Re: length of IV in ESP_NULL cipher

[Scott Fluhrer <sfluhrer@cisco.com>]

On Thu, 8 Jan 2004, Tarun Ahuja wrote:

> Hi all
>
> What should be the length of the IV in case of NULL cipher when using ESP
> protocol?
>
> As per RFC 2410
> "Because of the stateless nature of the NULL encryption algorithm, it is not
> necessary to transmit an IV or similar cryptographic
> synchronization data on a per packet (or even a per SA) basis".

To quote later on in RFC 2410:

   To facilitate interoperability, the IV size for this algorithm MUST
   be zero (0) bits.

>
> Which essentially means the length of the IV should be 0 but FreeSWAN uses a
> length of 4bytes IV (equal to blocksize) for NULL cipher.

Well, either FreeSWAN is broke (at least in this respect) or you are
mistaken about the operation of the FreeSWAN code.

-- 
scott