draft-ietf-dnssec-secext-05.txt   draft-ietf-dnssec-secext-06.txt 
DNS Security Working Group Donald E. Eastlake, 3rd DNS Security Working Group Donald E. Eastlake, 3rd
INTERNET-DRAFT CyberCash INTERNET-DRAFT CyberCash
UPDATES RFC 1034, 1035 Charles W. Kaufman UPDATES RFC 1034, 1035 Charles W. Kaufman
Iris Iris
Expires: 15 February 1996 16 August 1995 Expires: 10 April 1996 11 October 1995
Domain Name System Security Extensions Domain Name System Security Extensions
------ ---- ------ -------- ---------- ------ ---- ------ -------- ----------
Status of This Document Status of This Document
This draft, file name draft-ietf-dnssec-secext-05.txt, is intended to This draft, file name draft-ietf-dnssec-secext-06.txt, is intended to
be become a Proposed Standard RFC. Distribution of this document is be become a Proposed Standard RFC. Distribution of this document is
unlimited. Comments should be sent to the DNS Security Working Group unlimited. Comments should be sent to the DNS Security Working Group
mailing list <dns-security@tis.com> or to the authors. mailing list <dns-security@tis.com> or to the authors.
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six Internet-Drafts are draft documents valid for a maximum of six
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order) to this draft are gratefully acknowledged: order) to this draft are gratefully acknowledged:
Madelyn Badger Madelyn Badger
Matt Crawford Matt Crawford
James M. Galvin James M. Galvin
Olafur Gudmundsson Olafur Gudmundsson
Sandy Murphy Sandy Murphy
Masataka Ohta Masataka Ohta
Michael A. Patton Michael A. Patton
Jeffrey I. Schiller Jeffrey I. Schiller
Susan E. Thomson
Table of Contents Table of Contents
Status of This Document....................................1 Status of This Document....................................1
Abstract...................................................2 Abstract...................................................2
Acknowledgements...........................................2 Acknowledgements...........................................2
Table of Contents..........................................3 Table of Contents..........................................3
1. Overview of Contents....................................5 1. Overview of Contents....................................5
2. Overview of the Extensions.............................6 2. Overview of the Extensions.............................6
2.1 Services Not Provided..................................6 2.1 Services Not Provided..................................6
2.2 Key Distribution.......................................6 2.2 Key Distribution.......................................6
2.3 Data Origin Authentication and Integrity...............7 2.3 Data Origin Authentication and Integrity...............7
2.3.1 The SIG Resource Record..............................7 2.3.1 The SIG Resource Record..............................8
2.3.2 Authenticating Name and Type Non-existence...........8 2.3.2 Authenticating Name and Type Non-existence...........8
2.3.3 Special Considerations With Time-to-Live.............8 2.3.3 Special Considerations With Time-to-Live.............8
2.3.4 Special Considerations at Delegation Points..........9 2.3.4 Special Considerations at Delegation Points..........9
2.3.5 Special Considerations with CNAME RRs................9 2.3.5 Special Considerations with CNAME RRs................9
2.3.6 Signers Other Than The Zone..........................9 2.3.6 Signers Other Than The Zone.........................10
2.4 DNS Transaction Authentication........................10 2.4 DNS Transaction Authentication........................10
3. The KEY Resource Record................................11 3. The KEY Resource Record................................11
3.1 KEY RDATA format......................................11 3.1 KEY RDATA format......................................11
3.2 Object Types, DNS Names, and Keys.....................11 3.2 Object Types, DNS Names, and Keys.....................11
3.3 The KEY RR Flag Field.................................12 3.3 The KEY RR Flag Field.................................12
3.4 The Protocol Octet....................................14 3.4 The Protocol Octet....................................14
3.5 The KEY Algorithm Number and the MD5/RSA Algorithm....15 3.5 The KEY Algorithm Number and the MD5/RSA Algorithm....14
3.6 Interaction of Flags, Algorithm, and Protocol Bytes...15 3.6 Interaction of Flags, Algorithm, and Protocol Bytes...15
3.7 KEY RRs in the Construction of Responses..............16 3.7 KEY RRs in the Construction of Responses..............16
3.8 File Representation of KEY RRs........................16 3.8 File Representation of KEY RRs........................16
4. The SIG Resource Record................................18 4. The SIG Resource Record................................18
4.1 SIG RDATA Format......................................18 4.1 SIG RDATA Format......................................18
4.1.1 Signature Data......................................20 4.1.1 Signature Data......................................20
4.1.2 MD5/RSA Algorithm Signature Calculation.............21 4.1.2 MD5/RSA Algorithm Signature Calculation.............21
4.1.3 Zone Transfer (AXFR) SIG............................22 4.1.3 Zone Transfer (AXFR) SIG............................22
4.1.4 Transaction SIGs....................................22 4.1.4 Transaction SIGs....................................22
4.2 SIG RRs in the Construction of Responses..............23 4.2 SIG RRs in the Construction of Responses..............23
4.3 Processing Responses and SIG RRs......................24 4.3 Processing Responses and SIG RRs......................24
4.4 Signature Expiration, TTLs, and Validity..............24 4.4 Signature Expiration, TTLs, and Validity..............25
4.5 File Representation of SIG RRs........................25 4.5 File Representation of SIG RRs........................25
5. Non-existent Names and Types...........................26 5. Non-existent Names and Types...........................27
5.1 The NXT Resource Record...............................26 5.1 The NXT Resource Record...............................27
5.2 NXT RDATA Format......................................27 5.2 NXT RDATA Format......................................28
5.3 Example...............................................27 5.3 Example...............................................28
5.4 Interaction of NXT RRs and Wildcard RRs...............28 5.4 Interaction of NXT RRs and Wildcard RRs...............29
5.5 Blocking NXT Pseudo-Zone Transfers....................29 5.5 Blocking NXT Pseudo-Zone Transfers....................30
5.6 Special Considerations at Delegation Points...........29 5.6 Special Considerations at Delegation Points...........30
6. The AD and CD Bits and How to Resolve Securely.........30
6.1 The AD and CD Header Bits.............................30
6.2 Boot File Format......................................31
6.3 Chaining Through Zones................................32
6.4 Secure Time...........................................33
7. Operational Considerations.............................34 6. The AD and CD Bits and How to Resolve Securely.........31
7.1 Key Size Considerations...............................34 6.1 The AD and CD Header Bits.............................31
7.2 Key Storage...........................................35 6.2 Boot File Format......................................32
7.3 Key Generation........................................35 6.3 Chaining Through Zones................................33
7.4 Key Lifetimes.........................................35 6.4 Secure Time...........................................34
7.5 Signature Lifetime....................................36
7.6 Root..................................................36
8. Conformance............................................37 7. Operational Considerations.............................35
8.1 Server Conformance....................................37 7.1 Key Size Considerations...............................35
8.2 Resolver Conformance..................................37 7.2 Key Storage...........................................36
7.3 Key Generation........................................36
7.4 Key Lifetimes.........................................36
7.5 Signature Lifetime....................................37
7.6 Root..................................................37
9. Security Considerations................................38 8. Conformance............................................38
References................................................38 8.1 Server Conformance....................................38
8.2 Resolver Conformance..................................38
Authors Addresses.........................................39 9. Security Considerations................................39
Expiration and File Name..................................39 References................................................39
Appendix: Base 64 Encoding................................40 Authors Addresses.........................................41
Expiration and File Name..................................41
Appendix: Base 64 Encoding................................42
1. Overview of Contents 1. Overview of Contents
This draft describes extensions of the Domain Name System (DNS) This draft describes extensions of the Domain Name System (DNS)
protocol to support DNS security and public key distribution. It protocol to support DNS security and public key distribution. It
assumes that the reader is familiar with the Domain Name System, assumes that the reader is familiar with the Domain Name System,
particularly as described in RFCs 1034 and 1035. particularly as described in RFCs 1034 and 1035.
Section 2 provides an overview of the extensions and the key Section 2 provides an overview of the extensions and the key
distribution, data origin authentication, and transaction security distribution, data origin authentication, and transaction security
they provide. they provide.
Section 3 discusses the KEY resource record, its structure, use in Section 3 discusses the KEY resource record, its structure, use in
DNS responses, and file representation. These resource records DNS responses, and file representation. These resource records
represent the pubic keys of entities named in the DNS and are used represent the public keys of entities named in the DNS and are used
for key distribution. for key distribution.
Section 4 discusses the SIG digital signature resource record, its Section 4 discusses the SIG digital signature resource record, its
structure, use in DNS responses, and file representation. These structure, use in DNS responses, and file representation. These
resource records are used to authenticate other resource records in resource records are used to authenticate other resource records in
the DNS and optionally to authenticate DNS transactions. the DNS and optionally to authenticate DNS transactions.
Section 5 discusses the NXT resource record and its use in DNS Section 5 discusses the NXT resource record and its use in DNS
responses. The NXT RR permits authenticated denial in the DNS of the responses. The NXT RR permits authenticated denial in the DNS of the
existence of a name or of a particular type for an existing name. existence of a name or of a particular type for an existing name.
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It is part of the design philosophy of the DNS that the data in it is It is part of the design philosophy of the DNS that the data in it is
public and that the DNS gives the same answers to all inquirers. public and that the DNS gives the same answers to all inquirers.
Following this philosophy, no attempt has been made to include any Following this philosophy, no attempt has been made to include any
sort of access control lists or other means to differentiate sort of access control lists or other means to differentiate
inquirers. inquirers.
In addition, no effort has been made to provide for any In addition, no effort has been made to provide for any
confidentiality for queries or responses. (This service may be confidentiality for queries or responses. (This service may be
available via other protocols such as a network level security available via IPSEC. [put refs to IPSEC RFCs here if available])
protocol providing confidentiality.)
2.2 Key Distribution 2.2 Key Distribution
Resource records (RRs) are defined to associate keys with DNS names. Resource records (RRs) are defined to associate keys with DNS names.
This permits the DNS to be used as a general public key distribution This permits the DNS to be used as a general public key distribution
mechanism in support of the data origin authentication and mechanism in support of the data origin authentication and
transaction authentication DNS services as well as other security transaction authentication DNS services as well as other security
services. services.
The syntax of a KEY resource record (RR) is described in Section 3. The syntax of a KEY resource record (RR) is described in Section 3.
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key associated with that entity, and the actual public key key associated with that entity, and the actual public key
parameters. parameters.
Under conditions described in Section 3, security aware DNS servers Under conditions described in Section 3, security aware DNS servers
may automatically attempt to return KEY resources as additional may automatically attempt to return KEY resources as additional
information, along with those resource records actually requested, to information, along with those resource records actually requested, to
minimize the number of queries needed. minimize the number of queries needed.
2.3 Data Origin Authentication and Integrity 2.3 Data Origin Authentication and Integrity
Security is provided by associating with resource records in the DNS Authentication is provided by associating with resource records in
cryptographically generated digital signatures. Commonly, there will the DNS cryptographically generated digital signatures. Commonly,
be a single private key that signs for an entire zone. If a security there will be a single private key that signs for an entire zone. If
aware resolver reliably learns the public key of the zone, it can a security aware resolver reliably learns the public key of the zone,
verify, for any data read from that zone, that it was properly it can verify, for any data read from that zone, that it was properly
authorized and is reasonably current. The expected implementation is authorized and is reasonably current. The expected implementation is
for the zone private key to be kept off-line and used to re-sign all for the zone private key to be kept off-line and used to re-sign all
of the records in the zone periodically. of the records in the zone periodically.
The data origin authentication key belongs to the zone and not to the This data origin authentication key belongs to the zone and not to
servers that store copies of the data. That means compromise of a the servers that store copies of the data. That means compromise of
server or even all servers for a zone will not necessarily affect the a server or even all servers for a zone will not necessarily affect
degree of assurance that a resolver has that the data is genuine. the degree of assurance that a resolver has that it can determine
whether data is genuine.
A resolver can learn the public key of a zone either by reading it A resolver can learn the public key of a zone either by reading it
from DNS or by having it staticly configured. To reliably learn the from DNS or by having it staticly configured. To reliably learn the
public key by reading it from DNS, the key itself must be signed. public key by reading it from DNS, the key itself must be signed.
Thus, to provide a reasonable degree of security, the resolver must Thus, to provide a reasonable degree of security, the resolver must
be configured with at least the public key of one zone that it can be configured with at least the public key of one zone that it can
use to authenticate signatures. From that, it can securely read the use to authenticate signatures. From that, it can securely read the
public keys of other zones if the intervening zones in the DNS tree public keys of other zones if the intervening zones in the DNS tree
are secure. (It is in principle more secure to have the resolver are secure. (It is in principle more secure to have the resolver
manually configured with the public keys of multiple zones, since manually configured with the public keys of multiple zones, since
then the compromise of a single zone would not permit the faking of then the compromise of a single zone would not permit the faking of
information from other zones. It is also more administratively information from other zones. It is also more administratively
cumbersome, however, particularly when public keys change.) cumbersome, however, particularly when public keys change.)
Adding origin authentication and integrity requires no change to the Adding data origin authentication and integrity requires no change to
"on-the-wire" DNS protocol beyond the addition of the signature the "on-the-wire" DNS protocol beyond the addition of the signature
resource types (and, as a practical matter, the key resource type resource types and, as a practical matter, the key resource type
needed for key distribution). This service can be supported by needed for key distribution. This service can be supported by
existing resolver and server implementations so long as they can existing resolver and server implementations so long as they can
support the additional resource types (see Section 8) with the one support the additional resource types (see Section 8) with the one
exception that CNAME referals can not be authenticated if they are exception that CNAME referals can not be authenticated if they are
from non-security aware servers (see Section 2.3.5). from non-security aware servers (see Section 2.3.5).
If signatures are always separately retrieved and verified when If signatures are always separately retrieved and verified when
retrieving the information they authenticate, there will be more retrieving the information they authenticate, there will be more
trips to the server and performance will suffer. To avoid this, trips to the server and performance will suffer. To avoid this,
security aware servers mitigate that degradation by always sending security aware servers mitigate that degradation by always sending
the signature(s) needed. the signature(s) needed.
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2.3.1 The SIG Resource Record 2.3.1 The SIG Resource Record
The syntax of a SIG resource record (signature) is described in The syntax of a SIG resource record (signature) is described in
Section 4. It includes the type of the RR(s) being signed, the name Section 4. It includes the type of the RR(s) being signed, the name
of the signer, the time at which the signature was created, the time of the signer, the time at which the signature was created, the time
it expires (when it is no longer to be believed), its original time it expires (when it is no longer to be believed), its original time
to live (which may be longer than its current time to live but cannot to live (which may be longer than its current time to live but cannot
be shorter), the cryptographic algorithm in use, and the actual be shorter), the cryptographic algorithm in use, and the actual
signature. signature.
Every name in a zone supporting signed data will have associated with Every name in a secured zone will have associated with it at least
it at least one SIG resource record for each resource type under that one SIG resource record for each resource type under that name. A
name. A security aware server supporting the performance enhanced security aware server supporting the performance enhanced version of
version of the DNS protocol security extensions will attempt to the DNS protocol security extensions will attempt to return, with all
return, with all records retrieved, the corresponding SIGs. If a records retrieved, the corresponding SIGs. If a server does not
server does not support the protocol, the resolver must retrieve all support the protocol, the resolver must retrieve all the SIG records
the SIG records for a name and select the one or ones that sign the for a name and select the one or ones that sign the resource
resource record(s) that resolver is interested in. record(s) that resolver is interested in.
2.3.2 Authenticating Name and Type Non-existence 2.3.2 Authenticating Name and Type Non-existence
The above security mechanism provides only a way to sign existing RRs The above security mechanism provides only a way to sign existing RRs
in a zone. "Data origin" authentication is not obviously provided in a zone. "Data origin" authentication is not obviously provided
for the non-existence of a domain name in a zone or the non-existence for the non-existence of a domain name in a zone or the non-existence
of a type for an existing name. This gap is filled by the NXT RR of a type for an existing name. This gap is filled by the NXT RR
which authenticatably asserts a range of non-existent names in a zone which authenticatably asserts a range of non-existent names in a zone
and the non-existence types for the initial name in that range. and the non-existence types for the initial name in that range.
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In general, security aware servers must be used to securely CNAME in In general, security aware servers must be used to securely CNAME in
DNS. Security aware servers must (1) allow KEY, SIG, and NXT RRs DNS. Security aware servers must (1) allow KEY, SIG, and NXT RRs
along with CNAME RRs, (2) suppress CNAME processing on retrieval of along with CNAME RRs, (2) suppress CNAME processing on retrieval of
these types as well as on retrieval of the type CNAME, and (3) these types as well as on retrieval of the type CNAME, and (3)
automatically return SIG RRs authenticating the CNAME or CNAMEs automatically return SIG RRs authenticating the CNAME or CNAMEs
encountered in resolving a query. encountered in resolving a query.
2.3.6 Signers Other Than The Zone 2.3.6 Signers Other Than The Zone
There are two cases where a SIG resource record is signed by other There are two cases where a SIG resource record is signed by other
than the zone private key. One is for future support of dynamic than the zone private key. One is for support of dynamic update
update where an entity is permitted to authenticate/update its own where an entity is permitted to authenticate/update its own records.
records. The public key of the entity must be present in the DNS and The public key of the entity must be present in the DNS and be
be appropriately signed but the other RR(s) may be signed with the appropriately signed but the other RR(s) may be signed with the
entity's key. The other is for support of transaction authentication entity's key. The other is for support of transaction authentication
as described in Section 2.4 below. as described in Section 2.4 below.
2.4 DNS Transaction Authentication 2.4 DNS Transaction Authentication
The data origin authentication service described above protects The data origin authentication service described above protects
resource records but provides no protection for DNS message headers. resource records but provides no protection for DNS message headers.
If header bits are falsely set by a server, there is little that can If header bits are falsely set by a server, there is little that can
be done. However, it is possible to add transaction authentication. be done. However, it is possible to add transaction authentication.
Such authentication means that a resolver can be sure it is at least Such authentication means that a resolver can be sure it is at least
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This is accomplished by optionally adding a special SIG resource This is accomplished by optionally adding a special SIG resource
record to the end of the reply which digitally signs the record to the end of the reply which digitally signs the
concatenation of the server's response and the resolver's query. The concatenation of the server's response and the resolver's query. The
private key used belongs to the host composing the reply, not to the private key used belongs to the host composing the reply, not to the
zone being queried. The corresponding public key is stored in and zone being queried. The corresponding public key is stored in and
retrieved from the DNS. Because replies are highly variable, message retrieved from the DNS. Because replies are highly variable, message
authentication SIGs can not be pre-calculated. Thus it will be authentication SIGs can not be pre-calculated. Thus it will be
necessary to keep the private key on-line, for example in software or necessary to keep the private key on-line, for example in software or
in a directly connected piece of hardware. in a directly connected piece of hardware.
DNS level transaction authentication would be unnecessary if a lower DNS level transaction authentication will be unnecessary when IPSEC
level (i.e., IP level) end-to-end security protocol were available. end-to-end security protocol is generally available [refernce IPSEC
However, such a protocol is not yet standardized and when it is, RFCs when RFC numbers assigned]. However, there will be a
there will be a significant time during which there will be systems significant time during which there will be systems on which it will
on which it will be hard to add such a protocol but relatively easy be hard to add such a protocol but relatively easy to replace the DNS
to replace the DNS components. components.
3. The KEY Resource Record 3. The KEY Resource Record
The KEY resource record (RR) is used to document a key that is The KEY resource record (RR) is used to document a key that is
associated with a Domain Name System (DNS) name. It will be a public associated with a Domain Name System (DNS) name. It will be a public
key as only public keys are stored in the DNS. This can be the key as only public keys are stored in the DNS. This can be the
public key of a zone, of a host or other end entity, or a user. A public key of a zone, of a host or other end entity, or a user. A
KEY RR is, like any other RR, authenticated by a SIG RR. Security KEY RR is, like any other RR, authenticated by a SIG RR. Security
aware DNS implementations MUST be designed to handle at least two aware DNS implementations MUST be designed to handle at least two
simultaneously valid keys of the same type associated with a name. simultaneously valid keys of the same type associated with a name.
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under the entity name. For example, "j.random_user" on under the entity name. For example, "j.random_user" on
host.subdomain.domain could have a public key associated through a host.subdomain.domain could have a public key associated through a
KEY RR with name j\.random_user.host.subdomain.domain. It could be KEY RR with name j\.random_user.host.subdomain.domain. It could be
used in an security protocol where authentication of a user was used in an security protocol where authentication of a user was
desired. This key would be useful in IP or other security for a user desired. This key would be useful in IP or other security for a user
level service such a telnet, ftp, rlogin, etc. level service such a telnet, ftp, rlogin, etc.
Bit 6 on indicates that this is a key associated with the non- Bit 6 on indicates that this is a key associated with the non-
zone "entity" whose name is the RR owner name. This will commonly be zone "entity" whose name is the RR owner name. This will commonly be
a host but could, in some parts of the DNS tree, be some other type a host but could, in some parts of the DNS tree, be some other type
of entity such as an Autonomous System [draft-ietf-dnssec-as-map- of entity such as a telephone number [RFC 1530]. This is the public
*.txt]. This is the public key used in connection with the optional key used in connection with the optional DNS transaction
DNS transaction authentication service that can be used if the owner authentication service that can be used if the owner name is a DNS
name is a DNS server host. It could also be used in an IP-security server host. It could also be used in an IP-security protocol where
protocol where authentication of a host was desired such as routing, authentication of a host was desired such as routing, NTP, etc.
NTP, etc.
Bit 7 is the "zone" bit and indicates that this is a zone key Bit 7 is the "zone" bit and indicates that this is a zone key
for the zone whose name is the KEY RR owner name. This is the for the zone whose name is the KEY RR owner name. This is the
fundamental type of DNS data origin authentication public key. fundamental type of DNS data origin authentication public key.
Bit 8 is reserved to be the "IPSEC" bit and indicate that this Bit 8 is reserved to be the IPSEC bit and indicate that this key
key is valid for use in conjunction with the IP level security is valid for use in conjunction with the IP level security standard.
standard. This key could be used in connection with secured This key could be used in connection with secured communication on
communication on behalf of an end entity or user whose name is the behalf of an end entity or user whose name is the owner name of the
owner name of the KEY RR if the entity or user bits are on. The KEY RR if the entity or user bits are on. The presence of a KEY
presence of a KEY resource with the IPSEC and entity bits on and resource with the IPSEC and entity bits on and experimental and no-
experimental and no-key bits off is a guarantee that the host speaks key bits off is a guarantee that the host speaks IPSEC.
IPSEC.
Bit 9 is reserved to be the "MOSS" bit and indicate that this Bit 9 is reserved to be the "email" bit and indicate that this
key is valid for use in conjunction with MIME object security key is valid for use in conjunction with MIME security multiparts.
standard. This key could be used in connection with secured This key could be used in connection with secured communication on
communication on behalf of an end entity or user whose name is the behalf of an end entity or user whose name is the owner name of the
owner name of the KEY RR if the entity or user bits are on. The KEY RR if the entity or user bits are on.
presence of a KEY resource with the MOSS and entity bits on and
experimental and no-key bits off is a guarantee that the host speaks
MOSS.
Bits 10-11 are reserved and must be zero. Bits 10-11 are reserved and must be zero.
Bits 12-15 are the "signatory" field. If non-zero, it indicates Bits 12-15 are the "signatory" field. If non-zero, it indicates
that the key can validly sign RRs of the same name. If the owner that the key can validly sign RRs of the same name. If the owner
name is a wildcard, then RRs with any name which is in the wildcard's name is a wildcard, then RRs with any name which is in the wildcard's
scope can be signed. Fifteen different non-zero values are possible scope can be signed. Fifteen different non-zero values are possible
for this field and any differences in their meaning are reserved for for this field and any differences in their meaning are reserved for
definition in connection with possible future DNS dynamic update or definition in connection with DNS dynamic update or other new DNS
other new DNS commands. This field is meaningless for zone keys commands. This field is meaningless for zone keys which always have
which always have authority to sign any RRs in the zone. The authority to sign any RRs in the zone. The signatory field, like all
signatory field, like all other aspects of the KEY RR, is only other aspects of the KEY RR, is only effective if the KEY RR is
effective if the KEY RR is appropriately signed by a SIG RR. appropriately signed by a SIG RR.
3.4 The Protocol Octet 3.4 The Protocol Octet
It is anticipated that keys stored in DNS will be used in conjunction It is anticipated that keys stored in DNS will be used in conjunction
with Internet protocols other than DNS (keys with zone bit or with Internet protocols other than DNS (keys with zone bit or
signatory field non-zero) and IPSEC (keys with IPSEC bit set). The signatory field non-zero) and IPSEC (keys with IPSEC bit set). The
protocol octet is provided to indicate that a key is valid for such protocol octet is provided to indicate that a key is valid for such
use and, for end entity keys or the host part of user keys, that the use and, for end entity keys or the host part of user keys, that the
secure version of that protocol is implemented on that entity or secure version of that protocol is implemented on that entity or
host. host.
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adequate for all point to point IP communication meaning that adequate for all point to point IP communication meaning that
additional flag field bits would only be assigned, when appropriate additional flag field bits would only be assigned, when appropriate
as indicated above, to protocols with a store-and-forward nature as indicated above, to protocols with a store-and-forward nature
(other than DNS) or otherwise not subsumed into a point-to-point (other than DNS) or otherwise not subsumed into a point-to-point
paradigm. paradigm.
3.5 The KEY Algorithm Number and the MD5/RSA Algorithm 3.5 The KEY Algorithm Number and the MD5/RSA Algorithm
This octet is the key algorithm parallel to the same field for the This octet is the key algorithm parallel to the same field for the
SIG resource. The MD5/RSA algorithm described in this draft is SIG resource. The MD5/RSA algorithm described in this draft is
number 1. Numbers 2 through 253 are available for assignment should number 1. Numbers 2 through 252 are available for assignment should
sufficient reason arise. However, the designation of a new algorithm sufficient reason arise. However, the designation of a new algorithm
could have a major impact on interoperability and requires an IETF could have a major impact on interoperability and requires an IETF
standards action. Number 254 is reserved for private use and will standards action. Number 254 is reserved for private use and will
never be assigned a specific algorithm. For number 254, the public never be assigned a specific algorithm. For number 254, the public
key area shown in the packet diagram above will actually begin with key area shown in the packet diagram above will actually begin with
an Object Identifier (OID) indicating the private algorithm in use an Object Identifier (OID) indicating the private algorithm in use
and the remainder of the area is whatever is required by that and the remainder of the area is whatever is required by that
algorithm. Values 0 and 255 are reserved. algorithm. Number 253 is reserved for use where the date or other
labeling fields of SIGs are desired withouth any actual security. For
number 253, the public key area is null. Values 0 and 255 are
reserved.
If the no key bit is zero and the algorithm field is 1, indicating If the no key bit is zero and the algorithm field is 1, indicating
the MD5/RSA algorithm, the public key field is structured as follows: the MD5/RSA algorithm, the public key field is structured as follows:
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| pub exp length| public key exponent / | pub exp length| public key exponent /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| / | /
+- modulus / +- modulus /
| / | /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-/
To promote interoperability, the exponent and modulus are limited to To promote interoperability, the exponent and modulus are each
2552 bits in length. The public key exponent is a variable length limited to 2552 bits in length. The public key exponent is a
unsigned integer. Its length in octets is represented as one octet variable length unsigned integer. Its length in octets is
if it is in the range of 1 to 255 and by a zero octet followed by a represented as one octet if it is in the range of 1 to 255 and by a
two octet unsigned length if it is longer than 255 bytes. The public zero octet followed by a two octet unsigned length if it is longer
key modulus field is a multiprecision unsigned integer. The length than 255 bytes. The public key modulus field is a multiprecision
of the modulus can be determined from the RDLENGTH and the preceding unsigned integer. The length of the modulus can be determined from
RDATA fields including the exponent. Leading zero bytes are the RDLENGTH and the preceding RDATA fields including the exponent.
prohibited in the exponent and modulus. Leading zero bytes are prohibited in the exponent and modulus.
3.6 Interaction of Flags, Algorithm, and Protocol Bytes 3.6 Interaction of Flags, Algorithm, and Protocol Bytes
Various combinations of the no-key bit, algorithm byte, protocol Various combinations of the no-key bit, algorithm byte, protocol
byte, and any protocol indicating flags (such as the reserved IPSEC byte, and any protocol indicating flags (such as the reserved IPSEC
flag) are possible. (Not that the zone flag bit being on or the flag) are possible. (Note that the zone flag bit being on or the
signatory field being non-zero is effectively a DNS protocol flag signatory field being non-zero is effectively a DNS protocol flag
on.) The meaning of these combinations is indicated below: on.) The meaning of these combinations is indicated below:
NK = no key flag NK = no key flag
AL = alogrithm byte AL = alogrithm byte
PR = protocols indicated by protocol byte or protocol flags PR = protocols indicated by protocol byte or protocol flags
x represents any valid non-zero value. x represents any valid non-zero value.
AL PR NK Meaning AL PR NK Meaning
0 0 0 Illegal, claims key but has bad algorithm field. 0 0 0 Illegal, claims key but has bad algorithm field.
0 0 1 Authenticates total lack of security for owner. 0 0 1 Specifies total lack of security for owner.
0 x 0 Illegal, claims key but has bad algorithm field. 0 x 0 Illegal, claims key but has bad algorithm field.
0 x 1 Specified protocols insecure, others may be secure. 0 x 1 Specified protocols insecure, others may be secure.
x 0 0 Useless. Gives key but no protocols to use it. x 0 0 Useless. Gives key but no protocols to use it.
x 0 1 Useless. Denies key but for no protocols. x 0 1 Useless. Denies key but for no protocols.
x x 0 Authenticates key for protocols and certifies x x 0 Specifies key for protocols and certifies that
that those protocols are implemented with those protocols are implemented with security.
security.
x x 1 Algorithm not understood for protocol. x x 1 Algorithm not understood for protocol.
(remember, in reference to the above table, that a protocol (remember, in reference to the above table, that a protocol
byte of 255 means all protocols with protocol bytes assigned) byte of 255 means all protocols with protocol bytes assigned)
3.7 KEY RRs in the Construction of Responses 3.7 KEY RRs in the Construction of Responses
An explicit request for KEY RRs does not cause any special additional An explicit request for KEY RRs does not cause any special additional
information processing except, of course, for the corresponding SIG information processing except, of course, for the corresponding SIG
RR from a security aware server. RR from a security aware server.
skipping to change at page 17, line 4 skipping to change at page 16, line 50
will be included. On inclusion of A (or AAAA) RRs as additional will be included. On inclusion of A (or AAAA) RRs as additional
information, their KEY RRs will also be included but with lower information, their KEY RRs will also be included but with lower
priority than the relevant A (or AAAA) RRs. priority than the relevant A (or AAAA) RRs.
3.8 File Representation of KEY RRs 3.8 File Representation of KEY RRs
KEY RRs may appear as lines in a zone data file. KEY RRs may appear as lines in a zone data file.
The flag field, protocol, and algorithm number octets are then The flag field, protocol, and algorithm number octets are then
represented as unsigned integers. Note that if the "no key" flag is represented as unsigned integers. Note that if the "no key" flag is
on in the flags, nothing appears after the algorithm octet. on in the flags or the algorithm specified is 253, nothing appears
after the algorithm octet.
The remaining public key portion is represented in base 64 (see The remaining public key portion is represented in base 64 (see
Appendix) and may be divided up into any number of white space Appendix) and may be divided up into any number of white space
separated substrings, down to single base 64 digits, which are separated substrings, down to single base 64 digits, which are
concatenated to obtain the full signature. These substrings can span concatenated to obtain the full signature. These substrings can span
lines using the standard parenthesis. lines using the standard parenthesis.
Note that the public key may have internal sub-fields but these do Note that the public key may have internal sub-fields but these do
not appear in the master file representation. For example, with not appear in the master file representation. For example, with
algorithm 1 there is a public exponent and then a modulus and with algorithm 1 there is a public exponent and then a modulus and with
skipping to change at page 18, line 49 skipping to change at page 18, line 49
/ / / /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The value of the SIG RR type is 24. The value of the SIG RR type is 24.
The "type covered" is the type of the other RRs covered by this SIG. The "type covered" is the type of the other RRs covered by this SIG.
The algorithm number is an octet specifying the digital signature The algorithm number is an octet specifying the digital signature
algorithm used parallel to the algorithm octet for the KEY RR. The algorithm used parallel to the algorithm octet for the KEY RR. The
MD5/RSA algorithm described in this draft is number 1. Numbers 2 MD5/RSA algorithm described in this draft is number 1. Numbers 2
through 253 are available for assignment should sufficient reason through 252 are available for assignment should sufficient reason
arise to allocate them. However, the designation of a new algorithm arise to allocate them. However, the designation of a new algorithm
could have a major impact on the interoperability of the global DNS could have a major impact on the interoperability of the global DNS
systems and requires an IETF standards action. Number 254 is systems and requires an IETF standards action. Number 254 is
reserved for private use and will not be assigned a specific reserved for private use and will not be assigned a specific
algorithm. For number 254, the "signature" area shown above will algorithm. For number 254, the "signature" area shown above will
actually begin with an Object Identifier (OID) indicating the private actually begin with an Object Identifier (OID) indicating the private
algorithm in use and the remainder of the signature area is whatever algorithm in use and the remainder of the signature area is whatever
is required by that algorithm. Values 0 and 255 are reserved. is required by that algorithm. Number 253 is used when the time
fields or other non-signature fields of the SIG are desired without
any actual security. For number 253, the signature field will be
null. Values 0 and 255 are reserved.
The "labels" octet is an unsigned count of how many labels there are The "labels" octet is an unsigned count of how many labels there are
in the original SIG RR owner name not counting the null label for in the original SIG RR owner name not counting the null label for
root and not counting any initial "*" for a wildcard. If a secured root and not counting any initial "*" for a wildcard. If a secured
retrieval is the result of wild card substitution, it is necessary retrieval is the result of wild card substitution, it is necessary
for the resolver to use the original form of the name in verifying for the resolver to use the original form of the name in verifying
the digital signature. This field helps optimize the determination the digital signature. This field helps optimize the determination
of the original form reducing the effort in authenticating signed of the original form reducing the effort in authenticating signed
data. data.
If, on retrieval, the RR appears to have a longer name than indicated If, on retrieval, the RR appears to have a longer name than indicated
by "labels", the resolver can tell it is the result of wildcard by "labels", the resolver can tell it is the result of wildcard
substitution. If the RR owner name appears to be shorter than the substitution. If the RR owner name appears to be shorter than the
labels count, the SIG RR should be considered corrupt and ignored. labels count, the SIG RR should be considered corrupt and ignored.
The maximum number of labels possible in the current DNS is 127 but The maximum number of labels possible in the current DNS is 127 but
the entire octet is reserved and would be required should DNS names the entire octet is reserved and would be required should DNS names
ever be expanded to 255 labels. The following table give some ever be expanded to 255 labels. The following table gives some
examples. The value of "labels" is at the top, the retrieved owner examples. The value of "labels" is at the top, the retrieved owner
name on the left, and the table entry is the name to use in signature name on the left, and the table entry is the name to use in signature
verification except that "bad" means the RR is corrupt. verification except that "bad" means the RR is corrupt.
labels= | 0 | 1 | 2 | 3 | 4 | labels= | 0 | 1 | 2 | 3 | 4 |
--------+-----+------+--------+----------+----------+ --------+-----+------+--------+----------+----------+
.| . | bad | bad | bad | bad | .| . | bad | bad | bad | bad |
d.| *. | d. | bad | bad | bad | d.| *. | d. | bad | bad | bad |
c.d.| *. | *.d. | c.d. | bad | bad | c.d.| *. | *.d. | c.d. | bad | bad |
b.c.d.| *. | *.d. | *.c.d. | b.c.d. | bad | b.c.d.| *. | *.d. | *.c.d. | b.c.d. | bad |
skipping to change at page 20, line 32 skipping to change at page 20, line 35
The "signer's name" field is the domain name of the signer generating The "signer's name" field is the domain name of the signer generating
the SIG RR. This is frequently the zone which contained the RR(s) the SIG RR. This is frequently the zone which contained the RR(s)
being authenticated. The signer's name may be compressed with being authenticated. The signer's name may be compressed with
standard DNS name compression when being transmitted over the standard DNS name compression when being transmitted over the
network. network.
The structure of the "signature" field is described below. The structure of the "signature" field is described below.
4.1.1 Signature Data 4.1.1 Signature Data
The actual signature portion of the SIG RR binds the other RDATA Except for algorithm number 253 where it is null, the actual
fields to all of the "type covered" RRs with that owner name. These signature portion of the SIG RR binds the other RDATA fields to all
covered RRs are thereby authenticated. To accomplish this, a data of the "type covered" RRs with that owner name. These covered RRs
sequence is constructed as follows: are thereby authenticated. To accomplish this, a data sequence is
constructed as follows:
data = RDATA | RR(s)... data = RDATA | RR(s)...
where | is concatenation, RDATA is all the RDATA fields in the SIG RR where | is concatenation, RDATA is all the RDATA fields in the SIG RR
itself before the signature, and RR(s) are all the RR(s) of the type itself before the signature, and RR(s) are all the RR(s) of the type
covered with the same owner name and class as the SIG RR in canonical covered with the same owner name and class as the SIG RR in canonical
form and order. form and order.
For purposes of DNS security, the canonical form for an RR is the RR For purposes of DNS security, the canonical form for an RR is the RR
with domain names (1) fully expanded (no name compression via with domain names (1) fully expanded (no name compression via
pointers) and (2) all domain name letters set to lower case. For pointers) and (2) all domain name letters set to lower case.
purposes of DNS security, the canonical order for RRs is to sort them
in ascending order by name, then by type, as left justified unsigned For purposes of DNS security, the canonical order for RRs is to sort
octet sequences in network (transmission) order where a missing octet them in ascending order by name, then by type, as left justified
sorts before a zero octet. (See also ordering discussion in Section unsigned octet sequences in network (transmission) order where a
5.1.) Within any particular name and type they are similarly sorted missing octet sorts before a zero octet. (See also ordering
by RDATA as a left justified unsigned octet sequence. EXCEPT that the discussion in Section 5.1.) Within any particular name and type they
type SIG RR(s) covering any particular type appear immediately after are similarly sorted by RDATA as a left justified unsigned octet
the other RRs of that type. Thus if at name a.b there is one A RR sequence. EXCEPT that the type SIG RR(s) covering any particular type
and one KEY RR, their order with SIGs for concatenating the "data" to appear immediately after the other RRs of that type. Thus if at name
be signed would be as follows: a.b there is one A RR and one KEY RR, their order with SIGs for
concatenating the "data" to be signed would be as follows:
a.b. A .... a.b. A ....
a.b. SIG A ... a.b. SIG A ...
a.b. KEY ... a.b. KEY ...
a.b. SIG KEY ... a.b. SIG KEY ...
(SIGs on type ANY should not be included in a zone.) (SIGs on type ANY should not be included in a zone.)
How this data sequence is processed into the signature is algorithm How this data sequence is processed into the signature is algorithm
dependent. dependent.
skipping to change at page 22, line 30 skipping to change at page 22, line 35
The AXFR SIG must be calculated last of all zone key signed SIGs in The AXFR SIG must be calculated last of all zone key signed SIGs in
the zone. It really belongs to the zone as a whole, not to the zone the zone. It really belongs to the zone as a whole, not to the zone
name. The AXFR SIG is only retrieved as part of a zone transfer. name. The AXFR SIG is only retrieved as part of a zone transfer.
After validation of the AXFR SIG, the zone may be considered valid After validation of the AXFR SIG, the zone may be considered valid
without verification of all the internal zone SIGs in the zone; without verification of all the internal zone SIGs in the zone;
however, any SIGs signed by entity keys or the like must still be however, any SIGs signed by entity keys or the like must still be
validated. The AXFR SIG is transmitted first in a zone transfer so validated. The AXFR SIG is transmitted first in a zone transfer so
the receiver can tell immediately that they may be able to avoid the receiver can tell immediately that they may be able to avoid
verifying other zone signed SIGs. verifying other zone signed SIGs.
Dynamic zone RRs which might be added by some future dynamic zone Dynamic zone RRs which might be added by a dynamic zone update
update protocol and signed by an end entity or user key rather than a protocol and signed by an end entity or user key rather than a zone
zone key (see Section 3.2) are not included. They originate in the key (see Section 3.2) are not included in the AXFR SIG. They
network and will not, in general, be migrated to the recommended off originate in the network and will not, in general, be migrated to the
line zone signing procedure (see Section 8.2). Thus such dynamic RRs recommended off line zone signing procedure (see Section 8.2). Thus
are not directly signed by the zone, are not included in the AXFR such dynamic RRs are not directly signed by the zone, are not
SIG, and are not generally protected against omission during zone included in the AXFR SIG, and are not generally protected against
transfers. omission from zone transfers.
4.1.4 Transaction SIGs 4.1.4 Transaction SIGs
A response message from a security aware server may optionally A response message from a security aware server may optionally
contain a special SIG as the last item in the additional information contain a special SIG as the last item in the additional information
section to authenticate the transaction. section to authenticate the transaction.
This SIG has a "type covered" field of zero, which is not a valid RR This SIG has a "type covered" field of zero, which is not a valid RR
type. It is calculated by using a "data" (see Section 4.1.2) of the type. It is calculated by using a "data" (see Section 4.1.2) of the
entire preceding DNS reply message, including DNS header, entire preceding DNS reply message, including DNS header,
concatenated with the entire DNS query message that produced this concatenated with the entire DNS query message that produced this
response, including the query's DNS header. That is response, including the query's DNS header. That is
data = full response (less trailing message SIG) | full query
data = full response (less final transaction SIG) | full query
Verification of the transaction SIG (which is signed by the server Verification of the transaction SIG (which is signed by the server
host key, not the zone key) by the requesting resolver shows that the host key, not the zone key) by the requesting resolver shows that the
query and response were not tampered with in transit, that the query and response were not tampered with in transit, that the
response corresponds to the intended query, and that the response response corresponds to the intended query, and that the response
comes from the queried server. comes from the queried server.
4.2 SIG RRs in the Construction of Responses 4.2 SIG RRs in the Construction of Responses
Security aware servers MUST, for every authoritative RR the query Security aware servers MUST, for every authoritative RR the query
will return, attempt to send the available SIG RRs which authenticate will return, attempt to send the available SIG RRs which authenticate
the requested RR. The following rules apply to the inclusion of SIG the requested RR. The following rules apply to the inclusion of SIG
RRs in responses: RRs in responses:
1. when an RR is placed in a response, its SIG RR has a higher 1. when an RR is placed in a response, its SIG RR has a higher
priority for inclusion than other RRs that may need to be priority for inclusion than other RRs that may need to be
included. If space does not permit its inclusion, the response included. If space does not permit its inclusion, the response
MUST be considered truncated. MUST be considered truncated.
2. when a SIG RR is present for an RR to be included in the 2. when a SIG RR is present for an RR to be included in the
additional information section, the response MUST not be additional information section, the response MUST NOT be
considered truncated if space does not permit the inclusion of the considered truncated if space does not permit the inclusion of the
SIG RR. SIG RR.
Sending SIGs to authenticate non-authoritative data (glue records and Sending SIGs to authenticate non-authoritative data (glue records and
NS RRs for subzones) is unnecessary and must be avoided. Note that NS RRs for subzones) is unnecessary and must be avoided. Note that
KEYs for subzones are authoritative. KEYs for subzones are authoritative.
If a SIG covers any RR that would be in the answer section of the If a SIG covers any RR that would be in the answer section of the
response, its automatic inclusion MUST be the answer section. If it response, its automatic inclusion MUST be the answer section. If it
covers an RR that would appear in the authority section, its covers an RR that would appear in the authority section, its
skipping to change at page 23, line 48 skipping to change at page 24, line 6
appear in the additional information section. appear in the additional information section.
Optionally, DNS transactions may be authenticated by a SIG RR at the Optionally, DNS transactions may be authenticated by a SIG RR at the
end of the response in the additional information section (Section end of the response in the additional information section (Section
4.1.4). Such SIG RRs are signed by the DNS server originating the 4.1.4). Such SIG RRs are signed by the DNS server originating the
response. Although the signer field must be the name of the response. Although the signer field must be the name of the
originating server host, the owner name, class, TTL, and original originating server host, the owner name, class, TTL, and original
TTL, are meaningless. The class and TTL fields can be zero. To TTL, are meaningless. The class and TTL fields can be zero. To
conserve space, the owner name SHOULD be root (a single zero octet). conserve space, the owner name SHOULD be root (a single zero octet).
If transaction authentication is desired, that SIG RR must be If transaction authentication is desired, that SIG RR must be
considered higher priority than any other RR in the answer. considered higher priority for inclusion than any other RR in the
answer.
4.3 Processing Responses and SIG RRs 4.3 Processing Responses and SIG RRs
The following rules apply to the processing of SIG RRs included in a The following rules apply to the processing of SIG RRs included in a
response: response:
1. a security aware resolver that receives a response from what it 1. a security aware resolver that receives a response from what it
believes to be a security aware server via a communication path believes to be a security aware server via a communication path
that it believes to be secure with the AD bit (see Section 6.1) that it believes to be secure with the AD bit (see Section 6.1)
set, MAY choose to accept the RRs as received set, MAY choose to accept the RRs as received without verifying
without verifying the SIG RRs. the SIG RRs.
2. in other cases, a security aware resolver SHOULD verify the SIG 2. in other cases, a security aware resolver SHOULD verify the SIG
RRs for the RRs of interest. This may involve initiating RRs for the RRs of interest. This may involve initiating
additional queries for SIG or KEY RRs, at least in the case of additional queries for SIG or KEY RRs, at least in the case of
getting a response from an insecure server. (As explained in 4.2 getting a response from an insecure server. (As explained in 4.2
above, it will not be possible to secure CNAMEs being served up by above, it will not be possible to secure CNAMEs being served up by
old resolvers.) non-secure resolvers.)
NOTE: Implementors might expect the SHOULD to be a MUST. However, NOTE: Implementors might expect the above SHOULD to be a MUST.
local policy or the calling application may not require the However, local policy or the calling application may not require
security services. the security services.
3. If SIG RRs are received in response to a user query explicitly 3. If SIG RRs are received in response to a user query explicitly
specifying the SIG type, no special processing is required. specifying the SIG type, no special processing is required.
If the message does not pass reasonable checks or the SIG does not If the message does not pass reasonable checks or the SIG does not
check against the signed RRs, the SIG RR is invalid and should be check against the signed RRs, the SIG RR is invalid and should be
ignored. If all of the SIG RR(s) purporting to authenticate a set of ignored. If all of the SIG RR(s) purporting to authenticate a set of
RRs are invalid, then the set of RR(s) is not authenticated. RRs are invalid, then the set of RR(s) is not authenticated.
If the SIG RR is the last RR in a response in the additional If the SIG RR is the last RR in a response in the additional
skipping to change at page 25, line 18 skipping to change at page 25, line 24
are transmitted in a query response, the TTL should be trimmed so are transmitted in a query response, the TTL should be trimmed so
that current time plus the TTL does not extend beyond the signature that current time plus the TTL does not extend beyond the signature
expiration time. Thus, in general, the TTL on an transmitted RR expiration time. Thus, in general, the TTL on an transmitted RR
would be would be
min(sigExpTim,max(zoneMinTTL,min(originalTTL,currentTTL))) min(sigExpTim,max(zoneMinTTL,min(originalTTL,currentTTL)))
4.5 File Representation of SIG RRs 4.5 File Representation of SIG RRs
A SIG RR can be represented as a single logical line in a zone data A SIG RR can be represented as a single logical line in a zone data
file [RFC1033] but there are some special problems as described file [RFC1033] but there are some special considerations as described
below. (It does not make sense to include a transaction below. (It does not make sense to include a transaction
authenticating SIG RR in a file as it is a transient authentication authenticating SIG RR in a file as it is a transient authentication
that covers data including an ephemeral transaction number so it must that covers data including an ephemeral transaction number so it must
be calculated in real time by the DNS server.) be calculated in real time by the DNS server.)
There is no particular problem with the signer, covered type, and There is no particular problem with the signer, covered type, and
times. The time fields appears in the form YYYYMMDDHHMMSS where YYYY times. The time fields appears in the form YYYYMMDDHHMMSS where YYYY
is the year, the first MM is the month number (01-12), DD is the day is the year, the first MM is the month number (01-12), DD is the day
of the month (01-31), HH is the hour in 24 hours notation (00-23), of the month (01-31), HH is the hour in 24 hours notation (00-23),
the second MM is the minute (00-59), and SS is the second (00-59). the second MM is the minute (00-59), and SS is the second (00-59).
The original TTL and algorithm fields appear as unsigned integers. The original TTL and algorithm fields appear as unsigned integers.
If the original TTL, which applies to the type signed, is the same as
the TTL of the SIG RR itself, it may be omitted. The date field
which follows it is larger than the maximum possible TTL so there is
no ambiguity.
The "labels" field does not appear in the file representation as it The "labels" field does not appear in the file representation as it
can be calculated from the owner name. can be calculated from the owner name.
The key footprint appears as an unsigned decimal number. The key footprint appears as an unsigned decimal number.
However, the signature itself can be very long. It is the last data However, the signature itself can be very long. It is the last data
field and is represented in base 64 (see Appendix) and may be divided field and is represented in base 64 (see Appendix) and may be divided
up into any number of white space separated substrings, down to up into any number of white space separated substrings, down to
single base 64 digits, which are concatenated to obtain the full single base 64 digits, which are concatenated to obtain the full
signature. These substrings can be split between lines using the signature. These substrings can be split between lines using the
skipping to change at page 26, line 21 skipping to change at page 27, line 21
The nonexistence of a name in a zone is indicated by the NXT ("next") The nonexistence of a name in a zone is indicated by the NXT ("next")
RR for a name interval containing the nonexistent name. An NXT RR and RR for a name interval containing the nonexistent name. An NXT RR and
its SIG are returned in the authority section, along with the error, its SIG are returned in the authority section, along with the error,
if the server is security aware. The same is true for a non-existent if the server is security aware. The same is true for a non-existent
type under an existing name. NXT RRs will also be returned if an type under an existing name. NXT RRs will also be returned if an
explicit query is made for the NXT type. explicit query is made for the NXT type.
The existence of a complete set of NXT records in a zone means that The existence of a complete set of NXT records in a zone means that
any query for any name and type to a security aware server serving any query for any name and type to a security aware server serving
the zone should result in an reply containing at least one signed RR. the zone will result in an reply containing at least one signed RR.
NXT RRs do not appear in zone master files since they can be derived NXT RRs do not appear in zone master files since they can be derived
from the rest of the zone. from the rest of the zone.
5.1 The NXT Resource Record 5.1 The NXT Resource Record
The NXT resource record is used to securely indicate that RRs with an The NXT resource record is used to securely indicate that RRs with an
owner name in a certain name interval do not exist in a zone and to owner name in a certain name interval do not exist in a zone and to
indicate what zone signed type RRs are present for an existing name. indicate what zone signed type RRs are present for an existing name.
The owner name of the NXT RR is an existing name in the zone. It's The owner name of the NXT RR is an existing name in the zone. It's
RDATA is a "next" name and a type bit map. The presence of the NXT RR RDATA is a "next" name and a type bit map. The presence of the NXT RR
means that generally no name between its owner name and the name in means that generally no name between its owner name and the name in
its RDATA area exists and that no other types exist under its owner its RDATA area exists and that no other types exist under its owner
name. This implies a canonical ordering of all domain names in a name. This implies a canonical ordering of all domain names in a
zone. zone.
The ordering is to sort labels as unsigned left justified octet The ordering is to sort labels as unsigned left justified octet
strings where the absence of a octet sorts before a zero octet. strings where the absence of a octet sorts before a zero octet and
Names are then sorted by sorting on the highest level label and then, upper case letters are treated as lower case letters. Names are then
within those names with the same highest level label by the next sorted by sorting on the highest level label and then, within those
lower label, etc. Since we are talking about a zone, the zone name names with the same highest level label by the next lower label, etc.
itself always exists and all other names are the zone name with some Since we are talking about a zone, the zone name itself always exists
prefix of lower level labels. Thus the zone name itself always sorts and all other names are the zone name with some prefix of lower level
first. labels. Thus the zone name itself always sorts first.
There is a problem with the last NXT in a zone as it wants to have an There is a problem with the last NXT in a zone as it wants to have an
owner name which is the last existing name in sort order, which is owner name which is the last existing name in sort order, which is
easy, but it is not obvious what name to put in its RDATA to indicate easy, but it is not obvious what name to put in its RDATA to indicate
the entire remainder of the name space. This is handled by treating the entire remainder of the name space. This is handled by treating
the name space as circular and putting the zone name in the RDATA of the name space as circular and putting the zone name in the RDATA of
the last NXT. the last NXT.
There are special considerations due to interaction with wildcards as There are special considerations due to interaction with wildcards as
explained below. explained below.
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to be zero. Note that bit 30, for NXT, will always be on so the to be zero. Note that bit 30, for NXT, will always be on so the
minimum bit map length is actually four octets. The NXT bit map minimum bit map length is actually four octets. The NXT bit map
should be printed as a list of type mnemonics or decimal numbers should be printed as a list of type mnemonics or decimal numbers
similar to the WKS RR. similar to the WKS RR.
The size of the bit map can be inferred from the RDLENGTH and the The size of the bit map can be inferred from the RDLENGTH and the
length of the next domain name. length of the next domain name.
5.3 Example 5.3 Example
Assume zone foo.bar has entries for Assume zone foo.tld has entries for
big.foo.bar, big.foo.tld,
medium.foo.bar. medium.foo.tld.
small.foo.bar. small.foo.tld.
tiny.foo.bar. tiny.foo.tld.
Then a query to a security aware server for huge.foo.bar would Then a query to a security aware server for huge.foo.tld would
produce an error reply with the authority section data including the produce an error reply with the authority section data including
following: something like the following:
big.foo.bar. NXT medium.foo.bar. A, MX, SIG, NXT big.foo.tld. NXT medium.foo.tld. A MX SIG NXT
big.foo.tld. SIG NXT 1 3 ( ;type-cov=NXT, alg=1, labels=3
19960102030405 ;signature expiration
19951211100908 ;time signed
2143658709 ;key footprint
foo.tld. ;signer
MxFcby9k/yvedMfQgKzhH5er0Mu/vILz45IkskceFGgiWCn/GxHhai6VAuHAoNUz4YoU
1tVfSCSqQYn6//11U6Nld80jEeC8aTrO+KKmCaY= ;signature (640 bits)
)
Note that this response implies that big.foo.bar is an existing name Note that this response implies that big.foo.tld is an existing name
in the zone and thus has other RR types associated with it than NXT. in the zone and thus has other RR types associated with it than NXT.
However, only the NXT (and its SIG) RR appear in the response to this However, only the NXT (and its SIG) RR appear in the response to this
query for huge.foo.bar, which is a non-existent name. query for huge.foo.tld, which is a non-existent name.
5.4 Interaction of NXT RRs and Wildcard RRs 5.4 Interaction of NXT RRs and Wildcard RRs
Since, in some sense, a wildcard RR causes all possible names in an Since, in some sense, a wildcard RR causes all possible names in an
interval to exist, there should not be an NXT RR that would cover any interval to exist, there should not be an NXT RR that would cover any
part of this interval. Thus if *.X.ZONE exists you would expect an part of this interval. Thus if *.X.ZONE exists you would expect an
NXT RR that ends at X.ZONE and one that starts with the last name NXT RR that ends at X.ZONE and one that starts with the last name
covered by *.X.ZONE. However, this "last name covered" is something covered by *.X.ZONE. However, this "last name covered" is something
very ugly and long like \255\255\255....X.zone. So the NXT for the very ugly and long like \255\255\255....X.zone. So the NXT for the
interval following is simply given the owner name *.X.ZONE. This "*" interval following is simply given the owner name *.X.ZONE. This "*"
skipping to change at page 28, line 41 skipping to change at page 29, line 49
The existence of one or more wildcard RRs covering a name interval The existence of one or more wildcard RRs covering a name interval
makes it possible for a malicious server to hide any more specificly makes it possible for a malicious server to hide any more specificly
named RRs in the internal. The server can just falsely return the named RRs in the internal. The server can just falsely return the
wildcard match NXT instead of the more specificly named RRs. If wildcard match NXT instead of the more specificly named RRs. If
there is a zone wide wildcard, there will be an NXT RR whose owner there is a zone wide wildcard, there will be an NXT RR whose owner
name is the wild card and whose RDATA is the zone name. In this case name is the wild card and whose RDATA is the zone name. In this case
a server could conceal the existence of any more specific RRs in the a server could conceal the existence of any more specific RRs in the
zone. (It would be possible to design a more strict NXT feature zone. (It would be possible to design a more strict NXT feature
which would eliminate this possibility. But it would be more complex which would eliminate this possibility. But it would be more complex
and might be so constraining as to make any future dynamic update and might be so constraining as to make any dynamic update feature
feature that could create new names very difficult (see Section that could create new names very difficult (see Section 3.2).)
3.2).)
What name should be put into the RDATA of an RR with a name that is What name should be put into the RDATA of an NXT RR with an owner
within a wild card scope? Since the "next" existing name will be one name that is within a wild card scope? Since the "next" existing
that matches the wild card, the wild card name should be used. name will be one that matches the wild card, the wild card name
should be used. Inclusion of such NXTs within a wild card scope is
optional.
5.5 Blocking NXT Pseudo-Zone Transfers 5.5 Blocking NXT Pseudo-Zone Transfers
In a secure zone, a resolver can query for the initial NXT associated In a secure zone, a resolver can query for the initial NXT associated
with the zone name. Using the next domain name RDATA field from that with the zone name. Using the next domain name RDATA field from that
RR, it can query for the next NXT RR. By repeating this, it can walk RR, it can query for the next NXT RR. By repeating this, it can walk
through all the NXTs in the zone. If there are no wildcards, it can through all the NXTs in the zone. If there are no wildcards, it can
use this technique to find all names in a zone. If it does type ANY use this technique to find all names in a zone. If it does type ANY
queries, it can incrementally get all information in the zone and queries, it can incrementally get all information in the zone and
perhaps defeat attempts to administratively block zone transfers. perhaps defeat attempts to administratively block zone transfers.
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authenticate the non-existence of a name and both NXTs, if available, authenticate the non-existence of a name and both NXTs, if available,
on explicit query for type NXT. on explicit query for type NXT.
Insecure servers will never automatically return an NXT and may only Insecure servers will never automatically return an NXT and may only
return the NXT from the subzone on explicit queries. return the NXT from the subzone on explicit queries.
6. The AD and CD Bits and How to Resolve Securely 6. The AD and CD Bits and How to Resolve Securely
Retrieving or resolving authentic data from the Domain Name System Retrieving or resolving authentic data from the Domain Name System
(DNS) involves starting with one or more trusted public keys. With (DNS) involves starting with one or more trusted public keys. With
trusted keys, a browser willing to perform cryptography can progress trusted keys, a resolver willing to perform cryptography can progress
securely through the secure DNS zone structure to the zone of securely through the secure DNS zone structure to the zone of
interest as described in Section 6.3. Such trusted public keys would interest as described in Section 6.3. Such trusted public keys would
normally be configured in a manner similar to that described in normally be configured in a manner similar to that described in
Section 6.2. However, as a practical matter, a security aware Section 6.2. However, as a practical matter, a security aware
resolver would still gain some confidence in the results it returns resolver would still gain some confidence in the results it returns
even if it was not configured with any keys but trusted what it got even if it was not configured with any keys but trusted what it got
from a local well known server as a starting point. from a local well known server as a starting point.
Data stored at a server needs security labels of Authenticated, Data stored at a server needs security labels of Authenticated,
Pending, or Insecure. There is also a fourth transient state of Bad Pending, or Insecure. There is also a fourth transient state of Bad
which indicates that SIG checks have explicitly failed on the data. which indicates that SIG checks have explicitly failed on the data.
Such data is not retained at a security aware server. Authenticated Such Bad data is not retained at a security aware server.
means that the data has a valid SIG under a KEY traceable via a chain Authenticated means that the data has a valid SIG under a KEY
of zero or more SIG and KEY RRs to a KEY configured at the resolver traceable via a chain of zero or more SIG and KEY RRs to a KEY
via its boot file. Pending data has no authenticated SIGs and at configured at the resolver via its boot file. Pending data has no
least one additional SIG the browser is still trying to authenticate. authenticated SIGs and at least one additional SIG the resolver is
Insecure data is data which it is known can never be either still trying to authenticate. Insecure data is data which it is
authenticated or found bad because it is in a zone with no key or an known can never be either Authenticated or found Bad because it is in
experimental key. Behavior in terms of control of and flagging based a zone with no key or an experimental key. Behavior in terms of
on such data labels is described in Section 6.1. control of and flagging based on such data labels is described in
Section 6.1.
The proper validation of signatures requires a reasonably secure The proper validation of signatures requires a reasonably secure
shared opinion of the absolute time between resolvers and servers as shared opinion of the absolute time between resolvers and servers as
described in Section 6.4. described in Section 6.4.
In getting to the data of interest to respond to a query, a secure In getting to the data of interest to respond to a query, a secure
resolver may encounter genuine non-secure zones. It may proceed resolver may encounter genuine non-secure zones. It may proceed
through such zones but should report this as described in Section through such zones but should report this as described in Section
6.5. 6.5.
skipping to change at page 31, line 34 skipping to change at page 32, line 34
the checking disabled bit and thus will be answered by security aware the checking disabled bit and thus will be answered by security aware
servers only with authenticated data. Of course security aware servers only with authenticated data. Of course security aware
resolvers can not trust the AD bit unless they trust the server they resolvers can not trust the AD bit unless they trust the server they
are talking to and have a secure path to it. are talking to and have a secure path to it.
Any security aware resolver willing to do cryptography should assert Any security aware resolver willing to do cryptography should assert
the CD bit on all queries to reduce DNS latency time by allowing the CD bit on all queries to reduce DNS latency time by allowing
security aware servers to answer before they have resolved the security aware servers to answer before they have resolved the
validity of data. validity of data.
Security aware servers never return bad data. For non-security aware Security aware servers never return Bad data. For non-security aware
resolvers or security aware resolvers requesting service by having resolvers or security aware resolvers requesting service by having
the CD bit clear, security aware servers return only authenticated or the CD bit clear, security aware servers return only Authenticated or
insecure data with the AD bit set in the response. Security aware Insecure data with the AD bit set in the response. Security aware
resolvers will know that if data is insecure versus authentic by the resolvers will know that if data is Insecure versus Authentic by the
absence of SIG RRs. Security aware servers may return pending data absence of SIG RRs. Security aware servers may return Pending data
to security aware resolvers requesting the service by clearing the AD to security aware resolvers requesting the service by clearing the AD
bit in the response. The AD bit may only be set on a response if the bit in the response. The AD bit may only be set on a response if the
RRs in the response are either authenticated or insecure. RRs in the response are either Authenticated or Insecure.
6.2 Boot File Format 6.2 Boot File Format
The format for a boot file directive to configure a starting zone key The format for a boot file directive to configure a starting zone key
is as follows: is as follows:
pubkey name flags protocol algorithm key-data pubkey name flags protocol algorithm key-data
for a public key. "name" is the owner name (if the line is for a public key. "name" is the owner name (if the line is
translated into a KEY RR). Flags indicates the type of key and is translated into a KEY RR). Flags indicates the type of key and is
the same as the flag octet in the KEY RR. In particular, if the "no the same as the flag octet in the KEY RR. Algorithm is the algorithm
key" bit is on in flags, then all fields after algorithm may be in use where one is the MD5/RSA algorithm and 254 indicates a private
omitted. Algorithm is the algorithm in use where one is the MD5/RSA algorithm. The material after the algorithm is algorithm dependent
algorithm and 254 indicates a private algorithm. The material after and, for private algorithms, starts with the algorithm's identifying
the algorithm is algorithm dependent and, for private algorithms, OID. If the "no key" bit is on in flags or the algorithm is
starts with the algorithm's identifying OID. It is encoded in base specified as 253, then the key-data after algorithm may be omitted.
64 (see Appendix). It is treated as an octet stream and encoded in base 64 (see
Appendix).
A file of keys for cross certification or other purposes can be A file of keys for cross certification or other purposes can be
configured though the keyfile directive as follows: configured though the keyfile directive as follows:
keyfile filename keyfile filename
The file looks like a master file except that it can only contain KEY The file looks like a master file except that it can only contain KEY
and SIG RRs with the SIGs signed under a key configured with the and SIG RRs with the SIGs signed under a key configured with the
pubkey directive. pubkey directive.
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A resolver should keep track of the number of successive secure zones A resolver should keep track of the number of successive secure zones
traversed from a starting point to any secure zone it can reach. In traversed from a starting point to any secure zone it can reach. In
general, the lower such a distance number is, the greater the general, the lower such a distance number is, the greater the
confidence in the data. Data configured via a boot file directive confidence in the data. Data configured via a boot file directive
should be given a distance number of zero. Should a query encounter should be given a distance number of zero. Should a query encounter
different data for the same query with different distance values, different data for the same query with different distance values,
that with a larger value should be ignored. that with a larger value should be ignored.
A security conscious resolver should completely refuse to step from a A security conscious resolver should completely refuse to step from a
secure zone into a non-secure zone unless the non-secure zone is secure zone into a non-secure zone unless the non-secure zone is
certified to be non-secure or only experimentally secure by the certified to be non-secure, or only experimentally secure, by the
presence of an authenticated KEY RR for the non-secure zone with a no presence of an authenticated KEY RR for the non-secure zone with a no
key flag or the presence of a KEY RR with the experimental bit set. key flag or the presence of a KEY RR with the experimental bit set.
Otherwise the resolver is probably getting completely bogus or Otherwise the resolver is probably getting completely bogus or
spoofed data. spoofed data.
If legitimate non-secure zones are encountered in traversing the DNS If legitimate non-secure zones are encountered in traversing the DNS
tree, then no zone can be trusted as secure that can be reached only tree, then no zone can be trusted as secure that can be reached only
via information from such non-secure zones. Since the non-secure zone via information from such non-secure zones. Since the non-secure zone
data could have been spoofed, the "secure" zone reach via it could be data could have been spoofed, the "secure" zone reach via it could be
counterfeit. The "distance" to data in such zones or zones reached counterfeit. The "distance" to data in such zones or zones reached
skipping to change at page 34, line 33 skipping to change at page 35, line 33
length, and key generation (the least common operation) will vary length, and key generation (the least common operation) will vary
with the fourth power of the modulus length. The current best with the fourth power of the modulus length. The current best
algorithms for factoring a modulus and breaking RSA security vary algorithms for factoring a modulus and breaking RSA security vary
roughly with the square of the modulus itself. Thus going from a 640 roughly with the square of the modulus itself. Thus going from a 640
bit modulus to a 1280 bit modulus only increases the verification bit modulus to a 1280 bit modulus only increases the verification
time by a factor of 4 but increases the work factor of breaking the time by a factor of 4 but increases the work factor of breaking the
key by over 2^3000. [RSA FAQ] An upper bound of 2552 bit has been key by over 2^3000. [RSA FAQ] An upper bound of 2552 bit has been
established for the MD4/RSA DNS security algorithm for established for the MD4/RSA DNS security algorithm for
interoperability purposes. interoperability purposes.
However, larger keys increase size of the KEY and SIG RRs. This However, larger keys increase the size of the KEY and SIG RRs. This
increases the chance of DNS UDP packet overflow and the possible increases the chance of DNS UDP packet overflow and the possible
necessity for using higher overhead TCP in responses. necessity for using higher overhead TCP in responses.
The recommended minimum RSA algorithm modulus size, 640 bits, is The recommended minimum RSA algorithm modulus size, 640 bits, is
believed by the authors to be secure at this time and for some years believed by the authors to be secure at this time and for some years
but high level zones in the DNS tree may wish to set a higher but high level zones in the DNS tree may wish to set a higher
minimum, perhaps 1000 bits, for security reasons. (Since the United minimum, perhaps 1000 bits, for security reasons. (Since the United
States National Security Agency generally permits export of States National Security Agency generally permits export of
encryption systems using an RSA modulus of up to 512 bits, use of encryption systems using an RSA modulus of up to 512 bits, use of
that small a modulus, i.e. n, must be considered weak.) that small a modulus, i.e. n, must be considered weak.)
skipping to change at page 35, line 28 skipping to change at page 36, line 28
be tampered with if the host it resides on is compromised. For be tampered with if the host it resides on is compromised. For
maximum security, the master copy of the zone file should be off net maximum security, the master copy of the zone file should be off net
and should not be updated based on an unsecured network mediated and should not be updated based on an unsecured network mediated
communication. communication.
Note, however, that secure resolvers need to be configured with some Note, however, that secure resolvers need to be configured with some
trusted on-line public key information (or a secure path to such a trusted on-line public key information (or a secure path to such a
resolver). resolver).
Non-zone private keys, such as host or user keys, may have to be kept Non-zone private keys, such as host or user keys, may have to be kept
on line to be used for real-time purposes such a IPSEC session set-up on line to be used for real-time purposes such as DNS transaction
or secure mail. security, IPSEC session set-up, or secure mail.
7.3 Key Generation 7.3 Key Generation
Careful key generation is a sometimes over looked but absolutely Careful key generation is a sometimes over looked but absolutely
essential element in any cryptographically secure system. The essential element in any cryptographically secure system. The
strongest algorithms used with the longest keys are still of no use strongest algorithms used with the longest keys are still of no use
if an adversary can guess enough to lower the size of the likely key if an adversary can guess enough to lower the size of the likely key
space so that it can be exhaustively searched. Suggestions will be space so that it can be exhaustively searched. Suggestions will be
found in RFC 1750. found in RFC 1750.
skipping to change at page 38, line 8 skipping to change at page 39, line 8
RRs, (2) maintains appropriate information in its local caches and RRs, (2) maintains appropriate information in its local caches and
database to indicate which RRs have been authenticated and to what database to indicate which RRs have been authenticated and to what
extent they have been authenticated, (3) performs additional queries extent they have been authenticated, (3) performs additional queries
as necessary to attempt to obtain KEY, SIG, or NXT RRs from non- as necessary to attempt to obtain KEY, SIG, or NXT RRs from non-
security aware servers, (4) normally sets the CD query header bit on security aware servers, (4) normally sets the CD query header bit on
its queries. its queries.
9. Security Considerations 9. Security Considerations
This document concerns technical details of extensions to the Domain This document concerns technical details of extensions to the Domain
Name System (DNS) protocol to provide data integrity and data origin Name System (DNS) protocol to provide data integrity and origin
authentication, public key distribution, and optional transaction authentication, public key distribution, and optional transaction
security. security.
If should be noted that, at most, these extensions guarantee the If should be noted that, at most, these extensions guarantee the
validity of resource records, including KEY resource records, validity of resource records, including KEY resource records,
retrieved from the DNS. They do not magically solve other security retrieved from the DNS. They do not magically solve other security
problems. For example, using secure DNS you can have high confidence problems. For example, using secure DNS you can have high confidence
in the IP address you retrieve for a host; however, this does not in the IP address you retrieve for a host name; however, this does
stop someone for substituting an unauthorized host at that address or not stop someone for substituting an unauthorized host at that
capturing packets sent to that address and responding with packets address or capturing packets sent to that address and falsely
apparently from that address. Any reasonably complete security responding with packets apparently from that address. Any reasonably
system will require the protection of many other facets of the complete security system will require the protection of many other
Internet. facets of the Internet.
References References
[NETSEC] - Network Security: PRIVATE Communications in a PUBLIC [NETSEC] - Network Security: PRIVATE Communications in a PUBLIC
World, Charlie Kaufman, Radia Perlman, & Mike Speciner, Prentice Hall World, Charlie Kaufman, Radia Perlman, & Mike Speciner, Prentice Hall
Series in Computer Networking and Distributed Communications 1995. Series in Computer Networking and Distributed Communications 1995.
[PKCS1] - PKCS #1: RSA Encryption Standard, RSA Data Security, Inc., [PKCS1] - PKCS #1: RSA Encryption Standard, RSA Data Security, Inc.,
3 June 1991, Version 1.4. 3 June 1991, Version 1.4.
skipping to change at page 38, line 47 skipping to change at page 39, line 47
[RFC1034] - Domain Names - Concepts and Facilities, P. Mockapetris, [RFC1034] - Domain Names - Concepts and Facilities, P. Mockapetris,
November 1987 November 1987
[RFC1035] - Domain Names - Implementation and Specifications [RFC1035] - Domain Names - Implementation and Specifications
[RFC1305] - Network Time Protocol (v3), D. Mills, April 9 1992. [RFC1305] - Network Time Protocol (v3), D. Mills, April 9 1992.
[RFC1321] - The MD5 Message-Digest Algorithm, R. Rivest, April 16 [RFC1321] - The MD5 Message-Digest Algorithm, R. Rivest, April 16
1992. 1992.
[RFC1530] - Principles of Operation for the TPC.INT Subdomain:
General Principles and Policy, C. Malamud, M. Rose, October 6 1993.
[RFC1750] - Randomness Requirements for Security, D. Eastlake, S. [RFC1750] - Randomness Requirements for Security, D. Eastlake, S.
Crocker, J. Schiller, December 1994. Crocker, J. Schiller, December 1994.
[RSA FAQ] - RSADSI Frequently Asked Questions periodic posting. [RSA FAQ] - RSADSI Frequently Asked Questions periodic posting.
Authors Addresses Authors Addresses
Donald E. Eastlake, 3rd Donald E. Eastlake, 3rd
CyberCash, Inc. CyberCash, Inc.
318 Acton Street 318 Acton Street
skipping to change at page 39, line 25 skipping to change at page 41, line 25
Charles W. Kaufman Charles W. Kaufman
Iris Associates Iris Associates
1 Technology Park Drive 1 Technology Park Drive
Westford, MA 01886 USA Westford, MA 01886 USA
Telephone: +1 508-392-5276 Telephone: +1 508-392-5276
EMail: charlie_kaufman@iris.com EMail: charlie_kaufman@iris.com
Expiration and File Name Expiration and File Name
This draft expires 15 February1995. This draft expires 10 April 1995.
Its file name is draft-ietf-dnssec-secext-05.txt. Its file name is draft-ietf-dnssec-secext-06.txt.
Appendix: Base 64 Encoding Appendix: Base 64 Encoding
The following encoding technique is taken from RFC 1521 by Borenstein The following encoding technique is taken from RFC 1521 by Borenstein
and Freed. It is reproduced here in an edited form for convenience. and Freed. It is reproduced here in an edited form for convenience.
A 65-character subset of US-ASCII is used, enabling 6 bits to be A 65-character subset of US-ASCII is used, enabling 6 bits to be
represented per printable character. (The extra 65th character, "=", represented per printable character. (The extra 65th character, "=",
is used to signify a special processing function.) is used to signify a special processing function.)
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