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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force L. Velvindron, Ed. 3 Internet-Draft Hackers Mauritius 4 Intended status: Standards Track March 10, 2017 5 Expires: September 11, 2017 7 Increase minimum recommended modulus size to 2048 bits 8 draft-lvelvindron-dh-group-exchange-00 10 Abstract 12 The Diffie-Hellman Group Exchange for the Secure Shell (SSH) 13 Transport layer Protocol specifies that servers and clients should 14 support groups with a modulus length of k bits, where the recommended 15 minumum value is 1024 bits. Recent security research has shown that 16 a minimum value of 1024 bits is insufficient against state-sponsored 17 actors. As such, this document formally updates RFC 4419 [RFC4419] 18 such that the minimum recommended value for k is 2048 bits and the 19 group size is 2048 bits at minimum. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on September 11, 2017. 38 Copyright Notice 40 Copyright (c) 2017 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 57 2. 2048 bits Diffie-Hellman Group . . . . . . . . . . . . . . . 2 58 3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 59 4. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 4.1. Normative References . . . . . . . . . . . . . . . . . . 3 61 4.2. Informative References . . . . . . . . . . . . . . . . . 3 62 4.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1. Introduction 67 RFC4419 [RFC4419] specifies a recommended minimum size of 1024 for k, 68 which is the modulus length of the Diffie-Hellman Group. It also 69 suggests that in all cases, the size of the group needs be at least 70 1024 bits. This document updates RFC 4419 [RFC4419] so that the 71 minimum recommended size be 2048 bits 73 1.1. Requirements Language 75 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 76 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 77 document are to be interpreted as described in RFC 2119 [RFC2119]. 79 2. 2048 bits Diffie-Hellman Group 81 Recent research [LOGJAM] [1] strongly suggests that DH groups that 82 are 1024 bits can be broken by state actors, and possibly an 83 organization with enough computing resources. The authors show how 84 they are able to break 768 bits DH group and extrapolate the attack 85 to 1024 bits DH groups. In their analysis, they show that breaking 86 1024 bits can be done with enough computing resources. This document 87 updates section 3 Paragraph 9 : Servers and clients SHOULD support 88 groups with a modulus length of k bits where 2048 <= k <= 8192. The 89 recommended minimum values for min and max are 2048 and 8192, 90 respectively. This document also updates Section 3 Paragraph 11: In 91 all cases, ths size of the group SHOULD be at least 2048 bits. 93 3. Security Considerations 95 This document discusses security issues of DH groups that are 1024 96 bits in size, and formally updates the minimum size of DH groups to 97 be 2048 bits. 99 4. References 101 4.1. Normative References 103 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 104 Requirement Levels", BCP 14, RFC 2119, 105 DOI 10.17487/RFC2119, March 1997, 106 . 108 4.2. Informative References 110 [RFC4419] Friedl, M., Provos, N., and W. Simpson, "Diffie-Hellman 111 Group Exchange for the Secure Shell (SSH) Transport Layer 112 Protocol", RFC 4419, DOI 10.17487/RFC4419, March 2006, 113 . 115 4.3. URIs 117 [1] https://weakdh.org/imperfect-forward-secrecy-ccs15.pdf 119 Author's Address 121 Loganaden Velvindron (editor) 122 Hackers Mauritius 123 88, Avenue De Plevitz 124 Roches Brunes 125 MU 127 Phone: +230 59762817 128 Email: logan@hackers.mu