[Hipsec] HIT construction for ECC HIs

[Robert Moskowitz <[e-mail]>]

This may only be applied to Diet HIP, but ECC public keys have some 
interesting properties:

The Private key is a uniformly distributed random number.  From:

draft-mcgrew-fundamental-ecc-02.txt, sec 5.3.1:

    The private key z is an integer between 1 and q - 1, inclusive,
    generated uniformly at random.  (See Appendix B regarding random
    integers.)  The public key is the group element
    Y = alpha^z.  Each public key is associated with a particular
    particular parameter set as per Section 3.3.


Thus the private key is uniformly distributed from the set:

{ 1, 2, .... , q-1 }

Further a subset of the bits of the PK are uniformly distributed.

Thus it is conceivable that the HIT for an ECC HI is just 96 bits 
selected from the HI.  To put it within the ORCHID context, it could be 
a simple XOR with the HIP ECC context.

Comments?

Oh, this ASSuMEs that the EC private key was indeed uniformly randomly 
selected from the possible private keys...