PKIX Key Attestation Format
draft-ounsworth-pkix-key-attestation-01
The information below is for an old version of the document.
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| Authors | Mike Ounsworth , Richard Kettlewell , Bruno Couillard , Jean-Pierre Fiset | ||
| Last updated | 2023-03-13 | ||
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draft-ounsworth-pkix-key-attestation-01
LAMPS M. Ounsworth
Internet-Draft Entrust
Intended status: Standards Track R. Kettlewell
Expires: 14 September 2023 Entrust - nCipher
B. Couillard
JP Fiset
CRYPTO4A
13 March 2023
PKIX Key Attestation Format
draft-ounsworth-pkix-key-attestation-01
Abstract
This document describes syntax for conveying key origin attestation
information to a Certification Authority (CA) or other entity, so
that they may decide how much trust to place in the management
private of the key, for example to support a decision about whether
to issue a certificate. In contrast to other key attestation
formats, the one defined in this document requires only ASN.1 and the
standard PKIX modules.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ounsworth-pkix-key-
attestation/.
Discussion of this document takes place on the Limited Additional
Mechanisms for PKIX and SMIME (lamps) Working Group mailing list
(mailto:spasm@ietf.org), which is archived at
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https://www.ietf.org/mailman/listinfo/spasm/.
Source for this draft and an issue tracker can be found at
https://github.com/EntrustCorporation/draft-ounsworth-pq-composite-
keys.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Cryptographic Keys . . . . . . . . . . . . . . . . . . . . . 4
3.1. Trust Anchor Key . . . . . . . . . . . . . . . . . . . . 4
3.2. Intermediate CA Key . . . . . . . . . . . . . . . . . . . 4
3.3. Device Identity Key . . . . . . . . . . . . . . . . . . . 5
3.4. Device Certification Subkey . . . . . . . . . . . . . . . 5
3.5. Application Key . . . . . . . . . . . . . . . . . . . . . 6
4. Key Attestations . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Key Attestation Bundle . . . . . . . . . . . . . . . . . 6
4.2. Intermediate CA Certificate . . . . . . . . . . . . . . . 7
4.3. Device Identity Certificate . . . . . . . . . . . . . . . 8
4.4. Device Delegation Certificate . . . . . . . . . . . . . . 9
4.5. Key Attestation Certificate . . . . . . . . . . . . . . . 10
4.5.1. Vendor-Specific Information . . . . . . . . . . . . . 11
5. Key Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Distinctions between Key Use Policies . . . . . . . . . . 13
5.2. Recoverable Keys . . . . . . . . . . . . . . . . . . . . 13
5.3. Key Protection . . . . . . . . . . . . . . . . . . . . . 13
5.4. Vendor-Defined Key Use Policies . . . . . . . . . . . . . 13
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6. Embedding Key Attestations in Certification Requests . . . . 14
7. Implementation Considerations . . . . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9.1. Key Use Constraints . . . . . . . . . . . . . . . . . . . 15
9.2. Verification Model . . . . . . . . . . . . . . . . . . . 16
9.3. Recoverable Keys . . . . . . . . . . . . . . . . . . . . 17
9.4. Uniqueness of Keys . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . 18
Appendix A. Samples . . . . . . . . . . . . . . . . . . . . . . 18
Appendix B. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 18
Appendix C. Intellectual Property Considerations . . . . . . . . 19
Appendix D. Contributors and Acknowledgements . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
Key attestion refers to the originator of a cryptographic key pair
providing information about the provenance of that key pair, in a
manner that can be cryptographically verified. The information
provided may include, for example, the model and identity of the
device that created the key pair and any policies that may be
enforced upon the use of the private key, contained in a
cryptographic envelope that can be chained to a manufacturing public
key of the device vendor.
This information can be used by a Certification Authority (CA) to
decide whether to issue a certificate, to apply a given policy or
certificate template, or by other entities for their own purposes.
The CA may choose to publish some or all of the key attestation data
in the certificate for the use of parties that will rely on this
certificate.
Many devices, including Hardware Security Modules, provide
attestation information of some form in proprietary formats. A
common syntax for key attestations is required to reduce the
implementation burden on CA implementors and operators. Furthermore
it is desirable that the syntax is sympathetic to existing CA
implementations.
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2. 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
BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Cryptographic Keys
This section describes the cryptographic keys referenced in this
document.
3.1. Trust Anchor Key
A trust anchor key is a signing key held by a vendor. For the
purposes of this document, a trust anchor may be a proper Trust
Anchor as defined in [RFC5914], or a root certification authority as
defined in [RFC5280]. It is used either to directly sign device
identity keys as defined in Section 3.3 or to sign intermediate CA
keys. A trust anchor key MUST be associated with a vendor identity.
Constraints:
* A trust anchor key MUST only be used for purposes consistent with
signing intermediate CA keys or devices (i.e. signing delegation
certificates, CRLs, etc).
3.2. Intermediate CA Key
An intermediate CA key is a signing key held by a vendor and
certified by that vendor's trust anchor.
It can be used for one of two purposes:
* to certify device identity keys (see section Section 3.3) by
signing device identity certificates (see section Section 4.3)
* to certify further intermediate CA keys
The exact configuration and management of trust anchor keys and
intermediate CA keys is beyond the scope of this document. An
example configuration is that a vendor have an offline trust anchor,
and an intermediate CA in each of its manufacturing sites, certified
by the trust anchor key when a manufacturing site is created or
during maintenance or recovery activities.
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It may be impossible recertify a device after manufacture, and it may
be impossible for a manufacturer to know when a device has been
retired from use. Therefore:
* an intermediate CA need not track and public revocation
information
* intermediate CA keys MAY have a expiration date of 99991231235959Z
([RFC5280] section 4.1.2.5).
Constraints:
* An intermediate CA key MUST only be used for purposes consistent
with certifying intermediate CA keys (i.e. signing delegation
certificates, CRLs, etc) or devices.
3.3. Device Identity Key
A device identity key is a signing key held by a device. It is
assumed that the key is unique to the device and cannot be extracted
or used for any purpose other than the ones listed below. It is
envisaged that this key will persist for the lifetime of the device.
It can be used for one of two purposes:
* to sign key attestations directly
* to sign device delegation certificates (see section Section 4.4),
which are used to certify device certification subkeys (see
section Section 3.4).
Constraints:
* A device identity key MUST NOT be used for any purpose other than
signing key attestation certificates or device delegation
certificates.
3.4. Device Certification Subkey
A device certification key is a signing key held by a device. It is
assumed that the key is unique to the device and cannot be extracted
or used for any purpose other than the ones listed below. Depending
on the device architecture, it may also be limited to a particular
context or partition of the device; in this case it is assumed to be
unique to the particular context. A device certification key may
have any lifetime, from single use to the lifetime of the device.
It can be used for one of two purposes:
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* to sign key attestations directly
* to sign further device delegation certificates.
Constraints:
* A device certification subkey MUST NOT be used for any purpose
other than signing key attestation certificates (see section
Section 4.5) or device delegation certificates (see section
Section 4.4).
3.5. Application Key
An application key is a key created and managed by a device
(excluding the device identity key and device certification subkey
described above). Its purpose and lifetime are arbitrary - in other
words, it can be used for any purpose a user of the device wishes.
_(MikeO: maybe I'm a noob here, but the distinction between this an a
Device Certification Subkey could be stated more clearly. Maybe the
distinction "This is envisioned for cases where a device needs an
attested key which may be used for arbitrary purposes".)_
_(RJK: it's not really about what the device desires - these are the
keys that we are trying to attest the origin of. The user has some
higher-level purpose, e.g. code signing, which requires them to
define a code signing key and attest to its origins in an HSM; from
the point of view of this spec, their code-signing key is an
application key. Keeping this comment open in the hope we can find a
clear way of articulating this.)_
4. Key Attestations
A verifier is an entity which wishes to verify the origin of a key,
based on its trust in a trust anchor.
For example, it could be a certificate authority with an operational
constraint that it only certifies hardware-protected keys.
4.1. Key Attestation Bundle
A key attestation consists of a nonempty sequence of [RFC5280]
certificates, containing key attestation extensions as described
below.
Specifically, a key attestation consists of:
* Zero or more intermediate certificates (see section Section 4.2)
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* Exactly one device identity certificate (see section Section 4.3)
* Zero or more device delegation certificates (see section
Section 4.4)
* Exactly one key attestation certificate (see section Section 4.5)
The first certificate (whether it is an intermediate certificate or
the device identity certificate) is signed by a trust anchor key. A
verifier must decide through its own policies and processes which
trust anchors keys to trust and what policies to accept in key
attestations certified by them. A trust anchor key MUST be
associated with a vendor identity.
Constraints:
* A verifier MUST verify that each certificate is well-formed
(except that expiry and revocation information need not be
present)
* A verifier MUST verify that the first certificate is signed by a
trust anchor key
* A verifier MUST verify that each certificate, apart from the
first, is certified by the previous certificate in the key
attestation.
* A verifier MUST verify that the ordering of certificates is as
described above.
4.2. Intermediate CA Certificate
An intermediate CA delegation certificate certifies an intermediate
CA. Apart from the absence of any constraints on expiry time and
revocation, it is little different from any other intermediate CA's
certificate.
It MUST have the [RFC5280] basic constraints extension with the cA
boolean set to true.
It MAY have the [RFC5280] pathLenConstraint, and there is no change
to the [RFC5280] interpretation this field. Therefore, if it is
present, it must permit sufficiently many following certificates to
account for certificates signed by the device i.e. device identity
certificates (see section Section 4.3) and device delegation
certificates (see section Section 4.4).
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It MUST NOT have any of the extensions defined in the following
sections (Section 4.3, Section 4.4 and Section 4.5). A verifier may
detect an intermediate CA delegation by the presence of a true cA
boolean and the absence of these extensions.
Constraints:
* A verifier MUST honor pathLenConstraint if present.
* There may be any number of intermediate CA certificates, including
0.
4.3. Device Identity Certificate
A device identity certificate certifies a specific device by binding
its public device identity key (defined in Section 3.3) to a vendor-
specific representation of device identity such as vendor name,
model, and serial number. For a hardware device, it is envisaged
that a manufacturing facility will use its trust anchor or
intermediate CA to sign a device identity certificate for each device
as it is manufactured.
A device identity certificate MUST contain a DeviceInformation
extension, identified by id-device-information. This extension
contains the vendor identity, device model and device serial.
Together these are called the device identity and MUST uniquely
define a particular device.
id-device-information OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1567 }
DeviceInformation ::= SEQUENCE {
vendor UTF8STring -- manufacturer of device
model UTF8STring -- device model information
serial UTF8STring -- device instance information
}
EDNOTE: this is a temporary OID for the purposes of prototyping.
We are requesting IANA to assign a permanent OID, see Section 8.
A device identity certificate MUST have the [RFC5280] basic
constraints extension with the cA boolean set to true (since the
device is acting as a CA).
No significance is attached to the subject field of a device identity
certificate.
Constraints:
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* A verifier MUST reject any key attestation that does not contain
exactly one device identity certificate.
* A verifier MUST reject any device identity certificate whose
vendor identity as indicated in the vendor field does not match
the one associated with the trust anchor used to verify the key
attestation.
* Two distinct devices from the same vendor MUST NOT have the same
device identity, i.e. they must have different values for at least
one field of DeviceIdentity.
* Two distinct devices MUST NOT have the same device identity key.
As a matter of interpretation, it is envisaged that the uniquess
requirement on device identity keys (and all other keys in this
specification) is achieved by generating keys of adequate size, using
a cryptographically secure pseudorandom number generators, rather
than by maintaining an industry-wide database of all device identity
keys.
4.4. Device Delegation Certificate
A device delegation certificate certifies that a specific
certification subkey (defined in Section 3.4) belongs to a specific
device by binding it to a vendor-specific representation of the
device and the subkey's purpose. It is envisaged that a single
hardware device may have multiple certification subkeys each being
restricted to, for example, a single partition or application
context. The device may create new certification subkeys and
therefore new device delegation certificates over time, for instance
when the device is re-initialized, or if the device supports dynamic
creation of users or application contexts and needs to create
distinct certification subkeys for each.
A device delegation certificate MUST contain a
DeviceSubkeyInformation extension, identified by id-device-subkey-
information. This contains the vendor identity, device model, device
serial and key purpose. Note that this does not uniquely define the
certification subkey.
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id-device-subkey-information OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1568 }
DeviceSubkeyInformation ::= SEQUENCE {
vendor UTF8STring -- manufacturer of device
model UTF8STring -- device model information
serial UTF8STring -- device instance information
purpose UTF8String -- description of subkey purpose
}
EDNOTE: this is a temporary OID for the purposes of prototyping.
We are requesting IANA to assign a permanent OID, see Section 8.
The meaning of the purpose field is entirely dependent on the device.
It MUST have the [RFC5280] basic constraints extension with the cA
boolean set to true (since the device is acting as a CA).
No significance is attached to the subject field of a device
delegation certificate.
Constraints:
* A verifier MUST reject any device delegation certificate whose
device identity as indicated in the vendor, model and serial
fields does not match the values from the device identity
certificate.
* The purpose field may have any value.
* Two device delegation certificates signed by the same key MAY have
the same purpose field.
4.5. Key Attestation Certificate
A key attestation certificate certifies that an application key was
created in a particular device and is managed according to a
particular policy.
A key attestation certificate MUST contain a
ApplicationKeyInformation extension identified by id-application-key-
information. This contains the vendor identity, device model, device
serial and vendor-specific information.
A key attestation certicate MUST contain an [RFC5280] Extended Key
Usage extension documenting how the device will permit the key to be
used. See Section 5 for more details.
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ApplicationKeyInformation ::= SEQUENCE {
vendor UTF8STring -- manufacturer of device
model UTF8STring -- device model information
vendorinfo OCTET STRING -- vendor-specific information
}
EDNOTE: this is a temporary OID for the purposes of prototyping.
We are requesting IANA to assign a permanent OID, see Section 8.
If the key attestation certificate contains the [RFC5280] Basic
Constraints extension then it MUST have the cA boolean set to false.
No significance is attached to the subject field of a key attestation
certificate.
Constraints:
* A verifier MUST reject any key attestation certificate whose
device identity as indicated in the vendor, model and serial
fields does not match the values from the device identity
certificate.
* A verifier MUST reject any key attestation certificate which does
not contain exactly one [RFC5280] Extended Key Usage extension
* A verifier MUST reject any key attestation certificate which
permits operations inconsistent with its acceptable policies.
4.5.1. Vendor-Specific Information
The ApplicationKeyInformation.vendorInfo field of the key attestation
certificate MAY contain any octet string (including the empty
string). The interpretation is up to the vendor. For example, it
may be used to convey information about how the key was generated or
a vendor-specific description of the policies that govern its use.
5. Key Usage
Key attestation certificates contain an [RFC5280] s4.2.1.12 Extended
Key Usage extension describing how the device will permit the key to
be used.
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The standard ExtendedKeyUsage purposes defined in [RFC5280] are not
necessarily suitable in this context. For example the standard
ExtendedKeyUsage OIDs are also not necessarily suitable. For example
the device may have no information about whether a signing key is
intended to be used for server authentication, client authentication,
or any other application of digital signatures. For this reason an
additional set of key usage purposes are defined here.
id-Signature OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1613 }
-- the device will generate signatures with the key
id-Decryption OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1614 }
-- the device will decrypt messages with the key and return the plaintext
id-KeyAgreement OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1615 }
-- the device will use the key for key agreement
id-KeyTransport OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1616 }
-- the device will use the key for key transport
id-Recoverable OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1612 }
-- the key is can be recovered under administrative authorization
EDNOTE: these are a temporary OIDs for the purposes of
prototyping. We are requesting IANA to assign a permanent OID,
see Section 8.
EDNOTE: We should consult particurly with CAs to see if there are
other properties that would be beneficial to include in this list.
Constraints:
* If the device does not include id-Signature in the list of key use
purposes then it MUST NOT generate signatures with the key.
* If the device does not include id-Decryption in the list of key
use purposes then it MUST NOT decrypt ciphertexts with the key.
* If the device does not include id-KeyAgreement in the list of key
use purposes then it MUST NOT use the key for key agreement.
* If the device does not include id-KeyTransport in the list of key
use purposes then it MUST NOT use the key for key transport.
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* If the device does not include id-Recoverable in the list of key
use purposes then it MUST NOT permit recovery operations on the
key.
5.1. Distinctions between Key Use Policies
* Decryption means using the key to decrypt a ciphertext and
returning the plaintext to the caller, outside the device
* Key Transport means using the key to decrypt a ciphertext and
using the plaintext as key material, managed by the device
* Key Agreement means using the key to agree a secret shared with
another party, as prelude to further secure communication
5.2. Recoverable Keys
The id-Recoverable key use purpose indicates that the policies
controlling use of the key may be modified by a suitably authorized
administrator. This may be necessary, for example, to ensure that
the key remains available for use even when an authentication token
is lost or destroyed.
The scope of possible modifications, and the kind of authorization
required, are intentionally vague.
See Section 9.3 for further discussion.
5.3. Key Protection
These key use purposes are not intended to describe how applications
keys is protected by the device. For example one device may protect
keys by maintaining them inside a hardended boundary at all times;
another may allow keys to be used across multiple devices by
encrypting them under a shared master key, or by sharing them with
other authorized devices via a secure channel.
Provided the device is able to guarantee that the key use policy it
signs will be honored, the mechanism is uses to protect application
keys is not relevant.
5.4. Vendor-Defined Key Use Policies
A vendor may define key use policies outside the list above, for
example reflecting policies not envisaged by this document or to
cover device-specific functionality. For example they may describe a
policy in terms of their device's proprietary policy or access
control syntax and publish an OID reflecting that policy.
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A verifier MUST NOT accept such a vendor-defined policy unless they
fully understand the intended meaning.
6. Embedding Key Attestations in Certification Requests
A convenient way to convey a key attestation is to embed it into a
[RFC2986] certification request. This may be done via the
AttestationBundle extension, identified by the OID id-attestation-
bundle.
Constraints:
* A certification request SHOULD only have one embedded key
attestation.
* A CA MUST follow meet all the constraints on verifiers described
above.
* A CA MUST verify that the subject public key in the certification
request is the same as the subject public key in the key
attestation certificate.
*RJK TODO tidy up all this section
(MikeO: We'll need to be explicit about how to bundle this into a
[RFC2986] Attribute. Do we need an OID for the type? I assume the
values is straight-forward: it'll be a single item, which is the
OCTET STRING of the AttestationBundle?
Attribute { ATTRIBUTE:IOSet } ::= SEQUENCE { type
ATTRIBUTE.&id({IOSet}), values SET SIZE(1..MAX) OF
ATTRIBUTE.&Type({IOSet}{@type}) }
)
id-attestation-bundle OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1571 }
AttestationBundle ::= SEQUENCE OF Certificate
EDNOTE: this is a temporary OID for the purposes of prototyping.
We are requesting IANA to assign a permanent OID, see Section 8.
7. Implementation Considerations
... TODO document any (non-security) GOTCHAs ...
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8. IANA Considerations
The following Object Identifiers are to be assigned by IANA:
id-device-information OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1567 }
id-device-subkey-information OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1568 }
id-application-key-information OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1569 }
id-attestation-bundle OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1571 }
id-Signature OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1613 }
id-Decryption OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1614 }
id-KeyAgreement OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1615 }
id-KeyTransport OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1616 }
id-Recoverable OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1612 }
TODO: suggest to IANA which public arc we want these in (these are
just placeholders).
TODO update for our new EKU OIDs
*RJK: the OIDs are assigned by a free OID assignment service. If I
can have something under Entrust then I'll replace them with that.
9. Security Considerations
9.1. Key Use Constraints
The key use constraints describe above are essential. For example if
a device identity key could be used by a user to sign arbitrary
messages, that user could forge key attestations.
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9.2. Verification Model
An API that verifies a key attestion may be designed in a number of
different ways.
1. It may accept just a key attestation. It will verify it, and
return either an error indicator or the public trust anchor key,
vendor identity, public application key, and the policy governing
is use. The caller must check at least that the trust anchor key
is acceptable; the vendor identity from the key attestation
matches the one associated with the trust anchor; and that the
policy is acceptable, before using the application key. If the
caller is running in a context where there are multiple copies of
the application key (for example, the certification request
verification described in Section 6 it must also check that all
copies of the appcalition key match.
2. It may accept a key attestation, trust anchor, vendor identity
and at least one acceptable policy. It will verify the key
attestation using the trust anchor, and check that the vendor
identities in the key attestation match the trust anchor, and
check that the policy is acceptable. It will return either an
error indicator or the application key. If the caller is running
in a context where there are multiple copies of the application
key then it must also check that all copies of the appcalition
key match. Apart from that it can use the application key
without further checks.
3. It may accept a key attestation, trust anchor, vendor identity,
application key and at least one acceptable policy. It will
verify the key attestation using the trust anchor, and check that
the vendor identities in the key attestation match the trust
anchor, check that the policy is acceptable, and that the
application key is the expected value. It will return either an
error or a success indicator. The caller can use the application
key without further checks.
In all of these models the same set of checks must be done, but in
the first two some of the checks are delegated to the caller. The
advantage of the later models is that they are more robust against
the caller ommitting some of the necessary checks. For a publicly
available API this robustness is particularly appropriate.
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9.3. Recoverable Keys
The definition of recoverability is intentionally vague. Depending
on the device it may mean that, for example, a signature-only RSA key
could additionally be given decrypt permission, or it could mean that
private key material could be extracted in plaintext. The range of
possibilities is too broad to tie down in a device-independent
specification.
It should be noted that placing trust in a key does mean generally
placing trust in the operators and administrators of the device that
contains it, even without any possibility of administrator override
of the policy governing its use. For example, even if a key is not
recoverable, there is nothing to prevent a key owner exposing a
signature oracle for their key, allowing anyone to sign with it. As
such, if the key owner and the device administrator belong to the
same organization, and have aligned priorities, there is not much
practical difference between recoverable and non-recoverable keys.
However, in the example where a device is owned and managed by a
service provider but leased to an end user, the key owner and the
device administrators belong to separate organizations and have
different priorities. In that case a verifier may prefer to reject
recoverable keys.
9.4. Uniqueness of Keys
It's generally assumed that all keys are unique. This is the
expected outcome for properly generated cryptographic keys, and while
a collision is in principle possible by chance, it's much more likely
that a collision indicates a failure in the key generation process
(for example, [DSA1571]).
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
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[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>.
[RFC5914] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
Format", RFC 5914, DOI 10.17487/RFC5914, June 2010,
<https://www.rfc-editor.org/info/rfc5914>.
[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>.
[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.
10.2. Informative References
[DSA1571] Debian Project, "DSA-1571-1 openssl - predictable random
number generator", May 2008,
<https://www.debian.org/security/2008/dsa-1571>.
Appendix A. Samples
... either place samples here inline, or reference a github. I've
got a script I've used in other I-Ds to inline include files, if
that's useful here.
Appendix B. ASN.1 Module
... any ASN.1 that we are defining goes here ...
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-- TODO probably need some ASN.1 furniture around this
-- TODO need to import Certificate from RFC5280
id-device-information OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1567 }
DeviceInformation ::= SEQUENCE {
vendor UTF8STring -- manufacturer of device
model UTF8STring -- device model information
serial UTF8STring -- device instance information
}
id-device-subkey-information OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1568 }
DeviceSubkeyInformation ::= SEQUENCE {
vendor UTF8STring -- manufacturer of device
model UTF8STring -- device model information
serial UTF8STring -- device instance information
purpose UTF8String -- description of subkey purpose
}
id-application-key-information OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1569 }
ApplicationKeyInformation ::= SEQUENCE {
vendor UTF8STring -- manufacturer of device
model UTF8STring -- device model information
policy OBJECT IDENTIFIER -- policy governing key use
vendorinfo OCTET STRING -- vendor-specific information
}
id-attestation-bundle OBJECT IDENTIFIER ::=
{ 1 3 6 1 4 1 54392 5 1571 }
AttestationBundle ::= SEQUENCE OF Certificate
Appendix C. Intellectual Property Considerations
... mention any IP considerations here ...
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Appendix D. 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:
... list of helpful people ...
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].
Authors' Addresses
Mike Ounsworth
Entrust Limited
2500 Solandt Road -- Suite 100
Ottawa, Ontario K2K 3G5
Canada
Email: mike.ounsworth@entrust.com
Richard Kettlewell
Entrust - nCipher Security Limited
One Station Square
Cambridge
CB1 2GA
United Kingdom
Email: richard.kettlewell@entrust.com
Bruno Couillard
CRYPTO4A
1550 Laperriere Ave
Ottawa, On K1Z 7T2
Canada
Email: bruno@crypto4a.com
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Jean-Pierre Fiset
CRYPTO4A
1550 Laperriere Ave
Ottawa, On K1Z 7T2
Canada
Email: jp@crypto4a.com
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