Internet DRAFT - draft-ounsworth-pq-explicit-composite-keys
draft-ounsworth-pq-explicit-composite-keys
LAMPS M. Ounsworth
Internet-Draft S. Mister
Intended status: Standards Track J. Gray
Expires: 16 August 2022 Entrust
12 February 2022
Explicit Pairwise Composite Keys For Use In Internet PKI
draft-ounsworth-pq-explicit-composite-keys-01
Abstract
With the widespread adoption of post-quantum cryptography will come
the need for an entity to possess multiple public keys on different
cryptographic algorithms. Since the trustworthiness of individual
post-quantum algorithms is at question, a multi-key cryptographic
operation will need to be performed in such a way that breaking it
requires breaking each of the component algorithms individually.
This requires defining new structures for holding composite public
keys and composite signature data. This draft defines a structure
generic enough to be useful beyond the post-quantum transition for
any situation where a widely-supported but untrusted algorithm is
being migrated to newer cryptography.
This document defines structures for binding an explicit pair of
cryptographic algorithms together into a single object identifier,
and it provides ASN.1 structures for encoding these pairwise
composite public keys, private keys in wire protocols, as well as
using them in conjunction with composite signatures, encryption and
key transport mechanisms.
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 16 August 2022.
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Copyright Notice
Copyright (c) 2022 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Composite Structures . . . . . . . . . . . . . . . . . . . . 4
2.1. Composite Keys . . . . . . . . . . . . . . . . . . . . . 5
2.2. Composite Private Key . . . . . . . . . . . . . . . . . . 5
2.3. Composite Signature . . . . . . . . . . . . . . . . . . . 6
2.3.1. Explicit Signature Params . . . . . . . . . . . . . . 6
2.3.2. Explicit Composite Signature Algorithm . . . . . . . 7
2.3.3. Explicit Encryption and Key Exchange Params . . . . . 7
2.4. Encoding Rules . . . . . . . . . . . . . . . . . . . . . 7
3. In Practice . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. PEM Storage of Composite Private Keys . . . . . . . . . . 8
3.2. Asymmetric Key Packages (CMS) . . . . . . . . . . . . . . 8
3.3. Cryptographic protocols . . . . . . . . . . . . . . . . . 9
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5.1. Policy for Deprecated and Acceptable Algorithms . . . . . 10
5.2. Protection of Private Keys . . . . . . . . . . . . . . . 10
5.3. Checking for Compromised Key Reuse . . . . . . . . . . . 11
6. Appendices . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . 11
6.2. Examples of defining explicit pairs . . . . . . . . . . . 12
6.3. Intellectual Property Considerations . . . . . . . . . . 13
7. Contributors and Acknowledgements . . . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
During the transition to post-quantum cryptography, there will be
uncertainty as to the strength of cryptographic algorithms; we will
no longer fully trust traditional cryptography such as RSA, Diffie-
Hellman, DSA and their elliptic curve variants, but we will also not
fully trust their post-quantum replacements until they have had
sufficient scrutiny. Unlike previous cryptographic algorithm
migrations, the choice of when to migrate and which algorithms to
migrate to, is not so clear. Even after the migration period, it may
be advantageous for an entity's cryptographic identity to be composed
of multiple public-key algorithms.
The deployment of composite public keys and composite signatures
using post-quantum algorithms will face two challenges
* Algorithm strength uncertainty: During the transition period, some
post-quantum signature and encryption algorithms will not be fully
trusted, while also the trust in legacy public key algorithms will
start to erode. A relying party may learn some time after
deployment that a public key algorithm has become untrustworthy,
but in the interim, they may not know which algorithm an adversary
has compromised.
* Backwards compatibility: During the transition period, post-
quantum algorithms will not be supported by all clients.
This document provides a mechanism to address algorithm strength
uncertainty by providing formats for encoding multiple public keys
and private keys into existing fields.
This document provides structures to encode explicit composite
algorithm identifiers and parameters for use with composite
signature, encryption, and key transport mechanisms defined in ~~
TODO cite corresponding drafts properly ~~.
This document is intended for general applicability anywhere that
public key or private key structures are used within PKIX protocols.
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.
The following terms are used in this document:
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ALGORITHM: An information object class for identifying the type of
cryptographic operation to be performed. This document is primarily
concerned with algorithms for producing digital signatures, though
the public key structure could just as easily hold encryption keys.
BER: Basic Encoding Rules (BER) as defined in [X.690].
COMPONENT ALGORITHM: A single basic algorithm which is contained
within a composite algorithm.
COMPOSITE ALGORITHM: An algorithm which is a sequence of one or more
component algorithms, as defined in Section 2.
DER: Distinguished Encoding Rules as defined in [X.690].
EXPLICIT COMPOSITE: Composite structures where the
AlgorithmIdentifier OID explicitly defines the component algorithms.
This case allows simplification and compression of the data
structures.
GENERIC COMPOSITE: Composite structures that are agnostic to the
choice of Algorithms that they carry.
PUBLIC / PRIVATE KEY: The public and private portion of an asymmetric
cryptographic key, making no assumptions about which algorithm.
PRIMITIVE PUBLIC KEY / SIGNATURE: A public key or signature object of
a non-composite algorithm type.
SIGNATURE: A digital cryptographic signature, making no assumptions
about which algorithm.
2. Composite Structures
In order for public keys and signatures to be composed of pairs of
algorithms, we define encodings consisting of a sequence of public
key and signature primitives (aka "component algorithms") such that
these structures can be used as a drop-in replacement for existing
public key or signature fields such as those found in PKCS#10
[RFC2986], CMP [RFC4210], X.509 [RFC5280], CMS [RFC5652].
This section defines the following structures:
~~ TODO ~~
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2.1. Composite Keys
A composite key is a single key object that performs an atomic
signature or verification operation, using its encapsulated pair of
component keys.
Explicit pairs can easily be defined by simply providing an OBJECT
IDENTIFIER and two existing PUBLIC-KEY types to the pk-
explicitComposite object class, and assigning an OID to the resulting
structure. See examples of defining explicit pairs in Section 6.2.
-- TODO - CERT-KEY-USAGE should contain the intersection of the usages from firstPublicKey, secondPublicKey and the four listed below
-- pk-explicitComposite - Composite public key information object
pk-explicitComposite{OBJECT IDENTIFIER:id, PUBLIC-KEY:firstPublicKey, FirstPublicKeyType, PUBLIC-KEY:secondPublicKey, SecondPublicKeyType} PUBLIC-KEY ::= {
IDENTIFIER id
KEY ExplicitCompositePublicKey{firstPublicKey, FirstPublicKeyType, secondPublicKey, SecondPublicKeyType}
PARAMS ARE absent
CERT-KEY-USAGE {digitalSignature, nonRepudiation, keyCertSign, cRLSign}
}
The following ASN.1 object class then automatically generates the
public key structure from the types defined in pk-explicitComposite.
-- ExplicitCompositePublicKey - The data structure for a composite public key
-- sec-alg-identifier and SecondPublicKeyType are needed because PUBLIC-KEY contains
-- a set of public key types, not a single type.
-- TODO The parameters should be optional only if they are marked optional in the PUBLIC-KEY
ExplicitCompositePublicKey{PUBLIC-KEY:firstPublicKey, FirstPublicKeyType, PUBLIC-KEY:secondPublicKey, SecondPublicKeyType} ::= SEQUENCE {
firstPublicKey SEQUENCE {
params firstPublicKey.&Params OPTIONAL,
publicKey FirstPublicKeyType
},
secondPublicKey SEQUENCE {
params secondPublicKey.&Params OPTIONAL,
publicKey SecondPublicKeyType
}
}
2.2. Composite Private Key
EDNOTE: THIS IS WRONG. (copied from generic draft) we need to do some
work to come up with a private key structure.
The composite private key data is represented by the following
structure:
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CompositePrivateKey ::= SEQUENCE SIZE (2..MAX) OF OneAsymmetricKey
Each element is a OneAsymmetricKey [RFC5958] object for a component
private key.
The corresponding AlgorithmIdentifier for a composite private key
MUST use the id-alg-composite object identifier, and the parameters
field MUST be absent.
A CompositePrivateKey MUST contain at least one component private
key, and they MUST be in the same order as in the corresponding
CompositePublicKey.
2.3. Composite Signature
The structure pk-explicitComposite contains all the necessary
information in order for the ASN.1 compiler to generate composite
signature structures that are explicitely bound to the specified pair
of algorithms.
EDNOTE: Is this helping, or adding complexity for no reason? In
theory, explicit composite public keys can be used with generic
composite signature and encryption structures (ie the SEQUENC OF
model).
2.3.1. Explicit Signature Params
The following ASN.1 object class then automatically generates the
signature params structure from the types defined in pk-
explicitComposite.
-- ExplicitSignatureParams - The data structure for composite signature parameters
-- TODO firstParams and secondParams should be optional only if they are marked optional
-- in SIGNATURE-ALGORITHM
ExplicitSignatureParams{SIGNATURE-ALGORITHM:firstAlg, SIGNATURE-ALGORITHM:secondAlg} ::= SEQUENCE {
firstParams firstAlg.&Params OPTIONAL,
secondParams secondAlg.&Params OPTIONAL
}
EDNOTE: we need some help from the community on the ASN.1 here:
"OPTIONAL" is not really the right semantics here; we really mean
that they params here should be present or absent when the
corresponding params are present or absent in
ExplicitCompositePublicKey, which ought to be enforcable by the ASN.1
compiler, but we can't figure out the syntax for declaring that.
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2.3.2. Explicit Composite Signature Algorithm
The following ASN.1 object class then automatically generates the
signature algorithm structure from the types defined in pk-
explicitComposite.
-- TODO - Would it be possible to make these definitions compatible with n signature algorithms instead of 2? Is it desired?
-- sa-explicitCompositeSignatureAlgorithm - Composite signature algorithm information object
sa-explicitCompositeSignatureAlgorithm{OBJECT IDENTIFIER:algId, SIGNATURE-ALGORITHM:firstAlg, PUBLIC-KEY:firstPublicKey, FirstPublicKeyType, SIGNATURE-ALGORITHM:secondAlg, PUBLIC-KEY:secondPublicKey, SecondPublicKeyType} SIGNATURE-ALGORITHM ::= {
IDENTIFIER algId
VALUE ExplicitCompositeSignatureValue{firstAlg.&Value, secondAlg.&Value}
PARAMS TYPE ExplicitSignatureParams{firstAlg, secondAlg} ARE required
PUBLIC-KEYS { pk-explicitComposite{algId, firstPublicKey, FirstPublicKeyType, secondPublicKey, SecondPublicKeyType} }
SMIME-CAPS { IDENTIFIED BY algId }
}
2.3.3. Explicit Encryption and Key Exchange Params
~~ TODO ~~ Need analogous structures to the signature ones above.
2.4. Encoding Rules
Many protocol specifications will require that the composite public
key, composite private key, and composite signature data structures
be represented by an octet string.
When an octet string is required, the DER encoding of the composite
data structure SHALL be used directly.
When a bit string is required, the octets of the DER encoded
composite data structure SHALL be used as the bits of the bit string,
with the most significant bit of the first octet becoming the first
bit, and so on, ending with the least significant bit of the last
octet becoming the last bit of the bit string.
In the interests of simplicity and avoiding compatibility issues,
implementations that parse these structures MAY accept both BER and
DER.
3. In Practice
This section addresses practical issues of how this draft affects
other protocols and standards.
~~~ BEGIN EDNOTE 10~~~
EDNOTE 10: Possible topics to address:
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* The size of these certs and cert chains.
* In particular, implications for (large) composite keys /
signatures / certs on the handshake stages of TLS and IKEv2.
* If a cert in the chain is a composite cert then does the whole
chain need to be of composite Certs?
* We could also explain that the root CA cert does not have to be of
the same algorithms. The root cert SHOULD NOT be transferred in
the authentication exchange to save transport overhead and thus it
can be different than the intermediate and leaf certs.
* We could talk about overhead (size and processing).
* We could also discuss backwards compatibility.
* We could include a subsection about implementation considerations.
~~~ END EDNOTE 10~~~
3.1. PEM Storage of Composite Private Keys
CompositePrivateKeys can be encoded to the PEM format by placing a
CompositePrivateKey into the privateKey field of a PrivateKeyInfo or
OneAsymmetricKey object, and then applying the PEM encoding rules as
defined in [RFC7468] section 10 and 11 for plaintext and encrypted
private keys, respectively.
3.2. Asymmetric Key Packages (CMS)
The Cryptographic Message Syntax (CMS), as defined in [RFC5652], can
be used to digitally sign, digest, authenticate, or encrypt the
asymmetric key format content type.
When encoding composite private keys, the privateKeyAlgorithm in the
OneAsymmetricKey SHALL be set to id-alg-composite.
The parameters of the privateKeyAlgorithm SHALL be a sequence of
AlgorithmIdentifier objects, each of which are encoded according to
the rules defined for each of the different keys in the composite
private key.
The value of the privateKey field in the OneAsymmetricKey SHALL be
set to the DER encoding of the SEQUENCE of private key values that
make up the composite key. The number and order of elements in the
sequence SHALL be the same as identified in the sequence of
parameters in the privateKeyAlgorithm.
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The value of the publicKey (if present) SHALL be set to the DER
encoding of the corresponding CompositePublicKey. If this field is
present, the number and order of component keys MUST be the same as
identified in the sequence of parameters in the privateKeyAlgorithm.
The value of the attributes is encoded as usual.
3.3. Cryptographic protocols
This section talks about how protocols like (D)TLS and IKEv2 are
affected by this specifications. It will not attempt to solve all
these problems, but it will explain the rationale, how things will
work and what open problems need to be solved. Obvious issues that
need to be discussed.
* How does the protocol declare support for composite signatures?
TLS has hooks for declaring support for specific signature
algorithms, however it would need to be extended, because the
client would need to declare support for both the composite
infrastructure, as well as for the various component signature
algorithms.
* How does the protocol use the multiple keys. The obvious way
would be to have the server sign using its composite public key;
is this sufficient.
* Overhead; including certificate size, signature processing time,
and size of the signature.
* How to deal with crypto protocols that use public key encryption
algorithms; this document only lists how to work with signature
algorithms. Encoding composite public keys is straightforward;
encoding composite ciphertexts is less so - we decided to put that
off to another draft.
4. IANA Considerations
This draft does not define any OIDs, however derivative drafts that
define concrete algorithm pairs will. The authors suggest that IANA
assign OIDs for explicit composite pairs on the id-pkix arc under a
composite() arc.
id-alg-composite OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) algorithms(6) composite(??) }
5. Security Considerations
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5.1. Policy for Deprecated and Acceptable Algorithms
Traditionally, a public key, certificate, or signature contains a
single cryptographic algorithm. If and when an algorithm becomes
deprecated (for example, RSA-512, or SHA1), it is obvious that
structures using that algorithm are implicitly revoked.
In the composite model this is less obvious since a single public
key, certificate, or signature may contain a mixture of deprecated
and non-deprecated algorithms. Moreover, implementers may decide
that certain cryptographic algorithms have complementary security
properties and are acceptable in combination even though neither
algorithm is acceptable by itself.
Specifying a modified verification algorithm to handle these
situations is beyond the scope of this draft, but could be desirable
as the subject of an application profile document, or to be up to the
discretion of implementers.
2. Check policy to see whether A1, A2, ..., An constitutes a valid
combination of algorithms.
if not checkPolicy(A1, A2, ..., An), then
output "Invalid signature"
While intentionally not specified in this document, implementors
should put careful thought into implementing a meaningfull policy
mechinism within the context of their signature verification engines,
for example only algorithms that provide similar security levels
should be combined together.
5.2. Protection of Private Keys
Structures described in this document do not protect private keys in
any way unless combined with a security protocol or encryption
properties of the objects (if any) where the CompositePrivateKey is
used (see next Section).
Protection of the private keys is vital to public key cryptography.
The consequences of disclosure depend on the purpose of the private
key. If a private key is used for signature, then the disclosure
allows unauthorized signing. If a private key is used for key
management, then disclosure allows unauthorized parties to access the
managed keying material. The encryption algorithm used in the
encryption process must be at least as 'strong' as the key it is
protecting.
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5.3. Checking for Compromised Key Reuse
CA implementations need to be careful when checking for compromised
key reuse, for example as required by WebTrust regulations; when
checking for compromised keys, you MUST unpack the CompositePublicKey
structure and compare individual component keys. In other words,
when marking a key as revoked for key compromise, the individual
component keys should be marked, not the composite key as a whole.
6. Appendices
6.1. ASN.1 Module
<CODE STARTS>
Composite-Signatures-2019
{ TBD }
DEFINITIONS IMPLICIT TAGS ::= BEGIN
EXPORTS ALL;
IMPORTS
PUBLIC-KEY, SIGNATURE-ALGORITHM
FROM AlgorithmInformation-2009 -- RFC 5912 [X509ASN1]
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-algorithmInformation-02(58) }
SubjectPublicKeyInfo
FROM PKIX1Explicit-2009
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkix1-explicit-02(51) }
OneAsymmetricKey
FROM AsymmetricKeyPackageModuleV1
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) modules(0)
id-mod-asymmetricKeyPkgV1(50) } ;
--
-- Object Identifiers
--
id-alg-composite OBJECT IDENTIFIER ::= { TBD }
--
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-- Public Key
--
pk-Composite PUBLIC-KEY ::= {
IDENTIFIER id-alg-composite
KEY CompositePublicKey
PARAMS ARE absent
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
PRIVATE-KEY CompositePrivateKey
}
CompositePublicKey ::= SEQUENCE SIZE (2..MAX) OF SubjectPublicKeyInfo
CompositePrivateKey ::= SEQUENCE SIZE (2..MAX) OF OneAsymmetricKey
--
-- Signature Algorithm
--
sa-CompositeSignature SIGNATURE-ALGORITHM ::= {
IDENTIFIER id-alg-composite
VALUE CompositeSignatureValue
PARAMS TYPE CompositeParams ARE required
PUBLIC-KEYS { pk-Composite }
SMIME-CAPS { IDENTIFIED BY id-alg-composite } }
CompositeParams ::= SEQUENCE SIZE (2..MAX) OF AlgorithmIdentifier
CompositeSignatureValue ::= SEQUENCE SIZE (2..MAX) OF BIT STRING
END
<CODE ENDS>
6.2. Examples of defining explicit pairs
To add support for a new pair of algorithms, all that is required is
the following two constructs:
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id-sa-entrust-sha256RSAandECDSA OBJECT IDENTIFIER ::= { 1 2 3 4 }
sa-entrust-sha256RSAandECDSA SIGNATURE-ALGORITHM ::= sa-explicitCompositeSignatureAlgorithm{
id-sa-entrust-sha256RSAandECDSA,
sa-sha256WithRSAEncryption,
pk-rsa,
RSAPublicKey,
sa-ecdsaWithSHA256,
pk-ec,
ECPoint
}
TODO: run this through an ASN.1 compiler and list here what the final
generated structures look like.
6.3. Intellectual Property Considerations
The following IPR Disclosure relates to this draft:
https://datatracker.ietf.org/ipr/3588/
7. Contributors and Acknowledgements
This document incorporates contributions and comments from a large
group of experts. The Editors would especially like to acknowledge
the expertise and tireless dedication of the following people, who
attended many long meetings and generated millions of bytes of
electronic mail and VOIP traffic over the past year in pursuit of
this document:
John Gray (Entrust Datacard), Serge Mister (Entrust Datacard), Scott
Fluhrer (Cisco Systems), Panos Kampanakis (Cisco Systems), Daniel Van
Geest (ISARA), and Tim Hollebeek (Digicert).
We are grateful to all, including any contributors who may have been
inadvertently omitted from this list.
This document borrows text from similar documents, including those
referenced below. Thanks go to the authors of those documents.
"Copying always makes things easier and less error prone" -
[RFC8411].
8. References
8.1. Normative References
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[RFC1421] Linn, J., "Privacy Enhancement for Internet Electronic
Mail: Part I: Message Encryption and Authentication
Procedures", RFC 1421, DOI 10.17487/RFC1421, February
1993, <https://www.rfc-editor.org/info/rfc1421>.
[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>.
[RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification
Request Syntax Specification Version 1.7", RFC 2986,
DOI 10.17487/RFC2986, November 2000,
<https://www.rfc-editor.org/info/rfc2986>.
[RFC4210] Adams, C., Farrell, S., Kause, T., and T. Mononen,
"Internet X.509 Public Key Infrastructure Certificate
Management Protocol (CMP)", RFC 4210,
DOI 10.17487/RFC4210, September 2005,
<https://www.rfc-editor.org/info/rfc4210>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[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, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
[RFC5958] Turner, S., "Asymmetric Key Packages", RFC 5958,
DOI 10.17487/RFC5958, August 2010,
<https://www.rfc-editor.org/info/rfc5958>.
[RFC7468] Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
April 2015, <https://www.rfc-editor.org/info/rfc7468>.
[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>.
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[RFC8411] Schaad, J. and R. Andrews, "IANA Registration for the
Cryptographic Algorithm Object Identifier Range",
RFC 8411, DOI 10.17487/RFC8411, August 2018,
<https://www.rfc-editor.org/info/rfc8411>.
[X.690] ITU-T, "Information technology - ASN.1 encoding Rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ISO/IEC 8825-1:2015, November 2015.
8.2. Informative References
[I-D.ounsworth-pq-composite-sigs]
Ounsworth, M. and M. Pala, "Composite Keys and Signatures
For Use In Internet PKI", Work in Progress, Internet-
Draft, draft-ounsworth-pq-composite-sigs-03, 28 July 2020,
<http://www.ietf.org/internet-drafts/draft-ounsworth-pq-
composite-sigs-03.txt>.
Authors' Addresses
Mike Ounsworth
Entrust Limited
2500 Solandt Road -- Suite 100
Ottawa, Ontario K2K 3G5
Canada
Email: mike.ounsworth@entrust.com
Serge Mister
Entrust Limited
1000 Innovation Drive
Ottawa, Ontario K2K 1E3
Canada
Email: serge.mister@entrust.com
John Gray
Entrust Limited
1000 Innovation Drive
Ottawa, Ontario
Canada
Email: john.gray@entrust.com
Ounsworth, et al. Expires 16 August 2022 [Page 15]
