Re: replay field size

[Bill Sommerfeld <[e-mail]>]

> BTW, if the hash is used to ensure message integrity, and there is a
> separate MAC to ensure authenticity, then you could eliminate the hash. A
> MAC provides integrity verification as well, but it doesn't help you
> distinguish between a integrity violation and a key-mismatch. 

We are discussing HMAC-SHA1, which is a MAC built out of SHA1, not
pure SHA1, which is an unkeyed hash.

See: http://www.ietf.org/html.charters/ipsec-charter.html
and, in particular, the following documents referenced from it:

RFC's:
	IP Authentication Header (RFC 1826)
	HMAC: Keyed-Hashing for Message Authentication (RFC 2104)

I-D's:
	HMAC-SHA IP Authentication with Replay Prevention

Your time may be limited, but please read these three documents at a
minimum before commenting further on this proposal; they are
small... less than 70k of text.

					- Bill