Delay-Tolerant Networking E. Birrane
Internet-Draft K. McKeever
Intended status: Standards Track JHU/APL
Expires: January 2, 2018 July 1, 2017
Bundle Protocol Security Specification
draft-ietf-dtn-bpsec-05
Abstract
This document defines a security protocol providing end to end data
integrity and confidentiality services for the Bundle Protocol.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 2, 2018.
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Supported Security Services . . . . . . . . . . . . . . . 3
1.2. Specification Scope . . . . . . . . . . . . . . . . . . . 4
1.3. Related Documents . . . . . . . . . . . . . . . . . . . . 5
1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Design Decisions . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Block-Level Granularity . . . . . . . . . . . . . . . . . 6
2.2. Multiple Security Sources . . . . . . . . . . . . . . . . 7
2.3. Mixed Security Policy . . . . . . . . . . . . . . . . . . 7
2.4. User-Selected Cipher Suites . . . . . . . . . . . . . . . 8
2.5. Deterministic Processing . . . . . . . . . . . . . . . . 8
3. Security Blocks . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Block Definitions . . . . . . . . . . . . . . . . . . . . 8
3.2. Uniqueness . . . . . . . . . . . . . . . . . . . . . . . 9
3.3. Target Multiplicity . . . . . . . . . . . . . . . . . . . 9
3.4. Target Identification . . . . . . . . . . . . . . . . . . 10
3.5. Block Representation . . . . . . . . . . . . . . . . . . 10
3.6. Abstract Security Block . . . . . . . . . . . . . . . . . 11
3.7. Block Integrity Block . . . . . . . . . . . . . . . . . . 14
3.8. Block Confidentiality Block . . . . . . . . . . . . . . . 15
3.9. Block Interactions . . . . . . . . . . . . . . . . . . . 16
3.10. Cipher Suite Parameter and Result Identification . . . . 17
3.11. BSP Block Example . . . . . . . . . . . . . . . . . . . . 18
4. Canonical Forms . . . . . . . . . . . . . . . . . . . . . . . 19
5. Security Processing . . . . . . . . . . . . . . . . . . . . . 20
5.1. Bundles Received from Other Nodes . . . . . . . . . . . . 20
5.1.1. Receiving BCB Blocks . . . . . . . . . . . . . . . . 20
5.1.2. Receiving BIB Blocks . . . . . . . . . . . . . . . . 21
5.2. Bundle Fragmentation and Reassembly . . . . . . . . . . . 22
6. Key Management . . . . . . . . . . . . . . . . . . . . . . . 22
7. Security Policy Considerations . . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
8.1. Attacker Capabilities and Objectives . . . . . . . . . . 24
8.2. Attacker Behaviors and BPSec Mitigations . . . . . . . . 25
8.2.1. Eavesdropping Attacks . . . . . . . . . . . . . . . . 25
8.2.2. Modification Attacks . . . . . . . . . . . . . . . . 26
8.2.3. Topology Attacks . . . . . . . . . . . . . . . . . . 27
8.2.4. Message Injection . . . . . . . . . . . . . . . . . . 27
9. Cipher Suite Authorship Considerations . . . . . . . . . . . 28
10. Defining Other Security Blocks . . . . . . . . . . . . . . . 29
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
11.1. Bundle Block Types . . . . . . . . . . . . . . . . . . . 30
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
12.1. Normative References . . . . . . . . . . . . . . . . . . 30
12.2. Informative References . . . . . . . . . . . . . . . . . 31
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 31
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction
This document defines security features for the Bundle Protocol (BP)
[BPBIS] and is intended for use in Delay Tolerant Networks (DTNs) to
provide end-to-end security services.
The Bundle Protocol specification [BPBIS] defines DTN as referring to
"a networking architecture providing communications in and/or through
highly stressed environments" where "BP may be viewed as sitting at
the application layer of some number of constituent networks, forming
a store-carry-forward overlay network". The term "stressed"
environment refers to multiple challenging conditions including
intermittent connectivity, large and/or variable delays, asymmetric
data rates, and high bit error rates.
The BP might be deployed such that portions of the network cannot be
trusted, posing the usual security challenges related to
confidentiality and integrity. However, the stressed nature of the
BP operating environment imposes unique conditions where usual
transport security mechanisms may not be sufficient. For example,
the store-carry-forward nature of the network may require protecting
data at rest, preventing unauthorized consumption of critical
resources such as storage space, and operating without regular
contact with a centralized security oracle (such as a certificate
authority).
An end-to-end security service is needed that operates in all of the
environments where the BP operates.
1.1. Supported Security Services
BPSec provides end-to-end integrity and confidentiality services for
BP bundles.
Integrity services ensure that protected data within a bundle are not
changed from the time they are provided to the network to the time
they are delivered at their destination. Data changes may be caused
by processing errors, environmental conditions, or intentional
manipulation.
Confidentiality services ensure that protected data is unintelligible
to nodes in the DTN, except for authorized nodes possessing special
information. Confidentiality, in this context, applies to the
contents of protected data and does not extend to hiding the fact
that protected data exist in the bundle.
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NOTE: Hop-by-hop authentication is NOT a supported security service
in this specification, for three reasons.
1. The term "hop-by-hop" is ambiguous in a BP overlay, as nodes that
are adjacent in the overlay may not be adjacent in physical
connectivity. This condition is difficult or impossible to
detect and therefore hop-by-hop authentication is difficult or
impossible to enforce.
2. Networks in which BPSec may be deployed may have a mixture of
security-aware and not-security-aware nodes. Hop-by-hop
authentication cannot be deployed in a network if adjacent nodes
in the network have different security capabilities.
3. Hop-by-hop authentication is a special case of data integrity and
can be achieved with the integrity mechanisms defined in this
specification. Therefore, a separate authentication service is
not necessary.
1.2. Specification Scope
This document defines the security services provided by the BPSec.
This includes the data specification for representing these services
as BP extension blocks, and the rules for adding, removing, and
processing these blocks at various points during the bundle's
traversal of the DTN.
BPSec applies only to those nodes that implement it, known as
"security-aware" nodes. There might be other nodes in the DTN that
do not implement BPSec. While all nodes in a BP overlay can exchange
bundles, BPSec security operations can only happen at BPSec security-
aware nodes.
This specification does not address individual cipher suite
implementations. Different networking conditions and operational
considerations require varying strengths of security mechanism such
that mandating a cipher suite in this specification may result in too
much security for some networks and too little security in others.
It is expected that separate documents will be standardized to define
cipher suites compatible with BPSec, to include operational cipher
suites and interoperability cipher suites.
This specification does not address the implementation of security
policy and does not provide a security policy for the BPSec. Similar
to cipher suites, security policies are based on the nature and
capabilities of individual networks and network operational concepts.
This specification does provide policy considerations when building a
security policy.
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This specification does not address how to combine the BPSec security
blocks with other protocols, other BP extension blocks, or other best
practices to achieve security in any particular network
implementation.
1.3. Related Documents
This document is best read and understood within the context of the
following other DTN documents:
"Delay-Tolerant Networking Architecture" [RFC4838] defines the
architecture for DTNs and identifies certain security assumptions
made by existing Internet protocols that are not valid in a DTN.
The Bundle Protocol [BPBIS] defines the format and processing of
bundles, defines the extension block format used to represent BPSec
security blocks, and defines the canonicalization algorithms used by
this specification.
The Bundle Security Protocol [RFC6257] and Streamlined Bundle
Security Protocol [SBSP] documents introduced the concepts of using
BP extension blocks for security services in a DTN. The BPSec is a
continuation and refinement of these documents.
1.4. 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
[RFC2119].
This section defines terminology either unique to the BPSec or
otherwise necessary for understanding the concepts defined in this
specification.
o Bundle Source - the node which originates a bundle. The Node ID
of the BPA originating the bundle.
o Forwarder - any node that transmits a bundle in the DTN. The Node
ID of the Bundle Protocol Agent (BPA) that sent the bundle on its
most recent hop.
o Intermediate Receiver, Waypoint, or "Next Hop" - any node that
receives a bundle from a Forwarder that is not the Destination.
The Node ID of the BPA at any such node.
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o Path - the ordered sequence of nodes through which a bundle passes
on its way from Source to Destination. The path is not
necessarily known in advance by the bundle or any BPAs in the DTN.
o Security Block - a BPSec extension block in a bundle.
o Security Operation - the application of a security service to a
security target, notated as OP(security service, security target).
For example, OP(confidentiality, payload). Every security
operation in a bundle MUST be unique, meaning that a security
service can only be applied to a security target once in a bundle.
A security operation is implemented by a security block.
o Security Service - the security features supported by this
specification: integrity and confidentiality.
o Security Source - a bundle node that adds a security block to a
bundle. The Node ID of that node.
o Security Target - the block within a bundle that receives a
security-service as part of a security-operation.
2. Design Decisions
The application of security services in a DTN is a complex endeavor
that must consider physical properties of the network, policies at
each node, and various application security requirements. This
section identifies those desirable properties that guide design
decisions for this specification and are necessary for understanding
the format and behavior of the BPSec protocol.
2.1. Block-Level Granularity
Security services within this specification MUST allow different
blocks within a bundle to have different security services applied to
them.
Blocks within a bundle represent different types of information. The
primary block contains identification and routing information. The
payload block carries application data. Extension blocks carry a
variety of data that may augment or annotate the payload, or
otherwise provide information necessary for the proper processing of
a bundle along a path. Therefore, applying a single level and type
of security across an entire bundle fails to recognize that blocks in
a bundle may represent different types of information with different
security needs.
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For example, a payload block might be encrypted to protect its
contents and an extension block containing summary information
related to the payload might be integrity signed but unencrypted to
provide waypoints access to payload-related data without providing
access to the payload.
2.2. Multiple Security Sources
A bundle MAY have multiple security blocks and these blocks MAY have
different security sources.
The Bundle Protocol allows extension blocks to be added to a bundle
at any time during its existence in the DTN. When a waypoint adds a
new extension block to a bundle, that extension block may have
security services applied to it by that waypoint. Similarly, a
waypoint may add a security service to an existing extension block,
consistent with its security policy. For example, a node
representing a boundary between a trusted part of the network and an
untrusted part of the network may wish to apply payload encryption
for bundles leaving the trusted portion of the network.
When a waypoint adds a security service to the bundle, the waypoint
is the security source for that service. The security block(s) which
represent that service in the bundle may need to record this security
source as the bundle destination might need this information for
processing. For example, a destination node might interpret policy
as it related to security blocks as a function of the security source
for that block.
2.3. Mixed Security Policy
The security policy enforced by nodes in the DTN MAY differ.
Some waypoints may not be security aware and will not be able to
process security blocks. Therefore, security blocks MUST have their
processing flags set such that the block will be treated
appropriately by non-security-aware waypoints
Some waypoints will have security policies that require evaluating
security services even if they are not the bundle destination or the
final intended destination of the service. For example, a waypoint
may choose to verify an integrity service even though the waypoint is
not the bundle destination and the integrity service will be needed
by other node along the bundle's path.
Some waypoints will determine, through policy, that they are the
intended recipient of the security service and terminate the security
service in the bundle. For example, a gateway node may determine
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that, even though it is not the destination of the bundle, it should
verify and remove a particular integrity service or attempt to
decrypt a confidentiality service, before forwarding the bundle along
its path.
Some waypoints may understand security blocks but refuse to process
them unless they are the bundle destination.
2.4. User-Selected Cipher Suites
The security services defined in this specification rely on a variety
of cipher suites providing integrity signatures, cipher-text, and
other information necessary to populate security blocks. Users MAY
select different cipher suites to implement security services. For
example, some users might prefer a SHA2 hash function for integrity
whereas other users may prefer a SHA3 hash function instead. The
security services defined in this specification MUST provide a
mechanism for identifying what cipher suite has been used to populate
a security block.
2.5. Deterministic Processing
Whenever a node determines that it must process more than one
security block in a received bundle (either because the policy at a
waypoint states that it should process security blocks or because the
node is the bundle destination) the order in which security blocks
are processed MUST be deterministic. All nodes MUST impose this same
deterministic processing order for all security blocks. This
specification provides determinism in the application and evaluation
of security services, even when doing so results in a loss of
flexibility.
3. Security Blocks
3.1. Block Definitions
This specification defines two types of security block: the Block
Integrity Block (BIB) and the Block Confidentiality Block (BCB).
The BIB is used to ensure the integrity of its security target(s).
The integrity information in the BIB MAY be verified by any node
in between the BIB security source and the bundle destination.
Security-aware waypoints may add or remove BIBs from bundles in
accordance with their security policy.
The BCB indicates that the security target(s) have been encrypted
at the BCB security source in order to protect its content while
in transit. The BCB may be decrypted by security-aware nodes in
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the network, up to and including the bundle destination, as a
matter of security policy.
3.2. Uniqueness
Security operations in a bundle MUST be unique - the same security
service MUST NOT be applied to a security target more than once in a
bundle. Since a security operation is represented as a security
block, this limits what security blocks may be added to a bundle: if
adding a security block to a bundle would cause some other security
block to no longer represent a unique security operation then the new
block MUST NOT be added.
If multiple security blocks representing the same security operation
were allowed in a bundle at the same time, there would exist
ambiguity regarding block processing order and the property of
deterministic processing blocks would be lost.
Using the notation OP(service,target), several examples illustrate
this uniqueness requirement.
o Signing the payload twice: The two operations OP(integrity,
payload) and OP(integrity, payload) are redundant and MUST NOT
both be present in the same bundle at the same time.
o Signing different blocks: The two operations OP(integrity,
payload) and OP(integrity, extension_block_1) are not redundant
and both may be present in the same bundle at the same time.
Similarly, the two operations OP(integrity, extension_block_1) and
OP(integrity,extension_block_2) are also not redundant and may
both be present in the bundle at the same time.
o Different Services on same block: The two operations
OP(integrity,payload) and OP(confidentiality, payload) are not
inherently redundant and may both be present in the bundle at the
same time, pursuant to other processing rules in this
specification.
3.3. Target Multiplicity
Under special circumstances, a single security block may represent
multiple security operations as a way of reducing the overall number
of security blocks present in a bundle. In these circumstances,
reducing the number of security blocks in the bundle reduces the
amount of redundant information in the bundle.
A set of security operations may be represented by a single security
block if and only if the following conditions are true.
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o The security operations apply the same security service. For
example, they are all integrity operations or all confidentiality
operations.
o The cipher suite parameters and key information for the security
operations are identical.
o The security source for the security operations is the same.
Meaning the set of operations are being added/removed by the same
node.
o No security operations have the same security target, as that
would violate the need for security operations to be unique.
o None of the security operations conflict with security operations
already present in the bundle.
When representing multiple security operations in a single security
block, the information that is common across all operations is
represented once in the security block, and the information which is
different (e.g., the security targets) are represented individually.
When the security block is processed all security operations
represented by the security block MUST be applied/evaluated at that
time.
3.4. Target Identification
A security target is a block in the bundle to which a security
service applies. This target MUST be uniquely and unambiguously
identifiable when processing a security block. The definition of the
extension block header from [BPBIS] provides a "Block Number" field
suitable for this purpose. Therefore, a security target in a
security block MUST be represented as the Block Number of the target
block.
3.5. Block Representation
Each security block uses the Canonical Bundle Block Format as defined
in [BPBIS]. That is, each security block is comprised of the
following elements:
o Block Type Code
o Block Number
o Block Processing Control Flags
o CRC Type and CRC Field (if present)
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o Block Data Length
o Block Type Specific Data Fields
Security-specific information for a security block is captured in the
"Block Type Specific Data Fields".
3.6. Abstract Security Block
The structure of the security-specific portions of a security block
is identical for both the BIB and BCB Block Types. Therefore, this
section defines an Abstract Security Block (ASB) data structure and
discusses the definition, processing, and other constraints for using
this structure. An ASB is never directly instantiated within a
bundle, it is only a mechanism for discussing the common aspects of
BIB and BCB security blocks.
The fields of the ASB SHALL be as follows, listed in the order in
which they MUST appear.
Security Targets:
This field identifies the block(s) targetted by the security
operation(s) represented by this security block. Each target
block is represented by its unique Block Number. This field
SHALL be represented by a CBOR array of data items. Each
target within this CBOR array SHALL be represented by a CBOR
unsigned integer. This array MUST have at least 1 entry and
each entry MUST represent the Block Number of a block that
exists in the bundle. There MUST NOT be duplicate entries in
this array.
Cipher Suite Id:
This field identifies the cipher suite used to implement the
security service represented by this block and applied to each
security target. This field SHALL be represented by a CBOR
unsigned integer.
Cipher Suite Flags:
This field identifies which optional fields are present in the
security block. This field SHALL be represented as a CBOR
unsigned integer containing a bit field of 5 bits indicating
the presence or absence of other security block fields, as
follows.
Bit 1 (the most-significant bit, 0x10): reserved.
Bit 2 (0x08): reserved.
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Bit 3 (0x04): reserved.
Bit 4 (0x02): Security Source Present Flag.
Bit 5 (the least-significant bit, 0x01): Cipher Suite
Parameters Present Flag.
In this field, a value of 1 indicates that the associated
security block field MUST be included in the security block. A
value of 0 indicates that the associated security block field
MUST NOT be in the security block.
Security Source (Optional Field):
This field identifies the Endpoint that inserted the security
block in the bundle. If the security source field is not
present then the source MAY be inferred from other information,
such as the bundle source or the previous hop, as defined by
security policy. This field SHALL be represented by a CBOR
array in accordance with [BPBIS] rules for representing
Endpoint Identifiers (EIDs).
Cipher Suite Parameters (Optional Field):
This field captures one or more cipher suite parameters that
should be provided to security-aware nodes when processing the
security service described by this security block. This field
SHALL be represented by a CBOR array. Each entry in this array
is a single cipher suite parameter. A single cipher suite
parameter SHALL also be represented as a CBOR array comprising
a 2-tuple of the id and value of the parameter, as follows.
* Parameter Id. This field identifies which cipher suite
parameter is being specified. This field SHALL be
represented as a CBOR unsigned integer. Parameter ids are
selected as described in Section 3.10.
* Parameter Value. This field captures the value associated
with this parameter. This field SHALL be represented by the
applicable CBOR representation of the parameter, in
accordance with Section 3.10.
The logical layout of the cipher suite parameters array is
illustrated in Figure 1.
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+----------------+----------------+ +----------------+
| Parameter 1 | Parameter 2 | ... | Parameter N |
+------+---------+------+---------+ +------+---------+
| Id | Value | Id | Value | | Id | Value |
+------+---------+------+---------+ +------+---------+
Figure 1: Cipher Suite Parameters
Security Results:
This field captures the results of applying a security service
to the security targets of the security block. This field
SHALL be represented as a CBOR array of target results. Each
entry in this array represents the set of security results for
a specific security target. The target results MUST be ordered
identically to the Security Targets field of the security
block. This means that the first set of target results in this
array corresponds to the first entry in the Security Targets
field of the security block, and so on. There MUST be one
entry in this array for each entry in the Security Targets
field of the security block.
The set of security results for a target is also represented as
a CBOR array of individual results. An individual result is
represented as a 2-tuple of a result id and a result value,
defined as follows.
* Result Id. This field identifies which security result is
being specified. Some security results capture the primary
output of a cipher suite. Other security results contain
additional annotative information from cipher suite
processing. This field SHALL be represented as a CBOR
unsigned integer. Security result ids will be as specified
in Section 3.10.
* Result Value. This field captures the value associated with
the result. This field SHALL be represented by the
applicable CBOR representation of the result value, in
accordance with Section 3.10.
The logical layout of the security results array is illustrated
in Figure 2. In this figure there are N security targets for
this security block. The first security target contains M
results and the Nth security target contains K results.
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+------------------------------+ +------------------------------+
| Target 1 | | Target N |
+------------+----+------------+ +------------------------------+
| Result 1 | | Result M | ... | Result 1 | | Result K |
+----+-------+ .. +----+-------+ +----+-------+ .. +----+-------+
| Id | Value | | Id | Value | | Id | Value | | Id | Value |
+----+-------+ +----+-------+ +----+-------+ +----+-------+
Figure 2: Security Results
3.7. Block Integrity Block
A BIB is a bundle extension block with the following characteristics.
o The Block Type Code value is as specified in Section 11.1.
o The Block Type Specific Data Fields follow the structure of the
ASB.
o A security target listed in the Security Targets field MUST NOT
reference a security block defined in this specification (e.g., a
BIB or a BCB).
o The Cipher Suite Id MUST be documented as an end-to-end
authentication-cipher suite or as an end-to-end error-detection-
cipher suite.
o An EID-reference to the security source MAY be present. If this
field is not present, then the security source of the block SHOULD
be inferred according to security policy and MAY default to the
bundle source. The security source may also be specified as part
of key information described in Section 3.10.
Notes:
o It is RECOMMENDED that cipher suite designers carefully consider
the effect of setting flags that either discard the block or
delete the bundle in the event that this block cannot be
processed.
o Since OP(integrity, target) is allowed only once in a bundle per
target, it is RECOMMENDED that users wishing to support multiple
integrity signatures for the same target define a multi-signature
cipher suite.
o For some cipher suites, (e.g., those using asymmetric keying to
produce signatures or those using symmetric keying with a group
key), the security information MAY be checked at any hop on the
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way to the destination that has access to the required keying
information, in accordance with Section 3.9.
o The use of a generally available key is RECOMMENDED if custodial
transfer is employed and all nodes SHOULD verify the bundle before
accepting custody.
3.8. Block Confidentiality Block
A BCB is a bundle extension block with the following characteristics.
The Block Type Code value is as specified in Section 11.1.
The Block Processing Control flags value can be set to whatever
values are required by local policy, except that this block MUST
have the "replicate in every fragment" flag set if the target of
the BCB is the Payload Block. Having that BCB in each fragment
indicates to a receiving node that the payload portion of each
fragment represents cipher-text.
The Block Type Specific Data Fields follow the structure of the
ASB.
A security target listed in the Security Targets field MAY
reference the payload block, a non-security extension block, or a
BIB block. A BCB MUST NOT include another BCB as a security
target. A BCB MUST NOT target the primary block.
The Cipher Suite Id MUST be documented as a confidentiality cipher
suite.
Any additional bytes generated from applying the cipher suite to a
security target (such as additional authenticated text) MAY be
placed in an appropriate security result (e.g., an Integrity Check
Value) in accordance with cipher suite and security policy.
An EID-reference to the security source MAY be present. If this
field is not present, then the security source of the block SHOULD
be inferred according to security policy and MAY default to the
bundle source. The security source may also be specified as part
of key information described in Section 3.10.
The BCB modifies the contents of its security target(s). When a BCB
is applied, the security target body data are encrypted "in-place".
Following encryption, the security target Block Type Specific Data
Fields contains cipher-text, not plain-text. Other block fields
remain unmodified, with the exception of the Block Data Length field,
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which may be changed if the BCB is allowed to change the length of
the block (see below).
Fragmentation, reassembly, and custody transfer are adversely
affected by a change in size of the payload block due to ambiguity
about what byte range of the block is actually in any particular
fragment. Therefore, when the security target of a BCB is the bundle
payload, the BCB MUST NOT alter the size of the payload block body
data. This "in-place" encryption allows fragmentation, reassembly,
and custody transfer to operate without knowledge of whether or not
encryption has occurred.
If a BCB cannot alter the size of the security target (e.g., the
security target is the payload block or block length modifications
are disallowed by policy) then differences in the size of the cipher-
text and plain-text MUST be handled in the following way. If the
cipher-text is shorter in length than the plain-text, padding must be
used in accordance with the cipher suite policy. If the cipher-text
is larger than the plain-text, overflow bytes MUST be placed in
overflow parameters in the Security Result field.
Notes:
o It is RECOMMENDED that cipher suite designers carefully consider
the effect of setting flags that either discard the block or
delete the bundle in the event that this block cannot be
processed.
o The BCB block processing control flags MAY be set independently
from the processing control flags of the security target(s). The
setting of such flags SHOULD be an implementation/policy decision
for the encrypting node.
o A BCB MAY include information as part of additional authenticated
data to address parts of the target block that are not converted
to cipher-text.
3.9. Block Interactions
The security block types defined in this specification are designed
to be as independent as possible. However, there are some cases
where security blocks may share a security target creating processing
dependencies.
If confidentiality is being applied to a target that already has
integrity applied to it, then an undesirable condition occurs where a
security aware waypoint would be unable to check the integrity result
of a block because the block contents have been encrypted after the
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integrity signature was generated. To address this concern, the
following processing rules MUST be followed.
o If confidentiality is to be applied to a target, it MUST also be
applied to any integrity operation already defined for that
target. This means that if a BCB is added to encrypt a block,
another BCB MUST also be added to encrypt a BIB also targeting
that block.
o An integrity operation MUST NOT be applied to a security target if
a BCB in the bundle shares the same security target. This
prevents ambiguity in the order of evaluation when receiving a BIB
and a BCB for a given security target.
o An integrity value MUST NOT be evaluated if the BIB providing the
integrity value is the security target of an existing BCB block in
the bundle. In such a case, the BIB data contains cipher-text as
it has been encrypted.
o An integrity value MUST NOT be evaluated if the security target of
the BIB is also the security target of a BCB in the bundle. In
such a case, the security target data contains cipher-text as it
has been encrypted.
o As mentioned in Section 3.7, a BIB MUST NOT have a BCB as its
security target. BCBs may embed integrity results as part of
security results.
These restrictions on block interactions impose a necessary ordering
when applying security operations within a bundle. Specifically, for
a given security target, BIBs MUST be added before BCBs. This
ordering MUST be preserved in cases where the current BPA is adding
all of the security blocks for the bundle or whether the BPA is a
waypoint adding new security blocks to a bundle that already contains
security blocks.
3.10. Cipher Suite Parameter and Result Identification
Cipher suite parameters and security results each represent multiple
distinct pieces of information in a security block. Each piece of
information is assigned an identifier and a CBOR encoding.
Identifiers MUST be unique for a given cipher suite but do not need
to be unique across all cipher suites. Therefore, parameter ids and
security result ids are specified in the context of a cipher suite
definition.
Individual BPSec cipher suites SHOULD use existing registries of
identifiers and CBOR encodings, such as those defined in [COSE],
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whenever possible. Cipher suites MAY define their own identifiers
and CBOR encodings when necessary.
A cipher suite MAY include multiple instances of the same identifier
for a parameter or result in a security block. Parameters and
results are represented using CBOR, and any identification of a new
parameter or result MUST include how the value will be represented
using the CBOR specification. Ids themselves are always represented
as a CBOR unsigned integer.
3.11. BSP Block Example
An example of BPSec blocks applied to a bundle is illustrated in
Figure 3. In this figure the first column represents blocks within a
bundle and the second column represents the Block Number for the
block, using the terminology B1...Bn for the purpose of illustration.
Block in Bundle ID
+===================================+====+
| Primary Block | B1 |
+-----------------------------------+----+
| BIB | B2 |
| OP(integrity, target=B1) | |
+-----------------------------------+----+
| BCB | B3 |
| OP(confidentiality, target=B4) | |
+-----------------------------------+----+
| Extension Block | B4 |
+-----------------------------------+----+
| BIB | B5 |
| OP(integrity, target=B6) | |
+-----------------------------------+----+
| Extension Block | B6 |
+-----------------------------------+----+
| BCB | B7 |
| OP(confidentiality,targets=B8,B9) | |
+-----------------------------------+----+
| BIB (encrypted by B7) | B8 |
| OP(integrity, target=B9) | |
+-----------------------------------+----|
| Payload Block | B9 |
+-----------------------------------+----+
Figure 3: Sample Use of BPSec Blocks
In this example a bundle has four non-security-related blocks: the
primary block (B1), two extension blocks (B4,B6), and a payload block
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(B9). The following security applications are applied to this
bundle.
o An integrity signature applied to the canonicalized primary block.
This is accomplished by a single BIB (B2).
o Confidentiality for the first extension block (B4). This is
accomplished by a BCB block (B3).
o Integrity for the second extension block (B6). This is
accomplished by a BIB block (B5). NOTE: If the extension block B6
contains a representation of the serialized bundle (such as a hash
over all blocks in the bundle at the time of its last
transmission) then the BIB block is also providing an
authentication service.
o An integrity signature on the payload (B10). This is accomplished
by a BIB block (B8).
o Confidentiality for the payload block and it's integrity
signature. This is accomplished by a BCB block, B7, encrypting B8
and B9. In this case, the security source, key parameters, and
service are identical, so a single security block MAY be used for
this purpose, rather than requiring two BCBs one to encrypt B8 and
one to encrypt B9.
4. Canonical Forms
Security services require consistency and determinism in how
information is presented to cipher suites at the security source and
at a receiving node. For example, integrity services require that
the same target information (e.g., the same bits in the same order)
is provided to the cipher suite when generating an original signature
and when generating a comparison signature. Canonicalization
algorithms are used to construct a stable, end-to-end bit
representation of a target block.
Canonical forms are not transmitted, they are used to generate input
to a cipher suite for security processing at a security-aware node.
The canonicalization of the primary block is as specified in [BPBIS].
All non-primary blocks share the same block structure and are
canonicalized as specified in [BPBIS] with the following exception.
o If the service being applied is a confidentiality service, then
the Block Type Code, Block Number, Block Processing Control Flags,
CRC Type and CRC Field (if present), and Block Data Length fields
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MUST NOT be included in the canonicalization. Confidentiality
services are used solely to convert the Block Type Specific Data
Fields from plain-text to cipher-text.
o Reserved flags MUST NOT be included in any canonicalization as it
is not known if those flags will change in transit.
These canonicalization algorithms assume that Endpoint IDs do not
change from the time at which a security source adds a security block
to a bundle and the time at which a node processes that security
block.
Cipher suites MAY define their own canonicalization algorithms and
require the use of those algorithms over the ones provided in this
specification. In the event of conflicting canonicalization
algorithms, cipher suite algorithms take precedence over this
specification.
5. Security Processing
This section describes the security aspects of bundle processing.
5.1. Bundles Received from Other Nodes
Security blocks MUST be processed in a specific order when received
by a security-aware node. The processing order is as follows.
o All BCB blocks in the bundle MUST be evaluated prior to evaluating
any BIBs in the bundle. When BIBs and BCBs share a security
target, BCBs MUST be evaluated first and BIBs second.
5.1.1. Receiving BCB Blocks
If a received bundle contains a BCB, the receiving node MUST
determine whether it has the responsibility of decrypting the BCB
security target and removing the BCB prior to delivering data to an
application at the node or forwarding the bundle.
If the receiving node is the destination of the bundle, the node MUST
decrypt any BCBs remaining in the bundle. If the receiving node is
not the destination of the bundle, the node MAY decrypt the BCB if
directed to do so as a matter of security policy.
If the security policy of a security-aware node specifies that a
bundle should have applied confidentiality to a specific security
target and no such BCB is present in the bundle, then the node MUST
process this security target in accordance with the security policy.
This MAY involve removing the security target from the bundle. If
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the removed security target is the payload block, the bundle MAY be
discarded.
If an encrypted payload block cannot be decrypted (i.e., the
decryption key cannot be deduced or decryption fails), then the
bundle MUST be discarded and processed no further. If an encrypted
security target other than the payload block cannot be decrypted then
the associated security target and all security blocks associated
with that target MUST be discarded and processed no further. In both
cases, requested status reports (see [BPBIS]) MAY be generated to
reflect bundle or block deletion.
When a BCB is decrypted, the recovered plain-text MUST replace the
cipher-text in the security target Block Type Specific Data Fields.
If the Block Data Length field was modified at the time of encryption
it MUST be updated to reflect the decrypted block length.
If a BCB contains multiple security targets, all security targets
MUST be processed when the BCB is processed. Errors and other
processing steps SHALL be made as if each security target had been
represented by an individual BCB with a single security target.
5.1.2. Receiving BIB Blocks
If a received bundle contains a BIB, the receiving node MUST
determine whether it has the final responsibility of verifying the
BIB security target and removing it prior to delivering data to an
application at the node or forwarding the bundle. If a BIB check
fails, the security target has failed to authenticate and the
security target SHALL be processed according to the security policy.
A bundle status report indicating the failure MAY be generated.
Otherwise, if the BIB verifies, the security target is ready to be
processed for delivery.
A BIB MUST NOT be processed if the security target of the BIB is also
the security target of a BCB in the bundle. Given the order of
operations mandated by this specification, when both a BIB and a BCB
share a security target, it means that the security target MUST have
been encrypted after it was integrity signed and, therefore, the BIB
cannot be verified until the security target has been decrypted by
processing the BCB.
If the security policy of a security-aware node specifies that a
bundle should have applied integrity to a specific security target
and no such BIB is present in the bundle, then the node MUST process
this security target in accordance with the security policy. This
MAY involve removing the security target from the bundle. If the
removed security target is the payload or primary block, the bundle
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MAY be discarded. This action may occur at any node that has the
ability to verify an integrity signature, not just the bundle
destination.
If a receiving node does not have the final responsibility of
verifying the BIB it MAY still attempt to verify the BIB to prevent
the needless forwarding of corrupt data. If the check fails, the
node SHALL process the security target in accordance to local
security policy. It is RECOMMENDED that if a payload integrity check
fails at a waypoint that it is processed in the same way as if the
check fails at the destination. If the check passes, the node MUST
NOT remove the BIB prior to forwarding.
If a BIB contains multiple security targets, all security targets
MUST be processed if the BIB is processed by the Node. Errors and
other processing steps SHALL be made as if each security target had
been represented by an individual BIB with a single security target.
5.2. Bundle Fragmentation and Reassembly
If it is necessary for a node to fragment a bundle payload, and
security services have been applied to that bundle, the fragmentation
rules described in [BPBIS] MUST be followed. As defined there and
summarized here for completeness, only the payload block may be
fragmented; security blocks, like all extension blocks, can never be
fragmented.
Due to the complexity of payload block fragmentation, including the
possibility of fragmenting payload block fragments, integrity and
confidentiality operations are not to be applied to a bundle
representing a fragment. Specifically, a BCB or BIB MUST NOT be
added to a bundle if the "Bundle is a Fragment" flag is set in the
Bundle Processing Control Flags field.
Security processing in the presence of payload block fragmentation
MAY be handled by other mechanisms outside of the BPSec protocol or
by applying BPSec blocks in coordination with an encapsulation
mechanism.
6. Key Management
There exist a myriad of ways to establish, communicate, and otherwise
manage key information in a DTN. Certain DTN deployments might
follow established protocols for key management whereas other DTN
deployments might require new and novel approaches. BPSec assumes
that key management is handled as a separate part of network
management and this specification neither defines nor requires a
specific key management strategy.
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7. Security Policy Considerations
When implementing BPSec, several policy decisions must be considered.
This section describes key policies that affect the generation,
forwarding, and receipt of bundles that are secured using this
specification. No single set of policy decisions is envisioned to
work for all secure DTN deployments.
o If a bundle is received that contains more than one security
operation, in violation of BPSec, then the BPA must determine how
to handle this bundle. The bundle may be discarded, the block
affected by the security operation may be discarded, or one
security operation may be favored over another.
o BPAs in the network MUST understand what security operations they
should apply to bundles. This decision may be based on the source
of the bundle, the destination of the bundle, or some other
information related to the bundle.
o If a waypoint has been configured to add a security operation to a
bundle, and the received bundle already has the security operation
applied, then the receiver MUST understand what to do. The
receiver may discard the bundle, discard the security target and
associated BPSec blocks, replace the security operation, or some
other action.
o It is recommended that security operations only be applied to the
blocks that absolutely need them. If a BPA were to apply security
operations such as integrity or confidentiality to every block in
the bundle, regardless of need, there could be downstream errors
processing blocks whose contents must be inspected or changed at
every hop along the path.
o Adding a BIB to a security target that has already been encrypted
by a BCB is not allowed. If this condition is likely to be
encountered, there are (at least) three possible policies that
could handle this situation.
1. At the time of encryption, an integrity signature may be
generated and added to the BCB for the security target as
additional information in the security result field.
2. The encrypted block may be replicated as a new block and
integrity signed.
3. An encapsulation scheme may be applied to encapsulate the
security target (or the entire bundle) such that the
encapsulating structure is, itself, no longer the security
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target of a BCB and may therefore be the security target of a
BIB.
8. Security Considerations
Given the nature of DTN applications, it is expected that bundles may
traverse a variety of environments and devices which each pose unique
security risks and requirements on the implementation of security
within BPSec. For these reasons, it is important to introduce key
threat models and describe the roles and responsibilities of the
BPSec protocol in protecting the confidentiality and integrity of the
data against those threats. This section provides additional
discussion on security threats that BPSec will face and describes how
BPSec security mechanisms operate to mitigate these threats.
It should be noted that BPSEC addresses only the security of data
traveling over the DTN, not the underlying DTN itself. Additionally,
BPSec addresses neither the fitness of externally-defined
cryptographic methods nor the security of their implementation. It
is the responsibility of the BPSec implementer that appropriate
algorithms and methods are chosen. Furthermore, the BPSec protocol
does not address threats which share computing resources with the DTN
and/or BPSec software implementations. These threats may be
malicious software or compromised libraries which intend to intercept
data or recover cryptographic material. Here, it is the
responsibility of the BPSec implementer to ensure that any
cryptographic material, including shared secret or private keys, is
protected against access within both memory and storage devices.
The threat model described here is assumed to have a set of
capabilities identical to those described by the Internet Threat
Model in [RFC3552], but the BPSec threat model is scoped to
illustrate threats specific to BPSec operating within DTN
environments and therefore focuses on man-in-the-middle (MITM)
attackers.
8.1. Attacker Capabilities and Objectives
BPSec was designed to protect against MITM threats which may have
access to a bundle during transit from its source, Alice, to its
destination, Bob. A MITM node, Mallory, is a non-cooperative node
operating on the DTN between Alice and Bob that has the ability to
receive bundles, examine bundles, modify bundles, forward bundles,
and generate bundles at will in order to compromise the
confidentiality or integrity of data within the DTN. For the
purposes of this section, any MITM node is assumed to effectively be
security-aware even if it does not implement the BPSec protocol.
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There are three classes of MITM nodes which are differentiated based
on their access to cryptographic material:
o Unprivileged Node: Mallory has not been provisioned within the
secure environment and only has access to cryptographic material
which has been publicly-shared.
o Legitimate Node: Mallory is within the secure environment and
therefore has access to cryptographic material which has been
provisioned to Mallory (i.e., K_M) as well as material which has
been publicly-shared.
o Privileged Node: Mallory is a privileged node within the secure
environment and therefore has access to cryptographic material
which has been provisioned to Mallory, Alice and/or Bob (i.e.
K_M, K_A, and/or K_B) as well as material which has been publicly-
shared.
If Mallory is operating as a privileged node, this is tantamount to
compromise; BPSec does not provide mechanisms to detect or remove
Mallory from the DTN or BPSec secure environment. It is up to the
BPSec implementer or the underlying cryptographic mechanisms to
provide appropriate capabilities if they are needed. It should also
be noted that if the implementation of BPSec uses a single set of
shared cryptographic material for all nodes, a legitimate node is
equivalent to a privileged node because K_M == K_A == K_B.
A special case of the legitimate node is when Mallory is either Alice
or Bob (i.e., K_M == K_A or K_M == K_B). In this case, Mallory is
able to impersonate traffic as either Alice or Bob, which means that
traffic to and from that node can be decrypted and encrypted,
respectively. Additionally, messages may be signed as originating
from one of the endpoints.
8.2. Attacker Behaviors and BPSec Mitigations
8.2.1. Eavesdropping Attacks
Once Mallory has received a bundle, she is able to examine the
contents of that bundle and attempt to recover any protected data or
cryptographic keying material from the blocks contained within. The
protection mechanism that BPSec provides against this action is the
BCB, which encrypts the contents of its security target, providing
confidentiality of the data. Of course, it should be assumed that
Mallory is able to attempt offline recovery of encrypted data, so the
cryptographic mechanisms selected to protect the data should provide
a suitable level of protection.
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When evaluating the risk of eavesdropping attacks, it is important to
consider the lifetime of bundles on a DTN. Depending on the network,
bundles may persist for days or even years. If a bundle does persist
on the network for years and the cipher suite used for a BCB provides
inadequate protection, Mallory may be able to recover the protected
data before that bundle reaches its intended destination.
8.2.2. Modification Attacks
As a node participating in the DTN between Alice and Bob, Mallory
will also be able to modify the received bundle, including non-BPSec
data such as the primary block, payload blocks, or block processing
control flags as defined in [BPBIS]. Mallory will be able to
undertake activities which include modification of data within the
blocks, replacement of blocks, addition of blocks, or removal of
blocks. Within BPSec, both the BIB and BCB provide integrity
protection mechanisms to detect or prevent data manipulation attempts
by Mallory.
The BIB provides that protection to another block which is its
security target. The cryptographic mechanisms used to generate the
BIB should be strong against collision attacks and Mallory should not
have access to the cryptographic material used by the originating
node to generate the BIB (e.g., K_A). If both of these conditions
are true, Mallory will be unable to modify the security target or the
BIB and lead Bob to validate the security target as originating from
Alice.
Since BPSec security operations are implemented by placing blocks in
a bundle, there is no in-band mechanism for detecting or correcting
certain cases where Mallory removes blocks from a bundle. If Mallory
removes a BCB block, but keeps the security target, the security
target remains encrypted and there is a possibility that there may no
longer be sufficient information to decrypt the block at its
destination. If Mallory removes both a BCB (or BIB) and its security
target there is no evidence left in the bundle of the security
operation. Similarly, if Mallory removes the BIB but not the
security target there is no evidence left in the bundle of the
security operation. In each of these cases, the implementation of
BPSec MUST be combined with policy configuration at endpoints in the
network which describe the expected and required security operations
that must be applied on transmission and are expected to be present
on receipt. This or other similar out-of-band information is
required to correct for removal of security information in the
bundle.
A limitation of the BIB may exist within the implementation of BIB
validation at the destination node. If Mallory is a legitimate node
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within the DTN, the BIB generated by Alice with K_A can be replaced
with a new BIB generated with K_M and forwarded to Bob. If Bob is
only validating that the BIB was generated by a legitimate user, Bob
will acknowledge the message as originating from Mallory instead of
Alice. In order to provide verifiable integrity checks, both a BIB
and BCB should be used. Alice creates a BIB with the protected data
block as the security target and then creates a BCB with both the BIB
and protected data block as its security targets. In this
configuration, since Mallory is only a legitimate node and does not
have access to Alice's key K_A, Mallory is unable to decrypt the BCB
and replace the BIB.
8.2.3. Topology Attacks
If Mallory is in a MITM position within the DTN, she is able to
influence how any bundles that come to her may pass through the
network. Upon receiving and processing a bundle that must be routed
elsewhere in the network, Mallory has three options as to how to
proceed: not forward the bundle, forward the bundle as intended, or
forward the bundle to one or more specific nodes within the network.
Attacks that involve re-routing the packets throughout the network
are essentially a special case of the modification attacks described
in this section where the attacker is modifying fields within the
primary block of the bundle. Given that BPSec cannot encrypt the
contents of the primary block, alternate methods must be used to
prevent this situation. These methods MAY include requiring BIBs for
primary blocks, using encapsulation, or otherwise strategically
manipulating primary block data. The specifics of any such
mitigation technique are specific to the implementation of the
deploying network and outside of the scope of this document.
Furthermore, routing rules and policies may be useful in enforcing
particular traffic flows to prevent topology attacks. While these
rules and policies may utilize some features provided by BPSec, their
definition is beyond the scope of this specification.
8.2.4. Message Injection
Mallory is also able to generate new bundles and transmit them into
the DTN at will. These bundles may either be copies or slight
modifications of previously-observed bundles (i.e., a replay attack)
or entirely new bundles generated based on the Bundle Protocol,
BPSec, or other bundle-related protocols. With these attacks
Mallory's objectives may vary, but may be targeting either the bundle
protocol or application-layer protocols conveyed by the bundle
protocol.
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BPSec relies on cipher suite capabilities to prevent replay or forged
message attacks. A BCB used with appropriate cryptographic
mechanisms (e.g., a counter-based cipher mode) may provide replay
protection under certain circumstances. Alternatively, application
data itself may be augmented to include mechanisms to assert data
uniqueness and then protected with a BIB, a BCB, or both along with
other block data. In such a case, the receiving node would be able
to validate the uniqueness of the data.
9. Cipher Suite Authorship Considerations
Cipher suite developers or implementers should consider the diverse
performance and conditions of networks on which the Bundle Protocol
(and therefore BPSec) will operate. Specifically, the delay and
capacity of delay-tolerant networks can vary substantially. Cipher
suite developers should consider these conditions to better describe
the conditions when those suites will operate or exhibit
vulnerability, and selection of these suites for implementation
should be made with consideration to the reality. There are key
differences that may limit the opportunity to leverage existing
cipher suites and technologies that have been developed for use in
traditional, more reliable networks:
o Data Lifetime: Depending on the application environment, bundles
may persist on the network for extended periods of time, perhaps
even years. Cryptographic algorithms should be selected to ensure
protection of data against attacks for a length of time reasonable
for the application.
o One-Way Traffic: Depending on the application environment, it is
possible that only a one-way connection may exist between two
endpoints, or if a two-way connection does exist, the round-trip
time may be extremely large. This may limit the utility of
session key generation mechanisms, such as Diffie-Hellman, as a
two-way handshake may not be feasible or reliable.
o Opportunistic Access: Depending on the application environment, a
given endpoint may not be guaranteed to be accessible within a
certain amount of time. This may make asymmetric cryptographic
architectures which rely on a key distribution center or other
trust center impractical under certain conditions.
When developing new cipher suites for use with BPSec, the following
information SHOULD be considered for inclusion in these
specifications.
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o Cipher Suite Parameters. Cipher suites MUST define their
parameter ids, the data types of those parameters, and their CBOR
encoding.
o Security Results. Cipher suites MUST define their security result
ids, the data types of those results, and their CBOR encoding.
o New Canonicalizations. Cipher suites MAY define new
canonicalization algorithms as necessary.
10. Defining Other Security Blocks
Other security blocks (OSBs) may be defined and used in addition to
the security blocks identified in this specification. Both the usage
of BIB, BCB, and any future OSBs MAY co-exist within a bundle and MAY
be considered in conformance with BPSec if each of the following
requirements are met by any future identified security blocks.
o Other security blocks (OSBs) MUST NOT reuse any enumerations
identified in this specification, to include the block type codes
for BIB and BCB.
o An OSB definition MUST state whether it can be the target of a BIB
or a BCB. The definition MUST also state whether the OSB can
target a BIB or a BCB.
o An OSB definition MUST provide a deterministic processing order in
the event that a bundle is received containing BIBs, BCBs, and
OSBs. This processing order MUST NOT alter the BIB and BCB
processing orders identified in this specification.
o An OSB definition MUST provide a canonicalization algorithm if the
default non-primary-block canonicalization algorithm cannot be
used to generate a deterministic input for a cipher suite. This
requirement MAY be waived if the OSB is defined so as to never be
the security target of a BIB or a BCB.
o An OSB definition MAY NOT require any behavior of a BPSEC-BPA that
is in conflict with the behavior identified in this specification.
In particular, the security processing requirements imposed by
this specification MUST be consistent across all BPSEC-BPAs in a
network.
o The behavior of an OSB when dealing with fragmentation MUST be
specified and MUST NOT lead to ambiguous processing states. In
particular, an OSB definition should address how to receive and
process an OSB in a bundle fragment that may or may not also
contain its security target. An OSB definition should also
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address whether an OSB may be added to a bundle marked as a
fragment.
Additionally, policy considerations for the management, monitoring,
and configuration associated with blocks SHOULD be included in any
OSB definition.
NOTE: The burden of showing compliance with processing rules is
placed upon the standards defining new security blocks and the
identification of such blocks shall not, alone, require maintenance
of this specification.
11. IANA Considerations
A registry of cipher suite identifiers will be required.
11.1. Bundle Block Types
This specification allocates two block types from the existing
"Bundle Block Types" registry defined in [RFC6255] .
Additional Entries for the Bundle Block-Type Codes Registry:
+-------+-----------------------------+---------------+
| Value | Description | Reference |
+-------+-----------------------------+---------------+
| TBD | Block Integrity Block | This document |
| TBD | Block Confidentiality Block | This document |
+-------+-----------------------------+---------------+
Table 1
12. References
12.1. Normative References
[BPBIS] Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol",
draft-ietf-dtn-bpbis-06 (work in progress), July 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<http://www.rfc-editor.org/info/rfc3552>.
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[RFC6255] Blanchet, M., "Delay-Tolerant Networking Bundle Protocol
IANA Registries", RFC 6255, May 2011.
12.2. Informative References
[COSE] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
draft-ietf-cose-msg-24 (work in progress), November 2016.
[RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
Networking Architecture", RFC 4838, April 2007.
[RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell,
"Bundle Security Protocol Specification", RFC 6257, May
2011.
[SBSP] Birrane, E., "Streamlined Bundle Security Protocol",
draft-birrane-dtn-sbsp-01 (work in progress), October
2015.
Appendix A. Acknowledgements
The following participants contributed technical material, use cases,
and useful thoughts on the overall approach to this security
specification: Scott Burleigh of the Jet Propulsion Laboratory, Amy
Alford and Angela Hennessy of the Laboratory for Telecommunications
Sciences, and Angela Dalton and Cherita Corbett of the Johns Hopkins
University Applied Physics Laboratory.
Authors' Addresses
Edward J. Birrane, III
The Johns Hopkins University Applied Physics Laboratory
11100 Johns Hopkins Rd.
Laurel, MD 20723
US
Phone: +1 443 778 7423
Email: Edward.Birrane@jhuapl.edu
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Kenneth McKeever
The Johns Hopkins University Applied Physics Laboratory
11100 Johns Hopkins Rd.
Laurel, MD 20723
US
Phone: +1 443 778 2237
Email: Ken.McKeever@jhuapl.edu
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