Internet DRAFT - draft-housley-cms-mix-with-psk
draft-housley-cms-mix-with-psk
INTERNET-DRAFT R. Housley
Intended Status: Proposed Standard Vigil Security
Expires: 3 October 2018 3 April 2018
Using Pre-Shared Key (PSK) in the Cryptographic Message Syntax (CMS)
<draft-housley-cms-mix-with-psk-04.txt>
Abstract
The invention of a large-scale quantum computer would pose a serious
challenge for the cryptographic algorithms that are widely deployed
today. The Cryptographic Message Syntax (CMS) supports key transport
and key agreement algorithms that could be broken by the invention of
such a quantum computer. By storing communications that are
protected with the CMS today, someone could decrypt them in the
future when a large-scale quantum computer becomes available. Once
quantum-secure key management algorithms are available, the CMS will
be extended to support them, if current syntax the does not
accommodated them. In the near-term, this document describes a
mechanism to protect today's communication from the future invention
of a large-scale quantum computer by mixing the output of key
transport and key agreement algorithms with a pre-shared key.
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 http://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."
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
Housley [Page 1]
INTERNET-DRAFT Using PSK in the CMS April 2018
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. ASN.1 . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Version Numbers . . . . . . . . . . . . . . . . . . . . . 3
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. KeyTransPSKRecipientInfo . . . . . . . . . . . . . . . . . . . 5
4. KeyAgreePSKRecipientInfo . . . . . . . . . . . . . . . . . . . 7
5. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Normative References . . . . . . . . . . . . . . . . . . . . . 12
9. Informative References . . . . . . . . . . . . . . . . . . . . 13
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
The invention of a large-scale quantum computer would pose a serious
challenge for the cryptographic algorithms that are widely deployed
today. It is an open question whether or not it is feasible to build
a large-scale quantum computer, and if so, when that might happen.
However, if such a quantum computer is invented, many of the
cryptographic algorithms and the security protocols that use them
would become vulnerable.
The Cryptographic Message Syntax (CMS) [RFC5652][RFC5803] supports
key transport and key agreement algorithms that could be broken by
the invention of a large-scale quantum computer [C2PQ]. These
algorithms include RSA [RFC4055], Diffie-Hellman [RFC2631], and
Elliptic Curve Diffie-Hellman. As a result, an adversary that stores
CMS-protected communications today, could decrypt those
communications in the future when a large-scale quantum computer
becomes available.
Once quantum-secure key management algorithms are available, the CMS
Housley [Page 2]
INTERNET-DRAFT Using PSK in the CMS April 2018
will be extended to support them, if current syntax the does not
accommodated them.
In the near-term, this document describes a mechanism to protect
today's communication from the future invention of a large-scale
quantum computer by mixing the output of existing key transport and
key agreement algorithms with a pre-shared key (PSK). Secure
communication can be achieved today by mixing with a strong PSK with
the output of an existing key transport algorithm, like RSA, or an
existing key agreement algorithm, like Diffie-Hellman [RFC2631] or
Elliptic Curve Diffie-Hellman [RFC5753]. A security solution that is
believed to be quantum resistant can be achieved by using a PSK with
sufficient entropy along with a quantum resistant key derivation
function (KDF), like HKDF [RFC5869], and a quantum resistant
encryption algorithm, like 256-bit AES [AES]. In this way, today's
CMS-protected communication can be invulnerable to an attacker with a
large-scale quantum computer.
Note that the CMS also supports key management techniques based on
symmetric key-encryption keys and passwords, but they are not
discussed in this document because they are already quantum
resistant. The symmetric key-encryption key technique is quantum
resistant when used with an adequate key size. The password
technique is quantum resistant when used with a quantum-resistant key
derivation function and a sufficiently large password.
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. ASN.1
CMS values are generated using ASN.1 [X680], which uses the Basic
Encoding Rules (BER) and the Distinguished Encoding Rules (DER)
[X690].
1.3. Version Numbers
The major data structures include a version number as the first item
in the data structure. The version number is intended to avoid ASN.1
decode errors. Some implementations do not check the version number
prior to attempting a decode, and then if a decode error occurs, the
version number is checked as part of the error handling routine.
This is a reasonable approach; it places error processing outside of
Housley [Page 3]
INTERNET-DRAFT Using PSK in the CMS April 2018
the fast path. This approach is also forgiving when an incorrect
version number is used by the sender.
Whenever the structure is updated, a higher version number will be
assigned. However, to ensure maximum interoperability, the higher
version number is only used when the new syntax feature is employed.
That is, the lowest version number that supports the generated syntax
is used.
2. Overview
The CMS enveloped-data content type [RFC5652] and the CMS
authenticated-enveloped-data content type [RFC5083] support both key
transport and key agreement public-key algorithms to establish the
key used to encrypt the content. In both cases, the sender randomly
generates the key, and then all recipients obtain that key. For
enveloped-data, a content-encryption key is established. For
authenticated-enveloped-data, a content-authenticated-encryption key
is established. All recipients use the sender-generated key for
decryption.
This specification defines two quantum-resistant ways to establish
these keys. In both cases, a PSK MUST be distributed to the sender
and all of the recipients by some out-of-band means that does not
make it vulnerable to the future invention of a large-scale quantum
computer, and an identifier MUST be assigned to the PSK.
The content-encryption key or content-authenticated-encryption key is
established by following these steps:
1. The content-encryption key or the content-authenticated-encryption
key is generated at random.
2. The key-derivation key is generated at random.
3. The key-encryption key is established for each recipient. The
details depend on the key management algorithm used:
key transport: the key-derivation key is encrypted in the
recipient's public key, then the key derivation function (KDF)
is used to mix the pre-shared key (PSK) and the key-derivation
key to produce the key-encryption key; or
key agreement: the recipient's public key and the sender's
private key are used to generate a pairwise symmetric key, then
the key derivation function (KDF) is used to mix the pre-shared
key (PSK) and the pairwise symmetric key to produce the key-
encryption key.
Housley [Page 4]
INTERNET-DRAFT Using PSK in the CMS April 2018
4. The key-encryption key is used to encrypt the content-encryption
key or content-authenticated-encryption key.
As specified in Section 6.2.5 of [RFC5652], recipient information for
additional key management techniques are represented in the
OtherRecipientInfo type. Two key management techniques are specified
in this document. Each of these is identified by a unique ASN.1
object identifier.
The first key management technique, called keyTransPSK, see
Section 3, uses a key transport algorithm to transfer the key-
derivation key from the sender to the recipient, and then the key-
derivation key is mixed with the PSK using a KDF. The output of the
KDF is the key-encryption key for the encryption of the content-
encryption key or content-authenticated-encryption key.
The second key management technique, called keyAgreePSK, see
Section 4, uses a key agreement algorithm to establish a pairwise
key-encryption key, which is used to encrypt the key-derivation key,
and the then key-derivation key is mixed with the PSK using a KDF.
The output of the KDF is the key-encryption key for the encryption of
the content-encryption key or content-authenticated-encryption key.
3. KeyTransPSKRecipientInfo
Per-recipient information using keyTransPSK is represented in the
KeyTransPSKRecipientInfo type, and its use is indicated by the id-
ori-keyTransPSK object identifier. Each instance of
KeyTransPSKRecipientInfo establishes the content-encryption key or
content-authenticated-encryption key for one or more recipients that
have access to the same PSK.
The id-ori-keyTransPSK object identifier is:
id-ori OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) TBD1 }
id-ori-keyTransPSK OBJECT IDENTIFIER ::= { id-ori 1 }
Housley [Page 5]
INTERNET-DRAFT Using PSK in the CMS April 2018
The KeyTransPSKRecipientInfo type is:
KeyTransPSKRecipientInfo ::= SEQUENCE {
version CMSVersion, -- always set to 0
pskid PreSharedKeyIdentifier,
kdfAlgorithm KeyDerivationAlgorithmIdentifier,
keyEncryptionAlgorithm KeyEncryptionAlgorithmIdentifier,
ktris KeyTransRecipientInfos,
encryptedKey EncryptedKey }
PreSharedKeyIdentifier ::= OCTET STRING
KeyTransRecipientInfos ::= SEQUENCE OF KeyTransRecipientInfo
The fields of the KeyTransPSKRecipientInfo type have the following
meanings:
version is the syntax version number. The version MUST be 0. The
CMSVersion type is described in Section 10.2.5 of [RFC5652].
pskid is the identifier of the PSK used by the sender. The
identifier is an OCTET STRING, and it need not be human readable.
kdfAlgorithm identifies the key-derivation algorithm, and any
associated parameters, used by the sender to mix the key-
derivation key and the PSK to generate the key-encryption key.
The KeyDerivationAlgorithmIdentifier is described in Section
10.1.6 of [RFC5652].
keyEncryptionAlgorithm identifies a key-encryption algorithm used
to encrypt the content-encryption key. The
KeyEncryptionAlgorithmIdentifier is described in Section 10.1.3 of
[RFC5652].
ktris contains one KeyTransRecipientInfo type for each recipient;
it uses a key transport algorithm to establish the key-derivation
key. KeyTransRecipientInfo is described in Section 6.2.1 of
[RFC5652].
encryptedKey is the result of encrypting the content-encryption
key or the content-authenticated-encryption key with the key-
encryption key. EncryptedKey is an OCTET STRING.
Housley [Page 6]
INTERNET-DRAFT Using PSK in the CMS April 2018
4. KeyAgreePSKRecipientInfo
Per-recipient information using keyAgreePSK is represented in the
KeyAgreePSKRecipientInfo type, and its use is indicated by the id-
ori-keyAgreePSK object identifier. Each instance of
KeyAgreePSKRecipientInfo establishes the content-encryption key or
content-authenticated-encryption key for one or more recipients that
have access to the same PSK.
The id-ori-keyAgreePSK object identifier is:
id-ori-keyAgreePSK OBJECT IDENTIFIER ::= { id-ori 2 }
The KeyAgreePSKRecipientInfo type is:
KeyAgreePSKRecipientInfo ::= SEQUENCE {
version CMSVersion, -- always set to 0
pskid PreSharedKeyIdentifier,
originator [0] EXPLICIT OriginatorIdentifierOrKey,
ukm [1] EXPLICIT UserKeyingMaterial OPTIONAL,
kdfAlgorithm KeyDerivationAlgorithmIdentifier,
keyEncryptionAlgorithm KeyEncryptionAlgorithmIdentifier,
recipientEncryptedKeys RecipientEncryptedKeys }
The fields of the KeyAgreePSKRecipientInfo type have the following
meanings:
version is the syntax version number. The version MUST be 0. The
CMSVersion type is described in Section 10.2.5 of [RFC5652].
pskid is the identifier of the PSK used by the sender. The
identifier is an OCTET STRING, and it need not be human readable.
originator is a CHOICE with three alternatives specifying the
sender's key agreement public key. Implementations MUST support
all three alternatives for specifying the sender's public key.
The sender uses the corresponding private key and the recipient's
public key to generate a pairwise key. A key derivation function
(KDF) is used to mix the PSK and the pairwise key to produce a
key-encryption key. The OriginatorIdentifierOrKey type is
described in Section 6.2.2 of [RFC5652].
ukm is optional. With some key agreement algorithms, the sender
provides a User Keying Material (UKM) to ensure that a different
key is generated each time the same two parties generate a
pairwise key. Implementations MUST accept a
KeyAgreePSKRecipientInfo SEQUENCE that includes a ukm field.
Implementations that do not support key agreement algorithms that
Housley [Page 7]
INTERNET-DRAFT Using PSK in the CMS April 2018
make use of UKMs MUST gracefully handle the presence of UKMs. The
UserKeyingMaterial type is described in Section 10.2.6 of
[RFC5652].
kdfAlgorithm identifies the key-derivation algorithm, and any
associated parameters, used by the sender to mix the pairwise key
and the PSK. The KeyDerivationAlgorithmIdentifier is described in
Section 10.1.6 of [RFC5652].
keyEncryptionAlgorithm identifies a key-encryption algorithm used
to encrypt the content-encryption key or the content-
authenticated-encryption key. The
KeyEncryptionAlgorithmIdentifier type is described in Section
10.1.3 of [RFC5652].
recipientEncryptedKeys includes a recipient identifier and
encrypted key for one or more recipients. The
KeyAgreeRecipientIdentifier is a CHOICE with two alternatives
specifying the recipient's certificate, and thereby the
recipient's public key, that was used by the sender to generate a
pairwise key. The encryptedKey is the result of encrypting the
content-encryption key or the content-authenticated-encryption key
with the key-encryption key. EncryptedKey is an OCTET STRING.
The RecipientEncryptedKeys type is defined in Section 6.2.2 of
[RFC5652].
5. ASN.1 Module
This section contains the ASN.1 module for the two key management
techniques defined in this document. This module imports types from
other ASN.1 modules that are defined in [RFC5911] and [RFC5912].
CMSORIforPSK-2017
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) modules(0) id-mod-cms-ori-psk-2017(TBD0) }
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- EXPORTS All
IMPORTS
AlgorithmIdentifier{}, KEY-DERIVATION
FROM AlgorithmInformation-2009 -- [RFC5912]
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-algorithmInformation-02(58) }
Housley [Page 8]
INTERNET-DRAFT Using PSK in the CMS April 2018
OTHER-RECIPIENT, OtherRecipientInfo, CMSVersion,
KeyTransRecipientInfo, OriginatorIdentifierOrKey,
UserKeyingMaterial, RecipientEncryptedKeys, EncryptedKey,
KeyDerivationAlgorithmIdentifier, KeyEncryptionAlgorithmIdentifier
FROM CryptographicMessageSyntax-2009 -- [RFC5911]
{ iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs-9(9) smime(16) modules(0)
id-mod-cms-2004-02(41) } ;
--
-- OtherRecipientInfo Types (ori-)
--
SupportedOtherRecipInfo OTHER-RECIPIENT ::= {
ori-keyTransPSK |
ori-keyAgreePSK,
... }
--
-- Key Transport with Pre-Shared Key
--
ori-keyTransPSK OTHER-RECIPIENT ::= {
KeyTransPSKRecipientInfo IDENTIFIED BY id-ori-keyTransPSK }
id-ori OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) TBD1 }
id-ori-keyTransPSK OBJECT IDENTIFIER ::= { id-ori 1 }
KeyTransPSKRecipientInfo ::= SEQUENCE {
version CMSVersion, -- always set to 0
pskid PreSharedKeyIdentifier,
kdfAlgorithm KeyDerivationAlgorithmIdentifier,
keyEncryptionAlgorithm KeyEncryptionAlgorithmIdentifier,
ktris KeyTransRecipientInfos,
encryptedKey EncryptedKey }
PreSharedKeyIdentifier ::= OCTET STRING
KeyTransRecipientInfos ::= SEQUENCE OF KeyTransRecipientInfo
Housley [Page 9]
INTERNET-DRAFT Using PSK in the CMS April 2018
--
-- Key Agreement with Pre-Shared Key
--
ori-keyAgreePSK ORI-TYPE ::= {
KeyAgreePSKRecipientInfo IDENTIFIED BY id-ori-keyAgreePSK }
id-ori-keyAgreePSK OBJECT IDENTIFIER ::= { id-ori 2 }
KeyAgreePSKRecipientInfo ::= SEQUENCE {
version CMSVersion, -- always set to 0
pskid PreSharedKeyIdentifier,
originator [0] EXPLICIT OriginatorIdentifierOrKey,
ukm [1] EXPLICIT UserKeyingMaterial OPTIONAL,
kdfAlgorithm KeyDerivationAlgorithmIdentifier,
keyEncryptionAlgorithm KeyEncryptionAlgorithmIdentifier,
recipientEncryptedKeys RecipientEncryptedKeys }
END
6. Security Considerations
Implementations must protect the pre-shared key (PSK), key transport
private key, the agreement private key, the key-derivation key, and
the key-encryption key. Compromise of the PSK will make the
encrypted content vulnerable to the future invention of a large-scale
quantum computer. Compromise of the PSK and either the key transport
private key or the agreement private key may result in the disclosure
of all contents protected with that combination of keying material.
Compromise of the PSK and the key-derivation key may result in
disclosure of all contents protected with that combination of keying
material. Compromise of the key-encryption key may result in the
disclosure of all content-encryption keys or content-authenticated-
encryption keys that were protected with that keying materail, which
in turn may result in the disclosure of the content.
A large-scale quantum computer will essentially negate the security
provided by the key transport algorithm or the key agreement
algorithm, which means that the attacker with a large-scale quantum
computer can discover the key-derivation key. In addition a large-
scale quantum computer effectively cuts the security provided by a
symmetric key algorithm in half. Therefore, the PSK needs at least
256 bits of entropy to provide 128 bits of security. To match that
same level of security, the key derivation function needs to be
quantum-resistant and produce a key-encryption key that is at least
256 bits in length. Similarly, the content-encryption key or
content-authenticated-encryption key needs to be at least 256 bits in
length.
Housley [Page 10]
INTERNET-DRAFT Using PSK in the CMS April 2018
Implementations must randomly generate key-derivation keys as well as
the content-encryption keys or content-authenticated-encryption keys.
Also, the generation of public/private key pairs for the key
transport and key agreement algorithms rely on a random numbers. The
use of inadequate pseudo-random number generators (PRNGs) to generate
cryptographic keys can result in little or no security. An attacker
may find it much easier to reproduce the PRNG environment that
produced the keys, searching the resulting small set of
possibilities, rather than brute force searching the whole key space.
The generation of quality random numbers is difficult. [RFC4086]
offers important guidance in this area.
When using a PSK with a key transport or a key agreement algorithm, a
key-encryption key is produced to encrypt the content-encryption key
or content-authenticated-encryption key. If the key-encryption
algorithm is different than the algorithm used to protect the
content, then the effective security is determined by the weaker of
the two algorithms. If, for example, content is encrypted with
256-bit AES, and the key is wrapped with 128-bit AES, then at most
128 bits of protection is provided. Implementers must ensure that
the key-encryption algorithm is as strong or stronger than the
content-encryption algorithm or content-authenticated-encryption
algorithm.
Implementers SHOULD NOT mix quantum-resistant key management
algorithms with their non-quantum-resistant counterparts. For
example, the same content should not be protected with
KeyTransRecipientInfo and KeyTransPSKRecipientInfo. Likewise, the
same content should not be protected with KeyAgreeRecipientInfo and
KeyAgreePSKRecipientInfo. Doing so would make the content vulnerable
to the future invention of a large-scale quantum computer.
Implementers should not send the same content in different messages,
one using a quantum-resistant key management algorithm and the other
using a non-quantum-resistant key management algorithm, even if the
content-encryption key is generated independently. Doing so may
allow an eavesdropper to correlate the messages, making the content
vulnerable to the future invention of a large-scale quantum computer.
Implementers should be aware that cryptographic algorithms become
weaker with time. As new cryptoanalysis techniques are developed and
computing performance improves, the work factor to break a particular
cryptographic algorithm will be reduced. Therefore, cryptographic
algorithm implementations should be modular, allowing new algorithms
to be readily inserted. That is, implementors should be prepared for
the set of supported algorithms to change over time.
Housley [Page 11]
INTERNET-DRAFT Using PSK in the CMS April 2018
7. IANA Considerations
One object identifier for the ASN.1 module in the Section 5 was
assigned in the SMI Security for S/MIME Module Identifiers
(1.2.840.113549.1.9.16.0) [IANA-MOD] registry:
id-mod-cms-ori-psk-2017 OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) mod(0) TBD0 }
One object identifier for an arc to assign Other Recipient Info
Identifiers was assigned in the SMI Security for S/MIME Mail Security
(1.2.840.113549.1.9.16) [IANA-SMIME] registry:
id-ori OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) TBD1 }
This assignment created the new SMI Security for Other Recipient Info
Identifiers (1.2.840.113549.1.9.16.TBD1) [IANA-ORI] registry with the
following two entries with references to this document:
id-ori-keyTransPSK OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) id-ori(TBD1) 1 }
id-ori-keyAgreePSK OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) id-ori(TBD1) 2 }
8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5083] Housley, R., "Cryptographic Message Syntax (CMS)
Authenticated-Enveloped-Data Content Type", RFC 5083,
November 2007.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", RFC
5652, September 2009.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, May 2017.
[X680] ITU-T, "Information technology -- Abstract Syntax Notation
One (ASN.1): Specification of basic notation", ITU-T
Recommendation X.680, 2015.
Housley [Page 12]
INTERNET-DRAFT Using PSK in the CMS April 2018
[X690] ITU-T, "Information technology -- ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ITU-T Recommendation X.690, 2015.
9. Informative References
[AES] National Institute of Standards and Technology, FIPS Pub
197: Advanced Encryption Standard (AES), 26 November 2001.
[C2PQ] Hoffman, P., "The Transition from Classical to Post-
Quantum Cryptography", work-in-progress, draft-hoffman-
c2pq-03, February 2018.
[IANA-MOD] https://www.iana.org/assignments/smi-numbers/smi-
numbers.xhtml#security-smime-0.
[IANA-SMIME] https://www.iana.org/assignments/smi-numbers/smi-
numbers.xhtml#security-smime.
[IANA-ORI] https://www.iana.org/assignments/smi-numbers/smi-
numbers.xhtml#security-smime-13.
[RFC2631] Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC
2631, June 1999.
[RFC3560] Housley, R., "Use of the RSAES-OAEP Key Transport
Algorithm in Cryptographic Message Syntax (CMS)", RFC
3560, July 2003.
[RFC4086] D. Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", RFC 4086, June
2005.
[RFC5753] Turner, S., and D. Brown, "Use of Elliptic Curve
Cryptography (ECC) Algorithms in Cryptographic Message
Syntax (CMS)", RFC 5753, January 2010.
[RFC5869] Krawczyk, H., and P. Eronen, "HMAC-based Extract-and-
Expand Key Derivation Function (HKDF)", RFC 5869, May
2010.
[RFC5911] Hoffman, P., and J. Schaad, "New ASN.1 Modules for
Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911,
June 2010.
Housley [Page 13]
INTERNET-DRAFT Using PSK in the CMS April 2018
[RFC5912] Hoffman, P., and J. Schaad, "New ASN.1 Modules for the
Public Key Infrastructure Using X.509 (PKIX)" RFC 5912,
June 2010.
Acknowledgements
Many thanks to Burt Kaliski, Panos Kampanakis, Jim Schaad, Sean
Turner, and Daniel Van Geest for their review and insightful
comments. They have greatly improved the design and implementation
guidance.
Author's Address
Russell Housley
Vigil Security, LLC
918 Spring Knoll Drive
Herndon, VA 20170
USA
EMail: housley@vigilsec.com
Housley [Page 14]
