Randomness Improvements for Security Protocols
draft-irtf-cfrg-randomness-improvements-13

Document Type Active Internet-Draft (cfrg RG)
Last updated 2020-07-14 (latest revision 2020-06-24)
Replaces draft-sullivan-randomness-improvements, draft-cremers-cfrg-randomness-improvements
Stream IRTF
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Internet Research Task Force (IRTF)                           C. Cremers
Internet-Draft           CISPA Helmholtz Center for Information Security
Intended status: Informational                                L. Garratt
Expires: 26 December 2020                                   Cisco Meraki
                                                           S. Smyshlyaev
                                                               CryptoPro
                                                             N. Sullivan
                                                                 C. Wood
                                                              Cloudflare
                                                            24 June 2020

             Randomness Improvements for Security Protocols
               draft-irtf-cfrg-randomness-improvements-13

Abstract

   Randomness is a crucial ingredient for Transport Layer Security (TLS)
   and related security protocols.  Weak or predictable
   "cryptographically-strong" pseudorandom number generators (CSPRNGs)
   can be abused or exploited for malicious purposes.  An initial
   entropy source that seeds a CSPRNG might be weak or broken as well,
   which can also lead to critical and systemic security problems.  This
   document describes a way for security protocol implementations to
   augment their CSPRNGs using long-term private keys.  This improves
   randomness from broken or otherwise subverted CSPRNGs.

   This document is a product of the Crypto Forum Research Group (CFRG)
   in the IRTF.

Note to Readers

   Source for this draft and an issue tracker can be found at
   https://github.com/chris-wood/draft-irtf-cfrg-randomness-improvements
   (https://github.com/chris-wood/draft-irtf-cfrg-randomness-
   improvements).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

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Internet-Draft           Randomness Improvements               June 2020

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 26 December 2020.

Copyright Notice

   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/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   4
   3.  Randomness Wrapper  . . . . . . . . . . . . . . . . . . . . .   4
   4.  Tag Generation  . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Application to TLS  . . . . . . . . . . . . . . . . . . . . .   6
   6.  Implementation Guidance . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. Comparison to RFC 6979  . . . . . . . . . . . . . . . . . . .   7
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     11.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Secure and properly implemented random number generators, or
   "cryptographically-strong" pseudorandom number generators (CSPRNGs),
   should produce output that is indistinguishable from a random string
   of the same length.  CSPRNGs are critical building blocks for TLS and
   related transport security protocols.  TLS in particular uses CSPRNGs
   to generate several values: session IDs, ephemeral key shares, and
   ClientHello and ServerHello random values.  CSPRNG failures such as
   the Debian bug described in [DebianBug] can lead to insecure TLS

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