Elliptic Curve Algorithms for Cryptographic Message Syntax (CMS) Encrypted Key Package Content Type
Adds elliptic curve ECDH and ECDSA as options for protecting encrypted key packages in CMS.
Turner, S., "Elliptic Curve Algorithms for Cryptographic Message Syntax (CMS) Encrypted Key Package Content Type", RFC 6161, DOI 10.17487/RFC6161, April 2011, <https://www.rfc-editor.org/info/rfc6161>.
@misc{rfc6161,
series = {Request for Comments},
number = 6161,
howpublished = {RFC 6161},
publisher = {RFC Editor},
doi = {10.17487/RFC6161},
url = {https://www.rfc-editor.org/info/rfc6161},
author = {S. Turner},
title = {{Elliptic Curve Algorithms for Cryptographic Message Syntax (CMS) Encrypted Key Package Content Type}},
pagetotal = 3,
year = 2011,
month = apr,
} RFC text
Contents
Internet Engineering Task Force (IETF) S. Turner
Request for Comments: 6161 IECA
Updates: 6033 April 2011
Category: Standards Track
ISSN: 2070-1721
Elliptic Curve Algorithms for Cryptographic Message Syntax (CMS)
Encrypted Key Package Content Type
Abstract
This document describes the conventions for using several Elliptic
Curve cryptographic algorithms with the Cryptographic Message Syntax
(CMS) encrypted key package content type. Specifically, it includes
conventions necessary to implement Elliptic Curve Diffie-Hellman
(ECDH) with EnvelopedData and Elliptic Curve Digital Signature
Algorithm (ECDSA) with SignedData. This document extends RFC 6033.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6161.
Copyright Notice
Copyright (c) 2011 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
(http://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.
1. Introduction
This document describes the conventions for using Elliptic Curve
cryptographic algorithms with the Cryptographic Message Syntax (CMS)
encrypted key package content type [RFC6032]. Specifically, it
includes conventions necessary to implement the following CMS content
types: EnvelopedData [RFC5652] and SignedData [RFC5652]. This
document amends [RFC6033]. Familiarity with [RFC6033] and [RFC5753]
is assumed.
This document does not define any new algorithms; instead, it refers
to previously defined algorithms.
1.1 Terminology
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
[RFC2119].
2. EnvelopedData
When key agreement is used, standard (as opposed to cofactor) ECDH
[RFC6090][RFC5753] MAY be supported.
3. SignedData
If an implementation encapsulates EncryptedKeyPackage with SignedData
[RFC5652], then it MAY support the signature scheme ECDSA
[RFC6090][RFC5753].
4. Public Key Sizes
The easiest way to implement SignedData and EnvelopedData is with
public key certificates [RFC5280][RFC5480]. If an implementation
supports ECDSA or ECDH, then it MUST support keys on the P-256 curve.
5. Security Considerations
The security considerations from [RFC5280], [RFC5480], [RFC5652],
[RFC5753], [RFC6033], and [RFC6090] apply.
6. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Elliptic Curve Cryptography Subject Public Key
Information", RFC 5480, March 2009.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, September 2009.
[RFC5753] Turner, S. and D. Brown, "Use of Elliptic Curve
Cryptography (ECC) Algorithms in Cryptographic Message
Syntax (CMS)", RFC 5753, January 2010.
[RFC6032] Turner, S. and R. Housley, "Cryptographic Message Syntax
(CMS) Encrypted Key Package Content Type", RFC 6032,
December 2010.
[RFC6033] Turner, S., "Algorithms for Cryptographic Message Syntax
(CMS) Encrypted Key Package Content Type", RFC 6033,
December 2010.
[RFC6090] McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic
Curve Cryptography Algorithms", RFC 6090, February 2011.
Author's Address
Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA
EMail: turners@ieca.com
AI ELI5
On this page
§1Introduction
RFC 6161 describes conventions for using Elliptic Curve cryptographic algorithms with the Cryptographic Message Syntax (CMS) encrypted key package content type from RFC 6032. It covers two CMS content types, EnvelopedData and SignedData, and amends RFC 6033.
The document does not define any new algorithms. It refers to previously defined ones, and readers are assumed to be familiar with RFC 6033 and RFC 5753.
This note adds two more allowed tools for protecting a package of keys. It does not invent new tools, it just points to ones that already exist.
§2ECDH and ECDSA Choices
For EnvelopedData, when key agreement is used, standard (as opposed to cofactor) Elliptic Curve Diffie-Hellman (ECDH) MAY be supported. The algorithms are those in RFC 6090 and RFC 5753.
For SignedData, an implementation that encapsulates EncryptedKeyPackage with SignedData MAY support the signature scheme Elliptic Curve Digital Signature Algorithm (ECDSA). Both are optional: the words are MAY, not MUST.
ECDH is a way for two people to agree on a secret lock key without sharing it openly. ECDSA is a way to sign the box so people know who sent it. Both are allowed, but nobody is forced to use them.
§3Public Key Sizes
The easiest way to implement SignedData and EnvelopedData is with public key certificates, as profiled in RFC 5280 and RFC 5480.
If an implementation supports ECDSA or ECDH, then it MUST support keys on the P-256 curve. That gives everyone one curve they can rely on.
If you choose to use these tools, you must at least know one standard size of key, so that everyone can understand each other.
§4Security Considerations
The document adds no security text of its own. It says the security considerations from RFC 5280, RFC 5480, RFC 5652, RFC 5753, RFC 6033 and RFC 6090 apply.
The safety rules are the ones already written in the older documents, and they still count.