< draft-ietf-dnssec-dhk-02.txt   draft-ietf-dnssec-dhk-03.txt >
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Keys in the DNS
March 1998 November 1998
Expires September 1998 Expires May 1999
Storage of Diffie-Hellman Keys in the Domain Name System (DNS) Storage of Diffie-Hellman Keys in the Domain Name System (DNS)
------- -- -------------- ---- -- --- ------ ---- ------ ----- ------- -- -------------- ---- -- --- ------ ---- ------ -----
Donald E. Eastlake 3rd Donald E. Eastlake 3rd
Status of This Document Status of This Document
This draft, file name draft-ietf-dnssec-dhk-02.txt, is intended to be This draft, file name draft-ietf-dnssec-dhk-03.txt, is intended to be
become a Proposed Standard RFC. Distribution of this document is become a Proposed Standard RFC. Distribution of this document is
unlimited. Comments should be sent to the DNS security mailing list unlimited. Comments should be sent to the DNS security mailing list
<dns-security@tis.com> or to the author. <dns-security@tis.com> or to the author.
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.
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months. Internet-Drafts may be updated, replaced, or obsoleted by months. Internet-Drafts may be updated, replaced, or obsoleted by
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To learn the current status of any Internet-Draft, please check the To view the entire list of current Internet-Drafts, please check the
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Directories on ds.internic.net (East USA), ftp.isi.edu (West USA), Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern
ftp.nordu.net (North Europe), ftp.nis.garr.it (South Europe), Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific
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[Changes from previous draft: add IANA considerations section, update
author info, update file name and dates, add specific well known
groups]
INTERNET-DRAFT Diffie-Hellman Keys in the DNS 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 storing Diffie-Hellman keys in the Domain Name
System is described which utilizes DNS KEY resource records. System is described which utilizes DNS KEY resource records.
Acknowledgements Acknowledgements
skipping to change at page 3, line 4 skipping to change at page 2, line 25
thereof was taken from an Internet draft by: thereof was taken from an Internet draft by:
Ashar Aziz <ashar.aziz@eng.sun.com> Ashar Aziz <ashar.aziz@eng.sun.com>
Tom Markson <markson@incog.com> Tom Markson <markson@incog.com>
Hemma Prafullchandra <hemma@eng.sun.com> Hemma Prafullchandra <hemma@eng.sun.com>
In addition, the following person provided useful comments that have In addition, the following person provided useful comments that have
been incorporated: been incorporated:
Ran Atkinson <rja@inet.org> Ran Atkinson <rja@inet.org>
Thomas Narten <narten@raleigh.ibm.com>
INTERNET-DRAFT Diffie-Hellman Keys in the DNS 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...................................................2 Abstract...................................................2
Acknowledgements...........................................2 Acknowledgements...........................................2
Table of Contents..........................................3 Table of Contents..........................................3
1. Introduction............................................4 1. Introduction............................................4
1.1 About This Document....................................4
1.2 About Diffie-Hellman...................................4
2. Diffie-Hellman KEY Resource Records.....................5 2. Diffie-Hellman KEY Resource Records.....................5
3. Performance Considerations..............................6 3. Performance Considerations..............................6
4. Security Considerations.................................6 4. IANA Considerations.....................................6
5. Security Considerations.................................6
References.................................................7 References.................................................7
Author's Address...........................................7 Author's Address...........................................7
Expiration and File Name...................................7 Expiration and File Name...................................7
Appendix A: Well known prime/generator pairs...............8
A.1. Well-Known Group 1: A 768 bit prime..................8
A.2. Well-Known Group 2: A 1024 bit prime.................8
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Keys in the DNS
1. Introduction 1. Introduction
The Domain Name System (DNS) is the current global hierarchical The Domain Name System (DNS) is the current global hierarchical
replicated distributed database system for Internet addressing, mail replicated distributed database system for Internet addressing, mail
proxy, and similar information. The DNS has been extended to include proxy, and similar information. The DNS has been extended to include
digital signatures and cryptographic keys as described in [draft- digital signatures and cryptographic keys as described in [draft-
ietf-dnssec-secext2-*.txt]. Thus the DNS can now be used for secure ietf-dnssec-secext2-*.txt]. Thus the DNS can now be used for secure
key distribution. key distribution.
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]. [Schneier].
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. Since DNS SIG
RRs are primarily used as stored authenticators of zone information RRs are primarily used as stored authenticators of zone information
for many different resolvers, no Diffie-Hellman algorithm SIG RR is for many different resolvers, no Diffie-Hellman algorithm SIG RR is
defined. For example, assume that two parties have local secrets "i" defined. For example, assume that two parties have local secrets "i"
and "j". Assume they each respectively calculate X and Y as follows: and "j". 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 )
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Zi = Y**i ( mod p ) Zi = Y**i ( mod p )
Zj = X**j ( mod p ) Zj = X**j ( mod p )
Zi and Zj will both be equal to g**(ij)(mod p) and will be a shared Zi and Zj will both be equal to g**(ij)(mod p) and will be a shared
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).
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Keys in the DNS
2. Diffie-Hellman KEY Resource Records 2. Diffie-Hellman KEY Resource Records
Diffie-Hellman keys are stored in the DNS as KEY RRs using algorithm Diffie-Hellman keys are stored in the DNS as KEY RRs using algorithm
number 2. The structure of the RDATA portion of this RR is as shown number 2. The structure of the RDATA portion of this RR is as shown
below. The first 4 octets, including the flags, protocol, and below. The first 4 octets, including the flags, protocol, and
algorithm fields are common to all KEY RRs as described in [draft- algorithm fields are common to all KEY RRs as described in [draft-
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| public value length | public value (variable length)/ | public value length | public value (variable length)/
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ public value (g^i mod p) (variable length) | / public value (g^i mod p) (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Prime length is length of the Diffie-Hellman prime (p) in bytes if it Prime length is length of the Diffie-Hellman prime (p) in bytes if it
is 16 or greater. Prime contains the binary representation of the is 16 or greater. Prime contains the binary representation of the
Diffie-Hellman prime with most significant byte first (i.e., in Diffie-Hellman prime with most significant byte first (i.e., in
network order). If "prime length" field is 1 or 2, then the "prime" network order). If "prime length" field is 1 or 2, then the "prime"
field is actually an unsigned index into a table of up to 65,536 field is actually an unsigned index into a table of 65,536
predefined prime/generator pairs to be defined in which case the prime/generator pairs and the generator length SHOULD be zero. See
generator length should be zero. The meaning of a zero or 3 through Appedix A for defined table entries and Section 4 for information on
15 value for "prime length" is reserved. allocating additional table entries. The meaning of a zero or 3
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 The corresponding algorithm=2 SIG resource record is not used so no
format for it is defined. format for it is defined.
INTERNET-DRAFT Diffie-Hellman Keys in the DNS 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 overhead. While larger typically less than 512 bytes including overhead. While larger
transfers will perform correctly and work is underway to make larger transfers will perform correctly and work is underway to make larger
transfers more efficient, it is still advisable at this time to make transfers more efficient, it is still advisable to make reasonable
reasonable efforts to minimize the size of KEY RR sets stored within efforts to minimize the size of KEY RR sets stored within the DNS
the DNS consistent with adequate security. Keep in mind that in a consistent with adequate security. Keep in mind that in a secure
secure zone, an authenticating SIG RR will also be returned. zone, an authenticating SIG RR will also be returned.
4. Security Considerations 4. IANA Considerations
Assignment of meaning to Prime Lengths of 0 and 3 through 15 requires
an IETF consensus.
Well known prime/generator pairs number 0x0000 through 0x07FF can
only be assigned by an IETF standards action and this Proposed
Standard assigns 0x0001 through 0x0002. Pairs number 0s0800 through
0xBFFF can be assigned based on RFC documentation. Pairs number
0xC000 through 0xFFFF are available for private use and are not
centrally coordinated. Use of such private pairs outside of a closed
environment may result in conflicts.
5. Security Considerations
Many of the general security consideration in [draft-ietf-dnssec- Many of the general security consideration in [draft-ietf-dnssec-
secext2-*] apply. Keys retrieved from the DNS should not be trusted secext2-*] apply. Keys retrieved from the DNS should not be trusted
unless (1) they have been securely obtained from a secure resolver or unless (1) they have been securely obtained from a secure resolver or
independently verified by the user and (2) this secure resolver and independently verified by the user and (2) this secure resolver and
secure obtainment or independent verification conform to security secure obtainment or independent verification conform to security
policies acceptable to the user. As with all cryptographic policies acceptable to the user. As with all cryptographic
algorithms, evaluating the necessary strength of the key is essential algorithms, evaluating the necessary strength of the key is important
and dependent on local policy. and dependent on local 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. [Schneier] should be "large", etc. [Schneier]
INTERNET-DRAFT Diffie-Hellman Keys in the DNS INTERNET-DRAFT Diffie-Hellman Keys in the DNS
References References
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[draft-ietf-dnssec-secext2-*.txt] - Domain Name System Security [draft-ietf-dnssec-secext2-*.txt] - Domain Name System Security
Extensions, D. Eastlake. Extensions, D. Eastlake.
[Schneier] - Bruce Schneier, "Applied Cryptography: Protocols, [Schneier] - Bruce Schneier, "Applied Cryptography: Protocols,
Algorithms, and Source Code in C", 1996, John Wiley and Sons Algorithms, and Source Code in C", 1996, John Wiley and Sons
Author's Address Author's Address
Donald E. Eastlake 3rd Donald E. Eastlake 3rd
CyberCash, Inc. IBM
318 Acton Street 318 Acton Street
Carlisle, MA 01741 USA Carlisle, MA 01741 USA
Telephone: +1 978 287 4877 Telephone: +1-978-287-4877
+1 703 620-4200 (main office, Reston, VA) +1-914-784-7913
FAX: +1 978 371 7148 FAX: +1-978-371-7148
EMail: dee@cybercash.com EMail: dee3@us.ibm.com
Expiration and File Name Expiration and File Name
This draft expires in September 1998. This draft expires in April 1999.
Its file name is draft-ietf-dnssec-dhk-02.txt. Its file name is draft-ietf-dnssec-dhk-03.txt.
INTERNET-DRAFT Diffie-Hellman Keys in the DNS
Appendix A: Well known prime/generator pairs
These numbers are copied from the IPSEC effort where the derivation of
these values is more fully explained and additional information is available.
Richard Schroeppel performed all the mathematical and computational
work for this appendix.
A.1. Well-Known Group 1: A 768 bit prime
The prime is 2^768 - 2^704 - 1 + 2^64 * { [2^638 pi] + 149686 }. Its
decimal value is
155251809230070893513091813125848175563133404943451431320235
119490296623994910210725866945387659164244291000768028886422
915080371891804634263272761303128298374438082089019628850917
0691316593175367469551763119843371637221007210577919
Prime modulus: Length (32 bit words): 24, Data (hex):
FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
E485B576 625E7EC6 F44C42E9 A63A3620 FFFFFFFF FFFFFFFF
Generator: Length (32 bit words): 1, Data (hex): 2
A.2. Well-Known Group 2: A 1024 bit prime
The prime is 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
Its decimal value is
179769313486231590770839156793787453197860296048756011706444
423684197180216158519368947833795864925541502180565485980503
646440548199239100050792877003355816639229553136239076508735
759914822574862575007425302077447712589550957937778424442426
617334727629299387668709205606050270810842907692932019128194
467627007
Prime modulus: Length (32 bit words): 32, Data (hex):
FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1
29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD
EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245
E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED
EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381
FFFFFFFF FFFFFFFF
Generator: Length (32 bit words): 1, Data (hex): 2
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