Re: [openpgp] AEAD mode chunk size

[Marcus Brinkmann <[e-mail]>]

On 07/01/2018 07:12 PM, brian m. carlson wrote:
> I agree with this.  The original specification I submitted limited the
> value to something smaller for this reason.
...

> The reason I specified a lower bound of 64 bytes per chunk is that it
> doesn't make sense to have chunks that are, for example, 1 byte long.
> That's a great way to be wasteful and potentially DoS a recipient, since
> each AEAD chunk involves some block cipher overhead.
> 
> Of course, trailing chunks may be smaller, and that's okay; the document
> anticipates that.

I'd be fine with having a lower limit as well, and if the best way to
express that is "2^(6+c) with 0 <= c <= 10" instead of "2^c with 6 <= c
<= 16" then that's fine with me, too.

I dug your original change, it can be found here:
https://gitlab.com/openpgp-wg/rfc4880bis/merge_requests/4/diffs

Here is your original wording for reference:

  An implementation MUST support chunk size octets with values from 0
  to 10.  An implementation MAY support other chunk sizes.  Chunk size
  octets with values larger than 127 are reserved for future extensions.

Thanks!
Marcus