DTN Bundle Protocol Security (BPSec) COSE Context
draft-ietf-dtn-bpsec-cose-01
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 "Active".
|
|
|---|---|---|---|
| Author | Brian Sipos | ||
| Last updated | 2023-07-01 (Latest revision 2023-06-01) | ||
| Replaces | draft-bsipos-dtn-bpsec-cose | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-dtn-bpsec-cose-01
Delay-Tolerant Networking B. Sipos
Internet-Draft JHU/APL
Intended status: Standards Track 1 June 2023
Expires: 3 December 2023
DTN Bundle Protocol Security (BPSec) COSE Context
draft-ietf-dtn-bpsec-cose-01
Abstract
This document defines a security context suitable for using CBOR
Object Signing and Encryption (COSE) algorithms within Bundle
Protocol Security (BPSec) integrity and confidentiality blocks. A
profile for COSE, focused on asymmetric-keyed algorithms, and for
PKIX certificates are also defined for BPSec interoperation.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 3 December 2023.
Copyright Notice
Copyright (c) 2023 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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Sipos Expires 3 December 2023 [Page 1]
Internet-Draft DTN BPSec COSE June 2023
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. PKIX Environments and CA Policy . . . . . . . . . . . . . 4
1.3. Use of CDDL . . . . . . . . . . . . . . . . . . . . . . . 4
1.4. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. BPSec Security Context . . . . . . . . . . . . . . . . . . . 5
2.1. Security Scope . . . . . . . . . . . . . . . . . . . . . 5
2.2. Parameters . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1. Additional Header Maps . . . . . . . . . . . . . . . 7
2.2.2. AAD Scope . . . . . . . . . . . . . . . . . . . . . . 8
2.3. Results . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.1. Integrity Messages . . . . . . . . . . . . . . . . . 10
2.3.2. Confidentiality Messages . . . . . . . . . . . . . . 11
2.4. Key Considerations . . . . . . . . . . . . . . . . . . . 11
2.5. Canonicalization Algorithms . . . . . . . . . . . . . . . 12
2.5.1. Generating AAD . . . . . . . . . . . . . . . . . . . 12
2.5.2. Payload Data . . . . . . . . . . . . . . . . . . . . 13
2.6. Processing . . . . . . . . . . . . . . . . . . . . . . . 13
2.6.1. Node Authentication . . . . . . . . . . . . . . . . . 14
2.6.2. Policy Recommendations . . . . . . . . . . . . . . . 15
3. COSE Profile . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1. COSE Messages . . . . . . . . . . . . . . . . . . . . . . 16
3.2. Interoperability Algorithms . . . . . . . . . . . . . . . 16
3.3. Asymmetric Key Types and Identifiers . . . . . . . . . . 18
3.3.1. Policy Recommendations . . . . . . . . . . . . . . . 19
4. PKIX Certificate Profile . . . . . . . . . . . . . . . . . . 20
4.1. Multiple-Certificate Uses . . . . . . . . . . . . . . . . 21
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 21
6. Security Considerations . . . . . . . . . . . . . . . . . . . 22
6.1. Threat: BPSec Block Replay . . . . . . . . . . . . . . . 22
6.2. Threat: Untrusted End-Entity Certificate . . . . . . . . 23
6.3. Threat: Certificate Validation Vulnerabilities . . . . . 23
6.4. Threat: BP Node Impersonation . . . . . . . . . . . . . . 23
6.5. Threat: Unidentifiable Key . . . . . . . . . . . . . . . 23
6.6. Threat: Non-Trusted Public Key . . . . . . . . . . . . . 24
6.7. Threat: Passive Leak of Key Material . . . . . . . . . . 24
6.8. Threat: Algorithm Vulnerabilities . . . . . . . . . . . . 24
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
7.1. BPSec Security Context Identifiers . . . . . . . . . . . 25
7.2. BPSec COSE AAD Scope Flags . . . . . . . . . . . . . . . 25
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.1. Normative References . . . . . . . . . . . . . . . . . . 25
8.2. Informative References . . . . . . . . . . . . . . . . . 27
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 28
A.1. Symmetric Key COSE_Mac0 . . . . . . . . . . . . . . . . . 30
A.2. EC Keypair COSE_Sign1 . . . . . . . . . . . . . . . . . . 31
Sipos Expires 3 December 2023 [Page 2]
Internet-Draft DTN BPSec COSE June 2023
A.3. RSA Keypair COSE_Sign1 . . . . . . . . . . . . . . . . . 33
A.4. Symmetric KEK COSE_Encrypt . . . . . . . . . . . . . . . 36
A.5. EC Keypair COSE_Encrypt . . . . . . . . . . . . . . . . . 38
A.6. RSA Keypair COSE_Encrypt . . . . . . . . . . . . . . . . 41
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 45
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 45
1. Introduction
The Bundle Protocol Security (BPSec) Specification [RFC9172] defines
structure and encoding for Block Integrity Block (BIB) and Block
Confidentiality Block (BCB) types but does not specify any security
contexts to be used by either of the security block types. The CBOR
Object Signing and Encryption (COSE) specifications [RFC9052] and
[RFC9053] defines a structure, encoding, and algorithms to use for
cryptographic signing and encryption.
This document describes how to use the algorithms and encodings of
COSE within BPSec blocks to apply those algorithms to Bundle security
in Section 2. A bare minimum of interoperability algorithms and
algorithm parameters is specified by this document in Section 3. The
focus of the recommended algorithms is to allow BPSec to be used in a
Public Key Infrastructure (PKI) as described in Section 1.2 using a
certificate profile defined in Section 4.
Examples of specific uses are provided in Appendix A to aid in
implementation support of the interoperability algorithms.
1.1. Scope
This document describes a profile of COSE which is tailored for use
in BPSec and a method of including full COSE messages within BPSec
security blocks. This document does not address:
* Policies or mechanisms for issuing Public Key Infrastructure Using
X.509 (PKIX) certificates; provisioning, deploying, or accessing
certificates and private keys; deploying or accessing certificate
revocation lists (CRLs); or configuring security parameters on an
individual entity or across a network.
* Uses of COSE beyond the profile defined in this document.
* How those COSE algorithms are intended to be used within a larger
security context. Many header parameters used by COSE (e.g., key
identifiers) depend on the network environment and security policy
related to that environment.
Sipos Expires 3 December 2023 [Page 3]
Internet-Draft DTN BPSec COSE June 2023
1.2. PKIX Environments and CA Policy
This specification gives requirements about how to use PKIX
certificates issued by a Certificate Authority (CA), but does not
define any mechanisms for how those certificates come to be.
To support the PKIX uses defined in this document, the CA(s) issuing
certificates for BP nodes are aware of the end use of the
certificate, have a mechanism for verifying ownership of a Node ID,
and are issuing certificates directly for that Node ID. BPSec
security acceptors authenticate the Node ID of security sources when
verifying integrity (see Section 2.6.1) using a public key provided
by a PKIX certificate (see Section 2.6.1) following the certificate
profile of Section 4.
1.3. Use of CDDL
This document defines CBOR structure using the Concise Data
Definition Language (CDDL) of [RFC8610]. The entire CDDL structure
can be extracted from the XML version of this document using the
XPath expression:
'//sourcecode[@type="cddl"]'
The following initial fragment defines the top-level symbols of this
document's CDDL, including the ASB data structure with its parameter/
result sockets.
start = bpsec-cose-asb / external_aad /
primary-block / extension-block /
MAC_structure / Sig_structure / Enc_structure / COSE_KeySet
From the document [RFC9052] the definitions are taken for
MAC_structure, Sig_structure, Enc_structure, and COSE_KeySet. From
the document [RFC9171] the definitions are taken for primary-block
and extension-block.
1.4. Requirements Language
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.
Sipos Expires 3 December 2023 [Page 4]
Internet-Draft DTN BPSec COSE June 2023
2. BPSec Security Context
This document specifies a single security context for use in both
BPSec integrity and confidentiality blocks. This is done to save
code points allocated to this specification and to simplify the
encoding of COSE-in-BPSec; the BPSec block type uniquely defines the
acceptable parameters and COSE messages which can be present.
The COSE security context SHALL have the Security Context ID
specified in Section 7.1.
Both types of security block can use the same parameters, defined in
Section 2.2, to carry public key-related information and each type of
security block allows specific COSE message results, defined in
Section 2.3.
; Specialize the ASB for this context
bpsec-cose-asb = bpsec-context-use<
-1, ; Context ID TBD-COSE
$bpsec-cose-param,
$bpsec-cose-result
>
$ext-data-asb /= bpsec-cose-asb
Figure 1: COSE context declaration CDDL
2.1. Security Scope
The scope here refers to the set of information used by the security
context to cryptographically bind with the plaintext data being
integrity-protected or confidentiality-protected. This information
is generically referred to as additional authenticated data (AAD),
which is also the term used by COSE to describe the same data.
The sources for AAD within the COSE context are described below,
controlled by the AAD Scope parameter of Section 2.2.2, and
implemented as defined in Section 2.5.1. The purpose of this
parameter is similar to the AAD Scope parameter and Integrity Scope
parameter of [RFC9173] but expanded to allow including _any_ block in
the bundle as AAD.
Primary Block: The primary block identifies a bundle and, once
created, the contents of this block are immutable. Changes to the
primary block associated with the security target indicate that
the target is no longer in its original bundle. Including the
primary block as part of AAD ensures that security target appears
in the same bundle that the security source intended.
Sipos Expires 3 December 2023 [Page 5]
Internet-Draft DTN BPSec COSE June 2023
Canonical Block-Type-Specific Data: Including the block-type-
specific data (BTSD) of a non-target block as part of AAD ensures
that that other block's BTSD does not change after the security
block is added. This can guarantee that not only has the security
target BTSD not changed but the additional blocks' BTSD have not
changed.
Canonical Block Metadata: Including block metadata, which identifies
and types a block, as part of AAD ensures that the block presence
does not change after the security block is added. This metadata
explicitly excludes the CRC type and value fields because the CRC
is derived from the BTSD. The metadata of the security block and
the target block are also allowed, which binds the security result
to that specific target.
2.2. Parameters
Each COSE context parameter value SHALL consist of the COSE structure
indicated by Table 1 in its decoded (CBOR item) form. Each security
block SHALL contain no more than one of each parameter type per
target block.
+==============+========================+==================+
| Parameter ID | Parameter Structure | Reference |
+==============+========================+==================+
| 3 | additional-protected | Section 2.2.1 of |
| | | this document |
+--------------+------------------------+------------------+
| 4 | additional-unprotected | Section 2.2.1 of |
| | | this document |
+--------------+------------------------+------------------+
| 5 | AAD-scope | Section 2.2.2 of |
| | | this document |
+--------------+------------------------+------------------+
Table 1: COSE Context Parameters
When a parameter is not present and a default value is defined below,
the security acceptor SHALL use that default value to process the
target:
* The default additional-protected is '' (an empty byte string).
* The default additional-unprotected is {} (an empty map).
* The default AAD-scope is a map which indicates the AAD contains
the metadata of the primary, security, and target blocks.
Sipos Expires 3 December 2023 [Page 6]
Internet-Draft DTN BPSec COSE June 2023
2.2.1. Additional Header Maps
The two parameters Additional Protected and Additional Unprotected
allow de-duplicating header items which are common to all COSE
results. Both additional header values contain a CBOR map which is
to be merged with each of the result's unprotected headers. Although
the additional header items are all treated as unprotected from the
perspective of the COSE message, the additional protected map is
included within the external_aad (see Section 2.5.1). The expected
use of additional header map is to contain a certificate (chain) or
identifier (see Section 3.3) which applies to all results in the same
security block.
Following the same pattern as COSE, when both additional header maps
are present in a single security block they SHALL not contain any
duplicated labels. Security acceptors SHALL treat a pair of
additional header maps containing duplicated labels as invalid.
No more than one of each Additional Protected and Additional
Unprotected parameter SHALL be present in a single security block.
Security acceptors SHALL treat a security block with multiple
instances of either additional header type as invalid. There is no
well-defined behavior for a security acceptor to handle multiple
Additional Protected parameters.
Security sources SHOULD NOT include an additional header parameter
which represents an empty map. Security acceptors SHALL handle empty
header map parameters, specifically the Additional Protected
parameter because it is part of the external_aad.
Security acceptors SHALL treat the aggregate of both additional
header maps as being present in the unprotected header map of the
highest-layers of the COSE message of each result. For single-layer
messages (i.e., COSE_Encrypt0, COSE_MAC0, and COSE_Sign1) the
additional headers apply to the message itself (layer 1) and for
other messages the additional headers apply to the final recipients.
If the same header label is present in a additional header map and a
COSE layer's headers the item in the result header SHALL take
precedence (i.e., the additional header items are added only if they
are not already present in a layer's header).
Additional header maps SHALL NOT contain any private key material.
The security parameters are all stored in the bundle as plaintext and
are visible to any bundle handlers.
Sipos Expires 3 December 2023 [Page 7]
Internet-Draft DTN BPSec COSE June 2023
$bpsec-cose-param /= [3, additional-protected]
additional-protected = empty_or_serialized_map
$bpsec-cose-param /= [4, additional-unprotected]
additional-unprotected = header_map
Figure 2: Additional Headers CDDL
2.2.2. AAD Scope
The AAD Scope parameter controls what data is included in the AAD for
both integrity and confidentiality operations. The AAD Scope
parameter SHALL be encoded as a CBOR map containig keys representing
bundle block numbers (as uint items) and values representing a
collection of bit flags (as uint items) defined in Table 2.
All AAD Scope keys SHALL correspond with block numbers in the bundle
containing the AAD Scope parameter. Security acceptors SHALL treat
any AAD Scope with block numbers not actually present in the
containing bundle as invalid.
+==============+==============+==========================+
| Bit Position | Name | Description |
| (from LSbit) | | |
+==============+==============+==========================+
| 0 | AAD-metadata | If bit is set, indicates |
| | | that the block metadata |
| | | is included in the AAD. |
+--------------+--------------+--------------------------+
| 1 | AAD-btsd | If bit is set, indicates |
| | | that the BTSD is |
| | | included in the AAD. |
+--------------+--------------+--------------------------+
Table 2: AAD Scope Flags
Any AAD Scope value bits SHALL NOT all be set to zero, which would
represent the lack of presence in the AAD and serves no purpose.
When the map key identifies the primary block (block number zero) the
bits SHALL only have AAD-metadata set, as the primary block has no
BTSD. When the map key identifies the containing security block the
bits SHALL only have AAD-metadata set, as the security block BTSD
does not yet exist. When the map key identifies the target block the
bits SHALL only have AAD-metadata set, as the target block BTSD is
already part of the security operation (integrity or
confidentiality). All reserved bits SHALL be set to zero (which will
be elided by CBOR encoding) by security sources. All reserved bits
SHALL be ignored by security acceptors.
Sipos Expires 3 December 2023 [Page 8]
Internet-Draft DTN BPSec COSE June 2023
A CDDL representation of this definition is included in Figure 3 for
reference.
$bpsec-cose-param /= [5, AAD-scope]
AAD-scope = {
*uint => (uint .bits AAD-scope-flags)
}
AAD-scope-flags = &(
AAD-metadata: 0,
AAD-btsd: 1,
)
Figure 3: AAD Scope CDDL
The default value for this parameter (in Section 2.2) includes the
primary, target, and security block metadata.
For the same reasons that security blocks are restricted from
overlapping functions by [RFC9172], when a block is included as AAD
with the AAD-btsd flag set that block SHALL NOT be the target of a
BCB or other BTSD-altering function.
2.3. Results
Although each COSE context result is a COSE message, the types of
message allowed depend upon the security block type in which the
result is present: only MAC or signature messages are allowed in a
BIB and only encryption messages are allowed in a BCB.
The code points for Result ID values are identical to the existing
COSE message-marking tags in Section 2 of [RFC9052]. This avoids the
need for value-mapping between code points of the two registries.
When embedding COSE messages, the message CBOR structure SHALL be
encoded as a byte string used as the result value. This allows a
security acceptor to skip over unwanted results without needing to
decode the result structure. When embedding COSE messages, the CBOR-
tagged form SHALL NOT be used. The Result ID values already provide
the same information as the COSE tags (using the same code points).
These generic requirements are formalized in the CDDL fragment of
Figure 4.
Sipos Expires 3 December 2023 [Page 9]
Internet-Draft DTN BPSec COSE June 2023
$bpsec-cose-result /= [16, bstr .cbor COSE_Encrypt0]
$bpsec-cose-result /= [17, bstr .cbor COSE_Mac0]
$bpsec-cose-result /= [18, bstr .cbor COSE_Sign1]
$bpsec-cose-result /= [96, bstr .cbor COSE_Encrypt]
$bpsec-cose-result /= [97, bstr .cbor COSE_Mac]
$bpsec-cose-result /= [98, bstr .cbor COSE_Sign]
Figure 4: COSE context results CDDL
2.3.1. Integrity Messages
When used within a Block Integrity Block, the COSE context SHALL
allow only the Result IDs from Table 3. Each integrity result value
SHALL consist of the COSE message indicated by Table 3 in its non-
tagged encoded form.
+===========+====================+===========+
| Result ID | Result Structure | Reference |
+===========+====================+===========+
| 97 | encoded COSE_Mac | [RFC9052] |
+-----------+--------------------+-----------+
| 17 | encoded COSE_Mac0 | [RFC9052] |
+-----------+--------------------+-----------+
| 98 | encoded COSE_Sign | [RFC9052] |
+-----------+--------------------+-----------+
| 18 | encoded COSE_Sign1 | [RFC9052] |
+-----------+--------------------+-----------+
Table 3: COSE Integrity Results
Each integrity result SHALL use the "detached" payload form with null
payload value. The integrity result for COSE_Mac and COSE_Mac0
messages are computed by the procedure in Section 6.3 of [RFC9052].
The integrity result for COSE_Sign and COSE_Sign1 messages are
computed by the procedure in Section 4.4 of [RFC9052].
The COSE "protected attributes from the application" used for a
signature or MAC result SHALL be the encoded data defined in
Section 2.5.1. The COSE payload used for a signature or MAC result
SHALL be either the BTSD of the target, if the target is not the
primary block, or an empty byte string if the target is the primary
block.
Sipos Expires 3 December 2023 [Page 10]
Internet-Draft DTN BPSec COSE June 2023
2.3.2. Confidentiality Messages
When used within a Block Confidentiality Block, COSE context SHALL
allow only the Result IDs from Table 4. Each confidentiality result
value SHALL consist of the COSE message indicated by Table 4 in its
non-tagged encoded form.
+===========+=======================+===========+
| Result ID | Result Structure | Reference |
+===========+=======================+===========+
| 96 | encoded COSE_Encrypt | [RFC9052] |
+-----------+-----------------------+-----------+
| 16 | encoded COSE_Encrypt0 | [RFC9052] |
+-----------+-----------------------+-----------+
Table 4: COSE Confidentiality Results
Only algorithms which support Authenticated Encryption with
Authenticated Data (AEAD) SHALL be usable in the first (content)
layer of a confidentiality result. Because COSE encryption with AEAD
appends the authentication tag with the ciphertext, the size of the
BTSD will grow after an encryption operation. Security acceptors
MUST NOT assume that the size of the plaintext is the same as the
size of the ciphertext.
Each confidentiality result SHALL use the "detached" payload form
with null payload value. The confidentiality result for COSE_Encrypt
and COSE_Encrypt0 messages are computed by the procedure in
Section 5.3 of [RFC9052].
The COSE "protected attributes from the application" used for an
encryption result SHALL be the encoded data defined in Section 2.5.1.
The COSE payload used for an encryption result SHALL be the BTSD of
the target. Because confidentiality of the primary block is
disallowed by BPSec, there is no logic here for handling a BCB with a
target on the primary block.
2.4. Key Considerations
This specification does not impose any additional key requirements
beyond those already specified for each COSE algorithm required in
Section 3.
Sipos Expires 3 December 2023 [Page 11]
Internet-Draft DTN BPSec COSE June 2023
2.5. Canonicalization Algorithms
Generating or processing COSE messages for the COSE context follows
the profile defined in Section 3 with the "protected attributes from
the application" (i.e., the external_aad item) generated as defined
in Section 2.5.1.
2.5.1. Generating AAD
The encoding of this AAD is different from AAD of Section 4.7.2 of
[RFC9173] and the front items of IPPT of Section 3.7 of [RFC9173] due
to support for binding AAD to an arbitrary number of blocks.
The AAD used for both integrity and confidentiality messages SHALL be
the deterministically encoded form of a CBOR sequence containing the
following:
1. The first item SHALL be the AAD Scope value itself, which is a
CBOR map.
2. For each entry of the AAD Scope map, in ascending block number
order, the next items SHALL be one or both of the following:
1. If the map value has the AAD-metadata flag set, the next item
is block metadata taken from either:
* If the map key is block number zero, the next item SHALL
be the CBOR array (unencoded) form of the primary block of
the bundle.
* Otherwise, next items SHALL be the first three fields of
the block (i.e., the block type code, block number, and
control flags) identified by the block number in the map
key.
2. If the map value has the AAD-btsd flag set and the map key is
_not_ block number zero, the next item is the BTSD of the
block identified by the block number in the map key.
3. The last item SHALL be the Additional Protected header map, which
is a bstr, and has a default value of the empty bstr.
A CDDL representation of this data is shown below in Figure 5.
Sipos Expires 3 December 2023 [Page 12]
Internet-Draft DTN BPSec COSE June 2023
external_aad = bstr .cborseq AAD-list
AAD-list = [
AAD-scope,
*AAD-block,
; copy of additional-protected (or default empty bstr)
additional-protected
]
; each AAD item is a group, not a sub-array
AAD-block = (
? primary-block, ; present for block number zero
? block-metadata, ; present if AAD-metadata flag set
? bstr, ; present if AAD-btsd flag set
)
; Selected fields of a canonical block
block-metadata = (
block-type-code: uint,
block-number: uint,
block-control-flags,
)
Figure 5: COSE context AAD CDDL
2.5.2. Payload Data
When correlating between BPSec target BTSD and COSE plaintext or
payload, any byte string SHALL be handled in its decoded (CBOR item)
form. This means any CBOR header or tag in a source encoding are
ignored for the purposes of security processing. This also means
that if the source byte string was encoded in a non-conforming way,
for example in indefinite-length form or with a non-minimum-size
length, the security processing always treats it in a
deterministically encoded CBOR form.
2.6. Processing
This section describes block-level requirements for handling COSE
security data.
All security results generated for BIB or BCB blocks SHALL conform to
the COSE profile of Section 3 with header augmentation as defined in
Section 2.2.1.
Sipos Expires 3 December 2023 [Page 13]
Internet-Draft DTN BPSec COSE June 2023
2.6.1. Node Authentication
This section explains how the certificate profile of Section 4 is
used by a security acceptor to both validate an end-entity
certificate and to use that certificate to authenticate the security
source for an integrity result. For a confidentiality result, some
of the requirements in this section are implicit in an implementation
using a private key associated with a certificate used by a result
recipient. It is an implementation matter to ensure that a BP agent
is configured to generate or receive results associated with valid
certificates.
A security source MAY prohibit generating a result (either integrity
or confidentiality) for an end-entity certificate which is not
considered valid according to Section 2.6.1.2. Generating a result
which is likely to be discarded is wasteful of bundle size and
transport resources.
2.6.1.1. Certificate Identification
Because of the standard policy of using separate certificates for
transport, signing, and encryption (see Section 4.1) a single Node ID
is likely to be associated with multiple certificates, and any or all
of those certificates MAY be present within an "x5bag" in an
Additional Protected parameter (see Section 2.2.1). When present, a
security acceptor SHALL use an "x5chain" or "x5t" to identify an end-
entity certificate to use for result processing. Security acceptors
SHALL NOT assume that a validated certificate containing a NODE-ID
matching a security source is enough to associate a certificate with
a COSE message or recipient (see Section 3.3).
2.6.1.2. Certificate Validation
For each end-entity certificate contained in or identified by by a
COSE result, the security acceptor SHALL perform the certification
path validation of Section 6 of [RFC5280] up to one of the acceptor's
trusted CA certificates. When evaluating a certificate Validity
period, the security acceptor SHALL use the bundle Creation Timestamp
time (if not unknown) as the reference instead of the current time.
If enabled by local policy, the entity SHALL perform an OCSP check of
each certificate providing OCSP authority information in accordance
with [RFC6960]. If certificate validation fails or if security
policy disallows a certificate for any reason, the acceptor SHALL
treat the associated security result as failed. Leaving out part of
the certification chain can cause the entity to fail to validate a
certificate if the left-out certificates are unknown to the entity
(see Section 6.2).
Sipos Expires 3 December 2023 [Page 14]
Internet-Draft DTN BPSec COSE June 2023
For each end-entity certificate contained in or identified by a COSE
context result, the security acceptor SHALL apply security policy to
the Key Usage extension (if present) and Extended Key Usage extension
(if present) in accordance with Section 4.2.1.12 of [RFC5280] and the
profile in Section 4.
2.6.1.3. Node ID Authentication
If required by security policy, for each end-entity certificate
referenced by a COSE context integrity result the security acceptor
SHALL validate the certificate NODE-ID in accordance with Section 6
of [RFC6125] using the NODE-ID reference identifier from the Security
Source of the containing security block. If the NODE-ID validation
result is Failure or if the result is Absent and security policy
requires an authenticated Node ID, the security acceptor SHALL treat
the result as failed.
2.6.2. Policy Recommendations
A RECOMMENDED security policy is to enable the use of OCSP checking
when internet connectivity is present. A RECOMMENDED security policy
is that if an Extended Key Usage is present that it needs to contain
id-kp-bundleSecurity of [IANA-SMI] to be usable as an end-entity
certificate for COSE security results. A RECOMMENDED security policy
is to require a validated Node ID (of Section 2.6.1.3) and to ignore
any other identifiers in the end-entity certificate.
This policy relies on and informs the certificate requirements in
Section 3.3.1 and Section 4. This policy assumes that a DTN-aware CA
(see Section 1.2) will only issue a certificate for a Node ID when it
has verified that the private key holder actually controls the DTN
node; this is needed to avoid the threat identified in Section 6.4.
This policy requires that a certificate contain a NODE-ID and allows
the certificate to also contain network-level identifiers. A
tailored policy on a more controlled network could relax the
requirement on Node ID validation and/or Extended Key Usage presence.
3. COSE Profile
This section contains requirements which apply to the use of COSE
within the BPSec security context defined in this document. Other
variations of COSE within BPSec can be used but are not expected to
be interoperable or usable by all security acceptors.
Sipos Expires 3 December 2023 [Page 15]
Internet-Draft DTN BPSec COSE June 2023
3.1. COSE Messages
When generating a BPSec result, security sources SHALL use only COSE
labels with a uint value. When processing a BPSec result, security
acceptors MAY handle COSE labels with with a tstr value.
When used in a BPSec result, each COSE message SHALL contain an
explicit algorithm identifier in the lower (content) layers. When
available and not implied by the bundle source, a COSE message SHALL
contain a key identifier in the highest (recipient) layer. See
Section 3.3 for specifics about asymmetric key identifiers. When a
key identifier is not available, BPSec acceptors SHALL use the
Security Source (if available) and the Bundle Source to imply which
keys can be used for security operations. Using implied keys has an
interoperability risk, see Section 6.5 for details. A BPSec security
operation always occurs within the context of the immutable primary
block with its parameters (specifically the Source Node ID) and the
security block with its optional Security Source.
The algorithms required by this profile focuses on networks using
shared symmetric-keys, with recommended algorithms for Elliptic Curve
(EC) keypairs and RSA keypairs. The focus of this profile is to
enable interoperation between security sources and acceptors on an
open network, where more explicit COSE parameters make it easier for
BPSec acceptors to avoid assumptions and avoid out-of-band
parameters. The requirements of this profile still allow the use of
potentially not-easily-interoperable algorithms and message/recipient
configurations for use by private networks, where message size is
more important than explicit COSE parameters.
3.2. Interoperability Algorithms
The set of integrity algorithms needed for interoperability is listed
here. The full set of COSE algorithms available is managed at
[IANA-COSE].
Implementations conforming to this specification SHALL support the
symmetric keyed and key-encryption algorithms of Table 5.
Implementations capable of doing so SHOULD support the asymmetric
keyed and key-encryption algorithms of Table 5.
| The layer-1 required list is identical to the [RFC9173] context
| list.
Sipos Expires 3 December 2023 [Page 16]
Internet-Draft DTN BPSec COSE June 2023
+=================+============+============+======+================+
| BPSec Block | COSE | Name | Code | Implementation |
| | Layer | | | Requirements |
+=================+============+============+======+================+
| Integrity | 1 | HMAC | 5 | Required |
| | | 256/256 | | |
+-----------------+------------+------------+------+----------------+
| Integrity | 1 | ES256 | -7 | Recommended |
+-----------------+------------+------------+------+----------------+
| Integrity | 1 | EdDSA | -8 | Recommended |
+-----------------+------------+------------+------+----------------+
| Integrity | 1 | PS256 | -37 | Recommended |
+-----------------+------------+------------+------+----------------+
| Confidentiality | 1 | A256GCM | 3 | Required |
+-----------------+------------+------------+------+----------------+
| Confidentiality | 2 | A256KW | -5 | Required |
+-----------------+------------+------------+------+----------------+
| Confidentiality | 2 | ECDH-ES + | -31 | Recommended |
| | | A256KW | | |
+-----------------+------------+------------+------+----------------+
| Confidentiality | 2 | ECDH-SS + | -34 | Recommended |
| | | A256KW | | |
+-----------------+------------+------------+------+----------------+
| Confidentiality | 2 | RSAES-OAEP | -41 | Recommended |
| | | w/ SHA-256 | | |
+-----------------+------------+------------+------+----------------+
Table 5: Interoperability Algorithms
The following are recommended key and recipient uses within COSE/
BPSec:
Symmetric Key Integrity: When generating a BIB result from a
symmetric key, implementations SHALL use a COSE_Mac0 using the
private key directly. When a COSE_Mac0 is used with a direct key,
the headers SHALL include a key identifier ("kid" header).
EC Keypair Integrity: When generating a BIB result from an EC
keypair, implementations SHALL use a COSE_Sign1 using the private
key directly. When a COSE_Sign1 is used with an EC keypair, the
headers SHALL include a public key identifier (see Section 3.3).
RSA Keypair Integrity: When generating a BIB result from an RSA
Sipos Expires 3 December 2023 [Page 17]
Internet-Draft DTN BPSec COSE June 2023
keypair, implementations SHALL use a COSE_Sign1 using the private
key directly. When a COSE_Sign1 is used with an RSA keypair, the
headers SHALL include a public key identifier (see Section 3.3).
When a COSE signature is generated with an RSA keypair, the
signature uses a PSS salt in accordance with Section 2 of
[RFC8230].
Symmetric Key Confidentiality: When generating a BCB result from an
symmetric key, implementations SHALL use a COSE_Encrypt message
with a recipient containing an indirect (wrapped or derived)
content encryption key (CEK). When generating a BCB result from a
symmetric key, implementations SHOULD NOT use COSE_Encrypt0 or
COSE_Encrypt with direct CEK. Doing so risks key overuse and the
vulnerabilities associated with large amount of ciphertext from
the same key. When a COSE_Encrypt is used with an overall key-
encryption key (KEK), the recipient layer SHALL include a key
identifier for the KEK.
EC Keypair Confidentiality: When generating a BCB result from an EC
keypair, implementations SHALL use a COSE_Encrypt message with a
recipient containing an indirect (wrapped or derived) CEK. When a
COSE_Encrypt is used with an EC keypair, the recipient layer SHALL
include a public key identifier (see Section 3.3). When a
COSE_Encrypt is used with an EC keypair, the security source SHALL
either generate an ephemeral EC keypair or choose a unique PartyU
Nonce for each security operation. When processing a COSE_Encrypt
with an EC keypair, the security acceptor SHALL process all KDF
and HMAC context data from the recipient headers in accordance
with Section 5.2 of [RFC9053] even though the source is not
required to provide any of those parameters.
RSA Keypair Confidentiality: When generating a BCB result from an
RSA keypair, implementations SHALL use a COSE_Encrypt message with
a recipient containing a key-wrapped CEK. When a COSE_Encrypt is
used with an RSA keypair, the recipient layer SHALL include a
public key identifier (see Section 3.3).
3.3. Asymmetric Key Types and Identifiers
This section applies when a BIB uses a public key for verification or
key-wrap, or when a BCB uses a public key for encryption or key-wrap.
When using asymmetric keyed algorithms, the security source SHALL
include a public key container or public key identifier as a
recipient header. The public key identifier SHALL be either a "kid"
of [RFC9052], an "x5t" or "x5chain" of [RFC9360], or an equivalent
identifier.
Sipos Expires 3 December 2023 [Page 18]
Internet-Draft DTN BPSec COSE June 2023
When BIB result contains a "x5t" identifier, the security source MAY
include an appropriate PKIX certificate container ("x5chain" or
"x5bag" of [RFC9360]) in a direct COSE header or an additional header
security parameter (see Section 2.2.1). When a BIB result contains
an "x5chain", the security source SHOULD NOT also include an "x5t" as
the first certificate in the chain is implicitly the applicable end-
entity certificate. For a BIB, if all potential security acceptors
are known to possess related public key and/or certificate data then
the public key or additional header parameters can be omitted. Risks
of not including related data are described in Section 6.5 and
Section 6.6.
When present, public keys and certificates SHOULD be included as
additional header parameters rather than within result COSE messages.
This provides size efficiency when multiple security results are
present because they will all be from the same security source and
likely share the same public key material. Security acceptors SHALL
still process public keys or certificates present in a result message
or recipient as applying to that individual COSE level.
Security acceptors SHALL aggregate all COSE_Key objects from all
parameters within a single BIB or BCB, independent of encoded type or
order of parameters. Because each context contains a single set of
security parameters which apply to all results in the same context,
security acceptors SHALL treat all public keys as being related to
the security source itself and potentially applying to every result.
3.3.1. Policy Recommendations
The RECOMMENDED priority policy for including PKIX material for BIB
results is as follows:
1. When receivers are not known to possess certificate chains, a
full chain is included (as an "x5chain").
2. When receivers are known to possess root and intermediate CAs,
just the end-entity certificate is included (again as an
"x5chain").
3. When receivers are known to possess associated chains including
end-entity certificates, a certificate thumbnail (as an "x5t").
4. Some arbitrary identifier is used to correlate to an end-entity
certificate (as a "kid").
5. The BIB Security Source is used to imply an associated end-entity
certificate which identifies that Node ID.
Sipos Expires 3 December 2023 [Page 19]
Internet-Draft DTN BPSec COSE June 2023
When PKIX certificates are used by security acceptors and the end-
entity certificate is not explicitly trusted (i.e. pinned), the
security acceptor SHALL perform the certification path validation of
Section 2.6.1.2 up to one or more trusted CA certificates. Leaving
out part of the certification chain can cause the security acceptor
to fail to validate a BIB if the left-out certificates are unknown to
the acceptor (see Section 6.6).
Any end-entity certificate associated with a BPSec security source
SHALL adhere to the profile of Section 4.
4. PKIX Certificate Profile
This section contains requirements on certificates used for the COSE
context, while Section 3.3 contains requirements for how such
certificates are transported or identified.
All end-entity certificates used for BPSec SHALL conform to
[RFC5280], or any updates or successors to that profile.
This profile requires Version 3 certificates due to the extensions
used by this profile. Security acceptors SHALL reject as invalid
Version 1 and Version 2 end-entity certificates.
Security acceptors SHALL accept certificates that contain an empty
Subject field or contain a Subject without a Common Name. Identity
information in end-entity certificates SHALL be contained in the
Subject Alternative Name extension in accordance with Section 4.2.1.6
of [RFC5280].
A BPSec end-entity certificate SHALL contain a NODE-ID in its Subject
Alternative Name extension which authenticates the Node ID of the
security source (for integrity) or the security acceptor (for
confidentiality). The identifier type NODE-ID is defined in
Section 4.4.1 of [RFC9174].
All end-entity and CA certificates used for BPSec SHOULD contain both
a Subject Key Identifier extension in accordance with Section 4.2.1.2
of [RFC5280] and an Authority Key Identifier extension in accordance
with Section 4.2.1.1 of [RFC5280]. Security acceptors SHOULD NOT
rely on either a Subject Key Identifier and an Authority Key
Identifier being present in any received certificate. Including key
identifiers simplifies the work of an entity needing to assemble a
certification chain.
When allowed by CA policy, a BPSec end-entity certificate SHOULD
contain a PKIX Extended Key Usage extension in accordance with
Section 4.2.1.12 of [RFC5280]. When the PKIX Extended Key Usage
Sipos Expires 3 December 2023 [Page 20]
Internet-Draft DTN BPSec COSE June 2023
extension is present, it SHALL contain a key purpose id-kp-
bundleSecurity of [IANA-SMI]. The id-kp-bundleSecurity purpose MAY
be combined with other purposes in the same certificate.
When allowed by CA policy, a BPSec end-entity certificate SHALL
contain a PKIX Key Usage extension in accordance with Section 4.2.1.3
of [RFC5280]. The PKIX Key Usage bits which are consistent with COSE
security are: digitalSignature, nonRepudiation, keyEncipherment, and
keyAgreement. The specific algorithms used by COSE messages in
security results determine which of those key uses are exercised.
See Section 4.1 for discussion of key use policies across multiple
certificates.
A BPSec end-entity certificate MAY contain an Online Certificate
Status Protocol (OCSP) URI within an Authority Information Access
extension in accordance with Section 4.2.2.1 of [RFC5280]. Security
acceptors are not expected to have continuous internet connectivity
sufficient to perform OCSP verification.
4.1. Multiple-Certificate Uses
A RECOMMENDED security policy is to limit asymmetric keys (and thus
public key certificates) to single uses among the following:
Bundle transport: With key uses as defined in the convergence layer
specification(s). Transports can require additional Extended Key
Usage, such as id-kp-serverAuth or id-kp-clientAuth.
Block signing: With key use digitalSignature and/or nonRepudiation.
Block encryption: With key use keyEncipherment and/or keyAgreement.
This policy is the same one recommended by Section 6 of [RFC8551] for
email security and by Section 5.2 of [NIST-SP800-57] more generally.
Effectively this means that a BP node uses separate certificates for
transport (e.g., as a TCPCL entity), BIB signing (as a security
source), and BCB encryption (as a security acceptor).
5. Implementation Status
This section is to be removed before publishing as an RFC.
[NOTE to the RFC Editor: please remove this section before
publication, as well as the reference to [RFC7942],
[github-dtn-bpsec-cose], [github-dtn-demo-agent], and
[github-dtn-wireshark].]
Sipos Expires 3 December 2023 [Page 21]
Internet-Draft DTN BPSec COSE June 2023
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations can
exist.
An example implementation of COSE over BPSec blocks has been created
as a GitHub project [github-dtn-bpsec-cose] and is intended to use as
a proof-of-concept and as a possible source of interoperability
testing. This example implementation only handles CBOR encoding/
decoding and cryptographic functions, it does not construct actual
BIB or BCB and does not integrate with a BP Agent.
6. Security Considerations
This section separates security considerations into threat categories
based on guidance of BCP 72 [RFC3552].
All of the security considerations of the underlying BPSec [RFC9172]
apply to these new security contexts.
6.1. Threat: BPSec Block Replay
The bundle's primary block contains fields which uniquely identify a
bundle: the Source Node ID, Creation Timestamp, and fragment
parameters (see Section 4.3.1 of [RFC9171]). These same fields are
used to correlate Administrative Records with the bundles for which
the records were generated. Including the primary block in the AAD
Scope for integrity and confidentiality (see Section 2.2.2) binds the
verification of the secured block to its parent bundle and disallows
replay of any block with its BIB or BCB.
This profile of COSE limits the encryption algorithms to only AEAD in
order to include the context of the encrypted data as AAD. If an
agent mistakenly allows the use of non-AEAD encryption when
decrypting and verifying a BCB, the possibility of block replay
attack is present.
Sipos Expires 3 December 2023 [Page 22]
Internet-Draft DTN BPSec COSE June 2023
6.2. Threat: Untrusted End-Entity Certificate
The profile in Section 2.6.1 uses end-entity certificates chained up
to a trusted root CA. A security source can include a certificate
set which does not contain the full chain, possibly excluding
intermediate or root CAs. In an environment where security acceptors
are known to already contain needed root and intermediate CAs there
is no need to include those CAs, but this has a risk of an acceptor
not actually having one of the needed CAs.
6.3. Threat: Certificate Validation Vulnerabilities
Even when a security acceptor is operating properly an attacker can
attempt to exploit vulnerabilities within certificate check
algorithms or configuration to authenticate using an invalid
certificate. An invalid certificate exploit could lead to higher-
level security issues and/or denial of service to the Node ID being
impersonated.
There are many reasons, described in [RFC5280] and [RFC6125], why a
certificate can fail to validate, including using the certificate
outside of its valid time interval, using purposes for which it was
not authorized, or using it after it has been revoked by its CA.
Validating a certificate is a complex task and can require network
connectivity outside of the primary BP convergence layer network
path(s) if a mechanism such as OCSP [RFC6960] is used by the CA. The
configuration and use of particular certificate validation methods
are outside of the scope of this document.
6.4. Threat: BP Node Impersonation
When certificates are referenced by BIB results it is possible that
the certificate does not contain a NODE-ID or does contain one but
has a mismatch with the actual security source (see Section 1.2).
Having a CA-validated certificate does not alone guarantee the
identity of the security source from which the certificate is
provided; additional validation procedures in Section 2.6.1 bind the
Node ID based on the contents of the certificate.
6.5. Threat: Unidentifiable Key
The profile in Section 3.2 recommends key identifiers when possible
and the parameters in section Section 2.2 allow encoding public keys
where available. If the application using a COSE Integrity or COSE
Confidentiality context leaves out key identification data (in a COSE
recipient structure), the security acceptor for those BPSec blocks
only has the primary block available to use when verifying or
decrypting the target block. This leads to a situation, identified
Sipos Expires 3 December 2023 [Page 23]
Internet-Draft DTN BPSec COSE June 2023
in BPSec Security Considerations, where a signature is verified to be
valid but not from the expected Security Source.
Because the key identifier headers are unprotected (see Section 3.3),
there is still the possibility that an active attacker removes or
alters key identifier(s) in the result. This can cause the security
acceptor to not be able to properly verify a valid signature or not
use the correct private key to decrypt valid ciphertext.
6.6. Threat: Non-Trusted Public Key
The profile in Section 3.2 allows the use of PKIX which typically
involves end-entity certificates chained up to a trusted root CA. A
BIB can reference or contain end-entity certificates not previously
known to a security acceptor but the acceptor can still trust the
certificate by verifying it up to a trusted CA. In an environment
where security acceptors are known to already contain needed root and
intermediate CAs there is no need to include those CAs in a proper
chain within the security parameters, but this has a risk of an
acceptor not actually having one of the needed CAs.
Because the security parameters are not included as AAD, there is
still the possibility that an active attacker removes or alters
certification chain data in the parameters. This can cause the
security acceptor to be able to verify a valid signature but not
trust the public key used to perform the verification.
6.7. Threat: Passive Leak of Key Material
It is important that the key requirements of Section 2.2 apply only
to public keys and PKIX certificates. Including non-public key
material in ASB parameters will expose that material in the bundle
data and over the bundle convergence layer during transport.
6.8. Threat: Algorithm Vulnerabilities
Because this use of COSE leaves the specific algorithms chosen for
BIB and BCB use up to the applications securing bundle data, it is
important to use only COSE algorithms which are marked as
"recommended" in the IANA registry [IANA-COSE].
7. IANA Considerations
Registration procedures referred to in this section are defined in
[RFC8126].
Sipos Expires 3 December 2023 [Page 24]
Internet-Draft DTN BPSec COSE June 2023
7.1. BPSec Security Context Identifiers
Within the "Bundle Protocol" registry [IANA-BUNDLE], the following
entry has been added to the "BPSec Security Context Identifiers" sub-
registry.
+==========+=============+======================+
| Value | Description | Reference |
+==========+=============+======================+
| TBD-COSE | COSE | [This specification] |
+----------+-------------+----------------------+
Table 6: BPSec Security Context Identifiers
7.2. BPSec COSE AAD Scope Flags
Within the "Bundle Protocol" registry [IANA-BUNDLE], the IANA has
created and now maintains a new registry named "BPSec COSE AAD Scope
Flags" on the "Bundle Protocol" registry page. Table 7 shows the
initial values for this registry.
The registration policy for this registry is Specification Required.
The value range is unsigned 8-bit integer.
+===========================+==============+======================+
| Bit Position (from LSbit) | Name | Reference |
+===========================+==============+======================+
| 0 | AAD-metadata | [This specification] |
+---------------------------+--------------+----------------------+
| 1 | AAD-btsd | [This specification] |
+---------------------------+--------------+----------------------+
| 2-7 | Reserved | [This specification] |
+---------------------------+--------------+----------------------+
Table 7: BPSec COSE AAD Scope Flags
8. References
8.1. Normative References
[IANA-BUNDLE]
IANA, "Bundle Protocol",
<https://www.iana.org/assignments/bundle/>.
[IANA-COSE]
IANA, "CBOR Object Signing and Encryption (COSE)",
<https://www.iana.org/assignments/cose/>.
Sipos Expires 3 December 2023 [Page 25]
Internet-Draft DTN BPSec COSE June 2023
[IANA-SMI] IANA, "Structure of Management Information (SMI) Numbers",
<https://www.iana.org/assignments/smi-numbers/>.
[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>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013,
<https://www.rfc-editor.org/info/rfc6960>.
[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>.
[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>.
[RFC8230] Jones, M., "Using RSA Algorithms with CBOR Object Signing
and Encryption (COSE) Messages", RFC 8230,
DOI 10.17487/RFC8230, September 2017,
<https://www.rfc-editor.org/info/rfc8230>.
[RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", RFC 8551, DOI 10.17487/RFC8551,
April 2019, <https://www.rfc-editor.org/info/rfc8551>.
Sipos Expires 3 December 2023 [Page 26]
Internet-Draft DTN BPSec COSE June 2023
[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>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/info/rfc9052>.
[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/info/rfc9053>.
[RFC9172] Birrane, III, E. and K. McKeever, "Bundle Protocol
Security (BPSec)", RFC 9172, DOI 10.17487/RFC9172, January
2022, <https://www.rfc-editor.org/info/rfc9172>.
[RFC9174] Sipos, B., Demmer, M., Ott, J., and S. Perreault, "Delay-
Tolerant Networking TCP Convergence-Layer Protocol Version
4", RFC 9174, DOI 10.17487/RFC9174, January 2022,
<https://www.rfc-editor.org/info/rfc9174>.
[RFC9360] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Header Parameters for Carrying and Referencing X.509
Certificates", RFC 9360, DOI 10.17487/RFC9360, February
2023, <https://www.rfc-editor.org/info/rfc9360>.
8.2. Informative References
[NIST-SP800-57]
National Institute of Standards and Technology,
"Recommendation for Key Management - Part 1: General",
NIST Special Publication 800-57 Revision 4, DOI 10.6028/
NIST.SP.800-57pt1r5, May 2020,
<https://nvlpubs.nist.gov/nistpubs/SpecialPublications/
NIST.SP.800-57pt1r5.pdf>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/info/rfc3552>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
Sipos Expires 3 December 2023 [Page 27]
Internet-Draft DTN BPSec COSE June 2023
[RFC9171] Burleigh, S., Fall, K., and E. Birrane, III, "Bundle
Protocol Version 7", RFC 9171, DOI 10.17487/RFC9171,
January 2022, <https://www.rfc-editor.org/info/rfc9171>.
[RFC9173] Birrane, III, E., White, A., and S. Heiner, "Default
Security Contexts for Bundle Protocol Security (BPSec)",
RFC 9173, DOI 10.17487/RFC9173, January 2022,
<https://www.rfc-editor.org/info/rfc9173>.
[github-dtn-bpsec-cose]
Sipos, B., "DTN Bundle Protocol Security COSE Security
Context", <https://github.com/BrianSipos/dtn-bpsec-cose/>.
[github-dtn-demo-agent]
Sipos, B., "Demo Convergence Layer Agent",
<https://github.com/BrianSipos/dtn-demo-agent/>.
[github-dtn-wireshark]
Sipos, B., "Wireshark Plugin Dissectors for DTN",
<https://github.com/BrianSipos/dtn-demo-agent/>.
Appendix A. Examples
These examples are intended to have the correct structure of COSE
security blocks but in some cases use simplified algorithm parameters
or smaller key sizes than are required by the actual COSE profile
defined in this documents. Each example indicates how it differs
from the actual profile if there is a meaningful difference.
All of these examples operate within the context of the bundle
primary block of Figure 6 with a security target block of Figure 7.
All example figures use the extended diagnostic notation [RFC8610].
[
7, / BP version /
0, / flags /
0, / CRC type /
[1, "//dst/svc"], / destination /
[1, "//src/"], / source /
[1, "//src/"], / report-to /
[0, 40], / timestamp /
1000000 / lifetime /
]
Figure 6: Primary block CBOR diagnostic
Sipos Expires 3 December 2023 [Page 28]
Internet-Draft DTN BPSec COSE June 2023
[
1, / type code: payload /
1, / block num /
0, / flags /
0, / CRC type /
<<"hello">> / block-type-specific-data /
]
Figure 7: Target block CBOR diagnostic
All of the block integrity block examples operate within the context
of the "frame" block of Figure 8, and block confidentiality block
examples within the frame block of Figure 9.
[
11, / type code: BIB /
3, / block num /
0, / flags /
0, / CRC type /
'' / BTSD to be replaced /
]
Figure 8: Block integrity block frame CBOR diagnostic
[
12, / type code: BCB /
3, / block num /
0, / flags /
0, / CRC type /
'' / BTSD to be replaced /
]
Figure 9: Block confidentiality block CBOR diagnostic
All of the examples also operate within a security block containing
the AAD Scope parameter with only has-primary-ctx and has-target-ctx
flags set. This results in a consistent AAD-list as shown in
Figure 10, which is encoded as the byte string for COSE external_aad
in all of the examples.
{ 0: 0b01, 1: 0b01 }, / AAD-scope /
[ 7, 0, 0, [ 1, "//dst/svc" ], [ 1, "//src/" ], [ 1, "//src/" ],
[ 0, 40 ], 1000000 ], / primary-block /
1, 1, 0, / target block-metadata /
'' / additional-protected /
Figure 10: Example scope AAD-list CBOR-sequence diagnostic
Sipos Expires 3 December 2023 [Page 29]
Internet-Draft DTN BPSec COSE June 2023
The only differences between these examples which use EC or RSA
keypairs and a use of a PKIX public key certificate are: the
parameters would have an x5chain parameter instead of a COSE_Key
type, and the recipient would contain an "x5t" value instead of a
"kid" value. Neither of these is a change to a protected header so,
given the same private key, there would be no change to the signature
or wrapped-key data.
Because each of the encryption examples use the same CEK within the
same AAD, the target ciphertext is also identical. The target block
after application of the encryption is shown in Figure 11.
[
1, / type code: payload /
1, / block num /
0, / flags /
0, / CRC type /
h'1fd25f64a2ee1152e3e33a3b4ad83d6b368a8949adde' / ciphertext /
]
Figure 11: Encrypted Target block CBOR diagnostic
A.1. Symmetric Key COSE_Mac0
This is an example of a MAC with recipient having a 256-bit symmetric
key identified by a "kid".
[
{
/ kty / 1: 4, / symmetric /
/ kid / 2: 'ExampleMAC',
/ k / -1: h'13bf9cead057c0aca2c9e52471ca4b19ddfaf4c0784e3f3e8e39
99dbae4ce45c'
}
]
Figure 12: Symmetric Key
The external_aad is the encoded data from Figure 10. The payload is
the encoded target BTSD from Figure 7.
[
"MAC0", / context /
h'a10105', / protected /
h'a200010101880700008201692f2f6473742f7376638201662f2f7372632f8201
662f2f7372632f820018281a000f424001010040', / external_aad /
h'6568656c6c6f' / payload /
]
Sipos Expires 3 December 2023 [Page 30]
Internet-Draft DTN BPSec COSE June 2023
Figure 13: MAC_structure CBOR diagnostic
[1], / targets /
-1, / security context TBD-COSE /
1, / flags: params-present /
[1, "//src/"], / security source /
[ / parameters /
[
5, / AAD-scope /
{0: 0b01, 1: 0b01}, / primary metadata, target metadata /
]
],
[
[ / target block #1 /
[ / result /
17, / COSE_Mac0 tag /
<<[
<<{ / protected /
/ alg / 1:5 / HMAC 256//256 /
}>>,
{ / unprotected /
/ kid / 4:'ExampleMAC'
},
null, / payload detached /
h'5cf66fcdb1ae9514594c8854b30cec67898b12fb19bdb068dcb6e78d59
35ae64' / tag /
]>>
]
]
]
Figure 14: Abstract Security Block CBOR diagnostic
The final bundle is encoded as the byte string:
h'9f880700008201692f2f6473742f7376638201662f2f7372632f8201662f2f7372
632f820018281a000f4240850b0300005850810100018201662f2f7372632f818205
a2000101018181821158358443a10105a1044a4578616d706c654b6579f658205cf6
6fcdb1ae9514594c8854b30cec67898b12fb19bdb068dcb6e78d5935ae6485010100
00466568656c6c6fff'
A.2. EC Keypair COSE_Sign1
This is an example of a signature with a recipient having a P-256
curve EC keypair identified by a "kid". The associated public key is
included as a security parameter.
Sipos Expires 3 December 2023 [Page 31]
Internet-Draft DTN BPSec COSE June 2023
[
{ / signing private key /
/ kty / 1: 2, / EC2 /
/ kid / 2: 'ExampleEC2',
/ crv / -1: 1, / P-256 /
/ x / -2: h'44c1fa63b84f172b50541339c50beb0e630241ecb4eebbddb8b5
e4fe0a1787a8',
/ y / -3: h'059451c7630d95d0b550acbd02e979b3f4f74e645b74715fafbc
1639960a0c7a',
/ d / -4: h'dd6e7d8c4c0e0c0bd3ae1b4a2fa86b9a09b7efee4a233772cf51
89786ea63842'
}
]
Figure 15: Example Keys
The external_aad is the encoded data from Figure 10. The payload is
the encoded target BTSD from Figure 7.
[
"Signature1", / context /
h'a10126', / protected /
h'a200010101880700008201692f2f6473742f7376638201662f2f7372632f8201
662f2f7372632f820018281a000f424001010040', / external_aad /
h'6568656c6c6f' / payload /
]
Figure 16: Sig_structure CBOR diagnostic
Sipos Expires 3 December 2023 [Page 32]
Internet-Draft DTN BPSec COSE June 2023
[1], / targets /
-1, / security context TBD-COSE /
1, / flags: params-present /
[1, "//src/"], / security source /
[ / parameters /
[
5, / AAD-scope /
{0: 0b01, 1: 0b01}, / primary metadata, target metadata /
]
],
[
[ / target block #1 /
[ / result /
18, / COSE_Sign1 tag /
<<[
<<{ / protected /
/ alg / 1:-7 / ES256 /
}>>,
{ / unprotected /
/ kid / 4:'ExampleEC2'
},
null, / payload detached /
h'5552647e6fa90156b908a84eddd2f631ed7005147afa1437d792fa5508
586c20b5134c469ccacc44c4a3c26bef952823d789eb70eeecf4393d8c6818245651
4c' / signature /
]>>
]
]
]
Figure 17: Abstract Security Block CBOR diagnostic
The final bundle is encoded as the byte string:
h'9f880700008201692f2f6473742f7376638201662f2f7372632f8201662f2f7372
632f820018281a000f4240850b0300005870810100018201662f2f7372632f818205
a2000101018181821258558443a10126a1044a4578616d706c65454332f658405552
647e6fa90156b908a84eddd2f631ed7005147afa1437d792fa5508586c20b5134c46
9ccacc44c4a3c26bef952823d789eb70eeecf4393d8c68182456514c850101000046
6568656c6c6fff'
A.3. RSA Keypair COSE_Sign1
This is an example of a signature with a recipient having a 1024-bit
RSA keypair identified by a "kid". The associated public key is
included as a security parameter.
Sipos Expires 3 December 2023 [Page 33]
Internet-Draft DTN BPSec COSE June 2023
This key strength is not supposed to be a secure configuration, only
intended to explain the procedure. This signature uses a random
salt, so the full signature output is not deterministic.
[
{ / signing private key /
/ kty / 1: 3, / RSA /
/ kid / 2: 'ExampleRSA',
/ n / -1: h'b0b5fd85f52c91844007443c9f9371980025f76d51fc9c676812
31da610cb291ba637ce813bffdb2e9c653258607389ec97dad3db295fded67744ed6
20707db36804e74e56a494030a73608fc8d92f2f0578d2d85cc201ef0ff22d7835d2
d147d3b90a6884276235a01c2be99dfc597f79554362fc1eb03639cac5ccaddb29
25',
/ e / -2: h'010001',
/ d / -3: h'9b5d26ad6445ef1aab80b809e4f329684e9912d556c4166f041d
1b1fb93c04b4037ffd0dbe6f8a8a86e70bab6e0f6344983a9ada27ed9ff7de816fde
eb5e7be48e607ce5fda4581ca6338a9e019fb3689b28934192b6a190cdda910abb5a
86a2f7b6f9cd5011049d8de52ddfef73aa06df401c55623ec196720f54920deb4f
01',
/ p / -4: h'db22d94e7784a27b568cbf985307ea8d6430ff6b88c18a7086fd
4f57a326572f2250c39e48a6f8e2201661c2dfe12c7386835b649714d050aa36123e
c3d00e75',
/ q / -5: h'ce7016adc5f326b7520397c5978ee2f50e69279983d54c5d76f0
5bcd61de0879d7056c923540dff9cbae95dcc0e5e86b52b3c902dc9669c8021c6955
7effb9f1',
/ dP / -6: h'6a6fcaccea106a3b2e16bf18e57b7ad9a2488a4758ed68a8af6
86a194f0d585b7477760c738d6665aee0302bcf4237ad0530d83b4b86b887f5a4bdc
7eea427e1',
/ dQ / -7: h'28a4cae245b1dcb285142e027a1768b9c4af915b59285a93a04
22c60e05edd9e57663afd023d169bd0ad3bd62da8563d231840802ebbf271ad70b89
05ba3af91',
/ qInv / -8: h'07b5a61733896270a6bd2bb1654194c54e2bc0e061b543a4e
d9fa73c4bc79c87148aa92a451c4ab8262b6377a9c7b97f869160ca6f5d853ee4b65
f4f92865ca3'
}
]
Figure 18: Example Keys
The external_aad is the encoded data from Figure 10. The payload is
the encoded target BTSD from Figure 7.
Sipos Expires 3 December 2023 [Page 34]
Internet-Draft DTN BPSec COSE June 2023
[
"Signature1", / context /
h'a1013824', / protected /
h'a200010101880700008201692f2f6473742f7376638201662f2f7372632f8201
662f2f7372632f820018281a000f424001010040', / external_aad /
h'6568656c6c6f' / payload /
]
Figure 19: Sig_structure CBOR diagnostic
[1], / targets /
-1, / security context TBD-COSE /
1, / flags: params-present /
[1, "//src/"], / security source /
[ / parameters /
[
5, / AAD-scope /
{0: 0b01, 1: 0b01}, / primary metadata, target metadata /
]
],
[
[ / target block #1 /
[ / result /
18, / COSE_Sign1 tag /
<<[
<<{ / protected /
/ alg / 1:-37 / PS256 /
}>>,
{ / unprotected /
/ kid / 4:'ExampleRSA'
},
null, / payload detached /
h'38aab98a3681ba9d4ac014d1d70509447310e4d2d55ed450c8c0e17e98
162dd5325ac06d7daa8a7d4c2903c4f4c6e47e707581a45056240a6393294c96845e
d5b6ba3b4ff8ea0bd52ed33e082d0b683d67644de88216cc291ee24aaa84d712dae1
e6830bdf18017ac3903d418a779be32bc927315fe57ca7da5bad4d95241a
4c' / signature /
]>>
]
]
]
Figure 20: Abstract Security Block CBOR diagnostic
The final bundle is encoded as the byte string:
Sipos Expires 3 December 2023 [Page 35]
Internet-Draft DTN BPSec COSE June 2023
h'9f880700008201692f2f6473742f7376638201662f2f7372632f8201662f2f7372
632f820018281a000f4240850b03000058b1810100018201662f2f7372632f818205
a2000101018181821258968444a1013824a1044a4578616d706c65525341f6588038
aab98a3681ba9d4ac014d1d70509447310e4d2d55ed450c8c0e17e98162dd5325ac0
6d7daa8a7d4c2903c4f4c6e47e707581a45056240a6393294c96845ed5b6ba3b4ff8
ea0bd52ed33e082d0b683d67644de88216cc291ee24aaa84d712dae1e6830bdf1801
7ac3903d418a779be32bc927315fe57ca7da5bad4d95241a4c850101000046656865
6c6c6fff'
A.4. Symmetric KEK COSE_Encrypt
This is an example of an encryption with a random CEK and an explicit
key-encryption key (KEK) identified by a "kid". The keys used are
shown in Figure 21.
[
{
/ kty / 1: 4, / symmetric /
/ kid / 2: 'ExampleKEK',
/ k / -1: h'0e8a982b921d1086241798032fedc1f883eab72e4e43bb2d11cf
ae38ad7a972e'
},
{
/ kty / 1: 4, / symmetric /
/ kid / 2: 'ExampleCEK',
/ k / -1: h'13bf9cead057c0aca2c9e52471ca4b19ddfaf4c0784e3f3e8e39
99dbae4ce45c'
}
]
Figure 21: Example Keys
The external_aad is the encoded data from Figure 10.
[
"Encrypt", / context /
h'a10103', / protected /
h'a200010101880700008201692f2f6473742f7376638201662f2f7372632f8201
662f2f7372632f820018281a000f424001010040', / external_aad /
]
Figure 22: Enc_structure CBOR diagnostic
The ASB item for this encryption operation is shown in Figure 23 and
corresponds with the updated target block (containing the ciphertext)
of Figure 11.
Sipos Expires 3 December 2023 [Page 36]
Internet-Draft DTN BPSec COSE June 2023
[1], / targets /
-1, / security context TBD-COSE /
1, / flags: params-present /
[1, "//src/"], / security source /
[ / parameters /
[
5, / AAD-scope /
{0: 0b01, 1: 0b01}, / primary metadata, target metadata /
]
],
[
[ / target block #1 /
[ / result /
96, / COSE_Encrypt tag /
<<[
<<{ / protected /
/ alg / 1:3 / A256GCM /
}>>,
{ / unprotected /
/ iv / 5: h'6f3093eba5d85143c3dc484a'
},
null, / payload detached /
[
[ / recipient /
h'', / protected /
{ / unprotected /
/ alg / 1:-5, / A256KW /
/ kid / 4:'ExampleKEK'
},
h'917f2045e1169502756252bf119a94cdac6a9d8944245b5a9a26d4
03a6331159e3d691a708e9984d' / key-wrapped /
]
]
]>>
]
]
]
Figure 23: Abstract Security Block CBOR diagnostic
The final bundle is encoded as the byte string:
h'9f880700008201692f2f6473742f7376638201662f2f7372632f8201662f2f7372
632f820018281a000f4240850c030000586d810100018201662f2f7372632f818205
a200010101818182186058518443a10103a1054c6f3093eba5d85143c3dc484af681
8340a20124044a4578616d706c654b454b5828917f2045e1169502756252bf119a94
cdac6a9d8944245b5a9a26d403a6331159e3d691a708e9984d8501010000561fd25f
64a2ee1152e3e33a3b4ad83d6b368a8949addeff'
Sipos Expires 3 December 2023 [Page 37]
Internet-Draft DTN BPSec COSE June 2023
A.5. EC Keypair COSE_Encrypt
This is an example of an encryption with an P-256 curve ephemeral
sender keypair and a static recipient keypair identified by a "kid".
The keys used are shown in Figure 24.
[
{ / sender ephemeral private key /
/ kty / 1: 2, / EC2 /
/ crv / -1: 1, / P-256 /
/ x / -2: h'fedaba748882050d1bef8ba992911898f554450952070aeb4788
ca57d1df6bcc',
/ y / -3: h'ceaa8e7ff4751a4f81c70e98f1713378b0bd82a1414a2f493c1c
9c0670f28d62',
/ d / -4: h'a2e4ed4f2e21842999b0e9ebdaad7465efd5c29bd5761f5c2088
0f9d9c3b122a'
},
{ / recipient private key /
/ kty / 1: 2, / EC2 /
/ kid / 2: 'ExampleEC2',
/ crv / -1: 1, / P-256 /
/ x / -2: h'44c1fa63b84f172b50541339c50beb0e630241ecb4eebbddb8b5
e4fe0a1787a8',
/ y / -3: h'059451c7630d95d0b550acbd02e979b3f4f74e645b74715fafbc
1639960a0c7a',
/ d / -4: h'dd6e7d8c4c0e0c0bd3ae1b4a2fa86b9a09b7efee4a233772cf51
89786ea63842'
},
{
/ kty / 1: 4, / symmetric /
/ kid / 2: 'ExampleCEK',
/ k / -1: h'13bf9cead057c0aca2c9e52471ca4b19ddfaf4c0784e3f3e8e39
99dbae4ce45c'
}
]
Figure 24: Example Keys
The external_aad is the encoded data from Figure 10.
[
"Encrypt", / context /
h'a10103', / protected /
h'a200010101880700008201692f2f6473742f7376638201662f2f7372632f8201
662f2f7372632f820018281a000f424001010040', / external_aad /
]
Figure 25: Enc_structure CBOR diagnostic
Sipos Expires 3 December 2023 [Page 38]
Internet-Draft DTN BPSec COSE June 2023
The ASB item for this encryption operation is shown in Figure 26 and
corresponds with the updated target block (containing the ciphertext)
of Figure 11.
Sipos Expires 3 December 2023 [Page 39]
Internet-Draft DTN BPSec COSE June 2023
[1], / targets /
-1, / security context TBD-COSE /
1, / flags: params-present /
[1, "//src/"], / security source /
[ / parameters /
[
5, / AAD-scope /
{0: 0b01, 1: 0b01}, / primary metadata, target metadata /
]
],
[
[ / target block #1 /
[ / result /
96, / COSE_Encrypt tag /
<<[
<<{ / protected /
/ alg / 1:3 / A256GCM /
}>>,
{ / unprotected /
/ iv / 5: h'6f3093eba5d85143c3dc484a'
},
null, / payload detached /
[
[ / recipient /
h'', / protected /
{ / unprotected /
/ alg / 1:-31, / ECDH-ES + A256KW /
/ kid / 4:'ExampleEC2',
/ ephemeral key / -1:{
1:2,
-1:1,
-2:h'fedaba748882050d1bef8ba992911898f554450952070ae
b4788ca57d1df6bcc',
-3:h'ceaa8e7ff4751a4f81c70e98f1713378b0bd82a1414a2f4
93c1c9c0670f28d62'
}
},
h'cb530b03f1e4b09ec1a0ca19afafbf280284106ab407aaf9bfed6e
666c8f2f9ab5465cf11ef02756' / key-wrapped /
]
]
]>>
]
]
]
Figure 26: Abstract Security Block CBOR diagnostic
Sipos Expires 3 December 2023 [Page 40]
Internet-Draft DTN BPSec COSE June 2023
The final bundle is encoded as the byte string:
h'9f880700008201692f2f6473742f7376638201662f2f7372632f8201662f2f7372
632f820018281a000f4240850c03000058ba810100018201662f2f7372632f818205
a2000101018181821860589e8443a10103a1054c6f3093eba5d85143c3dc484af681
8340a301381e044a4578616d706c6545433220a401022001215820fedaba74888205
0d1bef8ba992911898f554450952070aeb4788ca57d1df6bcc225820ceaa8e7ff475
1a4f81c70e98f1713378b0bd82a1414a2f493c1c9c0670f28d625828cb530b03f1e4
b09ec1a0ca19afafbf280284106ab407aaf9bfed6e666c8f2f9ab5465cf11ef02756
8501010000561fd25f64a2ee1152e3e33a3b4ad83d6b368a8949addeff'
A.6. RSA Keypair COSE_Encrypt
This is an example of an encryption with a recipient having a
1024-bit RSA keypair identified by a "kid". The associated public
key is included as a security parameter.
This key strength is not supposed to be a secure configuration, only
intended to explain the procedure. This padding scheme uses a random
salt, so the full layer-2 ciphertext output is not deterministic.
Sipos Expires 3 December 2023 [Page 41]
Internet-Draft DTN BPSec COSE June 2023
[
{ / recipient private key /
/ kty / 1: 3, / RSA /
/ kid / 2: 'ExampleRSA',
/ n / -1: h'b0b5fd85f52c91844007443c9f9371980025f76d51fc9c676812
31da610cb291ba637ce813bffdb2e9c653258607389ec97dad3db295fded67744ed6
20707db36804e74e56a494030a73608fc8d92f2f0578d2d85cc201ef0ff22d7835d2
d147d3b90a6884276235a01c2be99dfc597f79554362fc1eb03639cac5ccaddb29
25',
/ e / -2: h'010001',
/ d / -3: h'9b5d26ad6445ef1aab80b809e4f329684e9912d556c4166f041d
1b1fb93c04b4037ffd0dbe6f8a8a86e70bab6e0f6344983a9ada27ed9ff7de816fde
eb5e7be48e607ce5fda4581ca6338a9e019fb3689b28934192b6a190cdda910abb5a
86a2f7b6f9cd5011049d8de52ddfef73aa06df401c55623ec196720f54920deb4f
01',
/ p / -4: h'db22d94e7784a27b568cbf985307ea8d6430ff6b88c18a7086fd
4f57a326572f2250c39e48a6f8e2201661c2dfe12c7386835b649714d050aa36123e
c3d00e75',
/ q / -5: h'ce7016adc5f326b7520397c5978ee2f50e69279983d54c5d76f0
5bcd61de0879d7056c923540dff9cbae95dcc0e5e86b52b3c902dc9669c8021c6955
7effb9f1',
/ dP / -6: h'6a6fcaccea106a3b2e16bf18e57b7ad9a2488a4758ed68a8af6
86a194f0d585b7477760c738d6665aee0302bcf4237ad0530d83b4b86b887f5a4bdc
7eea427e1',
/ dQ / -7: h'28a4cae245b1dcb285142e027a1768b9c4af915b59285a93a04
22c60e05edd9e57663afd023d169bd0ad3bd62da8563d231840802ebbf271ad70b89
05ba3af91',
/ qInv / -8: h'07b5a61733896270a6bd2bb1654194c54e2bc0e061b543a4e
d9fa73c4bc79c87148aa92a451c4ab8262b6377a9c7b97f869160ca6f5d853ee4b65
f4f92865ca3'
},
{
/ kty / 1: 4, / symmetric /
/ kid / 2: 'ExampleCEK',
/ k / -1: h'13bf9cead057c0aca2c9e52471ca4b19ddfaf4c0784e3f3e8e39
99dbae4ce45c'
}
]
Figure 27: Example Keys
The external_aad is the encoded data from Figure 10.
Sipos Expires 3 December 2023 [Page 42]
Internet-Draft DTN BPSec COSE June 2023
[
"Encrypt", / context /
h'a10103', / protected /
h'a200010101880700008201692f2f6473742f7376638201662f2f7372632f8201
662f2f7372632f820018281a000f424001010040', / external_aad /
]
Figure 28: Enc_structure CBOR diagnostic
The ASB item for this encryption operation is shown in Figure 29 and
corresponds with the updated target block (containing the ciphertext)
of Figure 11.
Sipos Expires 3 December 2023 [Page 43]
Internet-Draft DTN BPSec COSE June 2023
[1], / targets /
-1, / security context TBD-COSE /
1, / flags: params-present /
[1, "//src/"], / security source /
[ / parameters /
[
5, / AAD-scope /
{0: 0b01, 1: 0b01}, / primary metadata, target metadata /
]
],
[
[ / target block #1 /
[ / result /
96, / COSE_Encrypt tag /
<<[
<<{ / protected /
/ alg / 1:3 / A256GCM /
}>>,
{ / unprotected /
/ iv / 5: h'6f3093eba5d85143c3dc484a'
},
null, / payload detached /
[
[ / recipient /
h'', / protected /
{ / unprotected /
/ alg / 1:-41, / RSAES-OAEP w SHA-256 /
/ kid / 4:'ExampleRSA'
},
h'08ae2d939e1d16d0be9f2ff6fc51a7b5c1701359930212f0a3154c
acf20d1eadf81896f6cb124457d8ffef207568f1050a21b3ebc5030fab0cdc202d77
ea1dece4cbf6730ce28b98e0090d72d28f45209c6f3df086a94a9f91fb44795f152d
59f70c38eccd5b7463d3e71a340b16b6a0644cf781f125fce829410d851dda34
b3' / key-wrapped /
]
]
]>>
]
]
]
Figure 29: Abstract Security Block CBOR diagnostic
The final bundle is encoded as the byte string:
Sipos Expires 3 December 2023 [Page 44]
Internet-Draft DTN BPSec COSE June 2023
h'9f880700008201692f2f6473742f7376638201662f2f7372632f8201662f2f7372
632f820018281a000f4240850c03000058c6810100018201662f2f7372632f818205
a200010101818182186058aa8443a10103a1054c6f3093eba5d85143c3dc484af681
8340a2013828044a4578616d706c65525341588008ae2d939e1d16d0be9f2ff6fc51
a7b5c1701359930212f0a3154cacf20d1eadf81896f6cb124457d8ffef207568f105
0a21b3ebc5030fab0cdc202d77ea1dece4cbf6730ce28b98e0090d72d28f45209c6f
3df086a94a9f91fb44795f152d59f70c38eccd5b7463d3e71a340b16b6a0644cf781
f125fce829410d851dda34b38501010000561fd25f64a2ee1152e3e33a3b4ad83d6b
368a8949addeff'
Acknowledgments
The interoperability minimum algorithms and parameters are based on
those available in [RFC9173].
Author's Address
Brian Sipos
The Johns Hopkins University Applied Physics Laboratory
11100 Johns Hopkins Rd.
Laurel, MD 20723
United States of America
Email: brian.sipos+ietf@gmail.com
Sipos Expires 3 December 2023 [Page 45]