Harris has received an $875m contract to support the US Air Force's (USAF) cryptographic and information assurance products.
The multi-award IDIQ contract has a five-year base term, with an extension option of five years.
The contract covers development, production, and support throughout its lifecycle.
Harris president Chris Young said: "Secure communications on the battlefield is a critical element in keeping our warfighters safe and ensuring mission success.
"This award reflects our advanced technical capabilities and proven ability to deliver secure communication solutions."
During the different phases of the contract, Harris is required to provide material solutions analysis, technology development, technology maturation, and risk reduction.
Work under the contract also includes preliminary design, engineering and manufacturing development, and production and sustainment.
Harris' encrypted communication solutions include single integrated circuits to secure and wireless systems, and are fielded in a broad array of products such as tactical radios, unmanned aerial vehicles, remote sensors and missile/telemetry applications.
As part of a separate contract, Harris will upgrade the USAF's ballistic missile early warning system (BMEWS) precision acquisition of vehicle entry (PAVE) phased array warning system (PAWS), known as BPP.
The $7m contract will see Harris maintain the software posture of the BPP systems, resolve issues with existing early warning radar systems, and improve detection ability of incoming missiles.
The work will be performed at Beale Air Force Base, California, US, and is expected to be completed by February 2019.