LAMPS M. Ounsworth (Editor)
Internet-Draft Entrust Datacard
Intended status: Standards Track M. Pala
Expires: July 19, 2020 CableLabs
January 16, 2020
Composite Keys and Signatures For Use In Internet PKI
draft-ounsworth-pq-composite-sigs-02
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 document defines the structures CompositePublicKey,
CompositeSignatureValue, and CompositeParams, which are sequences of
the respective structure for each component algorithm. This document
also defines algorithms for generating and verifying composite
signatures. This document makes no assumptions about what the
component algorithms are, provided that their algorithm identifiers
and signature generation and verification algorithms are defined.
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 July 19, 2020.
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Copyright Notice
Copyright (c) 2020 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Composite Structures . . . . . . . . . . . . . . . . . . . . 5
2.1. Algorithm Identifier . . . . . . . . . . . . . . . . . . 5
2.2. Composite Keys . . . . . . . . . . . . . . . . . . . . . 6
2.2.1. Key Usage Bits . . . . . . . . . . . . . . . . . . . 6
2.3. Composite Public Key . . . . . . . . . . . . . . . . . . 7
2.4. Composite Private Key . . . . . . . . . . . . . . . . . . 8
2.5. Composite Signature . . . . . . . . . . . . . . . . . . . 9
2.6. Encoding Rules . . . . . . . . . . . . . . . . . . . . . 9
3. Composite Signature Algorithm . . . . . . . . . . . . . . . . 10
3.1. Composite Signature Generation . . . . . . . . . . . . . 10
3.2. Composite Signature Verification . . . . . . . . . . . . 12
4. In Practice . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1. PEM Storage of Composite Private Keys . . . . . . . . . . 14
4.2. Asymmetric Key Packages (CMS) . . . . . . . . . . . . . . 14
4.3. Cryptographic protocols . . . . . . . . . . . . . . . . . 15
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
6.1. Policy for Deprecated and Acceptable Algorithms . . . . . 16
6.2. Protection of Private Keys . . . . . . . . . . . . . . . 16
6.3. Checking for Compromised Key Reuse . . . . . . . . . . . 17
6.4. Composite Encryption and KEMs . . . . . . . . . . . . . . 17
7. Appendices . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . 17
7.2. Intellectual Property Considerations . . . . . . . . . . 19
8. Contributors and Acknowledgements . . . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
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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
o 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
also 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.
o 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 multiple signature values into existing public key and signature
fields, as well as an algorithm for validating a composite signature.
The issue of backwards compatibility is left open to be addressed in
separate draft(s).
This document is intended for general applicability anywhere that
public key structures or digital signatures are used within PKIX
structures.
EDNOTE: While the scope of this document is restricted to signatures,
we note that the same "CompositePublicKey" structure is equally
applicable to asymmetric encryption keys. Though a word of warning
that the corresponding "encrypt / decrypt with a composite public
key" logic is somewhat less obvious; a naive implementer might be
tempted to follow the same pattern as below and encrypt the message
with each public key separately and then concatenate the ciphertexts,
which is wrong, they need to be nested. Specifying the correct
implementation of such an encryption scheme is out of scope for this
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document, but would be good work for someone in the standards
community to pick up.
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:
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 basic algorithm, as
defined in Section 2.
DER:
Distinguished Encoding Rules as defined in [X.690].
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.
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2. Composite Structures
In order for public keys and signatures to be composed of multiple
algorithms, we define encodings consisting of a sequence of public
key and signature primitives (aka "component algorithms") such that
these structures can be used an a drop-in compatible way with
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:
o The id-alg-composite is an OID identifying a composite public key
or signature object.
o The CompositePublicKey carries all the public keys associated with
an identity within a single public key structure.
o The CompositePrivateKey carries all the private keys associated
with an identity within a single private key structure.
o The CompositeSignatureValue, carries a sequence of signatures that
are generated by a CompositePrivateKey, and can be verified with
the corresponding compositePublicKey.
EDNOTE: the choice to define composite algorithm parameters as a
sequence inside the existing fields avoids the exponential
proliferation of OIDs that are needed for each pairwise combination
of signature algorithms in other schemes for achieving multi-key
certificates. This scheme also naturally extends from 2-keypair to
n-keypair keys and certificates.
2.1. Algorithm Identifier
The same algorithm identifier is used for identifying a public key, a
private key, and a signature. Additional encoding information is
provided below for each of these objects.
id-alg-composite OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1) private(4)
enterprise(1) OpenCA(18227) Algorithms(2) id-alg-composite(1) }
EDNOTE: this is a temporary OID for the purposes of prototyping. We
are requesting IANA to assign a permanent OID, see Section 5.
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2.2. Composite Keys
A composite key is a single key object that performs an atomic
signature or verification operation, using its encapsulated sequence
of component keys.
The ASN.1 algorithm object for composite public and private keys is:
pk-Composite PUBLIC-KEY ::= {
IDENTIFIER id-alg-composite
KEY CompositePublicKey
PARAMS ARE absent
CERT-KEY-USAGE
{ digitalSignature, nonRepudiation, keyCertSign, cRLSign }
PRIVATE-KEY CompositePrivateKey
}
EDNOTE1: the authors are currently unsure whether the params should
be absent (ie this structure simply says "I am a composite
algorithm"), or used to duplicate some amount of information about
what the component algoritms are. See Section 2.3 for a longer
ENDOTE on this.
EDNOTE2: In order to reduce complexity, we are intentionally limiting
the scope of this draft to signature-type CERT-KEY-USAGEs, but we
note that it would be trivial to extend it to encryption-type keys.
2.2.1. Key Usage Bits
The intended application for the key is indicated in the keyUsage
certificate extension and defined in the CERT-KEY-USAGE field of pk-
Composite.
If the keyUsage extension is present in an end-entity certificate
that indicates id-alg-composite, then the keyUsage extension MUST
contain one or both of the following values:
nonRepudiation; and
digitalSignature.
If the keyUsage extension is present in a certification authority
certificate that indicates id-alg-composite, then the keyUsage
extension MUST contain one or more of the following values:
nonRepudiation;
digitalSignature;
keyCertSign; and
cRLSign.
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As this draft only covers composite signatures, the key usage bits
specified here apply to all component keys within a composite key.
2.3. Composite Public Key
Composite public key data is represented by the following structure:
CompositePublicKey ::= SEQUENCE SIZE (1..MAX) OF SubjectPublicKeyInfo
The corresponding AlgorithmIdentifier for a composite public key MUST
use the id-alg-composite object identifier, defined in Section 2.1,
and the parameters field MUST be absent.
A composite public key MUST contain at least one component public
key.
A CompositePublicKey MUST NOT contain a component public key which
itself describes a composite key; ie recursive CompositePublicKeys
are not allowed
Each element of a CompositePublicKey is a SubjectPublicKeyInfo object
one of the component public keys. When the CompositePublicKey must
be provided in octet string or bit string format, the data structure
is encoded as specified in Section 2.6.
~~~ Begin EDNOTE ~~~
EDNOTE: there has been a fair amout of discussion among the authors
about whether the component public key should contain a full
SubjectPublicKeyInfo for each component algorithm, or whether the
{algID, and algParams} should be move to the params of the PUBLIC-KEY
or OID, and only the BIT STRINGs of the component public key values
contained in the CompositePublicKey.
Using a wonky, simplified notation, the alternatives considered were:
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Current composite:
CompositeAlg: {
algorithm={id-alg-composite, none}
subjectPublicKey=SEQ SPKI[{{algID1, algParams1}, value1},
SPKI{{algID2, algParams2}, value2}, ..]
}
Alternative 1:
CompositeAlg: {
algorithm={id-alg-composite, {{algID1, algParams1},
{algID2, algParams2}, ..}
subjectPublicKey=SEQ BIT STRING[value1, value2, ..]
}
Alternative 2:
CompositeAlg: {
algorithm={id-alg-composite, {algID1, algID2, ..}}
subjectPublicKey=SEQ SPKI[{{algID1, algParams1}, value1},
{{algID2, algParams2}, value2}, ..]
}
The authors have decided, for the time being, to use the current
approach since it A) promotes ease of modifying existing software
whose APIs require SubjectPublicKeyInfos to be passed, and B) avoids
bloating wire protocols with duplicated information.
We note that the chosen approach means that the algorithm field
essentially carries no useful information about the key it's
describing. Analysis is required to see if there are any
circumstances in which this opens up cryptographic attacks, such as
algorithm substitution or stripping attacks. ~~~ End EDNOTE ~~~
2.4. Composite Private Key
The composite private key data is represented by the following
structure:
CompositePrivateKey ::= SEQUENCE SIZE (1..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.
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A CompositePrivateKey MUST contain at least one component private
key, and they MUST be in the same order as in the corresponding
CompositePublicKey.
2.5. Composite Signature
The ASN.1 algorithm object for a composite signature is:
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 } }
}
The id-alg-composite object identifier MUST be used to identify when
a signature has been created by a composite private key, and te
following algorithm parameters MUST be included:
CompositeParams ::= SEQUENCE SIZE (1..MAX) OF AlgorithmIdentifier
The signature's CompositeParams sequence MUST contain the same
component algorithms listed in the same order as in the associated
CompositePrivateKey and CompositePublicKey.
The output of the composite signature algorithm is the DER encoding
of the following structure:
CompositeSignatureValue ::= SEQUENCE SIZE (1..MAX) OF BIT STRING
Where each BIT STRING within the SEQUENCE is a signature value
produced by one of the component keys. It MUST contain MUST contain
one signature value produced by each componet key, and in the same
order as in the associated "CompositeParams", CompositePublicKey, and
CompositePrivateKey objects.
The choice of "SEQUENCE OF BIT STRING", rather than for example a
single BIT STRING containing the concatenated signature values, is to
gracefully handle variable-length signature values by taking
advantage of ASN.1's build-in length fields.
2.6. 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 or bit string.
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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. Composite Signature Algorithm
This section specifies the algorithms for generating and verifying
composite signatures.
This algorithm addresses algorithm strength uncertainty by providing
the verifier with parallel signatures from all the component
signature algorithms; thus breaking the composite signature would
require breaking all of the component signatures.
3.1. Composite Signature Generation
Generation of a composite signature involves applying each component
algorithm's signature routine to the input message according to its
specification, and then placing each component signature value into
the "CompositeSignatureValue" structure defined in Section 2.5.
The following algorithm is used to generate composite signature
values.
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Input:
K1, K2, .., Kn Private keys for the n component signature
algorithms
M Message to be signed, an octet string
Output:
S The signature, a CompositeSignatureValue
Signature Generation Procedure:
1. Generate the n component signatures independently,
according to their algorithm specifications.
for i := 1 to n
Si := Sign( Ki, M )
2. Encode each component signature S1, S2, .., Sn into a BIT STRING
according to its algorithm specification.
S ::= Sequence { S1, S2, .., Sn }
3. Output S
Since recursive composite public keys are disallowed in Section 2.3,
no component signature may itself be composite; ie the signature
generation routine MUST fail if one of the private keys K1, K2, ..,
Kn is composite with the OID id-alg-composite.
A composite signature MUST produce and include in the output a
signature value for every component key in the corresponding
CompositePublicKey.
EDNOTE1: With NIST's position that they will standardize use-case-
specific algorithm suites, the authors are aware of potential use-
cases where a PKI entity may want to have many public keys, but only
sign with a subset for each signature. At the present time, this
draft does not allow for this because the algorithm for verifying
"subset-signatures" in a way that is secure against algorithm
stripping attacks would be very complex and prone to implementation
errors (currently, the verifier can detect omitted signatures even if
it does not recognize all the algorithm OIDs because the count will
be wrong. In a subset-signature algorithm, additional mechanisms
would be needed to specify for each component key, whether it is
meant to produce a signature or not). The draft-compliant way to
achieve a "subset-signature" behaviour would be for each PKI entity
to have multiple public keys (and certificates) with overlapping
subsets of their component keys. We welcome public opinions on
whether this is sufficient, or whether this draft should specify a
subset-signature algorithm.
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EDNOTE2: The authors are also aware of a potential use-case of
combining signature and KEM keys inside a single public key /
certificate. This would give us back the "dual-usage key" property
that was so appealing about RSA. At the present time, this draft
does not allow for this because, again, the algorithm for verifying
"subset-signatures" in a secure way would be very complex. We also
welcome public opinions on this.
3.2. Composite Signature Verification
Verification of a composite signature involves applying each
component algorithm's verification routine according to its
specification.
In the absence of an application profile specifying otherwise,
compliant applications MUST output "Valid signature" (true) if and
only if all component signatures were successfully validated, and
"Invalid signature" (false) otherwise.
The following algorithm is used to perform this verification.
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Input:
P Signer's composite public key
M Message whose signature is to be verified, an octet string
S Composite Signature to be verified
A Composite Algorithm identifier
Output:
Validity "Valid signature" (true) if the composite signature
is valid, "Invalid signature" (false) otherwise.
Signature Verification Procedure::
1. Parse P, S, A into the component public keys, signatures,
and algorithm identifiers
P1, P2, .., Pn := Desequence( P )
S1, S2, .., Sn := Desequence( S )
A1, A2, .., An := Desequence( A )
If Error during Desequencing, or the three sequences have
different numbers of elements, or any of the public keys P1, P2, .., Pn or
algorithm identifiers A1, A2, .., An are composite with the OID
id-alg-composite then output "Invalid signature" and stop.
2. Check each component signature individually, according to its
algorithm specification.
If any fail, then the entire signature validation fails.
for i := 1 to n
if not verify( Pi, M, Si ), then
output "Invalid signature"
if all succeeded, then
output "Valid signature"
Since recursive composite public keys are disallowed in Section 2.3,
no component signature may be composite; ie the signature
verification procedure MUST fail if any of the public keys P1, P2,
.., Pn or algorithm identifiers A1, A2, .., An are composite with the
OID id-alg-composite.
It is expected that some use-cases for algorithm migration or high
performance will require verifiers to succeed when only a subset of
the component algorithms have been verified. Defining this
verification behaviour is out of scope for this document, and falls
to an application profile.
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4. In Practice
This section addresses practical issues of how this draft affects
other protocols and standards.
~~~ BEGIN EDNOTE ~~~
EDNOTE: Possible topics to address:
o The size of these certs and cert chains.
o In particular, implications for (large) composite keys /
signatures / certs on the handshake stages of TLS and IKEv2.
o If a cert in the chain is a composite cert then does the whole
chain need to be of composite Certs?
o 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.
o We could talk about overhead (size and processing).
o We could also discuss backwards compatibility.
o We could include a subsection about implementation considerations.
~~~ END EDNOTE ~~~
4.1. 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.
EDNOTE: Do we really need this? Isn't it obvious?
4.2. 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.
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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.
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.
4.3. 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.
o 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.
o 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.
o Overhead; including certificate size, signature processing time,
and size of the signature.
o 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.
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5. IANA Considerations
The ASN.1 module OID is TBD. The id-alg-composite OID is to be
assigned by IANA. The authors suggest to use the id-pkix arc for
this usage:
id-alg-composite OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) algorithms(6) composite(??) }
6. Security Considerations
6.1. 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-depricated algorithms. Moreover, implementers may decide
that certain cryptographic algorithms have complementary security
properties and are acceptable in combination even though neither
algoritm is acceptable by itself.
In Section 3.2, we specify that the signature verification routine
must include a step to check that the combination of algorithms is
acceptable under local policy:
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.
6.2. Protection of Private Keys
This structures described in this document do not protect the private
keys information 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 key information is vital to public key
cryptography. The consequences of disclosure depend on the purpose
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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 as 'strong' as the key it is protecting.
6.3. 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.
6.4. Composite Encryption and KEMs
This document deals only with signature keys. While the
CompositePublicKey and CompositePrivateKey structures could equally
be used to hold encryption or KEM keys, the authors warn that there
are non-trivial design decisions to be made when constructing a
multi-key public key encryption or KEM algorithm. Some of these
design and implementation decisions, if done incorrectly will result
in a catastrophic loss of security. We leave it to the community to
standardize analogous composite encryption and KEM schemes.
7. Appendices
7.1. 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)
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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 }
--
-- 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 (1..MAX) OF SubjectPublicKeyInfo
CompositePrivateKey ::= SEQUENCE SIZE (1..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 (1..MAX) OF AlgorithmIdentifier
CompositeSignatureValue ::= SEQUENCE SIZE (1..MAX) OF BIT STRING
END
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<CODE ENDS>
7.2. Intellectual Property Considerations
The authors are aware that Massimiliano Pala and CableLabs have
applied for Intellectual Property Rights around composite key,
signatures, and certificates. We have a verbal agreement with Max
that this IP will be made freely available to the community.
As of this version of the draft, the authors have reviewed and
provided feedback on the March 24, 2019 version of the IPR
disclosure, available at https://datatracker.ietf.org/ipr/3481/, and
are awaiting the posting of an updated version that covers this
draft.
EDNOTE: remove this section once the IPR disclosure is posted and
tagged against this draft.
8. 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].
9. References
9.1. Normative References
[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>.
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[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>.
[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>.
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9.2. Informative References
[I-D.pala-composite-crypto]
Pala, M., "Composite Public Keys and Signatures", draft-
pala-composite-crypto-00 (work in progress), February
2019.
[I-D.truskovsky-lamps-pq-hybrid-x509]
Truskovsky, A., Geest, D., Fluhrer, S., Kampanakis, P.,
Ounsworth, M., and S. Mister, "Multiple Public-Key
Algorithm X.509 Certificates", draft-truskovsky-lamps-pq-
hybrid-x509-01 (work in progress), August 2018.
Authors' Addresses
Mike Ounsworth
Entrust Datacard Limited
1000 Innovation Drive
Ottawa, Ontario K2K 1E3
Canada
Email: mike.ounsworth@entrustdatacard.com
Massimiliano Pala
CableLabs
Email: director@openca.org
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