AH is pretty useless and perhaps should be deprecated
mysidia at gmail.com
Tue Nov 17 02:07:31 UTC 2009
On Mon, Nov 16, 2009 at 6:23 PM, Jack Kohn <kohn.jack at gmail.com> wrote:
> However, i still dont understand why AH would be preferred over
> ESP-NULL in case of OSPFv3. The draft speaks of issues with replaying
> the OSPF packets. One could also do these things with AH.
> Am i missing something?
Neither protects against replay without additional measures.
However, AH is very close... consider using AH-authenticated
packets with the timestamp option and clock synchronization between
Discard packets arriving that are more than 5 minutes old.
In transport mode for security between LAN peers, ESP NULL verifies
the integrity of only the data payload in the packet. AH secures
the header, the IP header fields and options.
Therefore changing the timestamp to replay would be detected.
This evil act would not be detected if you are using ESP NULL, the
attacker can potentially replay this packet, while the SPI is still
good, and you'll never know.
One of AH's most visible disadvantages (cannot be used with NAT) is a
side-effect of the increased security coverage it provides. Many IPv4
networks require NAT, making AH impractical.
However, matters could change for IPv6 networks with high
security requirements, that need to validate authenticity of more
than just packet contents...
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