[Hipsec] Proposed new HASH Parameter

[Robert Moskowitz <[e-mail]>]

A new HIP Parameter:  HASH is proposed.  This is the HI Hash, or HIH.  
The values are:

       Hash              Value
       Reserved          0
       SHA-1             1
       SHA-2             2


2 will be MANDITORY to implement and 1 is SHOULD.  Once NIST comes out 
with a new hash, we will add it to the list.

The revised BEX that Tobias, with Miika's and my help is working on, 
will include this parameter and address the downgrade attacks that are 
introduced by HIH.

Tobias did a quick and dirty test with openssl speed on his machine 
during normal operation shows the following:

             The 'numbers' are in 1000s of bytes per second
             processed.
type        16 bytes     64 bytes    256 bytes    1024 bytes   8192 bytes
sha256      16335.80k    41030.10k    76838.89k   96992.97k   107657.16k
sha1        21577.09k    66409.19k   157907.49k  235312.60k   27521 8.50k

             Speed drops to 75-30% However, he assumes that it is still 
sufficiently fast.

             Code size shouldn't be an issue since the main difference
             between SHA-1 and SHA-256 lies in the number of rounds.
             However, since the lookup table for the  inversion step
             is a bit larger but not dramaticaly.

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