Internet DRAFT - draft-cem-compressed-curves
draft-cem-compressed-curves
TLS C. Mehner
Internet-Draft USAA
Intended status: Informational 25 October 2021
Expires: 28 April 2022
TLS Compressed Elliptic Curve Code Points
draft-cem-compressed-curves-01
Abstract
This document defines new Transport Layer Security (TLS) Supported
Groups to allow negotiation in TLS for encoding certain elliptic
curve public keys in a compressed form rather than the more verbose
method specified in [RFC8446] and [RFC8422].
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/.
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 28 April 2022.
Copyright Notice
Copyright (c) 2021 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.
Mehner Expires 28 April 2022 [Page 1]
Internet-Draft Compressed Curve Code Points October 2021
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 2
2. Supported Groups . . . . . . . . . . . . . . . . . . . . . . 2
2.1. ECDHE Parameters . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
5.1. Normative References . . . . . . . . . . . . . . . . . . 3
5.2. Informative References . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
Versions of TLS prior to 1.3 allowed for Elliptic Curve Cryptography
(ECC) Point Compression negotiation, by sending a however in TLS 1.3
and Section 5.1.2 of [RFC8422], that mechanism was deprecated in
favor of having one point encoding format for each negotiated curve.
Utilizing point compression is important to reduce the size of
negotiated curves within TLS in general, but especially with
[I-D.draft-ietf-tls-ctls].
The code points defined in this document are intended for use in TLS,
dTLS, cTLS, and other similar protocols that negotiate Elliptic Curve
Groups for key exchange.
1.1. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
All TLS notation comes from Section 3 of [RFC8446].
2. Supported Groups
This document defines three new TLS Supported Groups for the
compressed forms of secp256r1, secp384r1, and secp521r1 (collectively
colloquially called the NIST Curves). The compressed forms of these
groups are indicated by adding a letter 'c' at the end of the
descriptive name. The new groups are secp256r1c, secp384r1c, and
secp521r1c. TLS groups using compressed NIST curves MUST use these
newly defined group identifiers.
The "TLS Supported Groups" name space is maintained by IANA.
Mehner Expires 28 April 2022 [Page 2]
Internet-Draft Compressed Curve Code Points October 2021
enum {
secp256r1c(tbd1), secp384r1c(tbd2), secp521r1c(tbd3)
} NamedGroup;
struct {
NamedGroup named_group_list<2..2^16-1>;
} NamedGroupList;
2.1. ECDHE Parameters
In Section 4.2.8.2 of [RFC8446] the encoding method for ECDHE
Parameters is described, this document adds a new struct to serialize
the new parameters. The method for determining the values for the
elements of the serialized structure are documented in [SEC1].
For secp256r1c, secp384r1c, and secp521r1c, the contents are the
serialized value of the following struct defined using the
presentation language in Section 3 of [RFC8446]:
struct {
CompressedY;
opaque X[coordinate_length];
} CompressedPointRepresentation;
enum { evenY(2), oddY(3) } CompressedY
3. IANA Considerations
IANA is requested to assign the value tbd1 to secp256r1c, the value
tbd2 to secp384r1c, and the value tbd3 to secp521r1c in the "TLS
Supported Groups" registry. For these three new supported groups the
"DTLS OK" is set to 'Y'. For tbd1 and tbd2 the "Recommended" column
is set to 'Y' and for tbd3 the "Recommended" column is set to 'N'.
4. Security Considerations
The security considerations of [RFC8422] and [RFC8422] apply to the
selection of TLS named groups and the use of the curves specified in
this document.
5. References
5.1. Normative References
[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/info/rfc2119>.
Mehner Expires 28 April 2022 [Page 3]
Internet-Draft Compressed Curve Code Points October 2021
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
Curve Cryptography (ECC) Cipher Suites for Transport Layer
Security (TLS) Versions 1.2 and Earlier", RFC 8422,
DOI 10.17487/RFC8422, August 2018,
<https://www.rfc-editor.org/info/rfc8422>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[SEC1] Brown, D., "Standards for Efficient Cryptography 1 (SEC
1)", Standards for Efficient Cryptography Group , 21 May
2009, <https://www.secg.org/sec1-v2.pdf>.
5.2. Informative References
[I-D.draft-ietf-tls-ctls]
Rescorla, E., Barnes, R., and H. Tschofenig, "Compact TLS
1.3", Work in Progress, Internet-Draft, draft-ietf-tls-
ctls-04, 25 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-tls-ctls-
04.txt>.
Author's Address
Carl Mehner
USAA
Email: carl.mehner@usaa.com
Mehner Expires 28 April 2022 [Page 4]
