Status of this Memo

This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt.

The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html.

This Internet-Draft will expire on March 31, 2005.

Copyright Notice

Copyright (C) The Internet Society (2004).

Abstract

Until DNSSEC is fully deployed, so-called "islands of trust" will exist. This will lead to a large number of keys with no method within DNSSEC to manage the keys. This proposal seeks to address that issue using existing mechanisms to allow cross-signing of root (i.e. roots of islands) keys. This cross-signing of keys creates a non-hierarchical web of trust which permits the efficient gathering and validation of trust anchors.

Table of Contents

1.  Introduction
2.  Island CAs
3.  Key Signing
4.  Publication of Certificates
5.  Location of Island Publication URL
6.  Use of Certificates
7.  Variations
8.  Security Non-issues
9.  Acknowledgements
10.  Requirements notation
11.  Security Considerations
12.  References
12.1  Normative References
12.2  Informative References
§  Author's Address
§  Intellectual Property and Copyright Statements

1. Introduction

When DNSSEC signatures are validated the validators will follow a chain of authority from a pre-configured trust anchor to the data that is to be validated. The DNSSEC protocol[dnssecbis-protocol], DNSSECbis Protocol Definitions, Some Month 2004. clearly describes how these chains of trust are to be established but does not address the issue of the distribution of the trust anchors.

This document describes how an X.509 based public key infrastructure can be used to bootstrap the configuratation of a set of trust anchors. SEP keys are stored in certificates that are signed by the registries' Certificate Authorities. The system allows registries to indicate levels of trust which allows for prudent cross-signing.

The Certificate Authority and the certificates are discussed in Section 2Island CAs and Section 3Key Signing. Section 4Publication of Certificates and Section 5Location of Island Publication URL describe how the certificates are published. Section 6Use of Certificates describes how the certificates are used to establish the trust-anchors.

In this document the term secure entry point (SEP) key is used to describe the (sub)set of public key(s) that is intended as a secure entry point into the zone [RFC3757]. The term Island of security, or island for short, is used for a zone for which one of the SEP keys are used as a trust-anchor and which is therefore the start of a chain of authority.

2. Island CAs

The root of each island will publish an X.509 CA certificate. This will be a long-term, self-signed certificate, known as the Island Root CA (IRCA). This CA will then be used to create two subsidiary CAs, each with a shorter expiry, known as the High Assurance Island CA and the Low Assurance Island CA.

Each island will have a set of requirements for cross-signing, one for low assurance and one for high assurance. The reason for having two is to allow cross-signing of keys that the island's operators do not have high confidence in without exposing them to accusations of insufficient prudence.

3. Key Signing

Each island will issue a certificate signed by the Island Root CA for each of its own SEPs.

For each other island that meets the island's requirements for cross-signing, the island will issue certificates for their SEPs signed by either the Low or High Assurance Island CA, as appropriate.

Each certificate issued will contain an X.509v3 extension with the name of the domain associated with the signed public key.

Optionally, an IRCA or one of its subsidiaries might also sign the public key of the IRCA of other islands - this would require a high degree of trust, though. It also steps beyond the bounds of what can be easily done with standard X.509.

4. Publication of Certificates

Each island will maintain a URL (known as the Island Publication URL or IPU) where all current certificates issued by any of its CAs are available. This URL may also have a collection of certificates issued by other island CAs and also the CA certificates themselves of other islands. Note, however, that the presence of a certificate does not indicate any kind of trust in it - that is done purely by the certificate signatures.

5. Location of Island Publication URL

The location of each IPU will be held in the IRCA using an X.509v3 certificate extension registered for the purpose.

6. Use of Certificates

A resolver wishing to bootstrap its collection of trust anchors need only choose a small set of IRCAs to trust (or, with luck, a single one). Once it has done so, it can extract the IPU from the CA certificate, use HTTP to retrieve the certificate collection available there, check their (chained) signatures, extract the public keys from the certificates and use these as the initial set of SEPs for the domains named in the certificates.

Once the initial set of certificates has been retrieved, this process can be followed recursively for other IRCAs retrieved. Also, the set of trusted IRCAs could be expanded to include some or all of the retrieved IRCAs.

After the set of trusted trust anchors have been established, in-band mechanisms can be used to keep them up to date. If for some reason the set of trust anchors becomes too stale to update (for example, because the device has been offline for an extended period), then the process can be repeated from the start.

7. Variations

Instead of a URL, the certificate could contain a domain name and socket number.

8. Security Non-issues

Note that DNSSEC is not required to secure the domain names used for certificate retrieval, since the signature of the selected IRCA(s) will be sufficient to validate the retrieved certificates.

9. Acknowledgements

Thanks to Olaf Kolkman for comments on early drafts.

10. Requirements notation

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]Bradner, S., Key words for use in RFCs to Indicate Requirement Levels, March 1997..

11. Security Considerations

12. References

12.1 Normative References

12.2 Informative References

Author's Address

Intellectual Property Statement

The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79.

Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr.

The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org.

Disclaimer of Validity

This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Copyright Statement

Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.

Acknowledgment

Funding for the RFC Editor function is currently provided by the Internet Society.