ScyLight Workplan has been established based on an ESA internal ARTES ScyLight Call for Ideas.This activity have been selected in line with with the programme objectives for Line 4 (Quantum Cryptography Technologies). Line 4 covers the related development as well as in-orbit and service demonstration, including Quantum Key Generation and Distribution systems, and the demonstration of related end-to-end systems.This activity targets the protection of European critical infrastructure through the exploitation of secureoptical communication technologies. European critical infrastructure means critical infrastructure located in European Union states, the disruption or destruction of which would have a significant impact on at least two states (e.g. related to energy, health, transport, telecommunications, finance, security and space assets).The activity shall identify the potential deficiencies of existing secure solutions for critical infrastructure protection, including crypto key management and distribution. It shall identify the required technology developments, concepts of operation and possible scenarios for deployment in space in a 2020 - 2025 timeframe. The technical and operational requirements for space-based systems (e.g. low earth orbit satellites, geostationary satellites, ground segment) shall be established and a business case developed for the protection of critical infrastructures using optical communication technologies, such asquantum key distribution.