Last Call Review of draft-ietf-httpbis-encryption-encoding-08
review-ietf-httpbis-encryption-encoding-08-secdir-lc-sparks-2017-04-05-00

I have reviewed this document as part of the security directorate's
ongoing effort to review all IETF documents being processed by the
IESG.  These comments were written primarily for the benefit of the
security area directors.  Document editors and WG chairs should treat
these comments just like any other last call comments.

Document : draft-ietf-httpbis-encryption-encoding-08

Summary: This document is ready for publication as Proposed Standard (except
perhaps for one recommendation)

This document defines a content encoding for encrypting the contents of an HTTP
message that facilitates storing the encrypted contents and decrypting the
content for rendering incrementally (before the full content is received). The
draft is clear, and implementation should be straightforward. It's security
considerations section is detailed.

I did not verify the math that went into the provided examples.

My only concern is that the document suggests it would be ok to use a counter
to provide a unique salt value for each message. I suspect that provides the
kind of information leak the draft discusses avoiding.

I also pointed out a couple of nits to the editor, and those are addressed
already in his working copy (on github).