draft-ietf-dnsext-rfc2539bis-dhk-02.txt   draft-ietf-dnsext-rfc2539bis-dhk-03.txt 
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Information in the DNS
OBSOLETES: RFC 2539 Donald Eastlake 3rd OBSOLETES: RFC 2539 Donald E. Eastlake 3rd
Motorola Motorola Laboratories
Expires: November 2002 May 2002 Expires: January 2004 July 2003
Storage of Diffie-Hellman Keys in the Domain Name System (DNS)
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<draft-ietf-dnsext-rfc2539bis-dhk-02.txt>
Donald E. Eastlake 3rd Storage of Diffie-Hellman Keying Information in the DNS
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<draft-ietf-dnsext-rfc2539bis-dhk-03.txt>
Status of This Document Status of This Document
This draft is intended to be become a Draft Standard RFC.
Distribution of this document is unlimited. Comments should be sent Distribution of this document is unlimited. Comments should be sent
to the DNS extensions working group mailing list to the DNS extensions working group mailing list
<namedroppers@ops.ietf.org> or to the author. <namedroppers@ops.ietf.org> or to the author.
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INTERNET-DRAFT Diffie-Hellman Keys in the DNS
Abstract Abstract
A standard method for storing Diffie-Hellman keys in the Domain Name A standard method for encoding Diffie-Hellman keys in the Domain Name
System is described which utilizes DNS KEY resource records. System is described.
INTERNET-DRAFT Diffie-Hellman Information in the DNS
Acknowledgements Acknowledgements
Part of the format for Diffie-Hellman keys and the description Part of the format for Diffie-Hellman keys and the description
thereof was taken from a work in progress by Ashar Aziz, Tom Markson, thereof was taken from a work in progress by Ashar Aziz, Tom Markson,
and Hemma Prafullchandra. and Hemma Prafullchandra. In addition, the following persons
provided useful comments that were incorporated into the predecessor
In addition, the following persons provided useful comments that were of this document: Ran Atkinson, Thomas Narten.
incorporated into the predecessor of this document: Ran Atkinson,
Thomas Narten.
INTERNET-DRAFT Diffie-Hellman Keys in the DNS
Table of Contents Table of Contents
Status of This Document....................................1 Status of This Document....................................1
Abstract...................................................1
Abstract...................................................2
Acknowledgements...........................................2 Acknowledgements...........................................2
Table of Contents..........................................2
Table of Contents..........................................3 1. Introduction............................................3
1.1 About This Document....................................3
1. Introduction............................................4 1.2 About Diffie-Hellman...................................3
1.1 About This Document....................................4 2. Encoding Diffie-Hellman Keying Information..............4
1.2 About Diffie-Hellman...................................4 3. Performance Considerations..............................5
2. Diffie-Hellman KEY Resource Records.....................5 4. IANA Considerations.....................................5
3. Performance Considerations..............................6 5. Security Considerations.................................5
4. IANA Considerations.....................................6
5. Security Considerations.................................6
References.................................................7 Normative References.......................................6
Author's Address...........................................7 Informative Refences.......................................6
Author's Address...........................................6
Expiration and File Name...................................7 Expiration and File Name...................................7
Appendix A: Well known prime/generator pairs...............8 Appendix A: Well known prime/generator pairs...............8
A.1. Well-Known Group 1: A 768 bit prime..................8 A.1. Well-Known Group 1: A 768 bit prime..................8
A.2. Well-Known Group 2: A 1024 bit prime.................8 A.2. Well-Known Group 2: A 1024 bit prime.................8
A.3. Well-Known Group 3: A 1536 bit prime.................9 A.3. Well-Known Group 3: A 1536 bit prime.................9
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Information in the DNS
1. Introduction 1. Introduction
The Domain Name System (DNS) is the global hierarchical replicated The Domain Name System (DNS) is the global hierarchical replicated
distributed database system for Internet addressing, mail proxy, and distributed database system for Internet addressing, mail proxy, and
similar information. The DNS has been extended to include digital similar information [RFC 1034, 1035]. The DNS has been extended to
signatures and cryptographic keys as described in [RFC 2535]. include digital signatures and cryptographic keys as described in
[RFC 2535] and additonal work is underway which would require the
storage of keying and signature information in the DNS.
1.1 About This Document 1.1 About This Document
This document describes how to store Diffie-Hellman keys in the DNS. This document describes how to store Diffie-Hellman keys in the DNS.
Familiarity with the Diffie-Hellman key exchange algorithm is assumed Familiarity with the Diffie-Hellman key exchange algorithm is assumed
[Schneier, RFC 2631]. [Schneier, RFC 2631].
1.2 About Diffie-Hellman 1.2 About Diffie-Hellman
Diffie-Hellman requires two parties to interact to derive keying Diffie-Hellman requires two parties to interact to derive keying
information which can then be used for authentication. Since DNS SIG information which can then be used for authentication. Thus Diffie-
RRs are primarily used as stored authenticators of zone information Hellman is inherently a key agreement algorithm. As a result, no
for many different resolvers, no Diffie-Hellman algorithm SIG RR is format is defined for Diffie-Hellman "signature information". For
defined. For example, assume that two parties have local secrets "i" example, assume that two parties have local secrets "i" and "j".
and "j". Assume they each respectively calculate X and Y as follows: Assume they each respectively calculate X and Y as follows:
X = g**i ( mod p ) X = g**i ( mod p )
Y = g**j ( mod p ) Y = g**j ( mod p )
They exchange these quantities and then each calculates a Z as They exchange these quantities and then each calculates a Z as
follows: follows:
Zi = Y**i ( mod p ) Zi = Y**i ( mod p )
skipping to change at page 4, line 51 skipping to change at page 4, line 4
secret between the two parties that an adversary who does not know i secret between the two parties that an adversary who does not know i
or j will not be able to learn from the exchanged messages (unless or j will not be able to learn from the exchanged messages (unless
the adversary can derive i or j by performing a discrete logarithm the adversary can derive i or j by performing a discrete logarithm
mod p which is hard for strong p and g). mod p which is hard for strong p and g).
The private key for each party is their secret i (or j). The public The private key for each party is their secret i (or j). The public
key is the pair p and g, which must be the same for the parties, and key is the pair p and g, which must be the same for the parties, and
their individual X (or Y). their individual X (or Y).
For further information about Diffie-Hellman and precautions to take For further information about Diffie-Hellman and precautions to take
INTERNET-DRAFT Diffie-Hellman Information in the DNS
in deciding on a p and g, see [RFC 2631]. in deciding on a p and g, see [RFC 2631].
INTERNET-DRAFT Diffie-Hellman Keys in the DNS 2. Encoding Diffie-Hellman Keying Information
2. Diffie-Hellman KEY Resource Records When Diffie-Hellman keys appear within the RDATA portion of a RR,
they are encoded as shown below.
Diffie-Hellman keys are stored in the DNS as KEY RRs using algorithm The period of key validity is not included in this data but is
number 2. The structure of the RDATA portion of this RR is as shown indicated separately, for example by an RR which signs and
below. The first 4 octets, including the flags, protocol, and authenticates the RR containing the keying information.
algorithm fields are common to all KEY RRs as described in [RFC
2535]. The remainder, from prime length through public value is the
"public key" part of the KEY RR. The period of key validity is not in
the KEY RR but is indicated by the SIG RR(s) which signs and
authenticates the KEY RR(s) at that domain name.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| KEY flags | protocol | algorithm=2 | | KEY flags | protocol | algorithm=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| prime length (or flag) | prime (p) (or special) / | prime length (or flag) | prime (p) (or special) /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ prime (p) (variable length) | generator length | / prime (p) (variable length) | generator length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 5, line 51 skipping to change at page 5, line 5
allocating additional table entries. The meaning of a zero or 3 allocating additional table entries. The meaning of a zero or 3
through 15 value for "prime length" is reserved. through 15 value for "prime length" is reserved.
Generator length is the length of the generator (g) in bytes. Generator length is the length of the generator (g) in bytes.
Generator is the binary representation of generator with most Generator is the binary representation of generator with most
significant byte first. PublicValueLen is the Length of the Public significant byte first. PublicValueLen is the Length of the Public
Value (g**i (mod p)) in bytes. PublicValue is the binary Value (g**i (mod p)) in bytes. PublicValue is the binary
representation of the DH public value with most significant byte representation of the DH public value with most significant byte
first. first.
The corresponding algorithm=2 SIG resource record is not used so no INTERNET-DRAFT Diffie-Hellman Information in the DNS
format for it is defined.
INTERNET-DRAFT Diffie-Hellman Keys in the DNS
3. Performance Considerations 3. Performance Considerations
Current DNS implementations are optimized for small transfers, Current DNS implementations are optimized for small transfers,
typically less than 512 bytes including DNS overhead. Larger typically less than 512 bytes including DNS overhead. Larger
transfers will perform correctly and extensions have been transfers will perform correctly and extensions have been
standardized [RFC 2671] to make larger transfers more efficient, it standardized [RFC 2671] to make larger transfers more efficient, it
is still advisable at this time to make reasonable efforts to is still advisable at this time to make reasonable efforts to
minimize the size of KEY RR sets stored within the DNS consistent minimize the size of RR sets containing keying information consistent
with adequate security. Keep in mind that in a secure zone, at least with adequate security.
one authenticating SIG RR will also be returned.
4. IANA Considerations 4. IANA Considerations
Assignment of meaning to Prime Lengths of 0 and 3 through 15 requires Assignment of meaning to Prime Lengths of 0 and 3 through 15 requires
an IETF consensus as defined in [RFC 2434]. an IETF consensus as defined in [RFC 2434].
Well known prime/generator pairs number 0x0000 through 0x07FF can Well known prime/generator pairs number 0x0000 through 0x07FF can
only be assigned by an IETF standards action. RFC 2539, the Proposed only be assigned by an IETF standards action. RFC 2539, the Proposed
Standard predecessor of this document, assigned 0x0001 through Standard predecessor of this document, assigned 0x0001 through
0x0002. This document proposes to assign 0x0003. Pairs number 0s0800 0x0002. This document assigns 0x0003. Pairs number 0s0800 through
through 0xBFFF can be assigned based on RFC documentation. Pairs 0xBFFF can be assigned based on RFC documentation. Pairs number
number 0xC000 through 0xFFFF are available for private use and are 0xC000 through 0xFFFF are available for private use and are not
not centrally coordinated. Use of such private pairs outside of a centrally coordinated. Use of such private pairs outside of a closed
closed environment may result in conflicts. environment may result in conflicts.
5. Security Considerations 5. Security Considerations
Many of the general security consideration in [RFC 2535] apply. Keys Keying information retrieved from the DNS should not be trusted
retrieved from the DNS should not be trusted unless (1) they have unless (1) it has been securely obtained from a secure resolver or
been securely obtained from a secure resolver or independently independently verified by the user and (2) this secure resolver and
verified by the user and (2) this secure resolver and secure secure obtainment or independent verification conform to security
obtainment or independent verification conform to security policies policies acceptable to the user. As with all cryptographic
acceptable to the user. As with all cryptographic algorithms, algorithms, evaluating the necessary strength of the key is important
evaluating the necessary strength of the key is important and and dependent on security policy.
dependent on security policy.
In addition, the usual Diffie-Hellman key strength considerations In addition, the usual Diffie-Hellman key strength considerations
apply. (p-1)/2 should also be prime, g should be primitive mod p, p apply. (p-1)/2 should also be prime, g should be primitive mod p, p
should be "large", etc. [RFC 2631, Schneier] should be "large", etc. [RFC 2631, Schneier]
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Information in the DNS
References Normative References
[RFC 2631] - "Diffie-Hellman Key Agreement Method", E. Rescorla, June
1999.
[RFC 2434] - Guidelines for Writing an IANA Considerations Section in
RFCs, T. Narten, H. Alvestrand, October 1998.
Informative Refences
[RFC 1034] - P. Mockapetris, "Domain names - concepts and [RFC 1034] - P. Mockapetris, "Domain names - concepts and
facilities", November 1987. facilities", November 1987.
[RFC 1035] - P. Mockapetris, "Domain names - implementation and [RFC 1035] - P. Mockapetris, "Domain names - implementation and
specification", November 1987. specification", November 1987.
[RFC 2434] - Guidelines for Writing an IANA Considerations Section in
RFCs, T. Narten, H. Alvestrand, October 1998.
[RFC 2535] - Domain Name System Security Extensions, D. Eastlake 3rd, [RFC 2535] - Domain Name System Security Extensions, D. Eastlake 3rd,
March 1999. March 1999.
[RFC 2539] - Storage of Diffie-Hellman Keys in the Domain Name System [RFC 2539] - Storage of Diffie-Hellman Keys in the Domain Name System
(DNS), D. Eastlake, March 1999, obsoleted by this RFC. (DNS), D. Eastlake, March 1999, obsoleted by this RFC.
[RFC 2631] - Diffie-Hellman Key Agreement Method, E. Rescorla, June
1999.
[RFC 2671] - Extension Mechanisms for DNS (EDNS0), P. Vixie, August [RFC 2671] - Extension Mechanisms for DNS (EDNS0), P. Vixie, August
1999. 1999.
[Schneier] - Bruce Schneier, "Applied Cryptography: Protocols, [Schneier] - Bruce Schneier, "Applied Cryptography: Protocols,
Algorithms, and Source Code in C" (Second Edition), 1996, John Wiley Algorithms, and Source Code in C" (Second Edition), 1996, John Wiley
and Sons. and Sons.
Author's Address Author's Address
Donald E. Eastlake 3rd Donald E. Eastlake 3rd
Motorola Motorola Laboratories
155 Beaver Street 155 Beaver Street
Milford, MA 01757 USA Milford, MA 01757 USA
Telephone: +1-508-851-8280 (w) Telephone: +1-508-851-8280 (w)
+1-508-634-2066 (h) +1-508-634-2066 (h)
FAX: +1-508-851-8507 (w)
EMail: Donald.Eastlake@motorola.com EMail: Donald.Eastlake@motorola.com
INTERNET-DRAFT Diffie-Hellman Information in the DNS
Expiration and File Name Expiration and File Name
This draft expires in November 2002. This draft expires in January 2004.
Its file name is draft-ietf-dnsext-rfc2539bis-dhk-02.txt. Its file name is draft-ietf-dnsext-rfc2539bis-dhk-03.txt.
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Information in the DNS
Appendix A: Well known prime/generator pairs Appendix A: Well known prime/generator pairs
These numbers are copied from the IPSEC effort where the derivation of These numbers are copied from the IPSEC effort where the derivation of
these values is more fully explained and additional information is available. these values is more fully explained and additional information is available.
Richard Schroeppel performed all the mathematical and computational Richard Schroeppel performed all the mathematical and computational
work for this appendix. work for this appendix.
A.1. Well-Known Group 1: A 768 bit prime A.1. Well-Known Group 1: A 768 bit prime
skipping to change at page 9, line 5 skipping to change at page 9, line 5
Prime modulus: Length (32 bit words): 32, Data (hex): Prime modulus: Length (32 bit words): 32, Data (hex):
FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1 FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245 EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381 EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381
FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF
Generator: Length (32 bit words): 1, Data (hex): 2 Generator: Length (32 bit words): 1, Data (hex): 2
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Information in the DNS
A.3. Well-Known Group 3: A 1536 bit prime A.3. Well-Known Group 3: A 1536 bit prime
The prime is 2^1536 - 2^1472 - 1 + 2^64 * { [2^1406 pi] + 741804 }. The prime is 2^1536 - 2^1472 - 1 + 2^64 * { [2^1406 pi] + 741804 }.
Its decimal value is Its decimal value is
241031242692103258855207602219756607485695054850245994265411 241031242692103258855207602219756607485695054850245994265411
694195810883168261222889009385826134161467322714147790401219 694195810883168261222889009385826134161467322714147790401219
650364895705058263194273070680500922306273474534107340669624 650364895705058263194273070680500922306273474534107340669624
601458936165977404102716924945320037872943417032584377865919 601458936165977404102716924945320037872943417032584377865919
814376319377685986952408894019557734611984354530154704374720 814376319377685986952408894019557734611984354530154704374720
 End of changes. 

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