stateless address autoconfiguration for interfaces whose interface identifier is derived from an IEEE identifier. Use of the extension causes nodes to generate global scope addresses from interface identifiers that change over time, even in cases where the interface contains an embedded IEEE identifier. Changing the interface identifier (and the global scope addresses generated from it) over time makes it more difficult for eavesdroppers and other information collectors to identify when different addresses used in different transactions actually correspond to the same node.