DRIP Authentication Formats
draft-wiethuechter-drip-auth-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Adam Wiethuechter , Stuart W. Card , Robert Moskowitz | ||
| Last updated | 2020-03-23 | ||
| Replaced by | draft-ietf-drip-auth, draft-ietf-drip-auth, draft-ietf-drip-auth, draft-ietf-drip-auth, draft-ietf-drip-auth | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
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| Send notices to | (None) |
draft-wiethuechter-drip-auth-00
DRIP A. Wiethuechter
Internet-Draft S. Card
Intended status: Standards Track AX Enterprize
Expires: 24 September 2020 R. Moskowitz
HTT Consulting
23 March 2020
DRIP Authentication Formats
draft-wiethuechter-drip-auth-00
Abstract
This document describes how to include trust into the ASTM Remote ID
specification defined in ASTM3411 under a Broadcast Remote ID (RID)
scenario. It defines a few different message schemes (based on the
authentication message) that can be used to assure past messages sent
by a UA and also act as an assurance for UA trustworthiness in the
absence of Internet connectivity at the receiving node.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 24 September 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
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as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
2.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Problem Space And Document Focus . . . . . . . . . . . . 4
3.2. ASTM Authentication Message . . . . . . . . . . . . . . . 4
3.3. Thoughts on ASTM Authentication Message . . . . . . . . . 6
4. HIP Based Extensions to the ASTM Authentication Message . . . 7
4.1. Message Wrapper . . . . . . . . . . . . . . . . . . . . . 7
4.1.1. Inner Header . . . . . . . . . . . . . . . . . . . . 9
4.1.2. Trust Timestamp . . . . . . . . . . . . . . . . . . . 10
4.1.3. Payload . . . . . . . . . . . . . . . . . . . . . . . 10
4.1.4. Forward Error Correction . . . . . . . . . . . . . . 10
4.2. Signed Hash Lists . . . . . . . . . . . . . . . . . . . . 12
4.2.1. Hash Operation . . . . . . . . . . . . . . . . . . . 15
4.2.2. Pseudo-blockchain Hashes . . . . . . . . . . . . . . 15
4.2.3. Limitations . . . . . . . . . . . . . . . . . . . . . 16
4.3. Offline Claim . . . . . . . . . . . . . . . . . . . . . . 16
4.3.1. Claim: Registry on Aircraft . . . . . . . . . . . . . 17
4.3.2. Foward Error Correction . . . . . . . . . . . . . . . 22
5. Example Use Cases . . . . . . . . . . . . . . . . . . . . . . 22
5.1. Trusted Messages . . . . . . . . . . . . . . . . . . . . 22
5.2. Wrapped Signed Hashes . . . . . . . . . . . . . . . . . . 24
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
7. Security Considerations . . . . . . . . . . . . . . . . . . . 26
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.1. Normative References . . . . . . . . . . . . . . . . . . 27
9.2. Informative References . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction
UA Systems (UAS) are usually in a volatile environment when it comes
to communication. UA are generally small with little computational
(or flying) horsepower to carry standard communication equipment.
This limits the mediums of communication to few viable options.
Observer systems (e.g. smartphones and tablets) place further
constraints on the communication options. The Remote ID Broadcast
messages MUST be available to applications on these platforms without
modifying the devices.
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The ASTM standard focuses on two ways of communicating to a UAS for
RID: Broadcast and Network.
This document will focus on adding trust to Broadcast RID in the
current authentication message format, using the Host Identity
Protocol Version 2 (HIPv2) [RFC7401] Hierarchical HIT (HHIT)
[I-D.moskowitz-hip-hierarchical-hit].
2. Terms and Definitions
2.1. Requirements 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.
2.2. Definitions
HI
Host Identity. The public key portion of an assymetric keypair
from HIP. In this document it is assumed that the HI is based on
a EdDSA25519 keypair. This is supported by new crypto defined in
[I-D.moskowitz-hip-new-crypto].
HIT
Host Identity Tag. A 128 bit handle on the HI. Defined in HIPv2
[RFC7401].
HHIT
Hierarchical Host Identity Tag. A 128 bit handle on the HI contain
extra information not found in a standard HIT. Defined in
[I-D.moskowitz-hip-hierarchical-hit].
UA
Unmanned Aircraft. In this document UA's are typically though of
as drones of commerical or military variety. This is a very
strict definition which can be relaxed to include any and all
aircraft that are unmanned.
UAS
Unmanned Aircraft System. Composed of Unmanned Aircraft and all
required on-board subsystems, payload, control station, other
required off-board subsystems, any required launch and recovery
equipment, all required crew members, and C2 links between UA and
the control station.
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RID
Remote ID. A unique identifier found on all UA to be used in
communication and in regulation of UA operation.
Observer
Referred to in other UAS documents as a "user", but there are also
other classes of RID users, so we prefer "observer" to denote an
individual who has observed an UA and wishes to know something
about it, starting with its RID.
3. Background
3.1. Problem Space And Document Focus
The current standard for Remote ID (RID) does not, in any meaningful
capacity, address the concerns of trust in the UA space with
communication in the Broadcast RID environment. This is a
requirement that will need to be addressed eventually for various
different parties that have a stake in the UA industry.
The following subsections will provide a high level reference to the
ASTM standard for authentication messages and how their current
limitations effect trust in the Broadcast RID envirorment.
3.2. ASTM Authentication Message
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Page 0:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ ASTM Authentication Headers +---------------+
| | |
+-----------------------------------------------+ |
| |
| |
| |
| Authentication Data / Signature |
| |
| |
| |
+---------------------------------------------------------------+
Page 1 - 4:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| Authentication Data / Signature |
| |
| |
| |
| |
+---------------------------------------------------------------+
ASTM Header (1 byte):
Contains basic ASTM information such as message type and
protocol version.
ASTM Authentication Headers: (6 bytes)
Contains header information for the authentication message
from ASTM UAS RID Standard.
Authentication Data / Signature: (109 bytes: 17+23*4)
Opaque authentication data.
The above diagram is the format defined by ASTM that is the frame
which everything this document fits into. The specific details of
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the ASTM headers are abstracted away as they are not necessarily
required for this document.
3.3. Thoughts on ASTM Authentication Message
The format standardized by the ASTM is designed with a few major
considerations in mind, which the authors feel put significant
limitations on the expansion of the standard.
The primary consideration (in this context) is the use of the
Bluetooth 5.X Extended Frame format. This method allows for a 255
byte payload to be sent in what the ASTM refers to as a "Message
Pack".
The idea is to include up to five standard ASTM Broadcast RID
messages (each of which are 25 bytes) plus a single authentication
message (5 pages of 25 bytes each) in the Message Pack. The
reasoning is then the authentication message is for the entire
Message Pack.
The authors have no issues with this proposed approach; this is a
valid format to use for the authentication message provided by the
ASTM. However, by limiting the authentication message to ONLY five
pages in the standard it ignores the possibility of other formatting
options to be created and used.
Another issue with this format, not fully addressed in this document
is fragmentation. Under Bluetooth 4.X, each page is sent seperately
which can result in lose of pages on the reciever. This is
disasterous as the loss of even a single page means any signature is
incomplete.
With the current limitation of 5 pages, Forward Error Correction
(FEC) is nearly impossible without sacrificing the amount of data
sent. More pages would allow FEC to be performed on the Authentation
message pages so loss of pages can be mitigated.
All these problems are further amplified by the speed at which UA fly
and the Oberserver's position to recieve transmissions. There is no
guarentee that the Observer will recieve all the pages of even a 5
page Authentication Message in the time it takes a UA to traverse
across their line of sight. Worse still is that is not including
other UA in the area, which congestes the spectrum and could cause
further confusion attempting to collate messages from various UA.
This specific problem is out of scope for this document and our
solutions in general, but should be noted as a design consideration.
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4. HIP Based Extensions to the ASTM Authentication Message
The following section describes various methods that HIP can help
enable more trustworthy communication using the Authentication
Message as the base. Each diagram will show all pages of the format
filled out.
In the future it is probably necessary to have a AuthType assigned by
ASTM for DRIP related authentication message formats. How this is
accomplished and how it extends if more formats are proposed is still
TBD.
4.1. Message Wrapper
Page 0:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ ASTM Authentication Headers +---------------+
| | Inner Header |
+-----------------------------------------------+---------------+
| |
| |
| |
| HHIT |
| |
| |
| |
+---------------------------------------------------------------+
Page 1:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | Trust Timestamp /
+---------------+-----------------------------------------------+
/ | |
+---------------+ |
| |
| |
| Payload (Bytes 1-19) |
| |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | Payload (Bytes 20-24) /
+---------------+ +-------------------------------+
/ | |
+-------------------------------+ |
| |
| |
| |
| HHIT Signature (Bytes 1-18) |
| |
| |
| |
+---------------------------------------------------------------+
Page 3:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| HHIT Signature (Bytes 19-41) |
| |
| |
| |
| |
+---------------------------------------------------------------+
Page 4:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| HHIT Signature (Bytes 42-64) |
| |
| |
| |
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| |
+---------------------------------------------------------------+
Inner Header (1 byte):
See Inner Header section.
HHIT: (16 bytes)
HHIT using the EdDSA25519 HI.
Trust Timestamp: (4 bytes)
Timestamp denoting current time plus an offset to trust
message to.
Payload: (24 bytes)
Opaque payload data.
HHIT Signature: (64 bytes)
Signature over precedding fields using the EdDSA25519 keypair.
When this authentication format is recieved the HHIT is first looked
up in DNS by standard mechanisms to retrieve the HIP RR. From this
the HI can be used to perform signature verifiction. The data signed
is all the data preceding the 64 byte signature (excluding the ASTM
Headers and ASTM Authentication Headers).
When there is no Internet connectivity on the Observers device the HI
of the UA can be obtained by referencing the claim sent in the
Offline Based Authentication format, if sent by the UA.
4.1.1. Inner Header
When the payload is another ASTM message then the first byte of the
full message should be used to fill in the Inner Header field. This
byte can be signed but is primarily for identitying the inner message
type (for unpacking purposes if desired by the Observer device).
Another use of the Inner Header byte is holding the H-Alg and H-Len
fields if this format is used for Hashed Messages. See Section 5.2
for a detailed example of this. When this format is used all 24
bytes of the payload MUST be filled with hash values. This
requirement means that only even numbered hash lengths can be used.
Any other wrapped messages that are not 24 bytes long and require
padding on the payload MUST use the Inner Header to inform the
reciever the length of payload in octets.
To accomadate payload differences the use of AuthType in the ASTM
Authentication Headers section SHOULD be set in the range of 0xA-F
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(which is availible for Private Use). Only recommended values are
defined here, as the allocation in the reserved space of this header
is controlled by ASTM.
AuthType Values
-------- ------
Wrapped ASTM Message A
Wrapped Hashes B
Wrapped Message Length (octets) C
4.1.2. Trust Timestamp
Trust Timestamp MUST be current UNIX time plus an offset into the
future.
To avoid replay attacks the Trust Timestamp field must be well
founded. When wrapping a vector (position) message the payload WILL
contain (by ASTM rules) constantly changing data, this includes its
own timestamp. In this case the Trust Timestamp could be argued as
superfoulous.
Other message types, such as Basic ID and Self-ID are static messages
with no changing data. To protect a replay of these signed messages
the Trust Timestamp is the field during signing to be guarenteed to
change.
The offset used against the UNIX timestamp is not defined in this
document. Best practices to identify a acceptable offset should be
used taking into consideration the UA envirorment, and propgation
characteristics of the messages being sent.
4.1.3. Payload
The payload can be anything that fits within the 24 byte limit. An
example of what could be done with this format is found in
Section 5.1. If the payload is less than 24 bytes, null padding MUST
be used to fill up to 24 bytes and the AuthType of 0xC MUST be used
to identity message size.
4.1.4. Forward Error Correction
Due to the nature of the wireless link a FEC method is suggested.
Under DRIP the Message Wrapper format has two forms of FEC that can
be used.
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0 1 2 3
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+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| Foward Error Correction |
| |
| |
| |
| |
| |
+---------------------------------------------------------------+
4.1.4.1. Reed Solomon
The prefered form of FEC is using Reed Solomon. With this the entire
authentication message (all pages, including headers) are used to
generate 23 bytes of parity. This parity is appended in one page
allowing for recovery when any single page is lost in transmission.
4.1.4.2. Exclusive Or
This method of FEC is experimental and created by one of the authors
during initial prototyping. Note that this format of FEC requires a
10-page authentication message, currently unsupported by ASTM.
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+--------------+ +-----------------------------+
| Page 0: Data |-------------------->| Page 1: XOR(Page 0, Page 2) |
+--------------+----+ +---------->+-----------------------------+
| |
| |
+--------------+----|----+ +-----------------------------+
| Page 2: Data |----|--------------->| Page 3: XOR(Page 2, Page 4) |
+--------------+ | +--------->+-----------------------------+
| |
| |
+--------------+----|-----+ +-----------------------------+
| Page 4: Data |----|--------------->| Page 5: XOR(Page 4, Page 6) |
+--------------+ | +--------->+-----------------------------+
| |
| |
+--------------+----|-----+ +-----------------------------+
| Page 6: Data |----|--------------->| Page 7: XOR(Page 6, Page 8) |
+--------------+ | +--------->+-----------------------------+
| |
+-----|-----+
+--------------+----------+ | +-----------------------------+
| Page 8: Data | +--->| Page 9: XOR(Page 8, Page 0) |
+--------------+-------------------->+-----------------------------+
The above illustration shows the relationship between the 10 page
authentication message and the XOR operation performed.
The advantage of this format is that a large percentage of the pages
can be lost in transmission cand recovered using other pages
recieved.
The authors are well aware that this has a high overhead (100%) that
might be avoided using other methods. In some cases where wireless
links are highly congested or weak this could potentionally prove
useful.
4.2. Signed Hash Lists
Page 0:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ ASTM Authentication Headers +---------------+
| | H-Alg | H-Len |
+---------------------------------------------------------------+
| Hash of Previous Auth. Message |
+---------------------------------------------------------------+
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| Hash of Current Auth. Message |
+---------------------------------------------------------------+
| Message Hash |
+---------------------------------------------------------------+
| Message Hash |
+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+-------------------------------+
| ASTM Header | H-Alg | H-Len | PADDING |
+---------------+---------------+-------------------------------+
| Message Hash |
+---------------------------------------------------------------+
| Message Hash |
+---------------------------------------------------------------+
| Message Hash |
+---------------------------------------------------------------+
| Message Hash |
+---------------------------------------------------------------+
| Message Hash |
+---------------------------------------------------------------+
Page 2:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | PADDING |
+---------------+ +-------------------------------+
| | |
+-------------------------------+ |
| |
| |
| |
| HHIT Signature |
| |
| |
| |
+---------------------------------------------------------------+
Page 3:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
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| |
| |
| |
| HHIT Signature |
| |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| HHIT Signature |
| |
| |
| |
| |
+---------------------------------------------------------------+
H-Alg, H-Len: (4 bits), (4 bits)
These are fields for relaying information of the Hash
algorithm used for the messages and the Hash length (in octets).
For this example of the format a length of 4 bytes is
used.
H-Alg Values
----- ------
RESERVED 0
cSHAKE128 1 [SP800-185] (RECOMMENDED)
Hash of Previous Auth. Message: (4 bytes)
A hash of the previously sent Authentication message.
Hash of Current Auth. Message: (4 bytes)
A hash of the current Authentication message.
Message Hash: (4 bytes)
A hash of a previously sent message.
HHIT Signature: (64 bytes)
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EdDSA25519 signature using an EdDSA25519-based HI from HIP.
This format is designed to provide provenance to Broadcast RID
messages sent by a given UAS. It should be noted that the HHIT is
not provided in the format like others specified here - instead it
must be obtained via the Basic ID Message in a detached fashion.
By hashing previously sent messages and signing them we gain trust in
UAS previous reports. An observer who has been listening for any
length of time can hash received messages and cross check against
listed hashes. The signature is signed across the list of hashes.
4.2.1. Hash Operation
With cSHAKE128 NIST SP 800-185 [NIST.SP.800-185], the hash is
computed as follows:
cSHAKE128(MAC|Message, 8*H-Len, "", "RemoteID Auth Hash")
The message MAC is prepended to the message, as the MAC is the only
information that links a UA's messages from a specific UA.
4.2.2. Pseudo-blockchain Hashes
Two special hashes are included; a previous authentication hash,
which links to the previous signed hash list message, as well as a
current hash. This gives a pseudo-blockchain provenance to the
authentication message that could be traced back if the observer was
present for extended periods of time.
In regards to the creation and use of the current authentication hash
field:
During creation and signing of this message format this field MUST
be set to 0. So the signature will be based on this field being
0, as well as its own hash. It is an open question of if we
compute the hash, then sign or sign then compute.
There a few different ways to cycle this message. We can "roll
up" the hash of 'current' to 'previous' when needed or to
completely recompute the hash. This mostly depends on the
previous note.
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4.2.3. Limitations
With the current format proposed by ASTM only 7 messages can be
hashed reasonably in the above format. PADDING and redundant H-Alg,
H-Len fields could be removed. This would increase the total list of
hashes to 9 while losing word alignment of the hashes in each page.
To address this problem properly the authors feel that the
Authentication Messages needs to have a max bound of 10 pages,
instead of 5.
4.3. Offline Claim
Page 0:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ ASTM Authentication Headers +---------------+
| | |
+-----------------------------------------------+ |
| |
| |
| |
| Claim: Registry on Aircraft (Bytes 1-17) |
| |
| |
| |
+---------------------------------------------------------------+
Page 1-8:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| Claim: Registry on Aircraft (Bytes 18-200) |
| |
| |
| |
| |
| |
+---------------------------------------------------------------+
Page 9:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| Foward Error Correction |
| |
| |
| |
| |
| |
+---------------------------------------------------------------+
Certificate: Registry on Aircraft (200 bytes):
A certificate granted by the Registry that asserts the
binding of UA to the given Registry. Note that Page 8's final
byte is actually padding.
Foward Error Correction (FEC) (23 bytes):
FEC on the previous 9 pages.
This specific format does not currently fit within the ASTM
specification. Requiring a minimum of 200 bytes, this would require
the Authentication Message to have 10 pages, instead of the current 5
page limit. The rest of this section assumes 10 pages to demonstrate
how this message is laid out and works.
What this grants is the ability to authenticate UA information when
the receiving device of the observer (e.g. a smartphone with a
dedicated RID application) has no Internet service (e.g. LTE
signal).
By including the device HI along with a signature from the registry
the UA is under, we can assert trust of a given UA without requiring
the need for immediate reverse lookups online.
4.3.1. Claim: Registry on Aircraft
The bulk of this message is made up with the 200 byte claim titled
"Registry on Aircraft" (henceforth refered to as "Cra"). Below is
Cra fully marked out inside the ASTM Authentication Message.
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Page 0:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ ASTM Authentication Headers +---------------+
| | |
+-----------------------------------------------+ |
| |
| |
| Registry HHIT |
| |
| |
| +---------------+
| | UA HHIT (1) |
+-----------------------------------------------+---------------+
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| UA HHIT (2-16) |
| |
| |
| |
+---------------------------------------------------------------+
| |
| UA HI (1-8) |
| |
+---------------------------------------------------------------+
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| UA HI (9-31) |
| |
| |
| |
| |
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| |
+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+-------------------------------+
| ASTM Header | UA HI (32) | UA Expiration /
+---------------+---------------+-------------------------------+
/ Timestamp | |
+-------------------------------+ |
| |
| |
| |
| UA Signature (1-18) |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| UA Signature (19-41) |
| |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| UA Signature (42-64) |
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| |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | Registry Expiration Timestamp /
+---------------+-----------------------------------------------+
/ | |
+---------------+ |
| |
| |
| |
| Registry Signature (1-19) |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| Registry Signature (20-42) |
| |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
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| |
| |
| Registry Signature (43-64) |
| |
| |
| +---------------+
| | PADDING |
+-----------------------------------------------+---------------+
Registry HHIT (16 bytes):
Registry HHIT that UA is registered under and handle
for the HI used in the signing of full certificate.
Claim: Aircraft on Aircraft [Cra] (116 bytes):
UA HHIT (16 bytes):
Nominally the Aircraft HHIT (specificed here as UA)
UA HI (32 bytes):
Public half of EdDSA-25519 asymmetric keypair used
to sign Caa.
UA Expiration Timestamp (4 bytes):
UNIX current time (at time of signing) + offset
UA Signature (64 bytes):
Signature with UA keypair using the data of UA HHIT,
UA HI and UA Expiration Timestamp.
Registry Expiration Timestamp (4 bytes):
UNIX current time (at time of signing) + offset
Registry Signature (64 bytes):
Signature with Registry keypair using the data of
Registry HHIT, Caa and Registry Expiration Timestamp.
Cra is in practice a binding claim between the Registry and the
Aircraft, asserting the relationship between the two entities. Cra
signs another claim, Caa (Claim: Aircraft on Aircraft), that is
created during UA provisioning.
Importantly this claim allows offline signature verification from the
UA. This is as the UA HI is included in the claim. Also included is
the HHIT of the Registry to check the local shortlist of Registries
that the Observer device trusts (mapping HHITs to HIs).
More details about Caa, Cra, other claims and the provisioning
process can be found in [I-D.wiethuechter-tmrid-identity-claims].
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4.3.2. Foward Error Correction
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| Foward Error Correction |
| |
| |
| |
| |
| |
+---------------------------------------------------------------+
The prefered form of FEC is using Reed Solomon. With this the entire
authentication message (all pages, including headers) are used to
generate 23 bytes of parity. This parity is inserted into the final
page of the Claim format for recovery when any single page is lost in
transmission.
5. Example Use Cases
This section introduces potentional use cases of the HIP based
extensions to the proposed ASTM standard authentication message.
5.1. Trusted Messages
Using the HIP Based Authentication Wrapper any single Broadcast RID
message defined by ASTM can become what the authors refer to as a
"Trusted Message".
One specific use case that is useful in the UAS RID space is the
creation of a "Trusted Vector Message". By placing a previous [or
new] vector message into the payload section of this format a
verifiable broadcast can be created.
Due to being signed this creates an authentic vector that is hard to
spoof, which can confirm flight paths in near real time.
The figure below is a example of a "Trusted Vector Message".
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ ASTM Authentication Headers +---------------+
| | Vector Header |
+-----------------------------------------------+---------------+
| |
| |
| |
| HHIT |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | Trust Timestamp /
+---------------+-----------------------------------------------+
/ | |
+---------------+ |
| |
| |
| Vector Message (Bytes 1-19) |
| |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | Vector Message (Bytes 20-24) /
+---------------+ +-------------------------------+
/ | |
+-------------------------------+ |
| |
| |
| |
| HHIT Signature (Bytes 1-18) |
| |
| |
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+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| HHIT Signature (Bytes 19-41) |
| |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| HHIT Signature (Bytes 42-64) |
| |
| |
| |
| |
+---------------------------------------------------------------+
5.2. Wrapped Signed Hashes
Using the Message Wrapper a [short] list of hashes can be signed.
These hashes are of previous individual RID messages.
This follows the format of the Signed Hash List, excluding the
psuedo-blockchain hashes found in the Signed Hash List.
To the authors, this format has limited use due to numerous concerns
of replay attacks. It is suggested to instead use the full Signed
Hash List format.
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0 1 2 3
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+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ ASTM Authentication Headers +---------------+
| | H-Alg | H-Len |
+-----------------------------------------------+---------------+
| |
| |
| |
| HHIT |
| |
| |
| |
+---------------------------------------------------------------+
Page 1:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | Trust Timestamp /
+---------------+-----------------------------------------------+
/ | Message Hash /
+---------------+-----------------------------------------------+
/ | Message Hash /
+---------------+-----------------------------------------------+
/ | Message Hash /
+---------------+-----------------------------------------------+
/ | Message Hash /
+---------------+-----------------------------------------------+
/ | Message Hash /
+---------------------------------------------------------------+
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+---------------+-----------------------------------------------+
| ASTM Header / | Message Hash /
+---------------+---------------+-------------------------------+
/ | |
+-------------------------------+ |
| |
| |
| |
| HHIT Signature (Bytes 1-18) |
| |
| |
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+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| HHIT Signature (Bytes 19-41) |
| |
| |
| |
| |
+---------------------------------------------------------------+
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+-----------------------------------------------+
| ASTM Header | |
+---------------+ |
| |
| |
| |
| |
| HHIT Signature (Bytes 42-64) |
| |
| |
| |
| |
+---------------------------------------------------------------+
6. IANA Considerations
TBD
7. Security Considerations
TBD
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8. Acknowledgments
Ryan Quigley and James Mussi at AX Enterprize for early prototyping
to find holes in the draft specifications.
9. References
9.1. Normative References
[NIST.SP.800-185]
Kelsey, J., Change, S., and R. Perlner, "SHA-3 derived
functions: cSHAKE, KMAC, TupleHash and ParallelHash",
National Institute of Standards and Technology report,
DOI 10.6028/nist.sp.800-185, December 2016,
<https://doi.org/10.6028/nist.sp.800-185>.
[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>.
[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>.
9.2. Informative References
[I-D.moskowitz-hip-hierarchical-hit]
Moskowitz, R., Card, S., and A. Wiethuechter,
"Hierarchical HITs for HIPv2", Work in Progress, Internet-
Draft, draft-moskowitz-hip-hierarchical-hit-04, 3 March
2020, <https://tools.ietf.org/html/draft-moskowitz-hip-
hierarchical-hit-04>.
[I-D.moskowitz-hip-new-crypto]
Moskowitz, R., Card, S., and A. Wiethuechter, "New
Cryptographic Algorithms for HIP", Work in Progress,
Internet-Draft, draft-moskowitz-hip-new-crypto-04, 23
January 2020, <https://tools.ietf.org/html/draft-
moskowitz-hip-new-crypto-04>.
[I-D.wiethuechter-tmrid-identity-claims]
Wiethuechter, A., Card, S., and R. Moskowitz, "TMRID
Identity Claims", Work in Progress, Internet-Draft, draft-
wiethuechter-tmrid-identity-claims-01, 9 March 2020,
<https://tools.ietf.org/html/draft-wiethuechter-tmrid-
identity-claims-01>.
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[RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015,
<https://www.rfc-editor.org/info/rfc7401>.
Authors' Addresses
Adam Wiethuechter
AX Enterprize
4947 Commercial Drive
Yorkville, NY 13495
United States of America
Email: adam.wiethuechter@axenterprize.com
Stuart W. Card
AX Enterprize
4947 Commercial Drive
Yorkville, NY 13495
United States of America
Email: stu.card@axenterprize.com
Robert Moskowitz
HTT Consulting
Oak Park, MI 48237
United States of America
Email: rgm@labs.htt-consult.com
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