Hi Bas, Dual Certs was not designed to cover the mix and match PKI hierarchy, only PKIs with clear separation between them. If your use case requires such a mix and match, then we think that composite will probably be a better solution for that.
Regards, Rifaat On Fri, Jun 26, 2026 at 4:26 AM Bas Westerbaan <bas= [email protected]> wrote: > > > On Thu, Jun 25, 2026 at 8:19 PM Eric Rescorla <[email protected]> wrote: > >> Hi folks, >> >> We now have a number of proposals for somehow using both PQ + T >> signatures simultaneously for TLS. These include: >> >> - Dual Certificates: draft-yusef-tls-pqt-dual-certs >> - Composite Certificates: draft-reddy-tls-composite-mldsa >> - Multiple Certificate/CertificateVerify: >> https://mailarchive.ietf.org/arch/msg/tls/dVj5I_s8Hj5s4Fzmbv73qac_Ftk/ >> >> It seems to me that all of these share the same basic intuition, >> namely that it's more secure to use both PQ + T algorithms together >> instead of individually. It's not clear to me whether all of these >> approaches have the same security properties, but it seems likely that >> with enough work they can be made to the deliver on the basic value >> proposition of robust authentication as long as one of the algorithms >> is strong [0]. >> > > I don't see how dual certificates could be adjusted to be used in the case > of a classical certificate for a legacy server where you'd want a classical > leaf signature and a PQ CA signature. The obvious thing looses the > distinction between that certificate and the legacy certificate meant for a > legacy client, which leads to a downgrade. This is the same problem as with > multiple certificate(verify) messages, where I discussed it in a bit more > detail: > https://mailarchive.ietf.org/arch/msg/tls/Rn7GHZGXnWv_TRxBpMkRXAYQ-wk/ > _______________________________________________ > TLS mailing list -- [email protected] > To unsubscribe send an email to [email protected] >
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