Revisiting HRA and CCA Security in Lattice-Based Proxy Re-Encryption

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Proxy re-encryption (PRE) enables a semi-trusted proxy to transform ciphertexts between users without learning their plaintexts. In lattice-based PRE, honest re-encryption attack (HRA) security has become a common security goal. However, the relation between HRA and chosen-ciphertext (CCA) security, and the mechanisms needed to achieve HRA security, remain poorly understood. We first clarify the relation between the security notions. We formulate derivative-closure chosen-ciphertext security