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No, this is not possible. The homomorphism only works at one layer. A ciphertext in Paillier is $g^m\cdot r^n\bmod{n^2}$. The plaintext space is the multiplicative group of integers modulo $n$. So, for it to even have a chance to work, first of all, the modulus of the outer encryption would have to be greater than $n^2$, where $n$ is the modulus of the ...

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It can not do multiplication in the plaintext domain using two ciphertexts. In other words, given $E(m_1)$ and $E(m_2)$, you can not get $E(m_1\cdot m_2)$. You can only get $E(m_1+m_2)$. Given $E(m_1)$ and $m_2$, you can get $E(m_1\cdot m_2)$ however. But notice that $m_2$ in this case was not encrypted. On the site you reference, $C$ is not encrypted. It ...

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You should not use keys smaller than 1024, and even 1024 is considered too small today. However, if you want additive homomorphism, then you can you encrypt with "ElGamal in the exponent" over Elliptic curves. To explain what I mean by this, let $G$ be the base point (generator) for the Elliptic curve group, let $x$ be the ElGamal private key, and let ...

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