This sort of guidance will definitely be a useful addition. A little more wordsmithing on Stephen's proposed text follows: The decision on whether a header field is ok to compress or not is highly dependent on the context. As a generic guidance, header fields used for conveying highly valued information, such as the Authorization or Cookie header fields, can be considered to be on the more sensitive side. In addition, a header field with a short value has potentially a smaller entropy and can be more at risk. We know that compressing low-entropy sensitive header fields can create vulnerabilities so such cases are most likely the ones to not compress today. Note though that the criteria to apply here may evolve over time as we gain knowledge of new attacks. OLD We know that compressing low-entropy sensitive header fields can create vulnerabilities so such cases are most likely the ones to not compress today. Note though that the criteria to apply here may evolve over time as we gain knowledge of new attacks. NEW We currently know that compressing low-entropy sensitive header fields can create vulnerabilities so compression of such fields ought to be avoided. This guidance may evolve over time as we gain knowledge of new attacks. Thanks, --David > -----Original Message----- > From: Stephen Farrell [mailto:stephen.farrell@xxxxxxxxx] > Sent: Friday, January 23, 2015 10:45 AM > To: Jari Arkko; Hervé Ruellan > Cc: Martin Thomson; Black, David; ietf@xxxxxxxx; General Area Review Team > (gen-art@xxxxxxxx); fenix@xxxxxxxxxx; ietf-http-wg@xxxxxx > Subject: Re: [Gen-art] Gen-ART and OPS-Dir review of draft-ietf-httpbis- > header-compression-10 > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > > > On 23/01/15 15:35, Jari Arkko wrote: > > > >> I made a proposal at > >> https://github.com/http2/http2-spec/pull/704 > > > > Looked reasonable to me. > > Me too. Quibbling, I'd suggest: > > OLD: > > The decision on whether a header field is sensitive or > not is highly dependent on the context. As a generic > guidance, header fields used for conveying highly valued > information, such as the Authorization or Cookie header > fields, can be considered to be on the more sensitive > side. In addition, a header field with a short value > has potentially a smaller entropy and can be more at > risk. > > NEW: > > The decision on whether a header field is ok to > compress or > not is highly dependent on the context. As a generic > guidance, header fields used for conveying highly valued > information, such as the Authorization or Cookie header > fields, can be considered to be on the more sensitive > side. In addition, a header field with a short value > has potentially a smaller entropy and can be more at > risk. We know that compressing low-entropy sensitive > header fields can create vulnerabilities so such > cases are most likely the ones to not compress today. > Note though that the criteria to apply here may evolve > over time as we gain knowledge of new attacks. > > Cheers, > S. > > > > > > > > jari > > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1 > > iQEcBAEBAgAGBQJUwmyOAAoJEC88hzaAX42iJKkIAJtbLdBsQe12+yyg47yupU9x > xbJJ8WZj7vN9Owc9DbzPUczcejjxPUETWwiJ4gzGEnqOTgkH4Ljbt3DnZO1OrdwL > J5sdie+/x85WuimEgz8GLeOvHe3vyKAJzRIGuX4c4PFgxQ2EBQTJwMM9/qBx9Wp4 > gLNSMmvd0DT8mfozQokju4H4SsxEgFWIERpDO1Has/3ska0u0qhCrJgIdSSWWn08 > yvsjoPDfp+SPEJOa+vWoWqP971QXaGsm5lnhPDLTJ+u06cWpzeQerOEmS3dMYX4A > 0gcR73olUgS9gqVQ/HIYDKLxsOX3DXH0QSJhHOgYrE6GNPUX2bz7npN0PP7+x0s= > =Txbn > -----END PGP SIGNATURE-----