[CGA-EXT] Hashed DAD

"Pars Mutaf" <pars.mutaf@gmail.com> Thu, 28 February 2008 19:40 UTC

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Date: Thu, 28 Feb 2008 20:39:50 +0100
From: "Pars Mutaf" <pars.mutaf@gmail.com>
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Subject: [CGA-EXT] Hashed DAD
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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.



                     Hashed duplicate address detection


   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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