< draft-blacka-dnssec-opt-in-00.txt		draft-blacka-dnssec-opt-in-01.txt >
	DNSEXT R. Arends		DNSEXT R. Arends
	Internet-Draft Telematica Instituut		Internet-Draft Telematica Instituut
	Expires: April 13, 2004 M. Kosters		Expires: June 22, 2005 M. Kosters
	D. Blacka		D. Blacka
	Verisign, Inc.		Verisign, Inc.
	October 14, 2003		December 22, 2004
	DNSSEC Opt-In		DNSSEC Opt-In
	draft-blacka-dnssec-opt-in-00		draft-blacka-dnssec-opt-in-01
	Status of this Memo		Status of this Memo
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	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2003). All Rights Reserved.		Copyright (C) The Internet Society (2004).
	Abstract		Abstract
	In DNSSEC (RFC 2535bis, [3], [4], and [5]), delegations to unsigned		In DNSSEC (RFC 2535bis, [3], [4], and [5]), delegations to unsigned
	subzones are cryptographically secured. Maintaining this		subzones are cryptographically secured. Maintaining this
	cryptography is not practical or necessary. This document describes		cryptography is not practical or necessary. This document describes
	an experimental "Opt-In" model that allows administrators to omit		an experimental "Opt-In" model that allows administrators to omit
	this cryptography and manage the cost of adopting DNSSEC with large		this cryptography and manage the cost of adopting DNSSEC with large
	zones.		zones.
	Table of Contents		Table of Contents
	1. Definitions and Terminology . . . . . . . . . . . . . . . . 3		1. Definitions and Terminology . . . . . . . . . . . . . . . . . 3
	2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	3. Protocol Additions . . . . . . . . . . . . . . . . . . . . . 5		3. Experimental Status . . . . . . . . . . . . . . . . . . . . . 5
	3.1 Server Considerations . . . . . . . . . . . . . . . . . . . 6		4. Protocol Additions . . . . . . . . . . . . . . . . . . . . . . 6
	3.1.1 Delegations Only . . . . . . . . . . . . . . . . . . . . . . 6		4.1 Server Considerations . . . . . . . . . . . . . . . . . . 7
	3.1.2 Insecure Delegation Responses . . . . . . . . . . . . . . . 6		4.1.1 Delegations Only . . . . . . . . . . . . . . . . . . . 7
	3.1.3 Wildcards and Opt-In . . . . . . . . . . . . . . . . . . . . 6		4.1.2 Insecure Delegation Responses . . . . . . . . . . . . 7
	3.1.4 Dynamic Update . . . . . . . . . . . . . . . . . . . . . . . 7		4.1.3 Wildcards and Opt-In . . . . . . . . . . . . . . . . . 7
	3.2 Client Considerations . . . . . . . . . . . . . . . . . . . 7		4.1.4 Dynamic Update . . . . . . . . . . . . . . . . . . . . 8
	3.2.1 Delegations Only . . . . . . . . . . . . . . . . . . . . . . 7		4.2 Client Considerations . . . . . . . . . . . . . . . . . . 8
	3.2.2 Validation Process Changes . . . . . . . . . . . . . . . . . 7		4.2.1 Delegations Only . . . . . . . . . . . . . . . . . . . 8
	3.2.3 NSEC Record Caching . . . . . . . . . . . . . . . . . . . . 8		4.2.2 Validation Process Changes . . . . . . . . . . . . . . 8
	3.2.4 Use of the AD bit . . . . . . . . . . . . . . . . . . . . . 8		4.2.3 NSEC Record Caching . . . . . . . . . . . . . . . . . 9
	4. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 10		4.2.4 Use of the AD bit . . . . . . . . . . . . . . . . . . 9
	5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . 11		5. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
	6. Transition Issues . . . . . . . . . . . . . . . . . . . . . 13		6. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
	7. Security Considerations . . . . . . . . . . . . . . . . . . 14		7. Transition Issues . . . . . . . . . . . . . . . . . . . . . . 13
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 16		8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
	9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 17		9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
	Normative References . . . . . . . . . . . . . . . . . . . . 18		10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 17
	Informative References . . . . . . . . . . . . . . . . . . . 19		11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 19		11.1 Normative References . . . . . . . . . . . . . . . . . . . . 18
	A. Implementing Opt-In using "Views" . . . . . . . . . . . . . 21		11.2 Informative References . . . . . . . . . . . . . . . . . . . 18
	Intellectual Property and Copyright Statements . . . . . . . 23		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 19
			A. Implementing Opt-In using "Views" . . . . . . . . . . . . . . 20
			Intellectual Property and Copyright Statements . . . . . . . . 21
	1. Definitions and Terminology		1. Definitions and Terminology
	Throughout this document, familiarity with the DNS system (RFC 1035		Throughout this document, familiarity with the DNS system (RFC 1035
	[1]), DNS security extensions ([3], [4], and [5], referred to in this		[1]), DNS security extensions ([3], [4], and [5], referred to in this
	document as "RFC 2535bis"), and DNSSEC terminology (RFC 3090 [9]) is		document as "RFC 2535bis"), and DNSSEC terminology (RFC 3090 [10]) is
	assumed.		assumed.
	The following abbreviations and terms are used in this document:		The following abbreviations and terms are used in this document:
	RR: is used to refer to a DNS resource record.		RR: is used to refer to a DNS resource record.
			RRset: refers to a Resource Record Set, as defined by [8]. In this
	RRset: refers to a Resource Record Set, as defined by [7]. In this
	document, the RRset is also defined to include the covering RRSIG		document, the RRset is also defined to include the covering RRSIG
	records, if any exist.		records, if any exist.
	signed name: refers to a DNS name that has, at minimum, a (signed)		signed name: refers to a DNS name that has, at minimum, a (signed)
	NSEC record.		NSEC record.
	unsigned name: refers to a DNS name that does not (at least) have a		unsigned name: refers to a DNS name that does not (at least) have a
	NSEC record.		NSEC record.
	covering NSEC record/RRset: is the NSEC record used to prove		covering NSEC record/RRset: is the NSEC record used to prove
	(non)existence of a particular name or RRset. This means that for		(non)existence of a particular name or RRset. This means that for
	a RRset or name 'N', the covering NSEC record has the name 'N', or		a RRset or name 'N', the covering NSEC record has the name 'N', or
	has an owner name less than 'N' and "next" name greater than 'N'.		has an owner name less than 'N' and "next" name greater than 'N'.
	delegation: refers to a NS RRset with a name different from the		delegation: refers to a NS RRset with a name different from the
	current zone apex (non-zone-apex), signifying a delegation to a		current zone apex (non-zone-apex), signifying a delegation to a
	subzone.		subzone.
	secure delegation: refers to a signed name containing a delegation		secure delegation: refers to a signed name containing a delegation
	(NS RRset), and a signed DS RRset, signifying a delegation to a		(NS RRset), and a signed DS RRset, signifying a delegation to a
	signed subzone.		signed subzone.
	insecure delegation: refers to a signed name containing a delegation		insecure delegation: refers to a signed name containing a delegation
	(NS RRset), but lacking a DS RRset, signifying a delegation to an		(NS RRset), but lacking a DS RRset, signifying a delegation to an
	unsigned subzone.		unsigned subzone.
	Opt-In insecure delegation: refers to an unsigned name containing		Opt-In insecure delegation: refers to an unsigned name containing
	only a delegation NS RRset. The covering NSEC record uses the		only a delegation NS RRset. The covering NSEC record uses the
	Opt-In methodology described in this document.		Opt-In methodology described in this document.
	The key words "MUST, "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST, "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY, and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY, and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [6].		document are to be interpreted as described in RFC 2119 [7].
	2. Overview		2. Overview
	The cost to cryptographically secure delegations to unsigned zones is		The cost to cryptographically secure delegations to unsigned zones is
	high for large delegation-centric zones and zones where insecure		high for large delegation-centric zones and zones where insecure
	delegations will be updated rapidly. For these zones, the costs of		delegations will be updated rapidly. For these zones, the costs of
	maintaining the NSEC record chain may be extremely high relative to		maintaining the NSEC record chain may be extremely high relative to
	the gain of cryptographically authenticating existence of unsecured		the gain of cryptographically authenticating existence of unsecured
	zones.		zones.
	This document describes an experimental method of eliminating the		This document describes an experimental method of eliminating the
	superfluous cryptography present in secure delegations to unsigned		superfluous cryptography present in secure delegations to unsigned
	zones. Using "Opt-In", a zone administrator can choose to remove		zones. Using "Opt-In", a zone administrator can choose to remove
	insecure delegations from the NSEC chain. This is accomplished by		insecure delegations from the NSEC chain. This is accomplished by
	extending the semantics of the NSEC record by using a redundant bit		extending the semantics of the NSEC record by using a redundant bit
	in the type map.		in the type map.
	3. Protocol Additions		3. Experimental Status
			This document describes an EXPERIMENTAL extension to DNSSEC. It
			interoperates with non-experimental DNSSEC using the technique
			described in [6]. This experiment is identified with the following
			private algorithms (using algorithm 253):
			"3.optin.verisignlabs.com": is an alias for DNSSEC algorithm 3, DSA,
			and
			"4.optin.verisignlabs.com": is an alias for DNSSEC algorithm 5,
			RSASHA1.
			Servers wishing to sign and serve zones that utilize Opt-In MUST sign
			the zone with one or more of these private algorithms. This requires
			the signing tools and servers to support private algorithms, as well
			as Opt-In.
			Resolvers wishing to validate Opt-In zones MUST only do so when the
			zone is signed useing one or more of these private algorithms.
			The remainder of this document assumes that the servers and resolvers
			involved are aware of and are involved in this experiment.
			4. Protocol Additions
	In RFC 2535bis, delegation NS RRsets are not signed, but are instead		In RFC 2535bis, delegation NS RRsets are not signed, but are instead
	accompanied by a NSEC RRset of the same name and a DS record. The		accompanied by a NSEC RRset of the same name and a DS record. The
	security status of the subzone is determined by the presence or		security status of the subzone is determined by the presence or
	absence of the DS RRset, cryptographically proven by the NSEC record.		absence of the DS RRset, cryptographically proven by the NSEC record.
	Opt-In expands this definition by allowing insecure delegations to		Opt-In expands this definition by allowing insecure delegations to
	exist within an otherwise signed zone without the corresponding NSEC		exist within an otherwise signed zone without the corresponding NSEC
	record at the delegation's owner name. These insecure delegations		record at the delegation's owner name. These insecure delegations
	are proven insecure by using a covering NSEC record.		are proven insecure by using a covering NSEC record.
	skipping to change at page 5, line 49 ¶		skipping to change at page 6, line 49 ¶
	Opt-In, there MUST NOT be any insecure delegations (or any other		Opt-In, there MUST NOT be any insecure delegations (or any other
	records) between it and the RRsets indicated by the 'next domain		records) between it and the RRsets indicated by the 'next domain
	name' in the NSEC RDATA. If it is Opt-In, there MUST only be		name' in the NSEC RDATA. If it is Opt-In, there MUST only be
	insecure delegations between it and the next node indicated by the		insecure delegations between it and the next node indicated by the
	'next domain name' in the NSEC RDATA.		'next domain name' in the NSEC RDATA.
	In summary,		In summary,
	o An Opt-In NSEC type is identified by a zero-valued (or		o An Opt-In NSEC type is identified by a zero-valued (or
	not-specified) NSEC bit in the type bit map of the NSEC record.		not-specified) NSEC bit in the type bit map of the NSEC record.
	o A RFC2535bis NSEC type is identified by a one-valued NSEC bit in		o A RFC2535bis NSEC type is identified by a one-valued NSEC bit in
	the type bit map of the NSEC record.		the type bit map of the NSEC record.
	and,		and,
	o An Opt-In NSEC record does not assert the non-existence of a name		o An Opt-In NSEC record does not assert the non-existence of a name
	between its owner name and "next" name, although it does assert		between its owner name and "next" name, although it does assert
	that any name in this span MUST be an insecure delegation.		that any name in this span MUST be an insecure delegation.
	o An Opt-In NSEC record does assert the (non)existence of RRsets		o An Opt-In NSEC record does assert the (non)existence of RRsets
	with the same owner name.		with the same owner name.
	3.1 Server Considerations		4.1 Server Considerations
	Opt-In imposes some new requirements on authoritative DNS servers.		Opt-In imposes some new requirements on authoritative DNS servers.
	3.1.1 Delegations Only		4.1.1 Delegations Only
	This specification dictates that only insecure delegations may exist		This specification dictates that only insecure delegations may exist
	between the owner and "next" names of an Opt-In tagged NSEC record.		between the owner and "next" names of an Opt-In tagged NSEC record.
	Signing tools SHOULD NOT generate signed zones that violate this		Signing tools SHOULD NOT generate signed zones that violate this
	restriction. Servers SHOULD refuse to load and/or serve zones that		restriction. Servers SHOULD refuse to load and/or serve zones that
	violate this restriction.		violate this restriction.
	3.1.2 Insecure Delegation Responses		4.1.2 Insecure Delegation Responses
	When returning an Opt-In insecure delegation, the server MUST return		When returning an Opt-In insecure delegation, the server MUST return
	the covering NSEC RRset in the Authority section.		the covering NSEC RRset in the Authority section.
	In RFC 2535bis, NSEC records already must be returned along with the		In RFC 2535bis, NSEC records already must be returned along with the
	insecure delegation. The primary difference that this proposal		insecure delegation. The primary difference that this proposal
	introduces is that the Opt-In tagged NSEC record will have a		introduces is that the Opt-In tagged NSEC record will have a
	different owner name from the delegation RRset. This may require		different owner name from the delegation RRset. This may require
	implementations to do a NSEC search on cached responses.		implementations to do a NSEC search on cached responses.
	3.1.3 Wildcards and Opt-In		4.1.3 Wildcards and Opt-In
	RFC 2535bis describes the practice of returning NSEC records to prove		RFC 2535bis describes the practice of returning NSEC records to prove
	the non-existence of an applicable wildcard in non-existent name		the non-existence of an applicable wildcard in non-existent name
	responses. This NSEC record can be described as a "negative wildcard		responses. This NSEC record can be described as a "negative wildcard
	proof". The use of Opt-In NSEC records changes the necessity for		proof". The use of Opt-In NSEC records changes the necessity for
	this practice. For non-existent name responses when the query name		this practice. For non-existent name responses when the query name
	(qname) is covered by an Opt-In tagged NSEC record, servers MAY		(qname) is covered by an Opt-In tagged NSEC record, servers MAY
	choose to omit the wildcard proof record, and clients MUST NOT treat		choose to omit the wildcard proof record, and clients MUST NOT treat
	the absence of this NSEC record as a validation error.		the absence of this NSEC record as a validation error.
	The intent of the RFC 2535bis negative wildcard proof requirement is		The intent of the RFC 2535bis negative wildcard proof requirement is
	to prevent malicious users from undetectably removing valid wildcard		to prevent malicious users from undetectably removing valid wildcard
	responses. In order for this cryptographic proof to work, the		responses. In order for this cryptographic proof to work, the
	resolver must be able to prove:		resolver must be able to prove:
	1. The exact qname does not exist. This is done by the "normal"		1. The exact qname does not exist. This is done by the "normal"
	skipping to change at page 7, line 29 ¶		skipping to change at page 8, line 26 ¶
	of an Opt-In insecure delegation response for a similar reason: the		of an Opt-In insecure delegation response for a similar reason: the
	resolver cannot prove that the qname does or does not exist, and		resolver cannot prove that the qname does or does not exist, and
	therefore cannot prove that a wildcard expansion is valid.		therefore cannot prove that a wildcard expansion is valid.
	The presence of an Opt-In tagged NSEC record does not change the		The presence of an Opt-In tagged NSEC record does not change the
	practice of returning a NSEC along with a wildcard expansion. Even		practice of returning a NSEC along with a wildcard expansion. Even
	though the Opt-In NSEC will not be able to prove that the wildcard		though the Opt-In NSEC will not be able to prove that the wildcard
	expansion is valid, it will prove that the wildcard expansion is not		expansion is valid, it will prove that the wildcard expansion is not
	masking any signed records.		masking any signed records.
	3.1.4 Dynamic Update		4.1.4 Dynamic Update
	Opt-In changes the semantics of Secure DNS Dynamic Update [8]. In		Opt-In changes the semantics of Secure DNS Dynamic Update [9]. In
	particular, it introduces the need for rules that describe when to		particular, it introduces the need for rules that describe when to
	add or remove a delegation name from the NSEC chain. This document		add or remove a delegation name from the NSEC chain. This document
	does not attempt to define these rules. Until these rules are		does not attempt to define these rules. Until these rules are
	defined, servers MUST NOT process DNS Dynamic Update requests against		defined, servers MUST NOT process DNS Dynamic Update requests against
	zones that use Opt-In NSEC records.		zones that use Opt-In NSEC records.
	3.2 Client Considerations		4.2 Client Considerations
	Opt-In imposes some new requirements on security-aware resolvers		Opt-In imposes some new requirements on security-aware resolvers
	(caching or otherwise).		(caching or otherwise).
	3.2.1 Delegations Only		4.2.1 Delegations Only
	As stated in the "Server Considerations" section above, this		As stated in the "Server Considerations" section above, this
	specification restricts the namespace covered by Opt-In tagged NSEC		specification restricts the namespace covered by Opt-In tagged NSEC
	records to insecure delegations only. Thus, resolvers MUST reject as		records to insecure delegations only. Thus, resolvers MUST reject as
	invalid any records that fall within an Opt-In NSEC record's span		invalid any records that fall within an Opt-In NSEC record's span
	that are not NS records or corresponding glue records.		that are not NS records or corresponding glue records.
	3.2.2 Validation Process Changes		4.2.2 Validation Process Changes
	This specification does not change the resolver's resolution		This specification does not change the resolver's resolution
	algorithm. However, it does change the DNSSEC validation process.		algorithm. However, it does change the DNSSEC validation process.
	Resolvers MUST be able to use Opt-In tagged NSEC records to		Resolvers MUST be able to use Opt-In tagged NSEC records to
	cryptographically prove the validity and security status (as		cryptographically prove the validity and security status (as
	insecure) of a referral. Resolvers determine the security status of		insecure) of a referral. Resolvers determine the security status of
	the referred-to zone as follows:		the referred-to zone as follows:
	o In RFC 2535bis, the security status is proven by the existence or		o In RFC 2535bis, the security status is proven by the existence or
	absence of a DS RRset at the same name as the delegation. The		absence of a DS RRset at the same name as the delegation. The
	existence of the DS RRset indicates that the referred-to zone is		existence of the DS RRset indicates that the referred-to zone is
	signed. The absence of the DS RRset is proven using a verified		signed. The absence of the DS RRset is proven using a verified
	NSEC record of the same name that does not have the DS bit set in		NSEC record of the same name that does not have the DS bit set in
	the type map. This NSEC record MAY also be tagged as Opt-In.		the type map. This NSEC record MAY also be tagged as Opt-In.
	o Using Opt-In, the security status is proven by the existence of a		o Using Opt-In, the security status is proven by the existence of a
	DS record (for signed) or the presence of a verified Opt-In tagged		DS record (for signed) or the presence of a verified Opt-In tagged
	NSEC record that covers the delegation name. That is, the NSEC		NSEC record that covers the delegation name. That is, the NSEC
	record does not have the NSEC bit set in the type map, and the		record does not have the NSEC bit set in the type map, and the
	delegation name falls between the NSEC's owner and "next" name.		delegation name falls between the NSEC's owner and "next" name.
	Using Opt-In does not substantially change the nature of following		Using Opt-In does not substantially change the nature of following
	referrals within DNSSEC. At every delegation point, the resolver		referrals within DNSSEC. At every delegation point, the resolver
	will have cryptographic proof that the subzone is signed or unsigned.		will have cryptographic proof that the subzone is signed or unsigned.
	When receiving either an Opt-In insecure delegation response or a		When receiving either an Opt-In insecure delegation response or a
	non-existent name response where that name is covered by an Opt-In		non-existent name response where that name is covered by an Opt-In
	tagged NSEC record, the resolver MUST NOT require proof (in the form		tagged NSEC record, the resolver MUST NOT require proof (in the form
	of a NSEC record) that a wildcard did not exist.		of a NSEC record) that a wildcard did not exist.
	3.2.3 NSEC Record Caching		4.2.3 NSEC Record Caching
	Caching resolvers MUST be able to retrieve the appropriate covering		Caching resolvers MUST be able to retrieve the appropriate covering
	Opt-In NSEC record when returning referrals that need them. This		Opt-In NSEC record when returning referrals that need them. This
	requirement differs from RFC 2535bis in that the covering NSEC will		requirement differs from RFC 2535bis in that the covering NSEC will
	not have the same owner name as the delegation. Some implementations		not have the same owner name as the delegation. Some implementations
	may have to use new methods for finding these NSEC records.		may have to use new methods for finding these NSEC records.
	3.2.4 Use of the AD bit		4.2.4 Use of the AD bit
	The AD bit, as defined by [2] and [5], MUST NOT be set when:		The AD bit, as defined by [2] and [5], MUST NOT be set when:
	o sending a non-existent name (NXDOMAIN) response where the covering		o sending a non-existent name (NXDOMAIN) response where the covering
	NSEC is tagged as Opt-In.		NSEC is tagged as Opt-In.
	o sending an Opt-In insecure delegation response, unless the		o sending an Opt-In insecure delegation response, unless the
	covering (Opt-In) NSEC record's owner name equals the delegation		covering (Opt-In) NSEC record's owner name equals the delegation
	name.		name.
	This rule is based on what the Opt-In NSEC record actually proves:		This rule is based on what the Opt-In NSEC record actually proves:
	for names that exist between the Opt-In NSEC record's owner and		for names that exist between the Opt-In NSEC record's owner and
	"next" names, the Opt-In NSEC record cannot prove the non-existence		"next" names, the Opt-In NSEC record cannot prove the non-existence
	or existence of the name. As such, not all data in the response has		or existence of the name. As such, not all data in the response has
	been cryptographically verified, so the AD bit cannot be set.		been cryptographically verified, so the AD bit cannot be set.
	4. Benefits		5. Benefits
	Using Opt-In allows administrators of large and/or changing		Using Opt-In allows administrators of large and/or changing
	delegation-centric zones to minimize the overhead involved in		delegation-centric zones to minimize the overhead involved in
	maintaining the security of the zone.		maintaining the security of the zone.
	Opt-In accomplishes this by eliminating the need for NSEC records for		Opt-In accomplishes this by eliminating the need for NSEC records for
	insecure delegations. This, in a zone with a large number of		insecure delegations. This, in a zone with a large number of
	delegations to unsigned subzones, can lead to substantial space		delegations to unsigned subzones, can lead to substantial space
	savings (both in memory and on disk). Additionally, Opt-In allows for		savings (both in memory and on disk). Additionally, Opt-In allows
	the addition or removal of insecure delegations without modifying the		for the addition or removal of insecure delegations without modifying
	NSEC record chain. Zones that are frequently updating insecure		the NSEC record chain. Zones that are frequently updating insecure
	delegations (e.g., TLDs) can avoid the substantial overhead of		delegations (e.g., TLDs) can avoid the substantial overhead of
	modifying and resigning the affected NSEC records.		modifying and resigning the affected NSEC records.
	5. Example		6. Example
	Consider the zone EXAMPLE, shown below. This is a zone where all of		Consider the zone EXAMPLE, shown below. This is a zone where all of
	the NSEC records are tagged as Opt-In.		the NSEC records are tagged as Opt-In.
	Example A: Fully Opt-In Zone.		Example A: Fully Opt-In Zone.
	EXAMPLE. SOA ...		EXAMPLE. SOA ...
	EXAMPLE. RRSIG SOA ...		EXAMPLE. RRSIG SOA ...
	EXAMPLE. NS FIRST-SECURE.EXAMPLE.		EXAMPLE. NS FIRST-SECURE.EXAMPLE.
	EXAMPLE. RRSIG NS ...		EXAMPLE. RRSIG NS ...
	skipping to change at page 12, line 9 ¶		skipping to change at page 12, line 9 ¶
	A query for a nonexistent RRset will result in a response that		A query for a nonexistent RRset will result in a response that
	differs from RFC 2535bis by: the NSEC record will be tagged as		differs from RFC 2535bis by: the NSEC record will be tagged as
	Opt-In, there may be no NSEC record proving the non-existence of a		Opt-In, there may be no NSEC record proving the non-existence of a
	matching wildcard record, and the AD bit will not be set.		matching wildcard record, and the AD bit will not be set.
	A query for an insecure delegation RRset (or a referral) will return		A query for an insecure delegation RRset (or a referral) will return
	both the answer (in the Authority section) and the corresponding		both the answer (in the Authority section) and the corresponding
	Opt-In NSEC record to prove that it is not secure.		Opt-In NSEC record to prove that it is not secure.
	Example A.1: Response to query for WWW.UNSIGNED.EXAMPLE. A		Example A.1: Response to query for WWW.UNSIGNED.EXAMPLE. A
	RCODE=NOERROR, AD=0		RCODE=NOERROR, AD=0
	Answer Section:		Answer Section:
	Authority Section:		Authority Section:
	UNSIGNED.EXAMPLE. NS NS.UNSIGNED.EXAMPLE		UNSIGNED.EXAMPLE. NS NS.UNSIGNED.EXAMPLE
	SECOND-SECURE.EXAMPLE. NSEC EXAMPLE. NS RRSIG DS		SECOND-SECURE.EXAMPLE. NSEC EXAMPLE. NS RRSIG DS
	SECOND-SECURE.EXAMPLE. RRSIG NSEC ...		SECOND-SECURE.EXAMPLE. RRSIG NSEC ...
	Additional Section:		Additional Section:
	NS.UNSIGNED.EXAMPLE. A ...		NS.UNSIGNED.EXAMPLE. A ...
	In the Example A.1 zone, the EXAMPLE. node MAY use either style of		In the Example A.1 zone, the EXAMPLE. node MAY use either style of
	NSEC record, because there are no insecure delegations that occur		NSEC record, because there are no insecure delegations that occur
	between it and the next node, FIRST-SECURE.EXAMPLE. In other words,		between it and the next node, FIRST-SECURE.EXAMPLE. In other words,
	Example A would still be a valid zone if the NSEC record for EXAMPLE.		Example A would still be a valid zone if the NSEC record for EXAMPLE.
	was changed to the following RR:		was changed to the following RR:
	EXAMPLE. NSEC FIRST-SECURE.EXAMPLE. (SOA NS		EXAMPLE. NSEC FIRST-SECURE.EXAMPLE. (SOA NS
	RRSIG DNSKEY NSEC )		RRSIG DNSKEY NSEC )
	However, the other NSEC records (FIRST-SECURE.EXAMPLE. and		However, the other NSEC records (FIRST-SECURE.EXAMPLE. and
	SECOND-SECURE.EXAMPLE.) MUST be tagged as Opt-In because there are		SECOND-SECURE.EXAMPLE.) MUST be tagged as Opt-In because there are
	insecure delegations in the range they define. (NOT-SECURE.EXAMPLE.		insecure delegations in the range they define. (NOT-SECURE.EXAMPLE.
	and UNSIGNED.EXAMPLE., respectively).		and UNSIGNED.EXAMPLE., respectively).
	NOT-SECURE-2.EXAMPLE. is an example of an insecure delegation that is		NOT-SECURE-2.EXAMPLE. is an example of an insecure delegation that
	part of the NSEC chain and also covered by an Opt-In tagged NSEC		is part of the NSEC chain and also covered by an Opt-In tagged NSEC
	record. Because NOT-SECURE-2.EXAMPLE. is a signed name, it cannot be		record. Because NOT-SECURE-2.EXAMPLE. is a signed name, it cannot
	removed from the zone without modifying and resigning the prior NSEC		be removed from the zone without modifying and resigning the prior
	record. Delegations with names that fall between		NSEC record. Delegations with names that fall between
	NOT-SECURE-2.EXAMPLE. and SECOND-SECURE.EXAMPLE. may be added or		NOT-SECURE-2.EXAMPLE. and SECOND-SECURE.EXAMPLE. may be added or
	removed without resigning any NSEC records.		removed without resigning any NSEC records.
	6. Transition Issues		7. Transition Issues
	Opt-In is not backwards compatible with RFC 2535bis. RFC 2535bis		Opt-In is not backwards compatible with RFC 2535bis. RFC 2535bis
	compliant DNSSEC implementations will not recognize Opt-In tagged		compliant DNSSEC implementations will not recognize Opt-In tagged
	NSEC records as different from RFC 2535bis NSEC records. Because of		NSEC records as different from RFC 2535bis NSEC records. Because of
	this, RFC 2535bis implementations will reject all Opt-In insecure		this, RFC 2535bis implementations will reject all Opt-In insecure
	delegations within a zone as invalid.		delegations within a zone as invalid.
	7. Security Considerations		8. Security Considerations
	Opt-In allows for unsigned names, in the form of delegations to		Opt-In allows for unsigned names, in the form of delegations to
	unsigned subzones, to exist within an otherwise signed zone. All		unsigned subzones, to exist within an otherwise signed zone. All
	unsigned names are, by definition, insecure, and their validity or		unsigned names are, by definition, insecure, and their validity or
	existence cannot by cryptographically proven.		existence cannot by cryptographically proven.
	In general:		In general:
	o Records with unsigned names (whether existing or not) suffer from		o Records with unsigned names (whether existing or not) suffer from
	the same vulnerabilities as records in an unsigned zone. These		the same vulnerabilities as records in an unsigned zone. These
	vulnerabilites are described in more detail in [11] (note in		vulnerabilites are described in more detail in [12] (note in
	particular sections 2.3, "Name Games" and 2.6, "Authenticated		particular sections 2.3, "Name Games" and 2.6, "Authenticated
	Denial").		Denial").
	o Records with signed names have the same security whether or not		o Records with signed names have the same security whether or not
	Opt-In is used.		Opt-In is used.
	Note that with or without Opt-In, an insecure delegation may have its		Note that with or without Opt-In, an insecure delegation may have its
	contents undetectably altered by an attacker. Because of this, the		contents undetectably altered by an attacker. Because of this, the
	primary difference in security that Opt-In introduces is the loss of		primary difference in security that Opt-In introduces is the loss of
	the ability to prove the existence or nonexistence of an insecure		the ability to prove the existence or nonexistence of an insecure
	delegation within the span of an Opt-In NSEC record.		delegation within the span of an Opt-In NSEC record.
	In particular, this means that a malicious entity may be able to		In particular, this means that a malicious entity may be able to
	insert or delete records with unsigned names. These records are		insert or delete records with unsigned names. These records are
	normally NS records, but this also includes signed wildcard		normally NS records, but this also includes signed wildcard
	expansions (while the wildcard record itself is signed, its expanded		expansions (while the wildcard record itself is signed, its expanded
	name is an unsigned name).		name is an unsigned name).
	For example, if a resolver received the following response from the		For example, if a resolver received the following response from the
	example zone above:		example zone above:
	Example S.1: Response to query for WWW.DOES-NOT-EXIST.EXAMPLE. A		Example S.1: Response to query for WWW.DOES-NOT-EXIST.EXAMPLE. A
	RCODE=NOERROR		RCODE=NOERROR
	Answer Section:		Answer Section:
	Authority Section:		Authority Section:
	DOES-NOT-EXIST.EXAMPLE. NS NS.FORGED.		DOES-NOT-EXIST.EXAMPLE. NS NS.FORGED.
	EXAMPLE. NSEC FIRST-SECURE.EXAMPLE. SOA NS \		EXAMPLE. NSEC FIRST-SECURE.EXAMPLE. SOA NS \
	RRSIG DNSKEY		RRSIG DNSKEY
	EXAMPLE. RRSIG NSEC ...		EXAMPLE. RRSIG NSEC ...
	Additional Section:		Additional Section:
	The resolver would have no choice but to believe that the referral to		The resolver would have no choice but to believe that the referral to
	NS.FORGED. is valid. If a wildcard existed that would have been		NS.FORGED. is valid. If a wildcard existed that would have been
	expanded to cover "WWW.DOES-NOT-EXIST.EXAMPLE.", an attacker could		expanded to cover "WWW.DOES-NOT-EXIST.EXAMPLE.", an attacker could
	have undetectably removed it and replaced it with the forged		have undetectably removed it and replaced it with the forged
	delegation.		delegation.
	Note that being able to add a delegation is functionally equivalent		Note that being able to add a delegation is functionally equivalent
	to being able to add any record type: an attacker merely has to forge		to being able to add any record type: an attacker merely has to forge
	a delegation to nameserver under his/her control and place whatever		a delegation to nameserver under his/her control and place whatever
	records needed at the subzone apex.		records needed at the subzone apex.
	While in particular cases, this issue may not present a significant		While in particular cases, this issue may not present a significant
	security problem, in general it should not be lightly dismissed.		security problem, in general it should not be lightly dismissed.
	Therefore, it is strongly RECOMMENDED that Opt-In be used sparingly.		Therefore, it is strongly RECOMMENDED that Opt-In be used sparingly.
	In particular, zone signing tools SHOULD NOT default to Opt-In, and		In particular, zone signing tools SHOULD NOT default to Opt-In, and
	MAY choose to not support Opt-In at all.		MAY choose to not support Opt-In at all.
	8. IANA Considerations		9. IANA Considerations
	None.		None.
	9. Acknowledgments		10. Acknowledgments
	The contributions, suggestions and remarks of the following persons		The contributions, suggestions and remarks of the following persons
	(in alphabetic order) to this draft are acknowledged:		(in alphabetic order) to this draft are acknowledged:
	Mats Dufberg, Miek Gieben, Olafur Gudmundsson, Bob Halley, Olaf		Mats Dufberg, Miek Gieben, Olafur Gudmundsson, Bob Halley, Olaf
	Kolkman, Edward Lewis, Ted Lindgreen, Rip Loomis, Bill Manning,		Kolkman, Edward Lewis, Ted Lindgreen, Rip Loomis, Bill Manning,
	Dan Massey, Scott Rose, Mike Schiraldi, Jakob Schlyter, Brian		Dan Massey, Scott Rose, Mike Schiraldi, Jakob Schlyter, Brian
	Wellington.		Wellington.
	Normative References		11. References
			11.1 Normative References
	[1] Mockapetris, P., "Domain names - implementation and		[1] Mockapetris, P., "Domain names - implementation and
	specification", STD 13, RFC 1035, November 1987.		specification", STD 13, RFC 1035, November 1987.
	[2] Gudmundsson, O. and B. Wellington, "Redefinition of DNS AD bit",		[2] Wellington, B. and O. Gudmundsson, "Redefinition of DNS
	draft-ietf-dnsext-ad-is-secure-06 (work in progress), June 2002.		Authenticated Data (AD) bit", RFC 3655, November 2003.
	[3] Massey, D., Larson, M., Austein, R., Rose, S. and R. Arends,		[3] Arends, R., Austein, R., Massey, D., Larson, M. and S. Rose,
	"DNS Security Introduction and Requirements",		"DNS Security Introduction and Requirements",
	draft-ietf-dnsext-dnssec-intro-05 (work in progress), February		draft-ietf-dnsext-dnssec-intro-13 (work in progress), October
	2003.		2004.
	[4] Arends, R., "Resource Records for DNS Security Extensions",		[4] Arends, R., "Resource Records for the DNS Security Extensions",
	draft-ietf-dnsext-dnssec-records-02 (work in progress), November		draft-ietf-dnsext-dnssec-records-11 (work in progress), October
	2002.		2004.
	[5] Arends, R., "Protocol Modifications for the DNS Security		[5] Arends, R., "Protocol Modifications for the DNS Security
	Extensions", draft-ietf-dnsext-dnssec-protocol-00 (work in		Extensions", draft-ietf-dnsext-dnssec-protocol-09 (work in
	progress), October 2002.		progress), October 2004.
	Informative References		[6] Blacka, D., "DNSSEC Experiments",
			draft-blacka-dnssec-experiments-00 (work in progress), December
			2004.
	[6] Bradner, S., "Key words for use in RFCs to Indicate Requirement		11.2 Informative References
			[7] Bradner, S., "Key words for use in RFCs to Indicate Requirement
	Levels", BCP 14, RFC 2119, March 1997.		Levels", BCP 14, RFC 2119, March 1997.
	[7] Elz, R. and R. Bush, "Clarifications to the DNS Specification",		[8] Elz, R. and R. Bush, "Clarifications to the DNS Specification",
	RFC 2181, July 1997.		RFC 2181, July 1997.
	[8] Eastlake, D., "Secure Domain Name System Dynamic Update", RFC		[9] Eastlake, D., "Secure Domain Name System Dynamic Update", RFC
	2137, April 1997.		2137, April 1997.
	[9] Lewis, E., "DNS Security Extension Clarification on Zone		[10] Lewis, E., "DNS Security Extension Clarification on Zone
	Status", RFC 3090, March 2001.		Status", RFC 3090, March 2001.
	[10] Conrad, D., "Indicating Resolver Support of DNSSEC", RFC 3225,		[11] Conrad, D., "Indicating Resolver Support of DNSSEC", RFC 3225,
	December 2001.		December 2001.
	[11] Atkins, D. and R. Austein, "Threat Analysis Of The Domain Name		[12] Atkins, D. and R. Austein, "Threat Analysis of the Domain Name
	System", draft-ietf-dnsext-dns-threats-02 (work in progress),		System (DNS)", RFC 3833, August 2004.
	November 2002.
	Authors' Addresses		Authors' Addresses
	Roy Arends		Roy Arends
	Telematica Instituut		Telematica Instituut
	Drienerlolaan 5		Drienerlolaan 5
	7522 NB Enschede		7522 NB Enschede
	NL		NL
	EMail: roy.arends@telin.nl		EMail: roy.arends@telin.nl
	skipping to change at page 20, line 4 ¶		skipping to change at page 19, line 24 ¶
	Mark Kosters		Mark Kosters
	Verisign, Inc.		Verisign, Inc.
	21355 Ridgetop Circle		21355 Ridgetop Circle
	Dulles, VA 20166		Dulles, VA 20166
	US		US
	Phone: +1 703 948 3200		Phone: +1 703 948 3200
	EMail: markk@verisign.com		EMail: markk@verisign.com
	URI: http://www.verisignlabs.com		URI: http://www.verisignlabs.com
	David Blacka		David Blacka
	Verisign, Inc.		Verisign, Inc.
	21355 Ridgetop Circle		21355 Ridgetop Circle
	Dulles, VA 20166		Dulles, VA 20166
	US		US
	Phone: +1 703 948 3200		Phone: +1 703 948 3200
	EMail: davidb@verisign.com		EMail: davidb@verisign.com
	URI: http://www.verisignlabs.com		URI: http://www.verisignlabs.com
	Appendix A. Implementing Opt-In using "Views"		Appendix A. Implementing Opt-In using "Views"
	In many cases, it may be convenient to implement an Opt-In zone by		In many cases, it may be convenient to implement an Opt-In zone by
	combining two separately maintained "views" of a zone at request		combining two separately maintained "views" of a zone at request
	time. In this context, "view" refers to a particular version of a		time. In this context, "view" refers to a particular version of a
	zone, not to any specific DNS implementation feature.		zone, not to any specific DNS implementation feature.
	In this scenario, one view is the secure view, the other is the		In this scenario, one view is the secure view, the other is the
	insecure (or legacy) view. The secure view consists of an entirely		insecure (or legacy) view. The secure view consists of an entirely
	signed zone using Opt-In tagged NSEC records. The insecure view		signed zone using Opt-In tagged NSEC records. The insecure view
	contains no DNSSEC information. It is helpful, although not		contains no DNSSEC information. It is helpful, although not
	necessary, for the secure view to be a subset (minus DNSSEC records)		necessary, for the secure view to be a subset (minus DNSSEC records)
	of the insecure view.		of the insecure view.
	In addition, the only RRsets that may solely exist in the insecure		In addition, the only RRsets that may solely exist in the insecure
	view are non-zone-apex NS RRsets. That is, all non-NS RRsets (and the		view are non-zone-apex NS RRsets. That is, all non-NS RRsets (and
	zone apex NS RRset) MUST be signed and in the secure view.		the zone apex NS RRset) MUST be signed and in the secure view.
	These two views may be combined at request time to provide a virtual,		These two views may be combined at request time to provide a virtual,
	single Opt-In zone. The following algorithm is used when responding		single Opt-In zone. The following algorithm is used when responding
	to each query:		to each query:
	V_A is the secure view as described above.		V_A is the secure view as described above.
	V_B is the insecure view as described above.		V_B is the insecure view as described above.
	R_A is a response generated from V_A, following RFC 2535bis.		R_A is a response generated from V_A, following RFC 2535bis.
	R_B is a response generated from V_B, following DNS resolution as		R_B is a response generated from V_B, following DNS resolution as
	per RFC 1035 [1].		per RFC 1035 [1].
	R_C is the response generated by combining R_A with R_B, as		R_C is the response generated by combining R_A with R_B, as
	described below.		described below.
			A query is DNSSEC-aware if it either has the DO bit [11] turned
	A query is DNSSEC-aware if it either has the DO bit [10] turned
	on, or is for a DNSSEC-specific record type.		on, or is for a DNSSEC-specific record type.
	1. If V_A is a subset of V_B and the query is not DNSSEC-aware,		1. If V_A is a subset of V_B and the query is not DNSSEC-aware,
	generate and return R_B, otherwise		generate and return R_B, otherwise
	2. Generate R_A.		2. Generate R_A.
	3. If R_A's RCODE != NXDOMAIN, return R_A, otherwise		3. If R_A's RCODE != NXDOMAIN, return R_A, otherwise
	4. Generate R_B and combine it with R_A to form R_C:		4. Generate R_B and combine it with R_A to form R_C:
	For each section (ANSWER, AUTHORITY, ADDITIONAL), copy the		For each section (ANSWER, AUTHORITY, ADDITIONAL), copy the
	records from R_A into R_B, EXCEPT the AUTHORITY section SOA		records from R_A into R_B, EXCEPT the AUTHORITY section SOA
	record, if R_B's RCODE = NOERROR.		record, if R_B's RCODE = NOERROR.
	5. Return R_C.		5. Return R_C.
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	Internet Society.		Internet Society.
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