QUIC                                                             M. Duke
Internet-Draft                                                Google LLC
Intended status: Standards Track                           28 April                             12 May 2022
Expires: 30 October 13 November 2022

                             QUIC Version 2
                         draft-ietf-quic-v2-02
                         draft-ietf-quic-v2-03

Abstract

   This document specifies QUIC version 2, which is identical to QUIC
   version 1 except for some trivial details.  Its purpose is to combat
   various ossification vectors and exercise the version negotiation
   framework.  It also serves as a template for the minimum changes in
   any future version of QUIC.

   Note that "version 2" is an informal name for this proposal that
   indicates it is the second standards-track QUIC version.  The
   protocol specified here will receive a version number other than 2
   from IANA.

   Discussion of this work is encouraged to happen on the QUIC IETF
   mailing list quic@ietf.org or on the GitHub repository which contains
   the draft: https://github.com/quicwg/quic-v2.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at https://quicwg.org/
   quic-v2/draft-ietf-quic-v2.html.  Status information for this
   document may be found at https://datatracker.ietf.org/doc/draft-ietf-
   quic-v2/.

   Discussion of this document takes place on the QUIC Working Group
   mailing list (mailto:quic@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/quic/.

   Source for this draft and an issue tracker can be found at
   https://github.com/quicwg/quic-v2.

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
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   This Internet-Draft will expire on 30 October 13 November 2022.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Changes from  Differences with QUIC Version 1 . . . . . . . . . . . . . . . . .   4
     3.1.  Version Field . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Long Header Packet Types  . . . . . . . . . . . . . . . .   4
     3.3.  Cryptography changes  . . . . . . . . . . . . . . . . . .   4
       3.3.1.  Initial Salt  . . . . . . . . . . . . . . . . . . . .   4
       3.3.2.  HKDF Labels . . . . . . . . . . . . . . . . . . . . .   4
       3.3.3.  Retry Integrity Tag . . . . . . . . . . . . . . . . .   4   5
   4.  Version Negotiation Considerations  . . . . . . . . . . . . .   5
     4.1.  Compatible Negotiation Requirements . . . . . . . . . . .   5
   5.  TLS Resumption and NEW_TOKEN Tokens . . . . . . . . . . . . .   6
   6.  Ossification Considerations . . . . . . . . . . . . . . . . .   7
   7.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .   7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Appendix A.  Sample Packet Protection . . . . . . . . . . . . . .   9
     A.1.  Keys  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     A.2.  Client Initial  . . . . . . . . . . . . . . . . . . . . .  10
     A.3.  Server Initial  . . . . . . . . . . . . . . . . . . . . .  12
     A.4.  Retry . . . . . . . . . . . . . . . . . . . . . . . . . .  13
     A.5.  ChaCha20-Poly1305 Short Header Packet . . . . . . . . . .  13
   Appendix B.  Changelog  . . . . . . . . . . . . . . . . . . . . .  15
     B.1.  since draft-ietf-quic-v2-01 draft-ietf-quic-v2-02 . . . . . . . . . . . . . . .  15
     B.2.  since draft-ietf-quic-v2-00 draft-ietf-quic-v2-01 . . . . . . . . . . . . . . .  15
     B.3.  since draft-duke-quic-v2-02 draft-ietf-quic-v2-00 . . . . . . . . . . . . . . .  15
     B.4.  since draft-duke-quic-v2-01 draft-duke-quic-v2-02 . . . . . . . . . . . . . . .  15
     B.5.  since draft-duke-quic-v2-00 draft-duke-quic-v2-01 . . . . . . . . . . . . . . .  15
     B.6.  since draft-duke-quic-v2-00 . . . . . . . . . . . . . . .  16
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   QUIC [QUIC] has numerous extension points, including the version
   number that occupies the second through fifth octets bytes of every long
   header (see [RFC8999]). [QUIC-INVARIANTS]).  If experimental versions are rare,
   and QUIC version 1 constitutes the vast majority of QUIC traffic,
   there is the potential for middleboxes to ossify on the version octets bytes
   always being 0x00000001.

   Furthermore,

   In QUIC version 1 1, Initial packets are encrypted with keys
   derived from a universally known salt, which allow the version-
   specific salt as described in Section 5.2 of [QUIC-TLS].  Protecting
   Initial packets in this way allows observers to inspect the contents of these packets, their
   contents, which include includes the TLS Client Hello and or Server Hello
   messages.  Again, there is the potential for middleboxes may to ossify on
   the version 1 key derivation and packet formats.

   Finally [QUIC-VN] provides two mechanisms for endpoints to negotiate
   the QUIC version to use.  The "incompatible" version negotiation
   method can support switching from any initial QUIC version to any
   other version with full generality, at the cost of an additional
   round-trip at the start of the connection.  "Compatible" version
   negotiation eliminates the round-trip penalty but levies some
   restrictions on how much the two versions can differ semantically.

   QUIC version 2 is meant to mitigate ossification concerns and
   exercise the version negotiation mechanisms.  The only change is a
   tweak to the inputs of some crypto derivation functions to enforce
   full key separation.  Any endpoint that supports two versions needs
   to implement version negotiation to protect against downgrade
   attacks.

   [I-D.duke-quic-version-aliasing] is a more robust, but much more
   complicated, proposal to address these ossification problems.  By
   design, it requires incompatible version negotiation.  QUICv2 enables
   exercise of compatible version negotiation mechanism.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  Changes from  Differences with QUIC Version 1

   QUIC version 2 endpoints MUST implement the QUIC version 1
   specification as described in [QUIC], [QUIC-TLS], and [RFC9002], with [RFC9002].
   However, the following changes. differences apply in version 2.

3.1.  Version Field

   The version Version field of long headers is 0x709a50c4.

3.2.  Long Header Packet Types

   Initial packets use a packet type field of 0b01. 0-RTT packets use a
   packet type field of 0b10.  Handshake packets use a packet type field
   of 0b11.  Retry packets use a

   All version 2 long header packet type types are different.  The Type field of 0b00.
   values are:

   *  Initial: 0b01

   *  0-RTT: 0b10

   *  Handshake: 0b11

   *  Retry: 0b00

3.3.  Cryptography changes

3.3.1.  Initial Salt

   The salt used to derive Initial keys in Section 5.2 of [QUIC-TLS]
   changes to:

   initial_salt = 0xa707c203a59b47184a1d62ca570406ea7ae3e5d3

3.3.2.  HKDF Labels

   The labels used in [QUIC-TLS] to derive packet protection keys
   (Section 5.1), header protection keys (Section 5.4), Retry Integrity
   Tag keys (Section 5.8), and key updates (Section 6.1) change from
   "quic key" to "quicv2 key", from "quic iv" to "quicv2 iv", from "quic
   hp" to "quicv2 hp", and from "quic ku" to "quicv2 ku", to meet the
   guidance for new versions in Section 9.6 of that document.

3.3.3.  Retry Integrity Tag

   The key and nonce used for the Retry Integrity Tag (Section 5.8 of
   [QUIC-TLS]) change to:

   secret =
     0x3425c20cf88779df2ff71e8abfa78249891e763bbed2f13c048343d348c060e2
   key = 0xba858dc7b43de5dbf87617ff4ab253db
   nonce = 0x141b99c239b03e785d6a2e9f

4.  Version Negotiation Considerations

   QUIC version 2 is not intended to deprecate version 1.  Endpoints
   that support version 2 might continue support for version 1 to
   maximize compatibility with clients.  In particular, HTTP clients
   often use Alt-Svc [RFC7838] to discover QUIC support.  As this
   mechanism does not currently distinguish between QUIC versions, HTTP
   servers that support multiple versions reduce the probability of
   incompatibility and the cost associated with QUIC version negotiation
   or TCP fallback.  For example, an origin advertising support for "h3"
   in Alt-Svc SHOULD support QUIC version 1 as it was the original QUIC
   version used by HTTP/3 and therefore some clients will only support
   that version.

   Any QUIC endpoint that supports QUIC version 2 MUST send, process,
   and validate the version_information transport parameter specified in
   [QUIC-VN] to prevent version downgrade attacks.

   Note that version 2 meets that document's definition of a compatible
   version with version 1, and version 1 is compatible with version 2.
   Therefore, servers can use compatible negotiation to switch a
   connection between the two versions.  Endpoints that support both
   versions SHOULD support compatible version negotiation to avoid a
   round trip.

4.1.  Compatible Negotiation Requirements

   Compatible version negotiation between versions 1 and 2 follow the
   same requirements in either direction.  This section uses the terms
   "original version" and "negotiated version" from [QUIC-VN].

   If the server sends a Retry packet, it MUST use the original version.
   The client ignores Retry packets using other versions.  The client
   MUST NOT use a different version in the subsequent Initial that
   contains the Retry token.  The server MAY encode the QUIC version in
   its Retry token to validate that the client did not switch versions,
   and drop the packet if it switched.

   QUIC version 2 uses the same transport parameters to authenticate the
   Retry as QUIC version 1.  After switching to a negotiated version
   after a Retry, the server MUST include the relevant transport
   parameters to validate that the server sent the Retry and the
   connection IDs used in the exchange, as described in Section 7.3 of
   [QUIC].  Note that the version of the first Initial and the
   subsequent Retry are not authenticated by transport parameters.

   The server SHOULD start sending its Initial packets using the
   negotiated version as soon as it decides to change.  Before the
   server is able to process transport parameters from the client, it
   might need to respond to Initial packets from the client.  For these
   packets the server uses the original version.

   Once the client has processed a packet using the negotiated version,
   it SHOULD send subsequent Initial packets using that version.  The
   server MUST NOT discard its original version Initial receive keys
   until it successfully processes a packet with the negotiated version.

   Both endpoints MUST send Handshake or 1-RTT packets using the
   negotiated version.  An endpoint MUST drop packets using any other
   version.  Endpoints have no need to generate the keying material that
   would allow them to decrypt or authenticate these packets.

   If the server's version_information transport parameter does not
   contain a Chosen Version field equivalent to the version in the
   server's Handshake packet headers, the client MUST terminate the
   connection with a VERSION_NEGOTIATION_ERROR.

   The client MUST NOT send 0-RTT packets using the negotiated version,
   even after processing a packet of that version from the server.
   Servers can apply original version 0-RTT packets to a connection
   without additional considerations.

5.  TLS Resumption and NEW_TOKEN Tokens

   TLS session tickets and NEW_TOKEN tokens are specific to the QUIC
   version of the connection that provided them.  Clients SHOULD NOT use
   a session ticket or token from a QUICv1 QUIC version 1 connection to
   initiate a
   QUICv2 QUIC version 2 connection, or vice versa.

   Servers MUST validate the originating version of any session ticket
   or token and not accept one issued from a different version.  A
   rejected ticket results in falling back to a full TLS handshake,
   without 0-RTT.  A rejected token results in the client address
   remaining unverified, which limits the amount of data the server can
   send.

   After compatible version negotiation, any resulting session ticket
   maps to the negotiated version rather than original one.

6.  Ossification Considerations

   QUIC version 2 provides protection against some forms of
   ossification.  Devices that assume that all long headers will contain encode
   version 1, or that the version 1 Initial key derivation formula will
   remain version-invariant, will not correctly process version 2
   packets.

   However, many middleboxes such as firewalls focus on the first packet
   in a connection, which will often remain in the version 1 format due
   to the considerations above.

   Clients interested in combating firewall ossification can initiate a
   connection using version 2 if they are either reasonably certain the
   server supports it, or are willing to suffer a round-trip penalty if
   they are incorrect.

7.  Applicability

   This version of QUIC provides no change from QUIC version 1 relating
   to the capabilities available to applications.  Therefore, all
   Application Layer Protocol Negotiation (ALPN) ([RFC7301]) codepoints
   specified to operate over QUICv1 QUIC version 1 can also operate over this
   version of QUIC.  In particular, both the "h3" [I-D.ietf-quic-http]
   and "doq" [I-D.ietf-dprive-dnsoquic] ALPNs can operate over QUICv2. QUIC
   version 2.

   All QUIC extensions defined to work with version 1 also work with
   version 2.

8.  Security Considerations

   QUIC version 2 introduces no changes to the security or privacy
   properties of QUIC version 1.

   The mandatory version negotiation mechanism guards against downgrade
   attacks, but downgrades have no security implications, as the version
   properties are identical.

9.  IANA Considerations

   This document requests that IANA add the following entry to the QUIC
   version registry:

   Value: 0x709a50c4
   Status: provisional

   Specification: This Document

   Change Controller: IETF

   Contact: QUIC WG

10.  References

10.1.  Normative References

   [QUIC]     Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/rfc/rfc9000>.

   [QUIC-TLS] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
              QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
              <https://www.rfc-editor.org/rfc/rfc9001>.

   [QUIC-VN]  Schinazi, D. and E. Rescorla, "Compatible Version
              Negotiation for QUIC", Work in Progress, Internet-Draft,
              draft-ietf-quic-version-negotiation-07, 5 April 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
              version-negotiation-07>.

   [RFC9002]  Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
              and Congestion Control", RFC 9002, DOI 10.17487/RFC9002,
              May 2021, <https://www.rfc-editor.org/rfc/rfc9002>.

10.2.  Informative References

   [I-D.duke-quic-version-aliasing]
              Duke, M., "QUIC Version Aliasing", Work in Progress,
              Internet-Draft, draft-duke-quic-version-aliasing-07, 25
              October 2021, <https://datatracker.ietf.org/doc/html/
              draft-duke-quic-version-aliasing-07>.

   [I-D.ietf-dprive-dnsoquic]
              Huitema, C., Dickinson, S., and A. Mankin, "DNS over
              Dedicated QUIC Connections", Work in Progress, Internet-
              Draft, draft-ietf-dprive-dnsoquic-12, 20 April 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-dprive-
              dnsoquic-12>.

   [I-D.ietf-quic-http]
              Bishop, M., "Hypertext Transfer Protocol Version 3
              (HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
              quic-http-34, 2 February 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-quic-
              http-34>.

   [QUIC-INVARIANTS]
              Thomson, M., "Version-Independent Properties of QUIC",
              RFC 8999, DOI 10.17487/RFC8999, May 2021,
              <https://www.rfc-editor.org/rfc/rfc8999>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC7301]  Friedl, S., Popov, A., Langley, A., and E. Stephan,
              "Transport Layer Security (TLS) Application-Layer Protocol
              Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
              July 2014, <https://www.rfc-editor.org/rfc/rfc7301>.

   [RFC7838]  Nottingham, M., McManus, P., and J. Reschke, "HTTP
              Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
              April 2016, <https://www.rfc-editor.org/rfc/rfc7838>.

   [RFC8999]  Thomson, M., "Version-Independent Properties of QUIC",
              RFC 8999, DOI 10.17487/RFC8999, May 2021,
              <https://www.rfc-editor.org/rfc/rfc8999>.

Appendix A.  Sample Packet Protection

   This section shows examples of packet protection so that
   implementations can be verified incrementally.  Samples of Initial
   packets from both client and server plus a Retry packet are defined.
   These packets use an 8-byte client-chosen Destination Connection ID
   of 0x8394c8f03e515708.  Some intermediate values are included.  All
   values are shown in hexadecimal.

A.1.  Keys

   The labels generated during the execution of the HKDF-Expand-Label
   function (that is, HkdfLabel.label) and part of the value given to
   the HKDF-Expand function in order to produce its output are:

   client in: 00200f746c73313320636c69656e7420696e00

   server in: 00200f746c7331332073657276657220696e00

   quicv2 key: 001010746c73313320717569637632206b657900

   quicv2 iv: 000c0f746c7331332071756963763220697600

   quicv2 hp: 00100f746c7331332071756963763220687000

   The initial secret is common:

   initial_secret = HKDF-Extract(initial_salt, cid)
       = ddfcb7b82a430b7845210ad64b406977
         ed51b269a14bc69aa9ea9b366fa3b06b

   The secrets for protecting client packets are:

   client_initial_secret
       = HKDF-Expand-Label(initial_secret, "client in", "", 32)
       = 9fe72e1452e91f551b770005054034e4
         7575d4a0fb4c27b7c6cb303a338423ae

   key = HKDF-Expand-Label(client_initial_secret, "quicv2 key", "", 16)
       = 95df2be2e8d549c82e996fc9339f4563

   iv  = HKDF-Expand-Label(client_initial_secret, "quicv2 iv", "", 12)
       = ea5e3c95f933db14b7020ad8

   hp  = HKDF-Expand-Label(client_initial_secret, "quicv2 hp", "", 16)
       = 091efb735702447d07908f6501845794

   The secrets for protecting server packets are:

   server_initial_secret
       = HKDF-Expand-Label(initial_secret, "server in", "", 32)
       = 3c9bf6a9c1c8c71819876967bd8b979e
         fd98ec665edf27f22c06e9845ba0ae2f

   key = HKDF-Expand-Label(server_initial_secret, "quicv2 key", "", 16)
       = 15d5b4d9a2b8916aa39b1bfe574d2aad

   iv  = HKDF-Expand-Label(server_initial_secret, "quicv2 iv", "", 12)
       = a85e7ac31cd275cbb095c626

   hp  = HKDF-Expand-Label(server_initial_secret, "quicv2 hp", "", 16)
       = b13861cfadbb9d11ff942dd80c8fc33b

A.2.  Client Initial

   The client sends an Initial packet.  The unprotected payload of this
   packet contains the following CRYPTO frame, plus enough PADDING
   frames to make a 1162-byte payload:

   060040f1010000ed0303ebf8fa56f129 39b9584a3896472ec40bb863cfd3e868
   04fe3a47f06a2b69484c000004130113 02010000c000000010000e00000b6578
   616d706c652e636f6dff01000100000a 00080006001d00170018001000070005
   04616c706e0005000501000000000033 00260024001d00209370b2c9caa47fba
   baf4559fedba753de171fa71f50f1ce1 5d43e994ec74d748002b000302030400
   0d0010000e0403050306030203080408 050806002d00020101001c0002400100
   3900320408ffffffffffffffff050480 00ffff07048000ffff08011001048000
   75300901100f088394c8f03e51570806 048000ffff

   The unprotected header indicates a length of 1182 bytes: the 4-byte
   packet number, 1162 bytes of frames, and the 16-byte authentication
   tag.  The header includes the connection ID and a packet number of 2:

   d3709a50c4088394c8f03e5157080000449e00000002

   Protecting the payload produces output that is sampled for header
   protection.  Because the header uses a 4-byte packet number encoding,
   the first 16 bytes of the protected payload is sampled and then
   applied to the header as follows:

   sample = 23b8e610589c83c92d0e97eb7a6e5003

   mask = AES-ECB(hp, sample)[0..4]
        = 8e4391d84a

   header[0] ^= mask[0] & 0x0f
        = dd
   header[18..21] ^= mask[1..4]
        = 4391d848
   header = dd709a50c4088394c8f03e5157080000449e4391d848

   The resulting protected packet is:

   dd709a50c4088394c8f03e5157080000 449e4391d84823b8e610589c83c92d0e
   97eb7a6e5003f57764c5c7f0095ba54b 90818f1bfeecc1c97c54fc731edbd2a2
   44e3b1e639a9bc75ed545b98649343b2 53615ec6b3e4df0fd2e7fe9d691a09e6
   a144b436d8a2c088a404262340dfd995 ec3865694e3026ecd8c6d2561a5a3667
   2a1005018168c0f081c10e2bf14d550c 977e28bb9a759c57d0f7ffb1cdfb40bd
   774dec589657542047dffefa56fc8089 a4d1ef379c81ba3df71a05ddc7928340
   775910feb3ce4cbcfd8d253edd05f161 458f9dc44bea017c3117cca7065a315d
   eda9464e672ec80c3f79ac993437b441 ef74227ecc4dc9d597f66ab0ab8d214b
   55840c70349d7616cbe38e5e1d052d07 f1fedb3dd3c4d8ce295724945e67ed2e
   efcd9fb52472387f318e3d9d233be7df c79d6bf6080dcbbb41feb180d7858849
   7c3e439d38c334748d2b56fd19ab364d 057a9bd5a699ae145d7fdbc8f5777518
   1b0a97c3bdedc91a555d6c9b8634e106 d8c9ca45a9d5450a7679edc545da9102
   5bc93a7cf9a023a066ffadb9717ffaf3 414c3b646b5738b3cc4116502d18d79d
   8227436306d9b2b3afc6c785ce3c817f eb703a42b9c83b59f0dcef1245d0b3e4
   0299821ec19549ce489714fe2611e72c d882f4f70dce7d3671296fc045af5c9f
   630d7b49a3eb821bbca60f1984dce664 91713bfe06001a56f51bb3abe92f7960
   547c4d0a70f4a962b3f05dc25a34bbe8 30a7ea4736d3b0161723500d82beda9b
   e3327af2aa413821ff678b2a876ec4b0 0bb605ffcc3917ffdc279f187daa2fce
   8cde121980bba8ec8f44ca562b0f1319 14c901cfbd847408b778e6738c7bb5b1
   b3f97d01b0a24dcca40e3bed29411b1b a8f60843c4a241021b23132b9500509b
   9a3516d4a9dd41d3bacbcd426b451393 521828afedcf20fa46ac24f44a8e2973
   30b16705d5d5f798eff9e9134a065979 87a1db4617caa2d93837730829d4d89e
   16413be4d8a8a38a7e6226623b64a820 178ec3a66954e10710e043ae73dd3fb2
   715a0525a46343fb7590e5eac7ee55fc 810e0d8b4b8f7be82cd5a214575a1b99
   629d47a9b281b61348c8627cab38e2a6 4db6626e97bb8f77bdcb0fee476aedd7
   ba8f5441acaab00f4432edab3791047d 9091b2a753f035648431f6d12f7d6a68
   1e64c861f4ac911a0f7d6ec0491a78c9 f192f96b3a5e7560a3f056bc1ca85983
   67ad6acb6f2e034c7f37beeb9ed470c4 304af0107f0eb919be36a86f68f37fa6
   1dae7aff14decd67ec3157a11488a14f ed0142828348f5f608b0fe03e1f3c0af
   3acca0ce36852ed42e220ae9abf8f890 6f00f1b86bff8504c8f16c784fd52d25
   e013ff4fda903e9e1eb453c1464b1196 6db9b28e8f26a3fc419e6a60a48d4c72
   14ee9c6c6a12b68a32cac8f61580c64f 29cb6922408783c6d12e725b014fe485
   cd17e484c5952bf99bc94941d4b1919d 04317b8aa1bd3754ecbaa10ec227de85
   40695bf2fb8ee56f6dc526ef366625b9 1aa4970b6ffa5c8284b9b5ab852b905f
   9d83f5669c0535bc377bcc05ad5e48e2 81ec0e1917ca3c6a471f8da0894bc82a
   c2a8965405d6eef3b5e293a88fda203f 09bdc72757b107ab14880eaa3ef7045b
   580f4821ce6dd325b5a90655d8c5b55f 76fb846279a9b518c5e9b9a21165c509
   3ed49baaacadf1f21873266c767f6769

A.3.  Server Initial

   The server sends the following payload in response, including an ACK
   frame, a CRYPTO frame, and no PADDING frames:

   02000000000600405a020000560303ee fce7f7b37ba1d1632e96677825ddf739
   88cfc79825df566dc5430b9a045a1200 130100002e00330024001d00209d3c94
   0d89690b84d08a60993c144eca684d10 81287c834d5311bcf32bb9da1a002b00
   020304
   The header from the server includes a new connection ID and a 2-byte
   packet number encoding for a packet number of 1:

   d1709a50c40008f067a5502a4262b50040750001

   As a result, after protection, the header protection sample is taken
   starting from the third protected byte:

   sample = ebb7972fdce59d50e7e49ff2a7e8de76
   mask   = 41103f438e
   header = d0709a50c40008f067a5502a4262b5004075103e

   The final protected packet is then:

   d0709a50c40008f067a5502a4262b500 4075103e63b4ebb7972fdce59d50e7e4
   9ff2a7e8de76b0cd8c10100a1f13d549 dd6fe801588fb14d279bef8d7c53ef62
   66a9a7a1a5f2fa026c236a5bf8df5aa0 f9d74773aeccfffe910b0f76814b5e33
   f7b7f8ec278d23fd8c7a9e66856b8bbe 72558135bca27c54d63fcc902253461c
   fc089d4e6b9b19

A.4.  Retry

   This shows a Retry packet that might be sent in response to the
   Initial packet in Appendix A.2.  The integrity check includes the
   client-chosen connection ID value of 0x8394c8f03e515708, but that
   value is not included in the final Retry packet:

   cf709a50c40008f067a5502a4262b574 6f6b656e1dc71130cd1ed39d6efcee5c
   85806501

A.5.  ChaCha20-Poly1305 Short Header Packet

   This example shows some of the steps required to protect a packet
   with a short header.  This example uses AEAD_CHACHA20_POLY1305.

   In this example, TLS produces an application write secret from which
   a server uses HKDF-Expand-Label to produce four values: a key, an IV,
   a header protection key, and the secret that will be used after keys
   are updated (this last value is not used further in this example).

   secret
       = 9ac312a7f877468ebe69422748ad00a1
         5443f18203a07d6060f688f30f21632b

   key = HKDF-Expand-Label(secret, "quicv2 key", "", 32)
       = 3bfcddd72bcf02541d7fa0dd1f5f9eee
         a817e09a6963a0e6c7df0f9a1bab90f2

   iv  = HKDF-Expand-Label(secret, "quicv2 iv", "", 12)
       = a6b5bc6ab7dafce30ffff5dd

   hp  = HKDF-Expand-Label(secret, "quicv2 hp", "", 32)
       = d659760d2ba434a226fd37b35c69e2da
         8211d10c4f12538787d65645d5d1b8e2

   ku  = HKDF-Expand-Label(secret, "quicv2 ku", "", 32)
       = c69374c49e3d2a9466fa689e49d476db
         5d0dfbc87d32ceeaa6343fd0ae4c7d88

   The following shows the steps involved in protecting a minimal packet
   with an empty Destination Connection ID.  This packet contains a
   single PING frame (that is, a payload of just 0x01) and has a packet
   number of 654360564.  In this example, using a packet number of
   length 3 (that is, 49140 is encoded) avoids having to pad the payload
   of the packet; PADDING frames would be needed if the packet number is
   encoded on fewer bytes.

   pn                 = 654360564 (decimal)
   nonce              = a6b5bc6ab7dafce328ff4a29
   unprotected header = 4200bff4
   payload plaintext  = 01
   payload ciphertext = 0ae7b6b932bc27d786f4bc2bb20f2162ba

   The resulting ciphertext is the minimum size possible.  One byte is
   skipped to produce the sample for header protection.

   sample = e7b6b932bc27d786f4bc2bb20f2162ba
   mask   = 97580e32bf
   header = 5558b1c6

   The protected packet is the smallest possible packet size of 21
   bytes.

   packet = 5558b1c60ae7b6b932bc27d786f4bc2bb20f2162ba

Appendix B.  Changelog

      *RFC Editor's Note:* Please remove this section prior to
      publication of a final version of this document.

B.1.  since draft-ietf-quic-v2-02

   *  Editorial comments from Lucas Pardue

B.2.  since draft-ietf-quic-v2-01

   *  Ban use of NEW_TOKEN tokens across versions

   *  version-info transport parameter required for all v2 endpoints

   *  Explicitly list known ALPN compatibility

B.2.

B.3.  since draft-ietf-quic-v2-00

   *  Expanded requirements for compatible version negotiation

   *  Added test vectors

   *  Greased the packet type codepoints

   *  Random version number

   *  Clarified requirement to use QUIC-VN

   *  Banned use of resumption tokens across versions

B.3.

B.4.  since draft-duke-quic-v2-02

   *  Converted to adopted draft

   *  Deleted references to QUIC improvements

   *  Clarified status of QUIC extensions

B.4.

B.5.  since draft-duke-quic-v2-01

   *  Made the final version number TBD.

   *  Added ALPN considerations

B.5.

B.6.  since draft-duke-quic-v2-00

   *  Added provisional versions for interop

   *  Change the v1 Retry Tag secret

   *  Change labels to create full key separation

Author's Address

   Martin Duke
   Google LLC
   Email: martin.h.duke@gmail.com