Military Embedded Systems

Securing telemetry data with commercial encryption standards


December 01, 2021

Paul Cook


Securing telemetry data with commercial encryption standards

An industry perspective from Curtiss-Wright Defense Solutions

Telemetry data from military flight tests often needs to be secured, not only when at rest, but also while in motion across a network or a telemetry link.

While flight-test vehicles are generally not deployed in adversarial environments, their data can be particularly at risk due to the newness, and therefore the desirability, of the technology. For example, there is a risk of data loss on a hypersonic flight-test vehicle due to the possibility of a test aircraft being captured by other parties, by data being stolen by bad actors, or by data interception on what could be a very long flight path.

In the U.S., classified telemetry has been encrypted data since the late 1970s, due to a mandate that all telemetry data be made secure during transmission. Meanwhile, much of the unclassified data has historically been transmitted unencrypted. The telemetry industry has traditionally relied on the NSA to provide leadership and/or solutions to encrypt telemetry data for streaming (data-in-motion) applications. This system has worked well over the years but it’s not actually practical for data in transit that is not classified, data that is considered private, or programs with short development cycles.

Frequently, system designers are under the impression that NSA Suite A cryptography is their only option for protecting critical telemetry data. While Suite A is necessary for protecting some categories of sensitive information, in many other cases the Commercial National Security Algorithm Suite (CNSA) – a 2018 replacement of NSA Suite B – can be implemented if handled correctly. CNSA is a set of cryptographic algorithms designed to protect U.S. National Security Systems information up to the top-secret level. It offers notable advantages over Suite A, including less-restrictive foreign military sales, the ability to control the encryption keys (Suite A keys are produced and managed by the NSA), and typically faster and less expensive implementation.

Using a CNSA-type approach, users can avoid the additional controls associated with an NSA short title yet gain a certified solution for secure data transmission. Certifications for commercial implementations can be obtained through the National Institute of Standards and Technology (NIST) and the NSA. Recently, the process has changed to include a Commercial Solutions for Classified (CSfC) as a popular alternate approval path: The CSfC focuses on a CNSA encryption solution or AES-256 with various combinations of software and hardware implementations appropriate to the use case. The NIST also provides a process of certifying encryption devices similar to the processes within the NSA. The NIST uses a third-party lab to evaluate the encryption process and the key-management process, along with other dedicated tests to complete the Federal Information Processing Standard (FIPS-140-2) certification at one of four levels of security.

Typically, the encrypted telemetry is decrypted on the ground with a rackmount box that features the specific ground telemetry interface and uses a single-ended TTL [transistor-to-transistor logic] with 50-ohm drive capability. A better approach is to provide the encrypt and decrypt interfaces in a single assembly, which enables the data to be looped back, providing high assurance of the equipment’s operation.

An example of a telemetry encryption solution for flight-test programs is Curtiss-Wright’s MESP-100, a three-module set that secures two channels of streaming telemetry data using commercial grade AES-256. It supports both the encrypt-decrypt functions in one assembly and supports secure bidirectional transmissions when using two devices. (Figure 1.)

[Figure 1 | The MESP-100 encryption support package for flight test instrumentation (shown in PCM encoder stack) supports the use of commercial encryption to protect critical telemetry data.]

Such technology was developed to provide data privacy for exportable equipment for platforms that fall outside of the U.S. and provide an easier way to secure data not subject to the rigors of NSA Suite A. It protects streaming telemetry data originating from modern ARTM [advanced range telemetry] transmitters. It integrates a NIST-certified device from a well-known vendor of secure crypto modules and implements it in a traditional telemetry form factor (including expected interfaces), enabling the telem­etry community to secure unclassified data with the interfaces they are accustomed to from the NSA implementation.

Paul Cook is director of missile systems and RF product line manager at Teletronics Technology Corporation, a Curtiss-Wright company.

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