D-3.3 Ciphertext-to-Ciphertext Addition

CKKS’s ciphertext-to-ciphertext addition scheme is exactly the same as BFV’s ciphertext-to-ciphertext addition scheme (Summary D-2.4 in §D-2.4).

Summary D-3.3 CKKS Ciphertext-to-Ciphertext Addition

𝖱𝖫𝖶𝖤S,σ(ΔM1) + 𝖱𝖫𝖶𝖤S,σ(ΔM2)

= (A1, B1) + (A2, B2)

= (A1+ A2, B1+ B2)

= 𝖱𝖫𝖶𝖤S,σ(Δ(M1+ M2))