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Re: Derived versus Explicit IV



> 
> Thus the new ESP is compatible with the old ESP?

To answer both of your messages, here's what we're talking about:

Old ESP+DES (with 32-bit IV):		NEW ESP + ciph-des-derived:

32bits	SPI				32bits	SPI
32bits	IV				32bits	Sequence number
<var>	ciphertext			<var>	ciphertext
<var>	pad				<var>	pad
8bits	padlen				8bits	padlen
8bits	nextheader			8bits	nextheader


Looks like the same packet to me, especially when the "IV derived from
Sequence Number" algorithm is the same as the old RFC1829 "convert 32-bit IV
to 64 bit IV" algorithm.

Therefore, ciph-des-derived MUST be mandatory-to-implement, in order that
new products retain backwards compatability with old products.

> But are you saying that these vendors who have already shipped RFC1829
> compliant products do not wish to upgrade their product to the newer
> IPSec standard?

Yes, but we can't require that customers upgrade their deployed equipment
(especially with a "flag day" due to incompatabilities).

> Vendor's who released implementations on draft documents or on RFCs that
> have been obsoleted obviously realized that the protocol would change
> and they would have to upgrade their IPSec implementation.

RFC 1827/1829 are both IETF Proposed Standards. Like it or not, they're out
in the field, and have been for almost TWO YEARS. This is the price this
working group pays for its glacial progress.

-- 
Harald


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