draft-ietf-curdle-ssh-modp-dh-sha2-03.txt   draft-ietf-curdle-ssh-modp-dh-sha2-04.txt 
Internet Engineering Task Force M. Baushke Internet Engineering Task Force M. Baushke
Internet-Draft Juniper Networks, Inc. Internet-Draft Juniper Networks, Inc.
Updates: 4253, 4432 (if approved) March 27, 2017 Updates: 4250, 4253 (if approved) April 14, 2017
Intended status: Standards Track Intended status: Standards Track
Expires: September 28, 2017 Expires: October 16, 2017
More Modular Exponential (MODP) Diffie-Hellman (DH) Key Exchange (KEX) More Modular Exponential (MODP) Diffie-Hellman (DH) Key Exchange (KEX)
Groups for Secure Shell (SSH) Groups for Secure Shell (SSH)
draft-ietf-curdle-ssh-modp-dh-sha2-03 draft-ietf-curdle-ssh-modp-dh-sha2-04
Abstract Abstract
This document defines added Modular Exponential (MODP) Groups for the This document defines added Modular Exponential (MODP) Groups for the
Secure Shell (SSH) protocol using SHA-2 hashes. Secure Shell (SSH) protocol using SHA-2 hashes. This document
updates RFC 4250. This document updates RFC 4253.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 28, 2017. This Internet-Draft will expire on October 16, 2017.
Copyright Notice Copyright Notice
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1. Overview and Rationale 1. Overview and Rationale
Secure Shell (SSH) is a common protocol for secure communication on Secure Shell (SSH) is a common protocol for secure communication on
the Internet. Due to recent security concerns with SHA-1 [RFC6194] the Internet. Due to recent security concerns with SHA-1 [RFC6194]
and with MODP groups with less than 2048 bits [NIST-SP-800-131Ar1] and with MODP groups with less than 2048 bits [NIST-SP-800-131Ar1]
implementer and users request support for larger Diffie Hellman (DH) implementer and users request support for larger Diffie Hellman (DH)
MODP group sizes with data integrity verification using the SHA-2 MODP group sizes with data integrity verification using the SHA-2
family of secure hash algorithms as well as MODP groups providing family of secure hash algorithms as well as MODP groups providing
more security. more security.
skipping to change at page 2, line 29 skipping to change at page 2, line 41
transport of Top Secret information. For this reason, the new MODP transport of Top Secret information. For this reason, the new MODP
groups are being introduced starting with the MODP 3072-bit group 15 groups are being introduced starting with the MODP 3072-bit group 15
are all using SHA2-512 as the hash algorithm. are all using SHA2-512 as the hash algorithm.
The DH 2048-bit MODP group 14 is already present in most SSH The DH 2048-bit MODP group 14 is already present in most SSH
implementations and most implementations already have a SHA2-256 implementations and most implementations already have a SHA2-256
implementation, so diffie-hellman-group14-sha256 is provided as an implementation, so diffie-hellman-group14-sha256 is provided as an
easy to implement and faster to use key exchange for small embedded easy to implement and faster to use key exchange for small embedded
applications. applications.
It is intended that these new MODP groups with SHA-2 based hashes
update the [RFC4253] section 6.4 and [RFC4250] section 4.10
standards.
[TO BE REMOVED: Please send comments on this draft to [TO BE REMOVED: Please send comments on this draft to
curdle@ietf.org.] curdle@ietf.org.]
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
3. Key Exchange Algorithms 3. Key Exchange Algorithms
This memo adopts the style and conventions of [RFC4253] in specifying This memo adopts the style and conventions of [RFC4253] in specifying
how the use of new data key exchange is indicated in SSH. how the use of new data key exchange is indicated in SSH.
The following new key exchange algorithms are defined: The following new key exchange algorithms are defined:
Key Exchange Method Name Key Exchange Method Name
diffie-hellman-group14-sha256 diffie-hellman-group14-sha256
diffie-hellman-group15-sha512 diffie-hellman-group15-sha512
diffie-hellman-group16-sha512 diffie-hellman-group16-sha512
diffie-hellman-group17-sha512 diffie-hellman-group17-sha512
diffie-hellman-group18-sha512 diffie-hellman-group18-sha512
Figure 1 Figure 1
The SHA-2 family of secure hash algorithms are defined in The SHA-2 family of secure hash algorithms are defined in [RFC6234].
[FIPS-180-4].
The method of key exchange used for the name "diffie-hellman- The method of key exchange used for the name "diffie-hellman-
group14-sha256" is the same as that for "diffie-hellman-group14-sha1" group14-sha256" is the same as that for "diffie-hellman-group14-sha1"
except that the SHA2-256 hash algorithm is used. except that the SHA2-256 hash algorithm is used. It is recommended
that diffie-hellman-group14-sha256 SHOULD be supported to smooth the
transition to newer group sizes.
The group15 through group18 names are the same as those specified in The group15 through group18 names are the same as those specified in
[RFC3526] 3071-bit MODP Group 15, 4096-bit MODP Group 16, 6144-bit [RFC3526] 3071-bit MODP Group 15, 4096-bit MODP Group 16, 6144-bit
MODP Group 17, and 8192-bit MODP Group 18. MODP Group 17, and 8192-bit MODP Group 18.
The SHA2-512 algorithm is to be used when "sha512" is specified as a The SHA2-512 algorithm is to be used when "sha512" is specified as a
part of the key exchange method name. part of the key exchange method name.
4. IANA Considerations 4. IANA Considerations
This document augments the Key Exchange Method Names in [RFC4253]. This document augments the Key Exchange Method Names in [RFC4253] and
[RFC4250].
IANA is requested to add to the Key Exchange Method Names algorithm IANA is requested to add to the Key Exchange Method Names algorithm
registry with the following entries: registry [IANA-KEX] with the following entries:
Key Exchange Method Name Reference Key Exchange Method Name Reference
----------------------------- ---------- ----------------------------- ----------
diffie-hellman-group14-sha256 This Draft diffie-hellman-group14-sha256 This Draft
diffie-hellman-group15-sha512 This Draft diffie-hellman-group15-sha512 This Draft
diffie-hellman-group16-sha512 This Draft diffie-hellman-group16-sha512 This Draft
diffie-hellman-group17-sha512 This Draft diffie-hellman-group17-sha512 This Draft
diffie-hellman-group18-sha512 This Draft diffie-hellman-group18-sha512 This Draft
[TO BE REMOVED: This registration should take place at the following [TO BE REMOVED: This registration should take place at the following
skipping to change at page 4, line 22 skipping to change at page 4, line 35
+--------+----------+----------+----------+----------+----------+ +--------+----------+----------+----------+----------+----------+
| 14 | 2048-bit | 110 | 220- | 160 | 320- | | 14 | 2048-bit | 110 | 220- | 160 | 320- |
| 15 | 3072-bit | 130 | 260- | 210 | 420- | | 15 | 3072-bit | 130 | 260- | 210 | 420- |
| 16 | 4096-bit | 150 | 300- | 240 | 480- | | 16 | 4096-bit | 150 | 300- | 240 | 480- |
| 17 | 6144-bit | 170 | 340- | 270 | 540- | | 17 | 6144-bit | 170 | 340- | 270 | 540- |
| 18 | 8192-bit | 190 | 380- | 310 | 620- | | 18 | 8192-bit | 190 | 380- | 310 | 620- |
+--------+----------+---------------------+---------------------+ +--------+----------+---------------------+---------------------+
Figure 2 Figure 2
Using a fixed set of Diffie-Hellman parameters makes them a high
value target for precomputation. Generating additional sets of
primes to be used, or moving to larger values is a mitigation against
this issue. Care should be taken to avoid backdoored primes ([SNFS])
by using "nothing up my sleve" parameters.
6. References 6. References
6.1. Normative References 6.1. Normative References
[FIPS-180-4]
National Institute of Standards and Technology, "Secure
Hash Standard (SHS)", FIPS PUB 180-4, August 2015,
<http://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.180-4.pdf>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP) [RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)
Diffie-Hellman groups for Internet Key Exchange (IKE)", Diffie-Hellman groups for Internet Key Exchange (IKE)",
RFC 3526, DOI 10.17487/RFC3526, May 2003, RFC 3526, DOI 10.17487/RFC3526, May 2003,
<http://www.rfc-editor.org/info/rfc3526>. <http://www.rfc-editor.org/info/rfc3526>.
[RFC4250] Lehtinen, S. and C. Lonvick, Ed., "The Secure Shell (SSH)
Protocol Assigned Numbers", RFC 4250,
DOI 10.17487/RFC4250, January 2006,
<http://www.rfc-editor.org/info/rfc4250>.
[RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH) [RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253, Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
January 2006, <http://www.rfc-editor.org/info/rfc4253>. January 2006, <http://www.rfc-editor.org/info/rfc4253>.
6.2. Informative References 6.2. Informative References
[IANA-KEX]
Internet Assigned Numbers Authority (IANA), "Secure Shell
(SSH) Protocol Parameters: Key Exchange Method Names",
March 2017, <http://www.iana.org/assignments/ssh-
parameters/ssh-parameters.xhtml#ssh-parameters-16>.
[MFQ-U-OO-815099-15] [MFQ-U-OO-815099-15]
"National Security Agency/Central Security Service", "CNSA "National Security Agency/Central Security Service", "CNSA
Suite and Quantum Computing FAQ", January 2016, Suite and Quantum Computing FAQ", January 2016,
<https://www.iad.gov/iad/library/ia-guidance/ia-solutions- <https://www.iad.gov/iad/library/ia-guidance/ia-solutions-
for-classified/algorithm-guidance/cnsa-suite-and-quantum- for-classified/algorithm-guidance/cnsa-suite-and-quantum-
computing-faq.cfm>. computing-faq.cfm>.
[NIST-SP-800-131Ar1] [NIST-SP-800-131Ar1]
Barker, and Roginsky, "Transitions: Recommendation for the Barker, and Roginsky, "Transitions: Recommendation for the
Transitioning of the Use of Cryptographic Algorithms and Transitioning of the Use of Cryptographic Algorithms and
skipping to change at page 5, line 30 skipping to change at page 6, line 5
[RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For [RFC3766] Orman, H. and P. Hoffman, "Determining Strengths For
Public Keys Used For Exchanging Symmetric Keys", BCP 86, Public Keys Used For Exchanging Symmetric Keys", BCP 86,
RFC 3766, DOI 10.17487/RFC3766, April 2004, RFC 3766, DOI 10.17487/RFC3766, April 2004,
<http://www.rfc-editor.org/info/rfc3766>. <http://www.rfc-editor.org/info/rfc3766>.
[RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security [RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
Considerations for the SHA-0 and SHA-1 Message-Digest Considerations for the SHA-0 and SHA-1 Message-Digest
Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011, Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
<http://www.rfc-editor.org/info/rfc6194>. <http://www.rfc-editor.org/info/rfc6194>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<http://www.rfc-editor.org/info/rfc6234>.
[SNFS] Fried, , Gaudry, , Heninger, , and Thome, "A kilobit
hidden SNFS discrete logarithm computation", 2016,
<http://eprint.iacr.org/2016/961.pdf>.
Author's Address Author's Address
Mark D. Baushke Mark D. Baushke
Juniper Networks, Inc. Juniper Networks, Inc.
1133 Innovation Way 1133 Innovation Way
Sunnyvale, CA 94089-1228 Sunnyvale, CA 94089-1228
US US
Phone: +1 408 745 2952 Phone: +1 408 745 2952
Email: mdb@juniper.net Email: mdb@juniper.net
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