Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
draft-sheffer-uta-bcp195bis-00

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UTA Working Group                                             Y. Sheffer
Internet-Draft                                                    Intuit
Obsoletes: 7525 (if approved)                                    R. Holz
Intended status: Best Current Practice                             NICTA
Expires: 20 August 2020                                   P. Saint-Andre
                                                                 Mozilla
                                                        17 February 2020

  Recommendations for Secure Use of Transport Layer Security (TLS) and
                Datagram Transport Layer Security (DTLS)
                     draft-sheffer-uta-bcp195bis-00

Abstract

   Transport Layer Security (TLS) and Datagram Transport Layer Security
   (DTLS) are widely used to protect data exchanged over application
   protocols such as HTTP, SMTP, IMAP, POP, SIP, and XMPP.  Over the
   last few years, several serious attacks on TLS have emerged,
   including attacks on its most commonly used cipher suites and their
   modes of operation.  This document provides recommendations for
   improving the security of deployed services that use TLS and DTLS.
   The recommendations are applicable to the majority of use cases.

Status of This Memo

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   This Internet-Draft will expire on 20 August 2020.

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   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/

Sheffer, et al.          Expires 20 August 2020                 [Page 1]
Internet-Draft             TLS Recommendations             February 2020

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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  General Recommendations . . . . . . . . . . . . . . . . . . .   4
     3.1.  Protocol Versions . . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  SSL/TLS Protocol Versions . . . . . . . . . . . . . .   4
       3.1.2.  DTLS Protocol Versions  . . . . . . . . . . . . . . .   5
       3.1.3.  Fallback to Lower Versions  . . . . . . . . . . . . .   5
     3.2.  Strict TLS  . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Compression . . . . . . . . . . . . . . . . . . . . . . .   6
     3.4.  TLS Session Resumption  . . . . . . . . . . . . . . . . .   7
     3.5.  TLS Renegotiation . . . . . . . . . . . . . . . . . . . .   7
     3.6.  Server Name Indication  . . . . . . . . . . . . . . . . .   8
   4.  Recommendations: Cipher Suites  . . . . . . . . . . . . . . .   8
     4.1.  General Guidelines  . . . . . . . . . . . . . . . . . . .   8
     4.2.  Recommended Cipher Suites . . . . . . . . . . . . . . . .   9
       4.2.1.  Implementation Details  . . . . . . . . . . . . . . .  10
     4.3.  Public Key Length . . . . . . . . . . . . . . . . . . . .  11
     4.4.  Modular Exponential vs. Elliptic Curve DH Cipher
           Suites  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     4.5.  Truncated HMAC  . . . . . . . . . . . . . . . . . . . . .  12
   5.  Applicability Statement . . . . . . . . . . . . . . . . . . .  13
     5.1.  Security Services . . . . . . . . . . . . . . . . . . . .  13
     5.2.  Opportunistic Security  . . . . . . . . . . . . . . . . .  14
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
     6.1.  AES-GCM . . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.2.  Forward Secrecy . . . . . . . . . . . . . . . . . . . . .  16
     6.3.  Diffie-Hellman Exponent Reuse . . . . . . . . . . . . . .  17
     6.4.  Certificate Revocation  . . . . . . . . . . . . . . . . .  17
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  18
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
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