Choi et al. proposed the modified Paillier cryptosystem (M-Paillier cryptosystem). They use a special public-key g ∈ ZZ/nZZ such that gϕ(n) = 1+n mod n2, where n is the RSA modulus. The distribution of the public key g is different from that of the original one. In this paper, we study the security of the usage of the public key. Firstly, we prove that the one-wayness of the M-Paillier cryptosystem is as intractable as factoring the modulus n, if the public key g can be generated only by the public modulus n. Secondly, we prove that the oracle that can generate the public-key factors the modulus n. Thus the public keys cannot be generated without knowing the factoring of n. The Paillier cryptosystem can use the public key g = 1+n, which is generated only from the public modulus n. Thirdly, we propose a chosen ciphertext attack against the M-Paillier cryptosystem. Our attack can factor the modulus n by only one query to the decryption oracle. This type of total breaking attack has not been reported for the original Paillier cryptosystem. Finally, we discuss the relationship between the M-Paillier cryptosystem and the Okamoto-Uchiyama scheme.
CITATION STYLE
Sakurai, K., & Takagi, T. (2002). On the security of a modified paillier public-key primitive. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 2384, pp. 436–448). Springer Verlag. https://doi.org/10.1007/3-540-45450-0_33
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