Two-key generation for a cellular model with a helper

The problem of simultaneously generating two keys for a cellular model is investigated, in which each of four terminals, X₀, X₁, X₂, and X₃ observes one component of correlated sources. The terminal X0 wishes to generate secret keys K₁ and K₂ respectively, with terminals X₁ and X₂ under the help of terminal X₃. They are allowed to communicate over a public channel. Both K₁ and K₂ are required to be concealed from an eavesdropper that has access to the public discussion. The key capacity region is established by designing a unified achievable strategy to achieve the cut-set outer bounds, which greatly simplifies the proof.