Iljitsch;
Putting a 64-bit crypto-based host identifier in the bottom 64 bits of
IPv6 addresses shouldn't get in the way of regular IPv6 addressing
mechanisms and/or operation.
Putting a crypto-based host identifier in the address is unnecessary,
since there's really no need to include a strong host identifier in
every packet sent to a host. The locator alone is usually sufficient,
and if that's not sufficient, the sender can generally encrypt the
traffic with a secret known only to the intended destination.
Putting a 64 bit crypto-based identifier in IPv6 addresses isn't
something that would be done because it's the only way to arrive at
certain functionality, but rather because it's a convenient way to do
it.
Putting a 64 bit crypto-based identifier means people won't
type that long hexadecimal sequence.
That is, even if most people use DNS or something like that,
it is still inconvenient for DNS administrators. Note that
the value is psuedo random and completely different host
by host that copying some digit of other host does not work.
People relying on DNS do not notice even if a 64bit id from
DNS is different from the specified one. There is no one who
specifies the id.
So, there is no security nor convenience.
Masataka Ohta