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Ciphertext indistinguishability (IND-CPA) for symmetric cryptography
3 votes

First off, your definition is not IND-CPA: In the IND-CPA setting, the adversary has access to an encryption oracle. As you have already determined, no deterministic encryption scheme can be IND-CPA ...

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Size of Fresh Ciphertext's Noise in FHE over the integers
2 votes

Let's look at the ciphertext: $ c \leftarrow m + 2r + 2 \sum\limits_{i \in S} x_i \bmod x_0 = m + 2r + 2\sum\limits_{i \in S} (pq_i + r_i) + k(pq_0 + r_0) $ for some $k$. When we do modular ...

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