Subject: RE: [Ipsec] Query for IPv6 ICV

From: "Michael Roe" <[email-masked]>
Date: Thu, 11 Nov 2004 17:54:30 -0000

> I'm trying to establish an IPSEC session over IPv6 with
> Windows XP and FreeBSD (Kame's implementation) AH Transport
> mode with HMAC-MD5 authentication. Windows sends an ICV of
> 20 bytes (with 4 padded 0 bytes) and FreeBSD simply discards the packet.

With the Microsoft IPv6 stack, you need to specify the algorithm as
"HMAC-MD5-96" in the .sad file, not "HMAC-MD5".

"HMAC-MD5-96" will make it use HMAC-MD5-96, as described in RFC 2403,
("The Use of HMAC-MD5-96 within ESP and AH"), which is most likely
what you want for interoperability.

"HMAC-MD5" will make it use HMAC-MD5-128. This is a vendor specific
algorithm that is provided in addition to the IETF-standardized
algorithms. It is probably not what you want. 

Similarly, to get HMAC-SHA1-96, you need to specify "HMAC-SHA1-96", not
"HMAC-SHA1".

Hope this helps!

Mike

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