Re: [CGA-EXT] Hashed DAD

Hi Pars,
   There are not much details to go on, but I can already see that there 
are a couple of issues with this approach.

* It works only if ALL NODES in the network support your upgraded 
specification, since if there is even one unupgraded node it will 
destroy your scheme. This makes this proposal a non-starter.

* Even on a theoretical note, it is pretty simple to defeat.
This is an example exchange. Let's say there are two nodes A (the nice 
node) and M(the malicious node). A owns the address X.

a) A sends a DAD NS for Hash(X)
b) M gets this message
c) M sends a DAD NS for Hash(X)
d) A responds to M with the original address X
e) M can now defend the address X since he knows it

Cheers
Suresh

Pars Mutaf wrote:
> Hello,
> 
> Below is a IMHO better protection against DAD DoS attack for
> SEND.  It is very simple I won't bother you with a personal draft. :-)
> I hope the solution is OK.
> 
> Regards,
> pars
> 
> 
> 
> =========
> 
>                      Hashed duplicate address detection
> 
> 
> Abstract
> 
>    This document proposes a cheap defense against the
>    Duplicate Address Detection (DAD) denial-of-service attack in IPv6.
> 
> 1. Introduction
> 
>    Duplicate Address Detection (DAD) in IPv6 is vulnerable to a well-known
>    Denial-of-Service attack. Each time the victim performs DAD on a
>    tentative address, the attacker returns a positive response indicating
>    that the address is already in use. This attack prevents the victim
>    from configuring an IPv6 address.
> 
>    "Secure Neighbor Discovery counters this attack by requiring that the
>    Neighbor Advertisements sent as responses to DAD include an RSA
>    Signature option and proof of authorization to use the interface
>    identifier in the address being tested.  If these prerequisites are not
>    met, the node performing DAD discards the responses." [SEND]
> 
>    This solution leads to unnecessary energy consumption for
>    signature/verification and generating larger packets including an RSA
>    signature option. An attacker may be able to force a victim to
>    continuously use this solution and consume more energy than it would
>    using insecure DAD.
> 
>    This document proposes an alternative solution which is computationally
>    cheap and does not require the modification of the neighbor
>    advertisement packet.
> 
> 
> 2. Hashed duplicate address detection
> 
>    In the proposed solution, the node performing DAD on its tentative
>    address, computes a cryptographic hash of that address, and performs DAD
>    for the result.
> 
>    Each node in the subnet, using the same hash function, computes the hash
>    of its address and compares it to the hash result received from the node
>    that performs DAD. Upon match, the target node returns a neighbor
>    advertisement that contains its address (i.e. not the hash result but its
>    real address). This proves that the target node has really configured
>    that address.
> 
>    An attacker cannot know in advance which address is being tested.
>    Consequently, the DAD denial-of-service attack is defeated.
> 
> 3. Conclusion
> 
>    This document proposed a computationally cheap defense to the Duplicate
>    Address Detection (DAD) denial-of-service attack.
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