Prefix            FC00::/7 prefix to identify Local IPv6 unicast
                    addresses.

  L                 Set to 1 if the prefix is locally assigned.
                    Set to 0 may be defined in the future.  See
                    Section 3.2 for additional information.

  Global ID         40-bit global identifier used to create a
                    globally unique prefix.  See Section 3.2 for
                    additional information.

  Subnet ID         16-bit Subnet ID is an identifier of a subnet
                    within the site.

  Interface ID      64-bit Interface ID as defined in [ADDARCH].

The algorithm described below is intended to be used for locally
assigned Global IDs.  In each case the resulting global ID will be
used in the appropriate prefix as defined in Section 3.2.

 1) Obtain the current time of day in 64-bit NTP format [NTP].

 2) Obtain an EUI-64 identifier from the system running this
    algorithm.  If an EUI-64 does not exist, one can be created from
    a 48-bit MAC address as specified in [ADDARCH].  If an EUI-64
    cannot be obtained or created, a suitably unique identifier,
    local to the node, should be used (e.g., system serial number).

 3) Concatenate the time of day with the system-specific identifier
    in order to create a key.

 4) Compute an SHA-1 digest on the key as specified in [FIPS, SHA1];
    the resulting value is 160 bits.

 5) Use the least significant 40 bits as the Global ID.

 6) Concatenate FC00::/7, the L bit set to 1, and the 40-bit Global
    ID to create a Local IPv6 address prefix.

This algorithm will result in a Global ID that is reasonably unique
and can be used to create a locally assigned Local IPv6 address
prefix.