Ciphertext-to-Plaintext Addition

CKKS’s ciphertext-to-plaintext addition scheme is exactly the same as BFV’s ciphertext-to-plaintext addition scheme (Summary D-2.5 in §D-2.5).

$⟨$ Summary D-3.4 $⟩$ CKKS Ciphertext-to-Plaintext Addition

${𝖱𝖫𝖶𝖤}_{S, σ} (Δ M) + Δ Λ$

$= (A, B) + Δ Λ$

$= (A, B + Δ \cdot Λ)$

$= {𝖱𝖫𝖶𝖤}_{S, σ} (Δ (M + Λ))$