Following the Hu-Kriz method of computing the C 2 genuine dual Steenrod algebra (H F 2 ) ⋆ (H F 2 ), we calculate the C 4 equivariant Bredon cohomology of the classifying space R P ∞ρ = B C 4 Σ 2 as an RO(C 4 ) graded Greenfunctor. We prove that as a module over the homology of a point (which we also compute), this cohomology is not flat. As a result, it can't be used as a test module for obtaining generators in (H F 2 ) ⋆ (H F 2 ) as Hu-Kriz do in the C 2 case. Contents 1. Introduction Acknowledgment 2. Conventions and notations 3. The Tate diagram for C 2 and C 4 3.1. The Tate diagram for C 2 3.2. The RO(C 4 ) homology of a point 3.3. The Tate diagram for C 4 4. Equivariant classifying spaces 4.1. The case of C 2 5. The cohomology of B C 4 Σ 2 6. A cellular decomposition of B C 4 Σ 2 6.1. A decomposition using trivial spheres 7. The spectral sequence for B C 4 Σ 2 7.1. The E 1 page 7.2. The d 1 differentials 7.3. Bottom level computation 7.4. Middle level computation 7.5. Top level differentials 7.6. Coherent lifts 7.7. Top level generators 7.8. Mackey functor structure 7.9. Top level module relations 7.10. Top level cup products Appendix A. Pictures of the spectral sequence Appendix B. The RO(C 4 ) homology of a point in F 2 coefficients B.1. k * S nσ+mλ B.2. k * S −nσ−mλ B.3. k * S mλ−nσ B.4. k * S nσ−mλ B.5. Subtleties about quotients 1 4