The safe geological disposal of high-level radioactive waste requires a passive multi-barrier system. This paper describes the engineered barriers foreseen in the provisional Swiss repository concept, covering both design aspects as well as evidence for their long-term performance. Disposal canisters made of carbon steel will be used for the encapsulation of spent nuclear fuel and vitrified high-level waste. The canisters are designed to corrode slowly and predictably in the repository as well as to withstand external mechanical loads, leading to long lifetimes. The bentonite buffer surrounding the canisters, upon saturation with water, will swell and provide a stable environment around the high-level waste disposal canisters, limiting corrosion, inhibiting microbial activity, and ensuring an even distribution of mechanical loads. Furthermore, after the breaching of the canisters and the release of radionuclides, the buffer ensures diffusion-dominated transport and promotes sorption and immobilisation by precipitation. In addition, a compacted bentonite sealing element seals the drift and limits water flow along the repository components. The properties of these components are understood well enough to allow an adequate description of their evolution over long time-scales, thus allowing to demonstrate their barrier function and long-term performance.