All, I was able to work-around the API limitation and was able to successfully decrypt (yay!) the example from Section 5.1. Unfortunately, the plaintext output that I got has an additional byte at the end (as ASCII it is a newline). It may be best for the document to include the hex form of plaintext as h'546869732069732074686520636f6e74656e742e*0a*' to avoid any possible ambiguity.
Brian S. On Tue, Jul 21, 2026 at 2:37 AM Ilari Liusvaara <[email protected]> wrote: > On Mon, Jul 20, 2026 at 09:09:14PM -0400, Brian Sipos wrote: > > Ilari, > > Thank you, I now better understand the relationship to RFC 9180. It might > > be helpful to give an aside somewhere (intro section?) to explain that > the > > mechanism of this document is not compatible with strict minimal RFC 9180 > > implementations and requires the API of the bis document. > > It is compatible. RFC 9180 talks about using both, which COSE HPKE does > not do (unless using SuppPrivInfo, which is non-interoperable anyway). > The KE stuff uses info, but that is on layer >0, so should be small. > > The problem is libraries that do not implement single-shot aad at all, > which is something RFC 9180 does not talk about. However, the text > could be interpretted to encourage not supporting aad for single-shot. > > Note that if library supports multi-shot, you can emulate single-shot > by creating a context and then using it once (since that is how single- > shot internally works). > > > > I will continue to track this with Py cryptography library authors for > > eventual compatibility with the 9180bis spec. Do you have a feeling on > the > > stability of the current version of that draft? > > Where the specifications overlap (and not hitting any implementation > limits), the behavior is fully compatible. > > - RFC9180bis has higher minimum limits (e.g., on info size). > - RFC9180 has stuff RFC9180bis does not (e.g., auth modes). > - RFC9180bis has stuff RFC9180 does not (e.g., single-step KDFs). > > I suppose one should be careful with things like single-step KDF with > auth modes (I have written HPKE library that somehow supports that). > > > > > -Ilari > > _______________________________________________ > COSE mailing list -- [email protected] > To unsubscribe send an email to [email protected] >
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