Secure Command Mode(s)

Provide additional protection modes for commanding the spacecraft. These can be where the spacecraft will restrict command lock based on geographic location of ground stations, special operational modes within the flight software, or even temporal controls where the spacecraft will only accept commands during certain times.

Best Segment for Countermeasure Deployment

Space Segment

NIST Rev5 Controls

D3FEND Techniques

D3FEND Artifacts

ISO 27001

NASA Best Practice Guide

ESA Space Shield Mitigation

M2069

Related MITRE EMB3D Mitigations

No related MITRE EMB3D Mitigations

ID: CM0055

Created: 2022/10/19

Last Modified: 2023/11/29

Techniques Addressed by Countermeasure

ID		Name	Description
IA-0003		Crosslink via Compromised Neighbor	Threat actors may compromise a victim spacecraft via the crosslink communications of a neighboring spacecraft that has been compromised. spacecraft in close proximity are able to send commands back and forth. Threat actors may be able to leverage this access to compromise other spacecraft once they have access to another that is nearby.
IA-0004		Secondary/Backup Communication Channel	Threat actors may compromise alternative communication pathways which may not be as protected as the primary pathway. Depending on implementation the contingency communication pathways/solutions may lack the same level of security (i.e., physical security, encryption, authentication, etc.) which if forced to use could provide a threat actor an opportunity to launch attacks. Typically these would have to be coupled with other denial of service techniques on the primary pathway to force usage of secondary pathways.
	.01	Ground Station	Threat actors may establish a foothold within the backup ground/mission operations center (MOC) and then perform attacks to force primary communication traffic through the backup communication channel so that other TTPs can be executed (man-in-the-middle, malicious commanding, malicious code, etc.). While an attacker would not be required to force the communications through the backup channel vice waiting until the backup is used for various reasons. Threat actors can also utilize compromised ground stations to chain command execution and payload delivery across geo-separated ground stations to extend reach and maintain access on spacecraft. The backup ground/MOC should be considered a viable attack vector and the appropriate/equivalent security controls from the primary communication channel should be on the backup ground/MOC as well.
IA-0007		Compromise Ground System	Threat actors may initially compromise the ground system in order to access the target spacecraft. Once compromised, the threat actor can perform a multitude of initial access techniques, including replay, compromising FSW deployment, compromising encryption keys, and compromising authentication schemes. Threat actors may also perform further reconnaissance within the system to enumerate mission networks and gather information related to ground station logical topology, missions ran out of said ground station, birds that are in-band of targeted ground stations, and other mission system capabilities.
	.01	Compromise On-Orbit Update	Threat actors may manipulate and modify on-orbit updates before they are sent to the target spacecraft. This attack can be done in a number of ways, including manipulation of source code, manipulating environment variables, on-board table/memory values, or replacing compiled versions with a malicious one.
	.02	Malicious Commanding via Valid GS	Threat actors may compromise target owned ground systems components (e.g., front end processors, command and control software, etc.) that can be used for future campaigns or to perpetuate other techniques. These ground systems components have already been configured for communications to the victim spacecraft. By compromising this infrastructure, threat actors can stage, launch, and execute an operation. Threat actors may utilize these systems for various tasks, including Execution and Exfiltration.
IA-0008		Rogue External Entity	Threat actors may gain access to a victim spacecraft through the use of a rogue external entity. With this technique, the threat actor does not need access to a legitimate ground station or communication site.
	.01	Rogue Ground Station	Threat actors may gain access to a victim spacecraft through the use of a rogue ground system. With this technique, the threat actor does not need access to a legitimate ground station or communication site.
	.02	Rogue Spacecraft	Threat actors may gain access to a target spacecraft using their own spacecraft that has the capability to maneuver within close proximity to a target spacecraft to carry out a variety of TTPs (i.e., eavesdropping, side-channel, etc.). Since many of the commercial and military assets in space are tracked, and that information is publicly available, attackers can identify the location of space assets to infer the best positioning for intersecting orbits. Proximity operations support avoidance of the larger attenuation that would otherwise affect the signal when propagating long distances, or environmental circumstances that may present interference.
EX-0001		Replay	Replay attacks involve threat actors recording previously recorded data streams and then resending them at a later time. This attack can be used to fingerprint systems, gain elevated privileges, or even cause a denial of service.
	.01	Command Packets	Threat actors may interact with the victim spacecraft by replaying captured commands to the spacecraft. While not necessarily malicious in nature, replayed commands can be used to overload the target spacecraft and cause it's onboard systems to crash, perform a DoS attack, or monitor various responses by the spacecraft. If critical commands are captured and replayed, thruster fires, then the impact could impact the spacecraft's attitude control/orbit.
DE-0004		Masquerading	Threat actors may gain access to a victim spacecraft by masquerading as an authorized entity. This can be done several ways, including through the manipulation of command headers, spoofing locations, or even leveraging Insider's access (i.e., Insider Threat)
LM-0003		Constellation Hopping via Crosslink	Threat actors may attempt to command another neighboring spacecraft via crosslink. spacecraft in close proximity are often able to send commands back and forth. Threat actors may be able to leverage this access to compromise another spacecraft.
EXF-0001		Replay	Threat actors may exfiltrate data by replaying commands and capturing the telemetry or payload data as it is sent down. One scenario would be the threat actor replays commands to downlink payload data once the spacecraft is within certain location so the data can be intercepted on the downlink by threat actor ground terminals.

Space Threats Addressed by Countermeasure

ID	Description
SV-CF-2	Eavesdropping (RF and proximity)
SV-AC-1	Attempting access to an access-controlled system resulting in unauthorized access
SV-AC-2	Replay of recorded authentic communications traffic at a later time with the hope that the authorized communications will provide data or some other system reaction
SV-CF-1	Tapping of communications links (wireline, RF, network) resulting in loss of confidentiality; Traffic analysis to determine which entities are communicating with each other without being able to read the communicated information
SV-IT-1	Communications system spoofing resulting in denial of service and loss of availability and data integrity
SV-AC-4	Masquerading as an authorized entity in order to gain access/Insider Threat

Sample Requirements

Requirement	Rationale/Additional Guidance/Notes
The [organization] shall identify the applicable physical and environmental protection policies covering the development environment and spacecraft hardware. {PE-1,PE-14,SA-3,SA-3(1),SA-10(3)}
The [organization] shall develop and document program-specific access control policies for controlling information flow and leakage on-board the spacecraft.{AC-1,AC-3,AC-3(3),AC-3(4),AC-3(13)}
The [organization] shall develop and document program-specific identification and authentication policies for accessing the development environment and spacecraft. {AC-3,AC-14,IA-1,SA-3,SA-3(1)}
The [organization] shall protect documentation and Controlled Unclassified Information (CUI) as required, in accordance with the risk management strategy.{AC-3,CM-12,CP-2,PM-17,RA-5(4),SA-3,SA-3(1),SA-5,SA-10,SC-8(1),SC-28(3),SI-12}
The [organization] shall identify and properly classify mission sensitive design/operations information and access control shall be applied in accordance with classification guides and applicable federal laws, Executive Orders, directives, policies, regulations, and standards.{SV-CF-3,SV-AV-5}{AC-3,CM-12,CP-2,PM-17,RA-5(4),SA-3,SA-3(1),SA-5,SA-8(19),SC-8(1),SC-28(3),SI-12}	* Mission sensitive information should be classified as Controlled Unclassified Information (CUI) or formally known as Sensitive but Unclassified. Ideally these artifacts would be rated SECRET or higher and stored on classified networks. Mission sensitive information can typically include a wide range of candidate material: the functional and performance specifications, the RF ICDs, databases, scripts, simulation and rehearsal results/reports, descriptions of uplink protection including any disabling/bypass features, failure/anomaly resolution, and any other sensitive information related to architecture, software, and flight/ground /mission operations. This could all need protection at the appropriate level (e.g., unclassified, SBU, classified, etc.) to mitigate levels of cyber intrusions that may be conducted against the project’s networks. Stand-alone systems and/or separate database encryption may be needed with controlled access and on-going Configuration Management to ensure changes in command procedures and critical database areas are tracked, controlled, and fully tested to avoid loss of science or the entire mission.
The [organization] shall protect the security plan from unauthorized disclosure and modification.{SV-MA-6}{AC-3,PL-2,PL-7}
The [organization] shall ensure security requirements/configurations are placed in accordance with NIST 800-171 with enhancements in 800-172 on the development environments to prevent the compromise of source code from supply chain or information leakage perspective.{AC-3,SA-3,SA-3(1),SA-15}
The [organization] shall identify the key system components or capabilities that require isolation through physical or logical means.{SV-AC-6}{AC-3,SC-3,SC-7(13),SC-28(3),SC-32,SC-32(1)}	Fault management and security management capabilities would be classified as mission critical and likely need separated. Additionally, capabilities like TT&C, C&DH, GNC might need separated as well.
The [organization] shall ensure any update to on-board software, memory, or stored procedures has met high assurance standards before execution. {AC-3(2),CM-3,SA-8(8),SA-8(31),SA-10(2),SR-4(4)}
The [organization] shall implement a verifiable flaw remediation process into the developmental and operational configuration management process.{SV-SP-1,SV-SP-6,SV-SP-7,SV-SP-9,SV-SP-11}{CA-2,CA-5,SA-3,SA-3(1),SA-11,SI-3,SI-3(10)}	The verifiable process should also include a cross reference to mission objectives and impact statements. Understanding the flaws discovered and how they correlate to mission objectives will aid in prioritization.
The [organization] shall establish robust procedures and technical methods to perform testing to include adversarial testing (i.e.abuse cases) of the platform hardware and software.{CA-8,CP-4(5),RA-5,RA-5(1),RA-5(2),SA-3,SA-4(3),SA-11,SA-11(1),SA-11(2),SA-11(5),SA-11(7),SA-11(8),SA-15(7)}
The [organization] shall require subcontractors developing information system components or providing information system services (as appropriate) to demonstrate the use of a system development life cycle that includes [state-of-the-practice system/security engineering methods, software development methods, testing/evaluation/validation techniques, and quality control processes].{SV-SP-1,SV-SP-2,SV-SP-3,SV-SP-9}{SA-3,SA-4(3)}	Select the particular subcontractors, software vendors, and manufacturers based on the criticality analysis performed for the Program Protection Plan and the criticality of the components that they supply.
For FPGA pre-silicon artifacts that are developed, coded, and tested by a developer that is not accredited, the [organization] shall be subjected to a development environment and pre-silicon artifacts risk assessment by [organization]. Based on the results of the risk assessment, the [organization] may need to implement protective measures or other processes to ensure the integrity of the FPGA pre-silicon artifacts.{SV-SP-5}{SA-3,SA-3(1),SA-8(9),SA-8(11),SA-12,SA-12(1),SR-1,SR-5}	DOD-I-5200.44 requires the following: 4.c.2 “Control the quality, configuration, and security of software, firmware, hardware, and systems throughout their lifecycles... Employ protections that manage risk in the supply chain… (e.g., integrated circuits, field-programmable gate arrays (FPGA), printed circuit boards) when they are identifiable (to the supplier) as having a DOD end-use. “ 4.e “In applicable systems, integrated circuit-related products and services shall be procured from a Trusted supplier accredited by the Defense Microelectronics Activity (DMEA) when they are custom-designed, custommanufactured, or tailored for a specific DOD military end use (generally referred to as application-specific integrated circuits (ASIC)). “ 1.g “In coordination with the DOD CIO, the Director, Defense Intelligence Agency (DIA), and the Heads of the DOD Components, develop a strategy for managing risk in the supply chain for integrated circuit-related products and services (e.g., FPGAs, printed circuit boards) that are identifiable to the supplier as specifically created or modified for DOD (e.g., military temperature range, radiation hardened).
The [organization] shall require the developer of the system, system component, or system services to demonstrate the use of a system development life cycle that includes [state-of-the-practice system/security engineering methods, software development methods, testing/evaluation/validation techniques, and quality control processes].{SV-SP-1,SV-SP-2,SV-SP-3,SV-SP-9}{SA-3,SA-4(3)}	Examples of good security practices would be using defense-in-depth tactics across the board, least-privilege being implemented, two factor authentication everywhere possible, using DevSecOps, implementing and validating adherence to secure coding standards, performing static code analysis, component/origin analysis for open source, fuzzing/dynamic analysis with abuse cases, etc.
The [spacecraft] shall monitor security relevant telemetry points for malicious commanding attempts.{AC-17,AC-17(1),AC-17(10),AU-3(1),RA-10,SC-7,SC-16,SC-16(2),SC-16(3),SI-3(8),SI-4,SI-4(1),SI-4(13),SI-4(24),SI-4(25),SI-10(6)}
The [organization] shall ensure reused TT&C software has adequate uniqueness for command decoders/dictionaries so that commands are received by only the intended satellite.{SV-SP-6}{AC-17(10),SC-16(3),SI-3(9)}	The goal is to eliminate risk that compromise of one command database does not affect a different one due to reuse. The intent is to ensure that one SV can not process the commands from another SV. Given the crypto setup with keys and VCC needing to match, this requirement may be inherently met as a result of using type-1 cryptography. The intent is not to recreate entire command dictionaries but have enough uniqueness in place that it prevents a SV from receiving a rogue command. As long as there is some uniqueness at the receiving end of the commands, that is adequate.
The [spacecraft] shall provide the capability to restrict command lock based on geographic location of ground stations.{SV-AC-1}{AC-2(11),IA-10,SI-4(13),SI-4(25)}	This could be performed using command lockout based upon when the spacecraft is over selected regions. This should be configurable so that when conflicts arise, the Program can update. The goal is so the spacecraft won't accept a command when the spacecraft determines it is in a certain region.
The [spacecraft] shall uniquely identify and authenticate the ground station and other spacecraft before establishing a remote connection.{SV-AC-1,SV-AC-2}{AC-3,AC-17,AC-17(10),AC-20,IA-3,IA-4,SA-8(18),SI-3(9)}
The [spacecraft] shall authenticate the ground station (and all commands) and other spacecraft before establishing remote connections using bidirectional authentication that is cryptographically based.{SV-AC-1,SV-AC-2}{AC-3,AC-17,AC-17(2),AC-17(10),AC-18(1),AC-20,IA-3(1),IA-4,IA-4(9),IA-7,IA-9,SA-8(18),SA-8(19),SA-9(2),SC-7(11),SC-16(1),SC-16(2),SC-16(3),SC-23(3),SI-3(9)}	Authorization can include embedding opcodes in command strings, using trusted authentication protocols, identifying proper link characteristics such as emitter location, expected range of receive power, expected modulation, data rates, communication protocols, beamwidth, etc.; and tracking command counter increments against expected values.
The [spacecraft] shall implement cryptographic mechanisms to identify and reject wireless transmissions that are deliberate attempts to achieve imitative or manipulative communications deception based on signal parameters.{SV-AV-1,SV-IT-1}{AC-3,AC-20,SA-8(19),SC-8(1),SC-23(3),SC-40(3),SI-4(13),SI-4(24),SI-4(25),SI-10(6)}
The [spacecraft] shall employ the principle of least privilege, allowing only authorized accesses processes which are necessary to accomplish assigned tasks in accordance with system functions.{SV-AC-6}{AC-3,AC-6,AC-6(9),CA-9,CM-5,CM-5(5),CM-5(6),SA-8(2),SA-8(5),SA-8(6),SA-8(14),SA-8(23),SA-17(7),SC-2,SC-7(29),SC-32,SC-32(1),SI-3}
The [spacecraft] shall implement relay and replay-resistant authentication mechanisms for establishing a remote connection.{SV-AC-1,SV-AC-2}{AC-3,IA-2(8),IA-2(9),SA-8(18),SC-8(1),SC-16(1),SC-16(2),SC-23(3),SC-40(4)}
The [spacecraft] shall ensure that processes reusing a shared system resource (e.g., registers, main memory, secondary storage) do not have access to information (including encrypted representations of information) previously stored in that resource during a prior use by a process after formal release of that resource back to the system or reuse.{SV-AC-6}{AC-3,PM-32,SA-8(2),SA-8(5),SA-8(6),SA-8(19),SC-4,SI-3}
The [spacecraft] shall protect the confidentiality and integrity of the following information using cryptography while it is at rest: [all information].{AC-3,SA-8(19),SC-28,SC-28(1),SI-7(6)}	* The intent as written is for all transmitted traffic to be protected. This includes internal to internal communications and especially outside of the boundary.
The [spacecraft] shall maintain the confidentiality and integrity of information during preparation for transmission and during reception.{SV-AC-7}{AC-3,SA-8(19),SC-8,SC-8(1),SC-8(2),SC-16,SC-16(1)}	* Preparation for transmission and during reception includes the aggregation, packing, and transformation options performed prior to transmission and the undoing of those operations that occur upon receipt.
The [spacecraft] shall require multi-factor authorization for all updates to the task scheduling functionality within the spacecraft.{SV-AV-4}{AC-3(2)}	Multi-factor authorization could be the "two-man rule" where procedures are in place to prevent a successful attack by a single actor (note: development activities that are subsequently subject to review or verification activities may already require collaborating attackers such that a "two-man rule" is not appropriate).
The [spacecraft] shall require multi-factor authorization for new and updates to on-board stored command sequences.{SV-IT-5}{AC-3(2)}	Multi-factor authorization could be the "two-man rule" where procedures are in place to prevent a successful attack by a single actor (note: development activities that are subsequently subject to review or verification activities may already require collaborating attackers such that a "two-man rule" is not appropriate).
The [spacecraft] software subsystems shall provide non-identical methods, or functionally independent methods, for commanding a mission critical function when the software is the sole control of that function.{SV-MA-3,SV-AV-7}{AC-3(2)}
The [spacecraft] software subsystems shall provide two independent and unique command messages to deactivate a fault tolerant capability for a critical or catastrophic hazard.{SV-MA-3,SV-AV-7}{AC-3(2)}
The [spacecraft] shall require multi-factor authorization for all spacecraft [applications or operating systems] updates within the spacecraft.{SV-SP-9,SV-SP-11}{AC-3(2),CM-3(8),CM-5,PM-12,SA-8(8),SA-8(31),SA-10(2),SI-3(8),SI-7(12),SI-10(6)}	The intent is for multiple checks to be performed prior to executing these SV SW updates. One action is mere act of uploading the SW to the spacecraft. Another action could be check of digital signature (ideal but not explicitly required) or hash or CRC or a checksum. Crypto boxes provide another level of authentication for all commands, including SW updates but ideally there is another factor outside of crypto to protect against FSW updates. Multi-factor authorization could be the "two-man rule" where procedures are in place to prevent a successful attack by a single actor (note: development activities that are subsequently subject to review or verification activities may already require collaborating attackers such that a "two-man rule" is not appropriate).
The [spacecraft] shall provide two independent and unique command messages to deactivate a fault tolerant capability for a critical or catastrophic hazard.{AC-3(2),PE-10,SA-8(15)}
The [spacecraft] shall provide non-identical methods, or functionally independent methods, for commanding a mission critical function when the software is the sole control of that function.{AC-3(2),SI-3(8),SI-13}
The [spacecraft] shall enforce approved authorizations for controlling the flow of information within the platform and between interconnected systems so that information does not leave the platform boundary unless it is encrypted.{SV-AC-6}{AC-3(3),AC-3(4),AC-4,AC-4(6),AC-4(21),CA-3,CA-3(6),CA-3(7),CA-9,IA-9,SA-8(19),SC-8(1),SC-16(3)}
The [spacecraft] security implementation shall ensure that information should not be allowed to flow between partitioned applications unless explicitly permitted by the system.{AC-3(3),AC-3(4),AC-4,AC-4(6),AC-4(21),CA-9,IA-9,SA-8(3),SA-8(18),SA-8(19),SC-2(2),SC-7(29),SC-16,SC-32}
The [spacecraft] shall, when transferring information between different security domains, implements the following security policy filters that require fully enumerated formats that restrict data structure and content: connectors and semaphores implemented in the RTOS.{SV-AC-6}{AC-3(3),AC-3(4),AC-4(14),IA-9,SA-8(19),SC-16}
The [spacecraft] shall implement boundary protections to separate bus, communications, and payload components supporting their respective functions.{SV-AC-6}{AC-3(3),AC-3(4),CA-9,SA-8(3),SA-8(14),SA-8(18),SA-8(19),SA-17(7),SC-2,SC-2(2),SC-7(13),SC-7(21),SC-7(29),SC-16(3),SC-32,SI-3,SI-4(13),SI-4(25)}
The [spacecraft] shall isolate mission critical functionality from non-mission critical functionality by means of an isolation boundary (e.g.via partitions) that controls access to and protects the integrity of, the hardware, software, and firmware that provides that functionality.{SV-AC-6}{AC-3(3),AC-3(4),CA-9,SA-8(3),SA-8(19),SA-17(7),SC-2,SC-3,SC-3(4),SC-7(13),SC-7(29),SC-32,SC-32(1),SI-3,SI-7(10),SI-7(12)}
The [spacecraft] data within partitioned applications shall not be read or modified by other applications/partitions.{SV-AC-6}{AC-3(3),AC-3(4),SA-8(19),SC-2(2),SC-4,SC-6,SC-32}
The [spacecraft] shall prevent unauthorized access to system resources by employing an efficient capability based object model that supports both confinement and revocation of these capabilities when the platform security deems it necessary.{SV-AC-6}{AC-3(8),IA-4(9),PM-32,SA-8(2),SA-8(5),SA-8(6),SA-8(18),SA-8(19),SC-2(2),SC-4,SC-16,SC-32,SI-3}
All [spacecraft] commands which have unrecoverable consequence must have dual authentication prior to command execution.{AU-9(5),IA-3,IA-4,IA-10,PE-3,PM-12,SA-8(15),SA-8(21),SC-16(2),SC-16(3),SI-3(8),SI-3(9),SI-4(13),SI-4(25),SI-7(12),SI-10(6),SI-13}
The [spacecraft] shall have a method to ensure the integrity of these commands and validate their authenticity before execution.{AU-9(5),IA-3,IA-4,IA-10,PE-3,PM-12,SA-8(15),SA-8(21),SC-16(2),SC-16(3),SI-3(8),SI-3(9),SI-4(13),SI-4(25),SI-7(12),SI-10(6),SI-13}
The [organization] shall ensure that the allocated security safeguards operate in a coordinated and mutually reinforcing manner.{SV-MA-6}{CA-7(5),PL-7,PL-8(1),SA-8(19)}
The [organization] shall document and design a security architecture using a defense-in-depth approach that allocates the [organization]s defined safeguards to the indicated locations and layers: [Examples include: operating system abstractions and hardware mechanisms to the separate processors in the platform, internal components, and the FSW].{SV-MA-6}{CA-9,PL-7,PL-8,PL-8(1),SA-8(3),SA-8(4),SA-8(7),SA-8(9),SA-8(11),SA-8(13),SA-8(19),SA-8(29),SA-8(30)}
The [organization] shall implement a security architecture and design that provides the required security functionality, allocates security controls among physical and logical components, and integrates individual security functions, mechanisms, and processes together to provide required security capabilities and a unified approach to protection.{SV-MA-6}{PL-7,SA-2,SA-8,SA-8(1),SA-8(2),SA-8(3),SA-8(4),SA-8(5),SA-8(6),SA-8(7),SA-8(9),SA-8(11),SA-8(13),SA-8(19),SA-8(29),SA-8(30),SC-32,SC-32(1)}
The [spacecraft] shall have on-board intrusion detection/prevention system that monitors the mission critical components or systems.{SV-AC-1,SV-AC-2,SV-MA-4}{RA-10,SC-7,SI-3,SI-3(8),SI-4,SI-4(1),SI-4(7),SI-4(13),SI-4(24),SI-4(25),SI-10(6)}	The mission critical components or systems could be GNC/Attitude Control, C&DH, TT&C, Fault Management.
The [spacecraft] shall discriminate between valid and invalid input into the software and rejects invalid input.{SC-16(2),SI-3(8),SI-10,SI-10(3),SI-10(6)}
The [spacecraft] shall monitor [Program defined telemetry points] for malicious commanding attempts.{SV-AC-1,SV-AC-2}{SC-7,AU-3(1),AC-17(1)}	Source from AEROSPACE REPORT NO. TOR-2019-02178 Vehicle Command Counter (VCC) - Counts received valid commands Rejected Command Counter - Counts received invalid commands Command Receiver On/Off Mode - Indicates times command receiver is accepting commands Command Receivers Received Signal Strength - Analog measure of the amount of received RF energy at the receive frequency Command Receiver Lock Modes - Indicates when command receiver has achieved lock on command signal Telemetry Downlink Modes - Indicates when the satellite’s telemetry was transmitting Cryptographic Modes - Indicates the operating modes of the various encrypted links Received Commands - Log of all commands received and executed by the satellite System Clock - Master onboard clock GPS Ephemeris - Indicates satellite location derived from GPS Signals
The [spacecraft] shall only use or include critical commands for the purpose of providing emergency access where commanding authority is appropriately restricted.{SI-3(8),SI-10,SI-10(3)}