RATS Working Group G. Mandyam
Internet-Draft Qualcomm Technologies Inc.
Intended status: Standards Track L. Lundblade
Expires: August 23, 2020 Security Theory LLC
M. Ballesteros
J. O'Donoghue
Qualcomm Technologies Inc.
February 20, 2020
The Entity Attestation Token (EAT)
draft-ietf-rats-eat-03
Abstract
An Entity Attestation Token (EAT) provides a signed (attested) set of
claims that describe state and characteristics of an entity,
typically a device like a phone or an IoT device. These claims are
used by a relying party to determine how much it wishes to trust the
entity.
An EAT is either a CWT or JWT with some attestation-oriented claims.
To a large degree, all this document does is extend CWT and JWT.
Contributing
TBD
Status of This Memo
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provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 23, 2020.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. CDDL, CWT and JWT . . . . . . . . . . . . . . . . . . . . 4
1.2. Entity Overview . . . . . . . . . . . . . . . . . . . . . 5
1.3. EAT Operating Models . . . . . . . . . . . . . . . . . . 5
1.4. What is Not Standardized . . . . . . . . . . . . . . . . 6
1.4.1. Transmission Protocol . . . . . . . . . . . . . . . . 6
1.4.2. Signing Scheme . . . . . . . . . . . . . . . . . . . 7
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. The Claims . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Token ID Claim (cti and jti) . . . . . . . . . . . . . . 8
3.2. Timestamp claim (iat) . . . . . . . . . . . . . . . . . . 9
3.3. Nonce Claim (nonce) . . . . . . . . . . . . . . . . . . . 9
3.3.1. nonce CDDL . . . . . . . . . . . . . . . . . . . . . 9
3.4. Universal Entity ID Claim (ueid) . . . . . . . . . . . . 9
3.4.1. ueid CDDL . . . . . . . . . . . . . . . . . . . . . . 12
3.5. Origination Claim (origination) . . . . . . . . . . . . . 12
3.5.1. origination CDDL . . . . . . . . . . . . . . . . . . 12
3.6. OEM Identification by IEEE (oemid) . . . . . . . . . . . 12
3.6.1. oemid CDDL . . . . . . . . . . . . . . . . . . . . . 13
3.7. The Security Level Claim (security-level) . . . . . . . . 13
3.7.1. security-level CDDL . . . . . . . . . . . . . . . . . 14
3.8. Secure Boot and Debug Enable State Claims (boot-state) . 14
3.8.1. Secure Boot Enabled . . . . . . . . . . . . . . . . . 14
3.8.2. Debug Disabled . . . . . . . . . . . . . . . . . . . 15
3.8.3. Debug Disabled Since Boot . . . . . . . . . . . . . . 15
3.8.4. Debug Permanent Disable . . . . . . . . . . . . . . . 15
3.8.5. Debug Full Permanent Disable . . . . . . . . . . . . 15
3.8.6. boot-state CDDL . . . . . . . . . . . . . . . . . . . 15
3.9. The Location Claim (location) . . . . . . . . . . . . . . 15
3.9.1. location CDDL . . . . . . . . . . . . . . . . . . . . 16
3.10. The Age Claim (age) . . . . . . . . . . . . . . . . . . . 16
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3.10.1. age CDDL . . . . . . . . . . . . . . . . . . . . . . 16
3.11. The Uptime Claim (uptime) . . . . . . . . . . . . . . . . 16
3.11.1. uptime CDDL . . . . . . . . . . . . . . . . . . . . 16
3.12. The Submods Part of a Token (submods) . . . . . . . . . . 17
3.12.1. Two Types of Submodules . . . . . . . . . . . . . . 17
3.12.1.1. Non-token Submodules . . . . . . . . . . . . . . 17
3.12.1.2. Nested EATs . . . . . . . . . . . . . . . . . . 17
3.12.2. No Inheritance . . . . . . . . . . . . . . . . . . . 18
3.12.3. Security Levels . . . . . . . . . . . . . . . . . . 18
3.12.4. Submodule Names . . . . . . . . . . . . . . . . . . 18
3.12.5. submods CDDL . . . . . . . . . . . . . . . . . . . . 18
4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1. Common CDDL Types . . . . . . . . . . . . . . . . . . . . 19
4.2. CDDL for CWT-defined Claims . . . . . . . . . . . . . . . 19
4.3. JSON . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3.1. JSON Labels . . . . . . . . . . . . . . . . . . . . . 19
4.3.2. JSON Interoperability . . . . . . . . . . . . . . . . 20
4.4. CBOR . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.4.1. CBOR Labels . . . . . . . . . . . . . . . . . . . . . 20
4.4.2. CBOR Interoperability . . . . . . . . . . . . . . . . 21
4.5. Collected CDDL . . . . . . . . . . . . . . . . . . . . . 22
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
5.1. Reuse of CBOR Web Token (CWT) Claims Registry . . . . . . 23
5.1.1. Claims Registered by This Document . . . . . . . . . 23
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 24
6.1. UEID Privacy Considerations . . . . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25
7.1. Key Provisioning . . . . . . . . . . . . . . . . . . . . 25
7.1.1. Transmission of Key Material . . . . . . . . . . . . 25
7.2. Transport Security . . . . . . . . . . . . . . . . . . . 25
7.3. Multiple EAT Consumers . . . . . . . . . . . . . . . . . 26
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1. Normative References . . . . . . . . . . . . . . . . . . 26
8.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 30
A.1. Very Simple EAT . . . . . . . . . . . . . . . . . . . . . 30
A.2. Example with Submodules, Nesting and Security Levels . . 30
Appendix B. UEID Design Rationale . . . . . . . . . . . . . . . 30
B.1. Collision Probability . . . . . . . . . . . . . . . . . . 30
B.2. No Use of UUID . . . . . . . . . . . . . . . . . . . . . 33
Appendix C. Changes from Previous Drafts . . . . . . . . . . . . 34
C.1. From draft-rats-eat-01 . . . . . . . . . . . . . . . . . 34
C.2. From draft-mandyam-rats-eat-00 . . . . . . . . . . . . . 34
C.3. From draft-ietf-rats-eat-01 . . . . . . . . . . . . . . . 34
C.4. From draft-ietf-rats-eat-02 . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
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1. Introduction
Remote device attestation is a fundamental service that allows a
remote device such as a mobile phone, an Internet-of-Things (IoT)
device, or other endpoint to prove itself to a relying party, a
server or a service. This allows the relying party to know some
characteristics about the device and decide whether it trusts the
device.
Remote attestation is a fundamental service that can underlie other
protocols and services that need to know about the trustworthiness of
the device before proceeding. One good example is biometric
authentication where the biometric matching is done on the device.
The relying party needs to know that the device is one that is known
to do biometric matching correctly. Another example is content
protection where the relying party wants to know the device will
protect the data. This generalizes on to corporate enterprises that
might want to know that a device is trustworthy before allowing
corporate data to be accessed by it.
The notion of attestation here is large and may include, but is not
limited to the following:
o Proof of the make and model of the device hardware (HW)
o Proof of the make and model of the device processor, particularly
for security-oriented chips
o Measurement of the software (SW) running on the device
o Configuration and state of the device
o Environmental characteristics of the device such as its GPS
location
1.1. CDDL, CWT and JWT
An EAT token is either a CWT as defined in [RFC8392] or a JWT as
defined in [RFC7519]. This specification defines additional claims
for entity attestation.
This specification uses CDDL, [RFC8610], as the primary formalism to
define each claim. The implementor then interprets the CDDL to come
to either the CBOR [RFC7049] or JSON [ECMAScript] representation. In
the case of JSON, Appendix E of [RFC8610] is followed. Additional
rules are given in Section 4.3.2 of this document where Appendix E is
insufficient. (Note that this is not to define a general means to
translate between CBOR and JSON, but only to define enough such that
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the claims defined in this document can be rendered unambiguously in
JSON).
1.2. Entity Overview
An "entity" can be any device or device subassembly ("submodule")
that can generate its own attestation in the form of an EAT. The
attestation should be cryptographically verifiable by the EAT
consumer. An EAT at the device-level can be composed of several
submodule EAT's. It is assumed that any entity that can create an
EAT does so by means of a dedicated root-of-trust (RoT).
Modern devices such as a mobile phone have many different execution
environments operating with different security levels. For example,
it is common for a mobile phone to have an "apps" environment that
runs an operating system (OS) that hosts a plethora of downloadable
apps. It may also have a TEE (Trusted Execution Environment) that is
distinct, isolated, and hosts security-oriented functionality like
biometric authentication. Additionally, it may have an eSE (embedded
Secure Element) - a high security chip with defenses against HW
attacks that can serve as a RoT. This device attestation format
allows the attested data to be tagged at a security level from which
it originates. In general, any discrete execution environment that
has an identifiable security level can be considered an entity.
1.3. EAT Operating Models
At least the following three participants exist in all EAT operating
models. Some operating models have additional participants.
The Entity. This is the phone, the IoT device, the sensor, the sub-
assembly or such that the attestation provides information about.
The Manufacturer. The company that made the entity. This may be a
chip vendor, a circuit board module vendor or a vendor of finished
consumer products.
The Relying Party. The server, service or company that makes use of
the information in the EAT about the entity.
In all operating models, the manufacturer provisions some secret
attestation key material (AKM) into the entity during manufacturing.
This might be during the manufacturer of a chip at a fabrication
facility (fab) or during final assembly of a consumer product or any
time in between. This attestation key material is used for signing
EATs.
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In all operating models, hardware and/or software on the entity
create an EAT of the format described in this document. The EAT is
always signed by the attestation key material provisioned by the
manufacturer.
In all operating models, the relying party must end up knowing that
the signature on the EAT is valid and consistent with data from
claims in the EAT. This can happen in many different ways. Here are
some examples.
o The EAT is transmitted to the relying party. The relying party
gets corresponding key material (e.g. a root certificate) from the
manufacturer. The relying party performs the verification.
o The EAT is transmitted to the relying party. The relying party
transmits the EAT to a verification service offered by the
manufacturer. The server returns the validated claims.
o The EAT is transmitted directly to a verification service, perhaps
operated by the manufacturer or perhaps by another party. It
verifies the EAT and makes the validated claims available to the
relying party. It may even modify the claims in some way and re-
sign the EAT (with a different signing key).
All these operating models are supported and there is no preference
of one over the other. It is important to support this variety of
operating models to generally facilitate deployment and to allow for
some special scenarios. One special scenario has a validation
service that is monetized, most likely by the manufacturer. In
another, a privacy proxy service processes the EAT before it is
transmitted to the relying party. In yet another, symmetric key
material is used for signing. In this case the manufacturer should
perform the verification, because any release of the key material
would enable a participant other than the entity to create valid
signed EATs.
1.4. What is Not Standardized
The following is not standardized for EAT, just the same they are not
standardized for CWT or JWT.
1.4.1. Transmission Protocol
EATs may be transmitted by any protocol the same as CWTs and JWTs.
For example, they might be added in extension fields of other
protocols, bundled into an HTTP header, or just transmitted as files.
This flexibility is intentional to allow broader adoption. This
flexibility is possible because EAT's are self-secured with signing
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(and possibly additionally with encryption and anti-replay). The
transmission protocol is not required to fulfill any additional
security requirements.
For certain devices, a direct connection may not exist between the
EAT-producing device and the Relying Party. In such cases, the EAT
should be protected against malicious access. The use of COSE and
JOSE allows for signing and encryption of the EAT. Therefore, even
if the EAT is conveyed through intermediaries between the device and
Relying Party, such intermediaries cannot easily modify the EAT
payload or alter the signature.
1.4.2. Signing Scheme
The term "signing scheme" is used to refer to the system that
includes end-end process of establishing signing attestation key
material in the entity, signing the EAT, and verifying it. This
might involve key IDs and X.509 certificate chains or something
similar but different. The term "signing algorithm" refers just to
the algorithm ID in the COSE signing structure. No particular
signing algorithm or signing scheme is required by this standard.
There are three main implementation issues driving this. First,
secure non-volatile storage space in the entity for the attestation
key material may be highly limited, perhaps to only a few hundred
bits, on some small IoT chips. Second, the factory cost of
provisioning key material in each chip or device may be high, with
even millisecond delays adding to the cost of a chip. Third,
privacy-preserving signing schemes like ECDAA (Elliptic Curve Direct
Anonymous Attestation) are complex and not suitable for all use
cases.
Over time to faciliate interoperability, some signing schemes may be
defined in EAT profiles or other documents either in the IETF or
outside.
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document reuses terminology from JWT [RFC7519], COSE [RFC8152],
and CWT [RFC8392].
Claim Name. The human-readable name used to identify a claim.
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Claim Key. The CBOR map key or JSON name used to identify a claim.
Claim Value. The CBOR map or JSON object value representing the
value of the claim.
CWT Claims Set. The CBOR map or JSON object that contains the claims
conveyed by the CWT or JWT.
Attestation Key Material (AKM). The key material used to sign the
EAT token. If it is done symmetrically with HMAC, then this is a
simple symmetric key. If it is done with ECC, such as an IEEE
DevID [IDevID], then this is the private part of the EC key pair.
If ECDAA is used, (e.g., as used by Enhanced Privacy ID, i.e.
EPID) then it is the key material needed for ECDAA.
3. The Claims
This section describes new claims defined for attestation. It also
mentions several claims defined by CWT and JWT that are particularly
important for EAT.
Note also: * Any claim defined for CWT or JWT may be used in an EAT
including those in the CWT [IANA.CWT.Claims] and JWT IANA
[IANA.JWT.Claims] claims registries.
o All claims are optional
o No claims are mandatory
o All claims that are not understood by implementations MUST be
ignored
CDDL along with text descriptions is used to define each claim
indepdent of encoding. Each claim is defined as a CDDL group (the
group is a general aggregation and type definition feature of CDDL).
In the encoding section Section 4, the CDDL groups turn into CBOR map
entries and JSON name/value pairs.
3.1. Token ID Claim (cti and jti)
CWT defines the "cti" claim. JWT defines the "jti" claim. These are
equivalent to each other in EAT and carry a unique token identifier
as they do in JWT and CWT. They may be used to defend against re use
of the token but are distinct from the nonce that is used by the
relying party to guarantee freshness and defend against replay.
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3.2. Timestamp claim (iat)
The "iat" claim defined in CWT and JWT is used to indicate the date-
of-creation of the token.
3.3. Nonce Claim (nonce)
All EATs should have a nonce to prevent replay attacks. The nonce is
generated by the relying party, the end consumer of the token. It is
conveyed to the entity over whatever transport is in use before the
token is generated and then included in the token as the nonce claim.
This documents the nonce claim for registration in the IANA CWT
claims registry. This is equivalent to the JWT nonce claim that is
already registered.
The nonce must be at least 8 bytes (64 bits) as fewer are unlikely to
be secure. A maximum of 64 bytes is set to limit the memory a
constrained implementation uses. This size range is not set for the
already-registered JWT nonce, but it should follow this size
recommendation when used in an EAT.
Multiple nonces are allowed to accommodate multistage verification
and consumption.
3.3.1. nonce CDDL
nonce-type = [ + bstr .size (8..64) ]
nonce-claim = (
nonce => nonce-type
)
3.4. Universal Entity ID Claim (ueid)
UEID's identify individual manufactured entities / devices such as a
mobile phone, a water meter, a Bluetooth speaker or a networked
security camera. It may identify the entire device or a submodule or
subsystem. It does not identify types, models or classes of devices.
It is akin to a serial number, though it does not have to be
sequential.
UEID's must be universally and globally unique across manufacturers
and countries. UEIDs must also be unique across protocols and
systems, as tokens are intended to be embedded in many different
protocols and systems. No two products anywhere, even in completely
different industries made by two different manufacturers in two
different countries should have the same UEID (if they are not global
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and universal in this way, then relying parties receiving them will
have to track other characteristics of the device to keep devices
distinct between manufacturers).
There are privacy considerations for UEID's. See Section 6.1.
The UEID should be permanent. It should never change for a given
device / entity. In addition, it should not be reprogrammable.
UEID's are variable length. All implementations MUST be able to
receive UEID's that are 33 bytes long (1 type byte and 256 bits).
The recommended maximum sent is also 33 bytes.
When the entity constructs the UEID, the first byte is a type and the
following bytes the ID for that type. Several types are allowed to
accommodate different industries and different manufacturing
processes and to give options to avoid paying fees for certain types
of manufacturer registrations.
Creation of new types requires a Standards Action [RFC8126].
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+------+------+-----------------------------------------------------+
| Type | Type | Specification |
| Byte | Name | |
+------+------+-----------------------------------------------------+
| 0x01 | RAND | This is a 128, 192 or 256 bit random number |
| | | generated once and stored in the device. This may |
| | | be constructed by concatenating enough identifiers |
| | | to make up an equivalent number of random bits and |
| | | then feeding the concatenation through a |
| | | cryptographic hash function. It may also be a |
| | | cryptographic quality random number generated once |
| | | at the beginning of the life of the device and |
| | | stored. It may not be smaller than 128 bits. |
| 0x02 | IEEE | This makes use of the IEEE company identification |
| | EUI | registry. An EUI is either an EUI-48, EUI-60 or |
| | | EUI-64 and made up of an OUI, OUI-36 or a CID, |
| | | different registered company identifiers, and some |
| | | unique per-device identifier. EUIs are often the |
| | | same as or similar to MAC addresses. This type |
| | | includes MAC-48, an obsolete name for EUI-48. (Note |
| | | that while devices with multiple network interfaces |
| | | may have multiple MAC addresses, there is only one |
| | | UEID for a device) [IEEE.802-2001], [OUI.Guide] |
| 0x03 | IMEI | This is a 14-digit identifier consisting of an |
| | | 8-digit Type Allocation Code and a 6-digit serial |
| | | number allocated by the manufacturer, which SHALL |
| | | be encoded as a binary integer over 48 bits. The |
| | | IMEI value encoded SHALL NOT include Luhn checksum |
| | | or SVN information. [ThreeGPP.IMEI] |
+------+------+-----------------------------------------------------+
Table 1: UEID Composition Types
UEID's are not designed for direct use by humans (e.g., printing on
the case of a device), so no textual representation is defined.
The consumer (the relying party) of a UEID MUST treat a UEID as a
completely opaque string of bytes and not make any use of its
internal structure. For example, they should not use the OUI part of
a type 0x02 UEID to identify the manufacturer of the device. Instead
they should use the oemid claim that is defined elsewhere. The
reasons for this are:
o UEIDs types may vary freely from one manufacturer to the next.
o New types of UEIDs may be created. For example, a type 0x07 UEID
may be created based on some other manufacturer registration
scheme.
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o Device manufacturers are allowed to change from one type of UEID
to another anytime they want. For example, they may find they can
optimize their manufacturing by switching from type 0x01 to type
0x02 or vice versa. The main requirement on the manufacturer is
that UEIDs be universally unique.
3.4.1. ueid CDDL
ueid-claim = (
ueid => bstr .size (7..33)
)
3.5. Origination Claim (origination)
This claim describes the parts of the device or entity that are
creating the EAT. Often it will be tied back to the device or chip
manufacturer. The following table gives some examples:
+-------------------+-----------------------------------------------+
| Name | Description |
+-------------------+-----------------------------------------------+
| Acme-TEE | The EATs are generated in the TEE authored |
| | and configured by "Acme" |
| Acme-TPM | The EATs are generated in a TPM manufactured |
| | by "Acme" |
| Acme-Linux-Kernel | The EATs are generated in a Linux kernel |
| | configured and shipped by "Acme" |
| Acme-TA | The EATs are generated in a Trusted |
| | Application (TA) authored by "Acme" |
+-------------------+-----------------------------------------------+
TODO: consider a more structure approach where the name and the URI
and other are in separate fields.
TODO: This needs refinement. It is somewhat parallel to issuer claim
in CWT in that it describes the authority that created the token.
3.5.1. origination CDDL
origination-claim = (
origination => string-or-uri
)
3.6. OEM Identification by IEEE (oemid)
The IEEE operates a global registry for MAC addresses and company
IDs. This claim uses that database to identify OEMs. The contents
of the claim may be either an IEEE MA-L, MA-M, MA-S or an IEEE CID
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[IEEE.RA]. An MA-L, formerly known as an OUI, is a 24-bit value used
as the first half of a MAC address. MA-M similarly is a 28-bit value
uses as the first part of a MAC address, and MA-S, formerly known as
OUI-36, a 36-bit value. Many companies already have purchased one of
these. A CID is also a 24-bit value from the same space as an MA-L,
but not for use as a MAC address. IEEE has published Guidelines for
Use of EUI, OUI, and CID [OUI.Guide] and provides a lookup services
[OUI.Lookup]
Companies that have more than one of these IDs or MAC address blocks
should pick one and prefer that for all their devices.
Commonly, these are expressed in Hexadecimal Representation
[IEEE.802-2001] also called the Canonical format. When this claim is
encoded the order of bytes in the bstr are the same as the order in
the Hexadecimal Representation. For example, an MA-L like "AC-DE-48"
would be encoded in 3 bytes with values 0xAC, 0xDE, 0x48. For JSON
encoded tokens, this is further base64url encoded.
3.6.1. oemid CDDL
oemid-claim = (
oemid => bstr
)
3.7. The Security Level Claim (security-level)
EATs have a claim that roughly characterizes the device / entities
ability to defend against attacks aimed at capturing the signing key,
forging claims and at forging EATs. This is done by roughly defining
four security levels as described below. This is similar to the
security levels defined in the Metadata Service defined by the Fast
Identity Online (FIDO) Alliance (TODO: reference).
These claims describe security environment and countermeasures
available on the end-entity / client device where the attestation key
reside and the claims originate.
1 - Unrestricted There is some expectation that implementor will
protect the attestation signing keys at this level. Otherwise the
EAT provides no meaningful security assurances.
2- Restricted Entities at this level should not be general-purpose
operating environments that host features such as app download
systems, web browsers and complex productivity applications. It
is akin to the Secure Restricted level (see below) without the
security orientation. Examples include a Wi-Fi subsystem, an IoT
camera, or sensor device.
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3 - Secure Restricted Entities at this level must meet the criteria
defined by FIDO Allowed Restricted Operating Environments (TODO:
reference). Examples include TEE's and schemes using
virtualization-based security. Like the FIDO security goal,
security at this level is aimed at defending well against large-
scale network / remote attacks against the device.
4 - Hardware Entities at this level must include substantial defense
against physical or electrical attacks against the device itself.
It is assumed any potential attacker has captured the device and
can disassemble it. Example include TPMs and Secure Elements.
This claim is not intended as a replacement for a proper end-device
security certification schemes such as those based on FIPS (TODO:
reference) or those based on Common Criteria (TODO: reference). The
claim made here is solely a self-claim made by the Entity Originator.
3.7.1. security-level CDDL
security-level-type = &(
unrestricted: 1,
restricted: 2,
secure-restricted: 3,
hardware: 4
)
security-level-claim = (
security-level => security-level-type
)
3.8. Secure Boot and Debug Enable State Claims (boot-state)
This claim is an array of five Boolean values indicating the boot and
debug state of the entity.
3.8.1. Secure Boot Enabled
This indicates whether secure boot is enabled either for an entire
device or an individual submodule. If it appears at the device
level, then this means that secure boot is enabled for all
submodules. Secure boot enablement allows a secure boot loader to
authenticate software running either in a device or a submodule prior
allowing execution.
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3.8.2. Debug Disabled
This indicates whether debug capabilities are disabled for an entity
(i.e. value of 'true'). Debug disablement is considered a
prerequisite before an entity is considered operational.
3.8.3. Debug Disabled Since Boot
This claim indicates whether debug capabilities for the entity were
not disabled in any way since boot (i.e. value of 'true').
3.8.4. Debug Permanent Disable
This claim indicates whether debug capabilities for the entity are
permanently disabled (i.e. value of 'true'). This value can be set
to 'true' also if only the manufacturer is allowed to enabled debug,
but the end user is not.
3.8.5. Debug Full Permanent Disable
This claim indicates whether debug capabilities for the entity are
permanently disabled (i.e. value of 'true'). This value can only be
set to 'true' if no party can enable debug capabilities for the
entity. Often this is implemented by blowing a fuse on a chip as
fuses cannot be restored once blown.
3.8.6. boot-state CDDL
boot-state-type = [
secure-boot-enabled => bool,
debug-disabled => bool,
debug-disabled-since-boot => bool,
debug-permanent-disable => bool,
debug-full-permanent-disable => bool
]
boot-state-claim = (
boot-state => boot-state-type
)
3.9. The Location Claim (location)
The location claim is a CBOR-formatted object that describes the
location of the device entity from which the attestation originates.
It is comprised of a map of additional sub claims that represent the
actual location coordinates (latitude, longitude and altitude). The
location coordinate claims are consistent with the WGS84 coordinate
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system [WGS84]. In addition, a sub claim providing the estimated
accuracy of the location measurement is defined.
3.9.1. location CDDL
location-type = {
latitude => number,
longitude => number,
? altitude => number,
? accuracy => number,
? altitude-accuracy => number,
? heading => number,
? speed => number
}
location-claim = (
location => location-type
)
3.10. The Age Claim (age)
The "age" claim contains a value that represents the number of
seconds that have elapsed since the token was created, measurement
was made, or location was obtained. Typical attestable values are
sent as soon as they are obtained. However, in the case that such a
value is buffered and sent at a later time and a sufficiently
accurate time reference is unavailable for creation of a timestamp,
then the age claim is provided.
3.10.1. age CDDL
age-claim = (
age => uint
)
3.11. The Uptime Claim (uptime)
The "uptime" claim contains a value that represents the number of
seconds that have elapsed since the entity or submod was last booted.
3.11.1. uptime CDDL
uptime-claim = (
uptime => uint
)
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3.12. The Submods Part of a Token (submods)
Some devices are complex, having many subsystems or submodules. A
mobile phone is a good example. It may have several connectivity
submodules for communications (e.g., Wi-Fi and cellular). It may
have subsystems for low-power audio and video playback. It may have
one or more security-oriented subsystems like a TEE or a Secure
Element.
The claims for each these can be grouped together in a submodule.
The submods part of a token a single map/object with many entries,
one per submodule. There is only one submods map in a token. It is
identified by its specific label. It is a peer to other claims, but
it is not called a claim because it is a container for a claim set
rather than an individual claim. This submods part of a token allows
what might be called recursion. It allows claim sets inside of claim
sets inside of claims sets...
3.12.1. Two Types of Submodules
Each entry in the submod map one of two types:
o A non-token submodule that is a map or object directly containing
claims for the submodule.
o A nested EAT that is a fully-formed, independently signed EAT
token
3.12.1.1. Non-token Submodules
Essentially this type of submodule, is just a sub-map or sub-object
containing claims. It is recognized from the other type by being a
data item of type map in CBOR or by being an object in JSON.
The contents are claims about the submodule of types defined in this
document or anywhere else claims types are defined.
3.12.1.2. Nested EATs
This type of submodule is a fully formed EAT as described here. In
this case the submodule has key material distinct from the containing
EAT token that allows it to sign on its own.
When an EAT is nested in another EAT as a submodule the nested EAT
MUST use the CBOR CWT tag. This clearly distinguishes it from the
non-token submodules.
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3.12.2. No Inheritance
The subordinate modules do not inherit anything from the containing
token. The subordinate modules must explicitly include all of their
claims. This is the case even for claims like the nonce and age.
This rule is in place for simplicity. It avoids complex inheritance
rules that might vary from one type of claim to another. (TODO: fix
the boot claim which does have inheritance as currently described).
3.12.3. Security Levels
The security level of the non-token subordinate modules should always
be less than or equal to that of the containing modules in the case
of non-token submodules. It makes no sense for a module of lesser
security to be signing claims of a module of higher security. An
example of this is a TEE signing claims made by the non-TEE parts
(e.g. the high-level OS) of the device.
The opposite may be true for the nested tokens. They usually have
their own more secure key material. An example of this is an
embedded secure element.
3.12.4. Submodule Names
The label or name for each submodule in the submods map is a text
string naming the submodule. No submodules may have the same name.
3.12.5. submods CDDL
submods-type = { + submodule }
submodule = (
submod_name => eat-claims / eat-token
)
submod_name = tstr / int
submods-part = (
submods => submod-type
)
4. Encoding
This makes use of the types defined in CDDL Appendix D, Standard
Prelude.
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4.1. Common CDDL Types
string-or-uri = uri / tstr; See JSON section below for JSON encoding of string-or-uri
4.2. CDDL for CWT-defined Claims
This section provides CDDL for the claims defined in CWT. It is non-
normative as [RFC8392] is the authoritative definition of these
claims.
rfc8392-claim //= ( issuer => text )
rfc8392-claim //= ( subject => text )
rfc8392-claim //= ( audience => text )
rfc8392-claim //= ( expiration => time )
rfc8392-claim //= ( not-before => time )
rfc8392-claim //= ( issued-at => time )
rfc8392-claim //= ( cwt-id => bytes )
issuer = 1
subject = 2
audience = 3
expiration = 4
not-before = 5
issued-at = 6
cwt-id = 7
cwt-claim = rfc8392-claim
4.3. JSON
4.3.1. JSON Labels
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ueid = "ueid"
origination = "origination"
oemid = "oemid"
security-level = "security-level"
boot-state = "boot-state"
location = "location"
age = "age"
uptime = "uptime"
nested-eat = "nested-eat"
submods = "submods"
latitude = "lat"
longitude = "long""
altitude = "alt"
accuracy = "accry"
altitude-accuracy = "alt-accry"
heading = "heading"
speed = "speed"
4.3.2. JSON Interoperability
JSON should be encoded per RFC 8610 Appendix E. In addition, the
following CDDL types are encoded in JSON as follows:
o bstr - must be base64url encoded
o time - must be encoded as NumericDate as described section 2 of
[RFC7519].
o string-or-uri - must be encoded as StringOrURI as described
section 2 of [RFC7519].
4.4. CBOR
4.4.1. CBOR Labels
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ueid = To_be_assigned
origination = To_be_assigned
oemid = To_be_assigned
security-level = To_be_assigned
boot-state = To_be_assigned
location = To_be_assigned
age = To_be_assigned
uptime = To_be_assigned
submods = To_be_assigned
nonce = To_be_assigned
latitude = 1
longitude = 2
altitude = 3
accuracy = 4
altitude-accuracy = 5
heading = 6
speed = 7
4.4.2. CBOR Interoperability
Variations in the CBOR serializations supported in CBOR encoding and
decoding are allowed and suggests that CBOR-based protocols specify
how this variation is handled. This section specifies what formats
MUST be supported in order to achieve interoperability.
The assumption is that the entity is likely to be a constrained
device and relying party is likely to be a very capable server. The
approach taken is that the entity generating the token can use
whatever encoding it wants, specifically encodings that are easier to
implement such as indefinite lengths. The relying party receiving
the token must support decoding all encodings.
These rules cover all types used in the claims in this document.
They also are recommendations for additional claims.
Canonical CBOR encoding, Preferred Serialization and
Deterministically Encoded CBOR are explicitly NOT required as they
would place an unnecessary burden on the entity implementation,
particularly if the entity implementation is implemented in hardware.
o Integer Encoding (major type 0, 1) - The entity may use any
integer encoding allowed by CBOR. The server MUST accept all
integer encodings allowed by CBOR.
o String Encoding (major type 2 and 3) - The entity can use any
string encoding allowed by CBOR including indefinite lengths. It
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may also encode the lengths of strings in any way allowed by CBOR.
The server must accept all string encodings.
o Major type 2, bstr, SHOULD be have tag 21 to indicate conversion
to base64url in case that conversion is performed.
o Map and Array Encoding (major type 4 and 5) - The entity can use
any array or map encoding allowed by CBOR including indefinite
lengths. Sorting of map keys is not required. Duplicate map keys
are not allowed. The server must accept all array and map
encodings. The server may reject maps with duplicate map keys.
o Date and Time - The entity should send dates as tag 1 encoded as
64-bit or 32-bit integers. The entity may not send floating-point
dates. The server must support tag 1 epoch-based dates encoded as
64-bit or 32-bit integers. The entity may send tag 0 dates,
however tag 1 is preferred. The server must support tag 0 UTC
dates.
o URIs - URIs should be encoded as text strings and marked with tag
32.
o Floating Point - The entity may use any floating-point encoding.
The relying party must support decoding of all types of floating-
point.
o Other types - Use of Other types like bignums, regular expressions
and such, SHOULD NOT be used. The server MAY support them but is
not required to so interoperability is not guaranteed.
4.5. Collected CDDL
A generic-claim is any CBOR map entry or JSON name/value pair.
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eat-claims = { ; the top-level payload that is signed using COSE or JOSE
* claim
}
claim = (
ueid-claim //
origination-claim //
oemid-claim //
security-level-claim //
boot-state-claim //
location-claim //
age-claim //
uptime-claim //
submods-part //
cwt-claim //
generic-claim-type //
)
eat-token ; This is a set of eat-claims signed using COSE
TODO: copy the rest of the CDDL here (wait until the CDDL is more
settled so as to avoid copying multiple times)
5. IANA Considerations
5.1. Reuse of CBOR Web Token (CWT) Claims Registry
Claims defined for EAT are compatible with those of CWT so the CWT
Claims Registry is re used. No new IANA registry is created. All
EAT claims should be registered in the CWT and JWT Claims Registries.
5.1.1. Claims Registered by This Document
o Claim Name: UEID
o Claim Description: The Universal Entity ID
o JWT Claim Name: N/A
o Claim Key: 8
o Claim Value Type(s): byte string
o Change Controller: IESG
o Specification Document(s): *this document*
TODO: add the rest of the claims in here
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6. Privacy Considerations
Certain EAT claims can be used to track the owner of an entity and
therefore, implementations should consider providing privacy-
preserving options dependent on the intended usage of the EAT.
Examples would include suppression of location claims for EAT's
provided to unauthenticated consumers.
6.1. UEID Privacy Considerations
A UEID is usually not privacy-preserving. Any set of relying parties
that receives tokens that happen to be from a single device will be
able to know the tokens are all from the same device and be able to
track the device. Thus, in many usage situations ueid violates
governmental privacy regulation. In other usage situations UEID will
not be allowed for certain products like browsers that give privacy
for the end user. It will often be the case that tokens will not
have a UEID for these reasons.
There are several strategies that can be used to still be able to put
UEID's in tokens:
o The device obtains explicit permission from the user of the device
to use the UEID. This may be through a prompt. It may also be
through a license agreement. For example, agreements for some
online banking and brokerage services might already cover use of a
UEID.
o The UEID is used only in a particular context or particular use
case. It is used only by one relying party.
o The device authenticates the relying party and generates a derived
UEID just for that particular relying party. For example, the
relying party could prove their identity cryptographically to the
device, then the device generates a UEID just for that relying
party by hashing a proofed relying party ID with the main device
UEID.
Note that some of these privacy preservation strategies result in
multiple UEIDs per device. Each UEID is used in a different context,
use case or system on the device. However, from the view of the
relying party, there is just one UEID and it is still globally
universal across manufacturers.
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7. Security Considerations
The security considerations provided in Section 8 of [RFC8392] and
Section 11 of [RFC7519] apply to EAT in its CWT and JWT form,
respectively. In addition, implementors should consider the
following.
7.1. Key Provisioning
Private key material can be used to sign and/or encrypt the EAT, or
can be used to derive the keys used for signing and/or encryption.
In some instances, the manufacturer of the entity may create the key
material separately and provision the key material in the entity
itself. The manfuacturer of any entity that is capable of producing
an EAT should take care to ensure that any private key material be
suitably protected prior to provisioning the key material in the
entity itself. This can require creation of key material in an
enclave (see [RFC4949] for definition of "enclave"), secure
transmission of the key material from the enclave to the entity using
an appropriate protocol, and persistence of the private key material
in some form of secure storage to which (preferably) only the entity
has access.
7.1.1. Transmission of Key Material
Regarding transmission of key material from the enclave to the
entity, the key material may pass through one or more intermediaries.
Therefore some form of protection ("key wrapping") may be necessary.
The transmission itself may be performed electronically, but can also
be done by human courier. In the latter case, there should be
minimal to no exposure of the key material to the human (e.g.
encrypted portable memory). Moreover, the human should transport the
key material directly from the secure enclave where it was created to
a destination secure enclave where it can be provisioned.
7.2. Transport Security
As stated in Section 8 of [RFC8392], "The security of the CWT relies
upon on the protections offered by COSE". Similar considerations
apply to EAT when sent as a CWT. However, EAT introduces the concept
of a nonce to protect against replay. Since an EAT may be created by
an entity that may not support the same type of transport security as
the consumer of the EAT, intermediaries may be required to bridge
communications between the entity and consumer. As a result, it is
RECOMMENDED that both the consumer create a nonce, and the entity
leverage the nonce along with COSE mechanisms for encryption and/or
signing to create the EAT.
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Similar considerations apply to the use of EAT as a JWT. Although
the security of a JWT leverages the JSON Web Encryption (JWE) and
JSON Web Signature (JWS) specifications, it is still recommended to
make use of the EAT nonce.
7.3. Multiple EAT Consumers
In many cases, more than one EAT consumer may be required to fully
verify the entity attestation. Examples include individual consumers
for nested EATs, or consumers for individual claims with an EAT.
When multiple consumers are required for verification of an EAT, it
is important to minimize information exposure to each consumer. In
addition, the communication between multiple consumers should be
secure.
For instance, consider the example of an encrypted and signed EAT
with multiple claims. A consumer may receive the EAT (denoted as the
"receiving consumer"), decrypt its payload, verify its signature, but
then pass specific subsets of claims to other consumers for
evaluation ("downstream consumers"). Since any COSE encryption will
be removed by the receiving consumer, the communication of claim
subsets to any downstream consumer should leverage a secure protocol
(e.g.one that uses transport-layer security, i.e. TLS),
However, assume the EAT of the previous example is hierarchical and
each claim subset for a downstream consumer is created in the form of
a nested EAT. Then transport security between the receiving and
downstream consumers is not strictly required. Nevertheless,
downstream consumers of a nested EAT should provide a nonce unique to
the EAT they are consuming.
8. References
8.1. Normative References
[IANA.CWT.Claims]
IANA, "CBOR Web Token (CWT) Claims",
<http://www.iana.org/assignments/cwt>.
[IANA.JWT.Claims]
IANA, "JSON Web Token (JWT) Claims",
<https://www.iana.org/assignments/jwt>.
[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>.
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[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>.
[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>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[ThreeGPP.IMEI]
3GPP, "3rd Generation Partnership Project; Technical
Specification Group Core Network and Terminals; Numbering,
addressing and identification", 2019,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=729>.
[TIME_T] The Open Group Base Specifications, "Vol. 1: Base
Definitions, Issue 7", Section 4.15 'Seconds Since the
Epoch', IEEE Std 1003.1, 2013 Edition, 2013,
<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/
V1_chap04.html#tag_04_15>.
[WGS84] National Imagery and Mapping Agency, "National Imagery and
Mapping Agency Technical Report 8350.2, Third Edition",
2000, <http://earth-
info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf>.
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8.2. Informative References
[ASN.1] International Telecommunication Union, "Information
Technology -- ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T Recommendation
X.690, 1994.
[BirthdayAttack]
"Birthday attack",
<https://en.wikipedia.org/wiki/Birthday_attack.>.
[ECMAScript]
"Ecma International, "ECMAScript Language Specification,
5.1 Edition", ECMA Standard 262", June 2011,
<http://www.ecma-international.org/ecma-262/5.1/ECMA-
262.pdf>.
[IDevID] "IEEE Standard, "IEEE 802.1AR Secure Device Identifier"",
December 2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>.
[IEEE.802-2001]
"IEEE Standard For Local And Metropolitan Area Networks
Overview And Architecture", 2007,
<https://webstore.ansi.org/standards/ieee/
ieee8022001r2007>.
[IEEE.RA] "IEEE Registration Authority",
<https://standards.ieee.org/products-services/regauth/
index.html>.
[OUI.Guide]
"Guidelines for Use of Extended Unique Identifier (EUI),
Organizationally Unique Identifier (OUI), and Company ID
(CID)", August 2017,
<https://standards.ieee.org/content/dam/ieee-
standards/standards/web/documents/tutorials/eui.pdf>.
[OUI.Lookup]
"IEEE Registration Authority Assignments",
<https://regauth.standards.ieee.org/standards-ra-web/pub/
view.html#registries>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
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[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<https://www.rfc-editor.org/info/rfc4949>.
[Webauthn]
Worldwide Web Consortium, "Web Authentication: A Web API
for accessing scoped credentials", 2016.
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Appendix A. Examples
A.1. Very Simple EAT
This is shown in CBOR diagnostic form. Only the payload signed by
COSE is shown.
{
/ nonce / 9:h'948f8860d13a463e8e',
/ UEID / 10:h'0198f50a4ff6c05861c8860d13a638ea4fe2f',
/ boot-state / 12:{true, true, true, true, false}
/ time stamp (iat) / 6:1526542894,
}
A.2. Example with Submodules, Nesting and Security Levels
{
/ nonce / 9:h'948f8860d13a463e8e',
/ UEID / 10:h'0198f50a4ff6c05861c8860d13a638ea4fe2f',
/ boot-state / 12:{true, true, true, true, false}
/ time stamp (iat) / 6:1526542894,
/ seclevel / 11:3, / secure restricted OS /
/ submods / 17:
{
/ first submod, an Android Application / "Android App Foo" : {
/ seclevel / 11:1, / unrestricted /
/ app data / -70000:'text string'
},
/ 2nd submod, A nested EAT from a secure element / "Secure Element Eat" :
/ eat / 61( 18(
/ an embedded EAT, bytes of which are not shown /
))
/ 3rd submod, information about Linux Android / "Linux Android": {
/ seclevel / 11:1, / unrestricted /
/ custom - release / -80000:'8.0.0',
/ custom - version / -80001:'4.9.51+'
}
}
}
Appendix B. UEID Design Rationale
B.1. Collision Probability
This calculation is to determine the probability of a collision of
UEIDs given the total possible entity population and the number of
entities in a particular entity management database.
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Three different sized databases are considered. The number of
devices per person roughly models non-personal devices such as
traffic lights, devices in stores they shop in, facilities they work
in and so on, even considering individual light bulbs. A device may
have individually attested subsystems, for example parts of a car or
a mobile phone. It is assumed that the largest database will have at
most 10% of the world's population of devices. Note that databases
that handle more than a trillion records exist today.
The trillion-record database size models an easy-to-imagine reality
over the next decades. The quadrillion-record database is roughly at
the limit of what is imaginable and should probably be accommodated.
The 100 quadrillion datadbase is highly speculative perhaps involving
nanorobots for every person, livestock animal and domesticated bird.
It is included to round out the analysis.
Note that the items counted here certainly do not have IP address and
are not individually connected to the network. They may be connected
to internal buses, via serial links, Bluetooth and so on. This is
not the same problem as sizing IP addresses.
+---------+------------+--------------+------------+----------------+
| People | Devices / | Subsystems / | Database | Database Size |
| | Person | Device | Portion | |
+---------+------------+--------------+------------+----------------+
| 10 | 100 | 10 | 10% | trillion |
| billion | | | | (10^12) |
| 10 | 100,000 | 10 | 10% | quadrillion |
| billion | | | | (10^15) |
| 100 | 1,000,000 | 10 | 10% | 100 |
| billion | | | | quadrillion |
| | | | | (10^17) |
+---------+------------+--------------+------------+----------------+
This is conceptually similar to the Birthday Problem where m is the
number of possible birthdays, always 365, and k is the number of
people. It is also conceptually similar to the Birthday Attack where
collisions of the output of hash functions are considered.
The proper formula for the collision calculation is
p = 1 - e^{-k^2/(2n)}
p Collision Probability
n Total possible population
k Actual population
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However, for the very large values involved here, this formula
requires floating point precision higher than commonly available in
calculators and SW so this simple approximation is used. See
[BirthdayAttack].
p = k^2 / 2n
For this calculation:
p Collision Probability
n Total population based on number of bits in UEID
k Population in a database
+----------------------+--------------+--------------+--------------+
| Database Size | 128-bit UEID | 192-bit UEID | 256-bit UEID |
+----------------------+--------------+--------------+--------------+
| trillion (10^12) | 2 * 10^-15 | 8 * 10^-35 | 5 * 10^-55 |
| quadrillion (10^15) | 2 * 10^-09 | 8 * 10^-29 | 5 * 10^-49 |
| 100 quadrillion | 2 * 10^-05 | 8 * 10^-25 | 5 * 10^-45 |
| (10^17) | | | |
+----------------------+--------------+--------------+--------------+
Next, to calculate the probability of a collision occurring in one
year's operation of a database, it is assumed that the database size
is in a steady state and that 10% of the database changes per year.
For example, a trillion record database would have 100 billion states
per year. Each of those states has the above calculated probability
of a collision.
This assumption is a worst-case since it assumes that each state of
the database is completely independent from the previous state. In
reality this is unlikely as state changes will be the addition or
deletion of a few records.
The following tables gives the time interval until there is a
probability of a collision based on there being one tenth the number
of states per year as the number of records in the database.
t = 1 / ((k / 10) * p)
t Time until a collision
p Collision probability for UEID size
k Database size
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+---------------------+---------------+--------------+--------------+
| Database Size | 128-bit UEID | 192-bit UEID | 256-bit UEID |
+---------------------+---------------+--------------+--------------+
| trillion (10^12) | 60,000 years | 10^24 years | 10^44 years |
| quadrillion (10^15) | 8 seconds | 10^14 years | 10^34 years |
| 100 quadrillion | 8 | 10^11 years | 10^31 years |
| (10^17) | microseconds | | |
+---------------------+---------------+--------------+--------------+
Clearly, 128 bits is enough for the near future thus the requirement
that UEIDs be a minimum of 128 bits.
There is no requirement for 256 bits today as quadrillion-record
databases are not expected in the near future and because this time-
to-collision calculation is a very worst case. A future update of
the standard may increase the requirement to 256 bits, so there is a
requirement that implementations be able to receive 256-bit UEIDs.
B.2. No Use of UUID
A UEID is not a UUID [RFC4122] by conscious choice for the following
reasons.
UUIDs are limited to 128 bits which may not be enough for some future
use cases.
Today, cryptographic-quality random numbers are available from common
CPUs and hardware. This hardware was introduced between 2010 and
2015. Operating systems and cryptographic libraries give access to
this hardware. Consequently, there is little need for
implementations to construct such random values from multiple sources
on their own.
Version 4 UUIDs do allow for use of such cryptographic-quality random
numbers, but do so by mapping into the overall UUID structure of time
and clock values. This structure is of no value here yet adds
complexity. It also slightly reduces the number of actual bits with
entropy.
UUIDs seem to have been designed for scenarios where the implementor
does not have full control over the environment and uniqueness has to
be constructed from identifiers at hand. UEID takes the view that
hardware, software and/or manufacturing process directly implement
UEID in a simple and direct way. It takes the view that
cryptographic quality random number generators are readily available
as they are implemented in commonly used CPU hardware.
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Appendix C. Changes from Previous Drafts
The following is a list of known changes from the previous drafts.
This list is non-authoritative. It is meant to help reviewers see
the significant differences.
C.1. From draft-rats-eat-01
o Added UEID design rationale appendix
C.2. From draft-mandyam-rats-eat-00
This is a fairly large change in the orientation of the document, but
not new claims have been added.
o Separate information and data model using CDDL.
o Say an EAT is a CWT or JWT
o Use a map to structure the boot_state and location claims
C.3. From draft-ietf-rats-eat-01
o Clarifications and corrections for OEMID claim
o Minor spelling and other fixes
o Add the nonce claim, clarify jti claim
C.4. From draft-ietf-rats-eat-02
o Roll all EUIs back into one UEID type
o UEIDs can be one of three lengths, 128, 192 and 256.
o Added appendix justifying UEID design and size.
o Submods part now includes nested eat tokens so they can be named
and there can be more tha one of them
o Lots of fixes to the CDDL
o Added security considerations
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Authors' Addresses
Giridhar Mandyam
Qualcomm Technologies Inc.
5775 Morehouse Drive
San Diego, California
USA
Phone: +1 858 651 7200
EMail: mandyam@qti.qualcomm.com
Laurence Lundblade
Security Theory LLC
EMail: lgl@island-resort.com
Miguel Ballesteros
Qualcomm Technologies Inc.
5775 Morehouse Drive
San Diego, California
USA
Phone: +1 858 651 4299
EMail: mballest@qti.qualcomm.com
Jeremy O'Donoghue
Qualcomm Technologies Inc.
279 Farnborough Road
Farnborough GU14 7LS
United Kingdom
Phone: +44 1252 363189
EMail: jodonogh@qti.qualcomm.com
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