SCRAM minimum PBKDF#2 iteration count

[Simon Josefsson <simon@xxxxxxxxxxxxx>]

SCRAM currently contains:

      Servers SHOULD announce a hash iteration-count of at least 128.

I believe this is too low.  RFC 2898 (PKCS#5), an almost 10 year old
document contains:

   the difficulty of attack. For the methods in this document, a minimum
   of 1000 iterations is recommended. This will increase the cost of

A more recent document that uses PBKDF#2 is RFC 3962, published 2005,
and it uses a default of 4096 iterations.

There is a difference between a minimum value, and a default value.
Still, I believe we could reasonable suggest a minimum value of 4096
iterations for SCRAM.

Thoughts?

/Simon