Telemetry Link Security: Encryption, Authentication, and Anti-Spoofing for Commercial Missions

The command and telemetry links connecting your ground systems to your vehicle are attack surfaces. As commercial space operations scale and geopolitical tensions increase attention on space infrastructure, the security of these links is no longer an afterthought—it's a design requirement.

This article examines the practical security considerations for telemetry and command links in commercial launch and satellite operations, with attention to both the threat landscape and implementation constraints unique to space systems.

The Threat Model

Understanding what you're protecting against shapes your security architecture. For commercial space telemetry links, relevant threat categories include:

Eavesdropping. Passive interception of telemetry data can reveal vehicle state, operational patterns, payload characteristics, and system vulnerabilities. For commercial operators, telemetry may contain proprietary performance data or customer payload information subject to confidentiality requirements.

Command injection. Unauthorized commands could cause loss of mission, loss of vehicle, or—in the case of flight termination systems—unintended activation with safety implications. This is the highest-consequence threat for most systems.

Replay attacks. Recording legitimate commands for later retransmission. Even without understanding command content, an attacker could replay a previously-observed command sequence to trigger known vehicle responses.

Spoofing. Generating false telemetry to deceive ground operators about vehicle state. This could mask actual anomalies or create false indications that trigger inappropriate operator responses.

Jamming and denial of service. Disrupting the RF link to prevent command reception or telemetry downlink. While not a confidentiality or integrity attack, loss of link during critical mission phases has obvious safety implications.

Regulatory Context

Space Policy Directive 5 (SPD-5), published in 2020, established cybersecurity principles for space systems. While SPD-5 itself doesn't mandate specific technical controls, it establishes expectations that increasingly flow into contracts, insurance requirements, and licensing considerations.

SPD-5 principles relevant to telemetry link security include:

• Protection of command, control, and telemetry by encryption and authentication
• Protection against unauthorized access to critical functions
• Physical protection of ground systems and supply chain risk management
• Adoption of appropriate cybersecurity hygiene practices

NIST IR 8401 (Satellite Ground Segment: Applying the Cybersecurity Framework to Satellite Command and Control) provides detailed guidance on applying the NIST Cybersecurity Framework to satellite operations. NIST IR 8270 covers cybersecurity for commercial satellite operations more broadly.

For operators serving European customers or with ground stations in EU territory, NIS2 Directive requirements now apply to space as a sector of "high criticality," with specific cybersecurity and incident reporting obligations.

Encryption Implementation

Command Link Encryption

Command links warrant the strongest protection given the consequences of compromise. Implementation considerations:

Algorithm selection. AES-256 in appropriate modes (GCM for authenticated encryption) is the current standard for unclassified applications requiring strong protection. For systems with extended operational lifetimes, consider the NIST post-quantum cryptography standards finalized in 2024 (ML-KEM for key encapsulation, ML-DSA for signatures) for defense against future quantum computing threats.

Key management. Pre-positioned keys loaded before launch provide the simplest architecture but create challenges for long-duration missions. Key hierarchy approaches (master keys that derive session keys) extend operational flexibility while limiting exposure from any single key compromise.

Processing constraints. Space-qualified processors impose real computational limits. Ensure your encryption approach is compatible with available processing capacity while meeting latency requirements for time-critical commands.

Telemetry Encryption

Telemetry encryption protects data confidentiality but adds overhead to high-rate data streams. Practical approaches include:

• Full encryption of all telemetry—highest protection but highest overhead
• Selective encryption of sensitive parameters with clear-text housekeeping—reduces processing load but requires careful classification of data sensitivity
• Link-layer encryption at the modem level—protects all data transparently but may not be available for all ground station configurations

Authentication Mechanisms

Encryption without authentication is insufficient. An attacker who can modify encrypted data without detection can potentially induce faults or bypass security controls.

Command Authentication

Commands should be authenticated to verify:

1. Origin—command came from an authorized source
2. Integrity—command was not modified in transit
3. Freshness—command is not a replay of a previous valid command

Message Authentication Codes (MACs) using HMAC-SHA256 or AES-GMAC provide integrity and authentication. Sequence numbers or timestamps address replay protection. The authentication tag must be verified before command execution—failed authentication should reject the command and log the event.

Anti-Replay Mechanisms

Replay protection requires state synchronization between ground and space segments. Common approaches:

• Monotonic sequence numbers that increment with each command. The vehicle rejects any command with a sequence number not greater than the last accepted command.
• Timestamp-based windows requiring commands to include a timestamp within an acceptable range of the vehicle's current time. Requires time synchronization between ground and vehicle.
• Challenge-response protocols where the vehicle issues a nonce that must be included in subsequent commands. Provides strong replay protection but requires round-trip communication before command execution.

Anti-Spoofing for Telemetry

Protecting telemetry integrity ensures ground operators can trust the data they're receiving. Authentication approaches mirror command authentication: cryptographic MACs computed over telemetry data and verified by ground systems.

Detection mechanisms complement cryptographic protection:

• Statistical anomaly detection identifying telemetry patterns inconsistent with expected vehicle behavior
• Cross-validation between telemetry and independent tracking sources (radar, optical, GPS)
• Consistency checks between related parameters (e.g., propellant consumption vs. thrust history)

Implementation Challenges

Space systems impose constraints that complicate standard security implementations:

Processing limitations. Radiation-hardened processors lag commercial technology by a decade or more. Cryptographic operations that are trivial on modern terrestrial hardware may consume significant processing margin on space-qualified systems.

Key management complexity. You cannot physically access a satellite to replace compromised keys. Pre-mission key loading, secure key storage, and provisions for key update (if supported) require careful design.

Availability requirements. Security mechanisms must not prevent legitimate command execution during anomaly response. Design for graceful degradation—how does the system behave if cryptographic verification fails due to key synchronization loss rather than attack?

Legacy system integration. Ground infrastructure may include equipment that predates current security requirements. Retrofit solutions must integrate with existing ground system architectures without requiring complete replacement.

Practical Recommendations

Start security architecture during preliminary design, not integration. Retrofitting security into a system designed without it is expensive and often incomplete.

Document your threat model explicitly. What are you protecting against? What are the consequences of various attack scenarios? This analysis drives appropriate security control selection and justifies those choices to customers, insurers, and regulators.

Test security mechanisms under realistic conditions including degraded link quality, timing stress, and anomaly response scenarios. Security that only works under nominal conditions isn't security.

Plan for cryptographic agility. Algorithms considered secure today may be deprecated over your system's operational lifetime. Design for the ability to update cryptographic implementations—even if that capability goes unused.

The commercial space industry has historically treated link security as optional or addressed it only when customer contracts required it. That approach is increasingly untenable. Build security in from the start, document your approach, and be prepared to demonstrate compliance to an expanding set of stakeholders.