Open Network Handles
Michael J. O'Donnell
17 August, 2002
I propose a system of Open Network Handles to provide
permanent primitive network handles promiscuously to all who request
them. Handles provide an intermediate level of service between IP
numbers and domain names. While assignment of IP numbers is
constrained by routing considerations, the owner of a handle may
reassign it to different addresses over time for mobility or changes
p in configuration of resources. Unlike domain names, handles carry no
significance in natural language, so they should not have high
commercial value, nor should they attract disputes based on
assertions of rights in significant names.
This document describes several considerations and questions that
arise when planning a design of a network handle system.
- For now, I'm just listing issues as they occur to me.
- Still a chaotic list, I just added and refined a bit, and
converted from ``central'' to ``global.''
- Minor refinements.
I have no background in cryptographic key management. I hope that
someone with such knowledge will contribute.
- Although the focus of service is to answer queries by
resolving handles to addresses, the focus of design is the
establishment of ownership. Assuming that ownership is established
by knowledge of a secret key, the focus of design is resolving
each update request into a challenge to the appropriate secret
key. With public-key techniques, the focus of design is the
association of handles with public keys.
- A good design should add very little overhead to satisfactory
communications between queriers and handle owners who decide to
trust one another. The network handle system should avoid
interfering with such communications. It should aid queriers and
handle owners to establish communications, and it should provide
methods for authenticating contacts when they are challenged.
- A good design should separate discovery and
authentication as much as possible.
- Should handles be related systematically to authentication keys,
or should they be assigned independently? If handles are
determined by keys, we avoid attempts to catch numerologically
significant handles, and allow more end-to-end verification. But
transfer and upgrade are less efficient and more vulnerable when
we can't change the key for an existing handle. On the other hand,
the benefits for transfer and upgrade may require a central
authority, and we might be able to avoid such an authority
entirely with handles generated from keys. And accommodation of
naive owners seems to require that we allow weak password
protection, which doesn't appear to support an enforced key/handle
correspondence. The global system could keep cryptographic keys on
behalf of naive users, and provide weak password access.
- Perhaps we can allow arbitrary handle/key pairs, while still
providing permanent certificates of authenticity. If two agents
claim the same handle, they can produce time-stamped certificates
from a trusted certifier. The trusted certifier doesn't need to
survive (in fact demise and destruction of the private keys is an
advantage to confidence in authenticity). But a querier must
locate the proper owner of a handle in order to detect a
fraudulent one. What if each querier keeps the handle plus its
time stamp? We might also depend on a certifier who certifies
uniqueness, and not just timeliness. But that sounds like a
substantial burden on the continuity of the certifier. Does it
support fully transferable handles?
- The current DNS is a very successful and helpful proof of
concept for most of the design problems having to do with storing
tables and resolving queries.
- The system should support the most flexible possible notions of
virtual agents. In particular, an individual application running
on a host should be an agent, as well as the host in its
entirety. The system should also support distributed agents,
mobile agents, etc. Support for virtual agents appears mainly to
call for generalized addresses.
- In addition to normal addresses (which, at least to start, can
be exactly the sorts of addresses allowed by DNS), perhaps handles
should be able to resolve to other handles, constituting
permanent reassignments. As much as possible, a permanent
reassignment should be irrevocable. This provides something near
the utility of a transfer of handle. It can also be the basis for
upgrade of authentication/cryptographic techniques. It works even
if handles are rigidly determined from keys.
- In deciding whether to implement a particular extension of the
scope of addresses, the main consideration should be whether the
extension can be supported well by direct communication between
querier and handle owner. For example it makes a lot of sense to
support hunt groups of IP addresses, since a querier needs the
information in a hunt group precisely when he cannot reach the
handle owner at a single IP address. But it makes less sense to
provide network-extraneous information about the handle owner,
since the owner may send such information directly to the
- Transfer by reassignment of an independently assigned handle is
enforceable in the contractual sense. The receiver of such a
transfer may retain a signed certificate of transfer, may send in
test queries from time to time, and may seek relief for
misdirections by the source of the transfer (perhaps this requires
signed responses to queries). But it will be nicer to have
positive enforcement, in the sense of making it technically
difficult for the source of a transfer to renege. That sounds
difficult with independently assigned handles. Transfers might
also be achieved through an escrow service, but that adds cost and
also adds another agent who must be trusted.
- In terms of logical functionality, handles are pure atoms with
no meaningful relations to one another besides equality and
inequality. But the administration of handles imposes other
relations, such as a hierarchy of handle authorities, each
represented by a handle. The reassignment relation above is
another sort of administrative relation between handles. We should
minimize the number and complexity of relations that need to be
supported by the handle system itself.
- A hierarchical system is very attractive. In principle, it can
be achieved merely by implementing a top-level system of unique
handles, which may themselves refer to local handle resolvers. The
independence of local regions within handle space, allowing extra
services to be provided for local needs, is attractive. But there
should be a protocol which, if followed by the agents involved,
treats lower-level handles uniformly and transparently with
top-level handles for the purposes of query resolution.
- The natural structure of networks, and particularly of the
Internet, makes it relatively feasible and efficient to guarantee
that correct responses to queries will eventually come, but
relatively difficult to guard against incorrect responses.
Compare the value of a globally assigned handle to the value of
an independently assigned handle:
- The main incentives for registering multiple handles globally
instead of independently appear to be
On the other hand, flexibility and control actually favor independent
assignment, as well as key-management load. But the latter incentive
has little impact on naive users who opt for password protection, and
those are the most likely users to want to unload query resolution
- Let the global system bear the burden of running the query
- Maintain independent transferability.
- To reduce the incentive to let the global system provide
multiple handles, avoiding the need for local support, we need
effective distribution of handle system software.
- We can reduce or eliminate the incentive to grab many handles
from the global system so that they are independently
transferable, if we let agents promote their independently
assigned handles to the global system for the purpose of
transfer. This complicates the top-level tables, and makes it more
difficult to enforce a specific correspondence between handle and
key. We might allow promotion for the sole purpose of
escrowed reassignment with a timeout.
- Because the handle system makes no attempt to authenticate the
quality of handle owners, all harm due to bad behavior by a handle
owner must be avoided outside of the handle system.
- Denial of handle traffic to the owner-authorized address. This
sort of harm probably cannot be defended by any sort of end-to-end
- Duplication of handle traffic to a fraudulent address. If we
allow multiple-delivery addresses, or if the attacker diverts but
also forwards, this may occur without denying traffic to the
authorized address. For the purposes of spying, duplication may be
more harmful than denial. Querier and owner may defend by
end-to-end encryption, but the spy may still derive some benefit
from partial information.
- Diversion of handle traffic to a fraudulent address. This is
just the combination of the previous two. It may be harmful even
if the target of the diversion belongs to the handle
owner. Diversion is only a problem when a proper handle owner is
disenfranchised after confirmation of a handle
assignment. Hijacking of an initial handle assignment is no harm
(except possibly a denial of new-handle service if it is repeated
consistently), since it doesn't matter who gets which handle.
- Creation of traffic to an address whose owner doesn't want
it. There are so many other ways to accomplish this, that the
additional possibility of doing it through the handle system is
probably not very important.
- Denial of a new handle to an agent who requests one. This is
only a temporary harm, but if repeated consistently it can destroy
the utility of the system.
I have no background in threat analysis. I hope that someone who
understands such things will contribute.
- Attack by cracking the cryptographic authentication system and
entering a fraudulent address. This is detectable by the owner.
Partial defense: allow the owner to invalidate a compromised
handle. The attacker can also invalidate the handle, but this
reduces the harm from redirection to denial. Partial defense:
provide audit trails that are hard for an attacker to cover, even
when he has compromised the handle. E.g., notify a certain address
of every update to a given handle.
- Attack by cracking the authentication system and changing the
key. This is deadly if we allow liberal changes of key. The
possibility of this attack supports the decision to require
reassignment, which is highly auditable by lots of parties, as the
only way to change a key.
- Attack by discovering a private key through channels having
nothing to do with cryptography. Key management was, is, and will
probably remain the weak spot in cryptographically enforced
security. The defense appears to be the same as the defense
against key cracking.
- Accidental self-attack by losing a private key. Any attempt to
defend against this sort of self-attack appears to weaken the
defense against malicious outside attack. It is probably best to
leave this sort of defense completely out of band. If the problem
is large enough, a trusted agent might charge a fee to register
replacements for lost handles, based on out-of-band verification
- Accidental self-attack by announcing a reassignment, or other
irrevocable change. Defend by requiring confirmation before
committing irrevocable change.
- Attack by tricking a key owner into muffing key management or
making an irrevocable change. This is similar to the mental
viruses that induced computer owners to delete files by
fraudulently associating those files with computer viruses. The
defense appears to be good training, which depends critically on
keeping things simple, but exposing users to key-management
details in gentle doses. Seems pretty challenging.
- Attack by intercepting and modifying communications with
servers. I hope that this has been studied from the point of view
of other services. It doesn't appear to constitute a special
threat to a handle system. Defense: end-to-end authentication.
- Attack by flooding query servers with queries. This appears to
be the same as any denial-of-service by flooding attack.
- Attack by flooding a registrar with requests for new handles
and/or updates. Also appears to be the same as any
denial-of-service by flooding attack.
Open Network Handles
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