[Hipsec] ORCHIDv2

[Julien Laganier <[e-mail]>]

Folks,

Unless someone objects I am going to update the ORCHIDv2 draft to
reflect what we discussed earlier and is currently described in the
HIP base spec, that is, that ORCHIDs now encode a 4 bits index called
the Orchid Generation Algorithm -- see below.

--julien

Appendix E.  HIT Suites and HIT Generation

   The HIT as an ORCHID [I-D.ietf-hip-rfc4843-bis] consists of three
   parts: A 28-bit prefix, a 4-bit encoding of the ORCHID generation
   algorithm (OGA) and the representation of the public key.  The OGA is
   an index pointing to the specific algorithm by which the public key
   and the 96-bit hashed encoding is generated.  The OGA is protocol
   specific and is to be interpreted as defined below for all protocols
   that use the same context ID as HIP.  HIP groups sets of valid
   combinations of signature and hash algorithms into HIT Suites.  These
   HIT suites are addressed by an index, which is transmitted in the OGA
   field of the ORCHID.

   The set of used HIT Suites will be extended to counter the progress
   in computation capabilities and vulnerabilities in the employed
   algorithms.  The intended use of the HIT Suites is to introduce a new
   HIT Suite and phase out an old one before it becomes insecure.  Since
   the 4-bit OGA field only permits 15 HIT Suites (the HIT Suite with ID
   0 is reserved) to be used in parallel, phased-out HIT Suites must be
   reused at some point.  In such a case, there will be a rollover of
   the HIT Suite ID and the next newly introduced HIT Suite will start
   with a lower HIT Suite index than the previously introduced one.  The
   rollover effectively deprecates the reused HIT Suite.  For a smooth
   transition, the HIT Suite should be deprecated a considerable time
   before the HIT Suite index is reused.

   Since the number of HIT Suites is tightly limited to 16, the HIT
   Suites must be assigned carefully.  Hence, sets of suitable
   algorithms are grouped in a HIT Suite.

   The HIT Suite of the Responder's HIT determines the RHASH and the
   hash function to be used for the HMAC in HIP control packets as well
   as the signature algorithm family used for generating the HI.  The
   list of HIT Suites is defined in Table 11.

   The following HIT Suites are defined for HIT generation.  The input
   for each generation algorithm is the encoding of the HI as defined in
   Section 3.2.  The output is 96 bits long and is directly used in the
   ORCHID.