[Hipsec] Password authentication for HIP DEX

[Robert Moskowitz <[e-mail]>]

Password authentication for HIP DEX may be used for initial ACL 
bootstraping (how a new I introduces itself to R) of for emergency 
access (EMT needs access to a pacemaker or field tech needs access to a 
substation switch).

Note that if I does not have PKr from a source other than R1, this 
process is open to rogue attack then offline dictionary attack against 
the secret.  There is no way that R can protect its password from a 
misbehaving I.  This is a simple password authentication.  I am going to 
study 802.11s ECC zero-knowledge password authentication that Dan 
Harkins developed to see if I could use it instead...

Anyway on to the process, it is very simple.

P  ::= password
Pl ::=length of password

If Pl != 128 then P = AES-CMAC(0^128, P, Pl)

Add the following to I2:

ECR(PKr, MAC(P, n))

This parameter is included in the MAC of I2.  Only the owner of the R 
private key can look at the MAC result to see if it is correct.  Thus 
the passsword is not exposed to over the air intercept and dictionary 
attack.  It IS open to MR attack if I does not have PKr from a source 
other than R1.  I don't see an EMT in a hurry entering a 128bit HIT or 
160bit PKr to get access to a pacemaker...