Subject: [sidr] Multi-signature support and Algorithm agility

From: Roque Gagliano <[email-masked]>
Date: Wed, 21 Jul 2010 15:26:28 +0200

Hi WG,

In draft-ietf-sidr-rpki-algs Section 3 it was recommended to explore the idea of supporting multi-signatures to facilitate the process of algorithm agility. At the draft team we have been doing just that. 

This is a rather complex issue because it touches basic concepts in the RPKI design and most of SIDR documents. At the IETF78 meeting we will have only 10 minutes of discussion for all algorithm agility issues, so we wanted to present our findings to the mailing list to start the discussion.

The main conclusion that we would like to arrive is if we should draft the algorithm agility document as if multi-signatures is possible. In order to be able to answer that question,  I will send two separated emails with the following questions:

	1- which are the requirements that would justify multi-signature support from the algorithm roll-over? and what are the impacts in CA and validators implementations?
	2- what changes would be needed in current SIDR document?

Some context:

- Multi-signature is not supported in RFC 5280, which means that certificates and CRL will need to be single signed. This fact implies that in order to perform the algorithm transition, during the roll-over period, parallel structure will need to be maintained to attest an entity "right of use" of its resources in the context of RPKI. Depending on how the repositories are managed, the different RPKI hierarchies may or may not share common publication points.

- RFC 5652 defines the SignerInfos type as a set of SignerInfo objects. This means that a single CMS object can support several signatures and also carry several certificates associated with each one of those signatures. 

By allowing multiple signature in the CMS objects, the idea is that different PKI trees are maintained but used to verify the same CMS signed objects. Some use cases will be explored in a separate email.

When analyzing the impact of multiple signatures in the current SIDR documents, we only considered the ROA and Manifest objects. The provisioning protocol and the TA CMS objects are both signed by non-RPKI CAs and thus were not analyzed.

Regards,

Roque (for the algorithm agility team).

Note: Multi-signature support for ROAs were already explored in this WG in a different context.